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Found 2276 entries in the Bibliography.
Showing entries from 101 through 150
| 2022 |
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The thermospheric O/N2 ratio obtained from the TIMED/GUVI instrument for TIMED/GUVI observations of the O/N The authors ack nowledge the Global Ultraviolet Imager (GUVI) for the Reznychenko, M; Bogomaz, O; Kotov, D; Zhivolup, T; Koloskov, O; , Lisachenko; Published by: Ukrainian Antarctic Journal Published on: YEAR: 2022 DOI: 10.33275/1727-7485.1.2022.686 |
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In this article, we analyze vertical total electron content (VTEC) over Nepal for 4 periods: March 14–25, 2015, June 18–29, 2015, May 24–June 4, 2017, and September 3–14, 2017. In each period, there are quiet geomagnetic days and intense geomagnetic stormy days. The VTEC observed during these periods has observed both positive and negative ionospheric storms. We compared VTEC Receiver-Independent Exchange Format (RINEX) observations with the Global Ionospheric Map (GIM), Centre for Orbit Determination in Europe (CODE), and IGS working group (IGSG). We found in RINEX observation of the VTEC a noon bite out profile with predominance of morning and afternoon peaks and a nighttime peak, but this was not noticeable clearly with CODE and IGSG models. The comparison between RINEX TEC, CODE, and IGSG models shows that the GIM model does not estimate RINEX VTEC over Nepal. The disagreement between VTEC CODE/IGSG and VTEC RINEX is important during geomagnetically quiet periods, while there is good agreement between VTEC CODE/IGSG and VTEC RINEX during strong geomagnetic storms. We also find a greater disagreement between the models and the data at the equinoxes when the VTEC is larger. It is, therefore, necessary to introduce data from Nepal stations into the models CODE and IGSG in order to improve them Pandit, D; Amory-Mazaudier, Christine; Fleury, R; Chapagain, NP; Adhikari, B; Published by: Indian Journal of Physics Published on: YEAR: 2022 DOI: 10.1007/s12648-022-02441-w |
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We have investigated the global hemispheric differences in thermospheric ∑O/N2 and its impact on the ionospheric total electron content (TEC) at mid- and low-latitudes. Four intense storms of solar cycle 24 (SC-24) have been considered, three of them occurred in Spring equinox and one in Summer solstice season. Younas, Waqar; Khan, Majid; Amory-Mazaudier, C; Amaechi, Paul; Fleury, R; Published by: Advances in Space Research Published on: YEAR: 2022 DOI: 10.1016/j.asr.2021.10.027 |
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This paper presents the longitudinal dependence of ionospheric responses from Global Navigation Satellite System (GNSS) derived Total Electron Content (TEC) during two intense geomagnetic storms of May and September 2017. The GNSS-TEC is retrieved from four stations installed at the verge of low to mid-latitude Asian regions of Pakistan and China. Two ionospheric enhancements were observed during the storm of May 2017. The first one at local noon–afternoon during the storm main phase on 28 May was due to the southward turning of Interplanetary Magnetic Field (IMF-Bz) and eastward Prompt Penetration Electric Field (PPEF), with the maximum TEC enhancement at Wuhan. The second one at nighttime during the recovery phase of the storm on 29 May triggered ionospheric variations, mainly due to the later southward turning of the IMF-Bz as the Asian regions, were on the nightside with the westward PPEF. Negative storm time ionospheric responses were observed on 30 May, related to the change of the thermospheric composition as O/N2 depletion. Moreover, a significant increase in TEC was recorded during the main phase of the storm on 8 September 2017. This enhancement corresponded with the eastward PPEF and an increase in the O/N2. The TEC increment was also observed during the recovery phase on 9 September in the Pakistani stations. A minor storm on 7 September also gave rise to TEC enhancements, especially in western regions. However, the negative phase was registered from 9 to 10 September at each station because of the changes in the thermospheric composition as O/N2 depletion. Tariq, Arslan; Yuyan, Yang; Shah, Munawar; Shah, Ali; Iqbal, Talat; Liu, Libo; Published by: Advances in Space Research Published on: YEAR: 2022 DOI: 10.1016/j.asr.2022.08.050 |
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The Role of Solar Soft X-rays Irradiance in Thermospheric Structure We use a new Atmospheric Chemistry and Energetics one-dimensional (ACE1D) thermospheric model to show that the energies deposited by the solar soft x-rays in the lower Samaddar, Srimoyee; Venkataramani, Karthik; Bailey, Scott; , others; Published by: arXiv preprint arXiv:2209.10543 Published on: YEAR: 2022 DOI: 10.48550/arXiv.2209.10543 |
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This study investigates ionospheric responses to 2013 and 2015 St. Patrick’s Days (CME-driven), 1 June 2013 and 7 October 2015 (CIR-driven) geomagnetic storms over the African- Akala, AO; Afolabi, RO; Otsuka, Y; Published by: Advances in Space Research Published on: YEAR: 2022 DOI: 10.1016/j.asr.2022.10.029 |
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Time Delay Integration Imaging of the Nighttime Ionosphere from the ICON Observatory TIMED GUVI was on a high inclination orbit changing local time relatively slowly and missing a great deal of the equatorward low latitude regions at the wrong local times. Mende, SB; Frey, HU; England, SL; Immel, TJ; Eastes, RW; Published by: Space Science Reviews Published on: YEAR: 2022 DOI: 10.1007/s11214-022-00928-w |
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Tiny Remote-sensing Instrument for Thermospheric Oxygen and Nitrogen: A Concept Study The primary objective of this project is to develop the Tiny Remote-sensing Instrument for Thermospheric Oxygen and Nitrogen (TRITON), an innovative sensor concept to measure Published by: Published on: |
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We identified a few new storm‐time ionospheric phenomena by analyzing disturbances in topside ion density, electron temperature, and ion temperature at ∼840 km altitude measured Huang, Chao-Song; Zhang, Yongliang; Wang, Wenbin; Lin, Dong; Wu, Qian; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2022JA030468 |
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A Model of the Globally-averaged Thermospheric Energy Balance Similar to the MSIS data, we bin the GUVI temperatures by latitude It should be noted that GUVI observations at high values of While the GUVI observations cannot be compared directly Venkataramani, Karthik; Bailey, Scott; Samaddar, Srimoyee; Yonker, Justin; Published by: arXiv preprint arXiv:2211.05301 Published on: YEAR: 2022 DOI: 10.48550/arXiv.2211.05301 |
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The present study provides a multi‐instrument analysis of the ionospheric response to the effects of the St. Patrick s Day storm of 17–18 March 2015. Simultaneous observations from 85 Kader, Sk; Dashora, N; Niranjan, K; Published by: Space Weather Published on: YEAR: 2022 DOI: 10.1029/2022SW003157 |
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Lithosphere–atmosphere–ionosphere coupling (LAIC) is studied through various physical or chemical quantities, obtained from different sources, which are observables of the involved Politis, Dimitrios; Potirakis, Stelios; Kundu, Subrata; Chowdhury, Swati; Sasmal, Sudipta; Hayakawa, Masashi; Published by: Symmetry Published on: YEAR: 2022 DOI: 10.3390/sym14091939 |
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Scintillations of transionospheric satellite signals during geomagnetic storms can severely threaten navigation accuracy and the integrity of space assets. We analyze vertical Total Shahzad, Rasim; Shah, Munawar; Abbas, Ayesha; Hafeez, Amna; Calabia, Andres; Melgarejo-Morales, Angela; Naqvi, Najam; Published by: Annales Geophysicae Discussions Published on: YEAR: 2022 DOI: 10.5194/angeo-2022-18 |
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The GUVI measurements indicated that the atomic oxygen (O) to molecular nitrogen (N2) (2021a) used the TIMED/GUVI limb measurements and TIEGCM simulations to investigate Lin, Chin; Sutton, Eric; Wang, Wenbin; Cai, Xuguang; Liu, Guiping; Henney, Carl; Cooke, David; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2021JA029831 |
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Retrospect and prospect of ionospheric weather observed by FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2 FORMOSAT-3/COSMIC (F3/C) constellation of six micro-satellites was launched into the circular low-earth orbit at 800 km altitude with a 72-degree inclination angle on 15 April 2006 Liu, Tiger; Lin, Charles; Lin, Chi-Yen; Lee, I-Te; Sun, Yang-Yi; Chen, Shih-Ping; Chang, Fu-Yuan; Rajesh, Panthalingal; Hsu, Chih-Ting; Matsuo, Tomoko; , others; Published by: Terrestrial, Atmospheric and Oceanic Sciences Published on: YEAR: 2022 DOI: 10.1007/s44195-022-00019-x |
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AIAA SCITECH 2022 Forum : Design and Development of High-Performance Imaging LIDARs for Extreme Radiation Environments of Europa Page 1 1 Design and Development of High Katake, Anup; San Martin, Alejandro; Skulsky, Eli; Serricchio, Fred; Trawny, Nikolas; Bakalski, Ivelin; Machan, Roman; Published by: Published on: YEAR: 2022 DOI: 10.2514/6.2022-2204 |
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Atmospheric disturbances caused by seismic activity are a complex phenomenon. The Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) (LAIC) mechanism gives a detailed idea Kundu, Subrata; Chowdhury, Swati; Ghosh, Soujan; Sasmal, Sudipta; Politis, Dimitrios; Potirakis, Stelios; Yang, Shih-Sian; Chakrabarti, Sandip; Hayakawa, Masashi; Published by: Journal of Sensors Published on: YEAR: 2022 DOI: 10.1155/2022/3201104 |
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They based on the thermospheric O/N 2 density data measured by the global ultraviolet imager (GUVI) onboard the thermosphere, ionosphere, mesosphere energetics, and dynamics ( Published by: Atmosphere Published on: YEAR: 2022 DOI: 10.3390/atmos13030480 |
| 2021 |
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The results of the study of the variability of the electron concentration in the ionosphere in January 2009 are presented. Variations in the electron density in the ionosphere above individual stations and in the global electron content are considered based on the observation data and the results of the model calculations. Comparison of the ionospheric variability obtained from the results of calculations using the models of the upper atmosphere (GSM TIP) and the entire atmosphere (EAGLE) showed that the atmospheric-ionospheric interaction can play one of the key roles in the variability of the ionosphere at midlatitudes. The paper also discusses the issue of simulating the effects of stratospheric warming in 2009 using the EAGLE model. Klimenko, M.; Ratovsky, K.; Klimenko, V.; Bessarab, F.; Sukhodolov, T.; Rozanov, E.; Published by: Russian Journal of Physical Chemistry B Published on: sep YEAR: 2021 DOI: 10.1134/S1990793121050171 atmosphere; global electron abundance; Ionosphere; model of the entire atmosphere; neutral composition of the upper atmosphere; sudden stratospheric warming |
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We study the local-time, seasonal and solar cycle variations of Nitric Oxide (NO) infrared radiative emission, as observed by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the NASA’s Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, over Indian longitude sector. It covers nineteen (January 2002-December 2020) years of NO radiative emission data in the altitude region of 100–155 km. The NO volume emission rate (VER) shows a strong local-time variation with maximum and minimum, respectively, during local-noon and local-midnight. The peak altitude of NO VER decreases by about 18 km from the midnight to the lowest altitude of 117 km at noon. The mean NO VER also undergoes a significant change between the day and night. The mean daytime NO VER is more than double the night-time counterpart. The seasonal variation of peak NO VER shows a maximum during the month of December and a minimum during March. The peak altitude is maximum during September and minimum during June unlike the peak NO VER. The lowest peak altitude, maximum VER and maximum intensity are observed during winter. The relative change in NO VER between the winter and the summer seasons, peaks around 116 km, increases with altitude above 108 km. The long-term trend of NO VER/intensity shows a clear solar cycle variation with higher values during the higher solar activity periods. The NO intensity exhibits a strong correlation with sunspot number (SSN), F10.7 solar index and Lyman-α during both 23rd and 24th solar cycles, although the peak VER does not coincide with the peak SSN. Published by: Advances in Space Research Published on: sep YEAR: 2021 DOI: 10.1016/j.asr.2021.05.003 Indian longitude; Nitric Oxide Radiative Emission; TIMED-SABER satellite observation |
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Model of the E-Layer Critical Frequency for the Auroral Region A new foE model for the auroral region is constructed; the model is based on an analysis of the models of auroral electron precipitations, the boundaries of the discrete and diffusive aurora, the main ionospheric trough, and measurements of the E-layer critical frequency foE. The model is an analytical model. It consists of solar (foEsol) and auroral (foEavr) components. The solar component of the model does not depend of geomagnetic activity. It depends on solar activity via the F index, which is determined by the solar radio emission flux at a wavelength of 10.7 cm over the previous day and three solar rotations. The auroral component of the model does not depend of solar activity. It depends on geomagnetic activity via the effective Kp* index, which takes into account the prehistory of changes in this activity. The model indirectly takes into account the dependence of the relative contribution of foEsol and foEavr to the total foE value on the difference in the heights of the maxima of these model components via the addition of a coefficient. The model qualitatively takes into account the effect of the winter anomaly in foEavr via the addition of a function. It is found that the errors of the new foE model in the auroral region at the nighttime hours are much lower than those in the international IRI model (with the STORM-E option) for both moderate and high geomagnetic activity. For example, the comparison with data from ionospheric stations shows that the IRI model underestimates foE in these conditions by approximately a factor of 2 on average. The average shift in foE relative to the experimental data in the new model does not exceed 20\%. Deminov, M.; Shubin, V.; Badin, V.; Published by: Geomagnetism and Aeronomy Published on: sep YEAR: 2021 DOI: 10.1134/S0016793221050054 |
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Ion temperature data recorded by Millstone Hill incoherent scatter radar (42.61° N, 288.51° E) over four full solar cycles (from 1970 to 2018) are analyzed to depict its climatological behavior in the range of altitudes between 100 and 550 km. The ion temperature dependencies on altitude, local time, month of the year, and solar activity level are studied through a climatological analysis based on binning and boxplot representation of statistical values. Binned observations of ion temperature are compared with International Reference Ionosphere (IRI) modeled values (IRI-2016 version). This comparison reveals several shortcomings in the IRI modeling of the ion temperature at ionosphere altitudes, in particular for the altitudinal, diurnal, seasonal, and solar activity description. The main finding of this study is that the overall IRI overestimation of the ion temperature can be probably ascribed to the long-term ionosphere cooling. Moreover, the study suggests that the IRI ion temperature model needs to implement the seasonal and solar activity dependence, and introduce a more refined diurnal description to allow multiple diurnal maxima seen in observations. The IRI ion temperature anchor point at 430 km is investigated in more detail to show how also a better description of the altitude dependence is desirable for modeling purposes. Some hints and clues are finally given to improve the IRI ion temperature model. Pignalberi, Alessio; Aksonova, Kateryna; Zhang, Shun-Rong; Truhlik, Vladimir; Gurram, Padma; Pavlou, Charalambos; Published by: Advances in Space Research Published on: sep YEAR: 2021 DOI: 10.1016/j.asr.2020.10.025 Climatological analysis; International Reference Ionosphere model; ion temperature; Millstone Hill incoherent scatter radar |
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This work analyzes the geo-effectiveness of Coronal Mass Ejection- (CME-) induced storms by investigating the responses of ionospheric Vertical Total Electron Content (VTEC) and the Equatorial Ionization Anomaly (EIA) over the Indian sector to two storms. One of the storms occurred on February 19, 2014 (SYM-H: −120 nT), while the other occurred on June 23, 2015 (SYM-H: −204 nT). Both storms were driven by full halo CMEs. Global TEC maps were used to characterize VTEC variations during the storms. June 23, 2015 storm was characterized with stronger solar progenitors, right from its origin, although the VTEC response to the storm was not influenced by their strong progenitors. The CMEs that caused the selected storms are large (Halo CMEs). We inferred that irrespective of the strength of solar origin of a storm, the response of ionization distribution over equatorial and low-latitude regions to it depends on the season of storm occurrence, local time of the storm onset, and PPEF orientation. From the VTEC variations for the three Indian stations namely, Trivandrum (geographic latitude: 8.52°N, geographic longitude: 76.94°E, magnetic latitude: 0.37°N), Hyderabad (17.39°N, 78.49°E, 10.15°N) and Delhi (28.70°N, 77.10°E, 22.70°N), we observed that EIA disturbances were more prominent over Hyderabad than over Delhi. The February 19, 2014 storm was characterized by a localized EIA crest at latitude a little above Hyderabad, while in June 23, 2015 storm localized EIA crest was observed directly on Hyderabad. IRI-2016 model generally underestimated VTEC at the three Indian equatorial and low-latitude locations. Solar cycle 24 was characterized with low heliospheric pressure due to its weak polar field strength. The lower pressure allowed CMEs to expand greatly as they transit through space. As they expand, the strengths of the magnetic field inside them decrease, and such lower-strength magnetic fields cause geomagnetic storms that are less geoeffective, even when their solar/interplanetary progenitors are strong and healthy. This associated weak polar field strength of solar cycle 24 caused weak fountain effect with the attendant inability to exhibit storm-time super-fountain effect in the dayside of the equatorial/low-latitude regions. Simi, K.; Akala, A.; Krishna, Siva; Amaechi, Paul; Ogwala, Aghogho; Ratnam, Venkata; Oyedokun, O.; Published by: Advances in Space Research Published on: oct YEAR: 2021 DOI: 10.1016/j.asr.2021.06.013 Coronal mass ejection; Disturbance dynamo electric field; geomagnetic storm; prompt penetration electric field; total electron content |
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Assessment of the predictive capabilities of NIGTEC model over Nigeria during geomagnetic storms The Nigerian Total Electron Content (NIGTEC) is a regional neural network-based model developed by the Nigerian Centre for Atmospheric Research to predict the Total Electron Content (TEC) at any location over Nigeria. The addition of the disturbance storm time (Dst) index as one of NIGTEC s input layer neurons raises a question of its accuracy during geomagnetic storms. In this paper, the capability of NIGTEC in predicting the variability of TEC during geomagnetic storms has been assessed. TEC data predicted by NIGTEC is compared with those derived from Global Navigation Satellite System (GNSS) over Lagos (6.5oN, 3.4oE) and Toro (10.1oN, 9.12oE) during the intense storms in March 2012 and 2013. The model s predictive capability is evaluated in terms of Root Mean Square Error (RMSE). NIGTEC reproduced a fairly good storm time morphology in VTEC driven by the prompt penetration electric field and the increase in thermospheric O/N2. Nevertheless, it failed to predict the increase in TEC after the intense sudden impulse of 60 nT on 8 March 2012. And it could not capture the changes in VTEC driven by the storm time equatorward neutral wind especially during 18:00–24:00 UT. Consequently, the RMSEs were higher during this time window, and the highest RMSE value was obtained during the most intense storm in March 2012. Amaechi, Paul; Humphrey, Ibifubara; Adewoyin, David; Published by: Geodesy and Geodynamics Published on: nov YEAR: 2021 DOI: 10.1016/j.geog.2021.09.003 geomagnetic storm; global navigation satellite system; Nigerian Total Electron Content (NIGTEC); total electron content |
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Impact of the intense geomagnetic storm of August 2018 on the equatorial and low latitude ionosphere We study the impact of an intense geomagnetic storm of 25–26 August 2018 on the equatorial and low latitude ionosphere over Asia, Africa, and America. For this purpose, we have used storm-time observations from multi-site ground-based Global Positioning System receivers and magnetic observatories located at equatorial and low latitudes along the three longitudes. The storm-time variation of the electron density is assessed by the global, regional, and vertical total electron content obtained from the GPS receiver data. Both positive phases of the storm and negative ones are observed in the three longitudinal sectors during the main phase until the late recovery phases of the storm. A significant increase in the electron density around the equatorial ionization anomaly crests is seen during the main phase of the storm. The storm-time response of the thermosphere is characterized by the global \$\mathrm\\frac\O\\N\_\2\\\\$maps provided by the Global Ultraviolet Spectrographic Imager onboard the satellite Thermosphere Ionosphere Mesosphere Energetics and Dynamics. The expected hemispheric asymmetry of the thermosphere can be associated with possible differences in heating and convection in the middle and lower latitudes. Moreover, the unprecedented behavior of the neutrals over the East-African and Asian longitudes can be attributed to the strong northward meridional wind circulations. Finally, the storm-induced disturbances of the horizontal component of the Earth’s magnetic field and the ionospheric electric currents have been investigated by ground-based magnetometers data. A large decrease in the horizontal component of the geomagnetic field is observed over the local dayside sector (Asian) that is associated with the enhanced ring current effect. The wavelet analysis of the magnetic data indicates the existence of short-term and diurnal oscillations during the storm period. These oscillations are associated with the prompt penetration and the disturbance of dynamo-electric fields. It can be inferred that physical factors such as the ionospheric electrodynamics, the thermosphere neutral composition, and the neutral wind circulations play an important role in the observed storm-time response of the ionosphere. Imtiaz, Nadia; Hammou Ali, Omar; Rizvi, Haider; Published by: Astrophysics and Space Science Published on: nov YEAR: 2021 DOI: 10.1007/s10509-021-04009-2 Disturbance dynamo electric field; global electron content; prompt penetration electric field; Vertical total electron content |
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\textlessp\textgreater\textlessstrong class="journal-contentHeaderColor"\textgreaterAbstract.\textless/strong\textgreater This paper presents a new technique to derive thermospheric temperature from space-based disk observations of far ultraviolet airglow. The technique, guided by findings from principal component analysis of synthetic daytime Lyman–Birge–Hopfield (LBH) disk emissions, uses a ratio of the emissions in two spectral channels that together span the LBH (2,0) band to determine the change in band shape with respect to a change in the rotational temperature of \textlessspan class="inline-formula"\textgreaterN$_\textrm2$\textless/span\textgreater. The two-channel-ratio approach limits representativeness and measurement error by only requiring measurement of the relative magnitudes between two spectral channels and not radiometrically calibrated intensities, simplifying the forward model from a full radiative transfer model to a vibrational–rotational band model. It is shown that the derived temperature should be interpreted as a column-integrated property as opposed to a temperature at a specified altitude without utilization of a priori information of the thermospheric temperature profile. The two-channel-ratio approach is demonstrated using NASA GOLD Level 1C disk emission data for the period of 2–8 November 2018 during which a moderate geomagnetic storm has occurred. Due to the lack of independent thermospheric temperature observations, the efficacy of the approach is validated through comparisons of the column-integrated temperature derived from GOLD Level 1C data with the GOLD Level 2 temperature product as well as temperatures from first principle and empirical models. The storm-time thermospheric response manifested in the column-integrated temperature is also shown to corroborate well with hemispherically integrated Joule heating rates, ESA SWARM mass density at 460 km, and GOLD Level 2 column \textlessspan class="inline-formula"\textgreater\textlessmath xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"\textgreater\textlessmrow class="chem"\textgreater\textlessmi mathvariant="normal"\textgreaterO\textless/mi\textgreater\textlessmo\textgreater/\textless/mo\textgreater\textlessmsub\textgreater\textlessmi mathvariant="normal"\textgreaterN\textless/mi\textgreater\textlessmn mathvariant="normal"\textgreater2\textless/mn\textgreater\textless/msub\textgreater\textless/mrow\textgreater\textless/math\textgreater\textlessspan\textgreater\textlesssvg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7003ba1ac83e7c29f962255ae440df67"\textgreater\textlesssvg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-14-6917-2021-ie00001.svg" width="29pt" height="14pt" src="amt-14-6917-2021-ie00001.png"/\textgreater\textless/svg:svg\textgreater\textless/span\textgreater\textless/span\textgreater ratio.\textless/p\textgreater Cantrall, Clayton; Matsuo, Tomoko; Published by: Atmospheric Measurement Techniques Published on: nov YEAR: 2021 DOI: 10.5194/amt-14-6917-2021 |
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Recent studies revealed that the long-lasting daytime ionospheric enhancements of Total Electron Content (TEC) were sometimes observed in the Asian sector during the recovery phase of geomagnetic storms (e.g., Lei (J Geophys Res Space Phys 123: 3217–3232, 2018), Li (J Geophys Res Space Phys 125: e2020JA028238, 2020). However, they focused only on the dayside ionosphere, and no dedicated studies have been performed to investigate the nighttime ionospheric behavior during such kinds of storm recovery phases. In this study, we focused on two geomagnetic storms that happened on 7–8 September 2017 and 25–26 August 2018, which showed the prominent daytime TEC enhancements in the Asian sector during their recovery phases, to explore the nighttime large-scale ionospheric responses as well as the small-scale Equatorial Plasma Irregularities (EPIs). It is found that during the September 2017 storm recovery phase, the nighttime ionosphere in the American sector is largely depressed, which is similar to the daytime ionospheric response in the same longitude sector; while in the Asian sector, only a small TEC increase is observed at nighttime, which is much weaker than the prominent daytime TEC enhancement in this longitude sector. During the recovery phase of the August 2018 storm, a slight TEC increase is observed on the night side at all longitudes, which is also weaker than the prominent daytime TEC enhancement. For the small-scale EPIs, they are enhanced and extended to higher latitudes during the main phase of both storms. However, during the recovery phases of the first storm, the EPIs are largely enhanced and suppressed in the Asian and American sectors, respectively, while no prominent nighttime EPIs are observed during the second storm recovery phase. The clear north–south asymmetry of equatorial ionization anomaly crests during the second storm should be responsible for the suppression of EPIs during this storm. In addition, our results also suggest that the dusk side ionospheric response could be affected by the daytime ionospheric plasma density/TEC variations during the recovery phase of geomagnetic storms, which further modulates the vertical plasma drift and plasma gradient. As a result, the growth rate of post-sunset EPIs will be enhanced or inhibited. Wan, Xin; Xiong, Chao; Gao, Shunzu; Huang, Fuqing; Liu, Yiwen; Aa, Ercha; Yin, Fan; Cai, Hongtao; Published by: Satellite Navigation Published on: nov YEAR: 2021 DOI: 10.1186/s43020-021-00055-x Equatorial plasma irregularity; Geomagneitc storm; Ionospheric response; longitudinal variations; Storm recovery phase |
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The equatorial plasma bubble (EPB) is a common event that occurred at the F-layer of the ionosphere due to plasma irregularities. Its occurrence can be observed around sunset and midnight hours, depending on the season. In this study, ROTI plot measurement was utilized in EPB detection, where the data was obtained from the Department of Survey and Mapping Malaysia (JUPEM). The seasonal variation of EPB in Langkawi, Malaysia was investigated for both post-sunset and post-midnight occurrence within the period of moderate solar activity year (2011). The result showed that EPB was varied with season, where both post-sunset and post-midnight EPB were highly observed during the equinoctial month (March and April) compared to June solstice. However, the post-sunset EPBs were found dominant during equinox while post-midnight EPBs were during June solstice. Rosli, Nur; Hamid, Nurul; Abdullah, Mardina; Buhari, Suhaila; Sarudin, Idahwati; Published by: Published on: nov YEAR: 2021 DOI: 10.1109/IconSpace53224.2021.9768743 solar activity; equatorial plasma bubble (EPB); GPS; Ionosphere; Plasma measurements; Plasmas; post-midnight; Southeast Asia; Time-frequency analysis |
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In this study the statistics of ionospheric total electron content (TEC), derived from a GSV4004B dual-frequency Global Positioning System (GPS) receiver at Agartala station (23.450°N, 91.150°E) located in northern equatorial ionization anomaly (EIA) crest region of the Indian subcontinent, is reported with a performance analysis of IRI-2016 and IRI-2012 models during the ascending, maxima, declining and minima phases (2013-2018) of the solar cycle 24. Variations of model total electron content, as obtained from the IRI-2016 and IRI-2012 for the three options of topside electron density namely NeQuick, IRI 2001 and IRI 01-corr, are compared with the observed total electron content during different periods of interest viz. monthly, seasonal, annual and the correlations with solar activity parameters viz. sunspot number (SSN), 10.7 cm solar radio flux (F10.7), solar EUV flux, are also investigated. All the three options of IRI-2016 and IRI-2012 models show an earlier occurrence of diurnal maximum total electron content, as compared to the observed diurnal maximum GPS total electron content, throughout all the months during the complete period of observation. As the solar activity decreases (from 2015 to 2018), the model starts underestimating GPS total electron content, which becomes significantly high during the very low solar activity period of 2017-18 for all the months. IRI-2016 model underestimates the GPS total electron content before the hours of diurnal maximum and overestimates after the hours of diurnal maximum in the years from 2013-2018. IRI-2012 model underestimates the GPS total electron content before the hours of diurnal maximum and overestimates after the hours of diurnal maximum in the years from 2013-17 but overestimate during the whole day in the year of 2018. Overestimation by IRI-2012 is much more than that by IRI-2016 in the year of 2018. Predictions given by IRI-2016 are better than that given by IRI-2012 for our region. The seasonal mean maximum total electron content values are highest during the spring equinox months and lowest during the winter months except the year of 2014 and 2013. The correlation analysis, between the GPS total electron content and solar indices, show that the correlation coefficient is higher for the solar EUV flux, as compared to the sunspot number (SSN) and 10.7 cm solar radio flux (F10.7). Patari, Arup; Paul, Bapan; Guha, Anirban; Published by: Astrophysics and Space Science Published on: may YEAR: 2021 DOI: 10.1007/s10509-021-03950-6 EIA; EUV flux; F10.7; GPS TEC; IRI-2012 TEC; IRI-2016 TEC; SSN |
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Latitudinal Dependence of Ionospheric Responses to Some Geomagnetic Storms during Low Solar Activity The Latitudinal dependence in the response of the Ionospheric F2-layer electron density (NmF2) and peak height (hmF2) to three geomagnetic storms of May and August 2010 has been examined. The data-sets used for the study were obtained from Ilorin, Nigeria (1.87° S/76.67° E), San Vito, Italy (34.68° N/90.38° E), Hermanus, South Africa (42.34° S/82.15° E), and Pruhonice, Czech Republic (45.66° N/90.38° E) geomagnetic coordinates. The quiet time result shows that the rise in NmF2 began earlier at San Vito, followed by Pruhonice. The rate of ionization was observed to be highest in Ilorin, while, the rate of decay in NmF2 is faster at Hermanus. For disturbed NmF2 condition, remarkable similarities in the NmF2 responses during geomagnetic storms were recorded from Hermanus in the mid-latitude and Ilorin, an equatorial station. NmF2 enhancements (\textgreater6 hours) that is consistent with the increase in hmF2 were observed at all the mid-latitude stations during the main phase of the 02 May, 2010 storm, without any noticeable change over ILN. Similarly, 12 hours of positive phase was observed at ILN and HMN, with 30 hours of NmF2 depletions at PRN and SVT during the recovery phase. ILN is in the equatorial Trough, so most of the NmF2 produced at this region is lifted to the higher latitudes by the fountain effect during the main phase. The suppression of the zonal electric field at ILN is responsible for the NmF2 enhancement during the recovery phase, while the mid-latitude responses have been attributed to the effect of the thermospheric winds and neutral composition changes. Joshua, B.; Adeniyi, J.; Olawepo, A.; Rabiu, Babatunde; Daniel, Okoh; Adebiyi, S.; Adebesin, B.; Ikubanni, S.; Abdurahim, B.; Published by: Geomagnetism and Aeronomy Published on: may YEAR: 2021 DOI: 10.1134/S0016793221030063 Electric field; Electron density; Geomagnetic storms; magnetosphere; peak height |
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We investigate the influence of 27-day variations in solar activity related to the rotation of the Sun around its axis on the thermosphere–ionosphere system at different latitudes and heights, using the results of the calculations of the model of the Earth’s upper atmosphere. Based on the results of the model calculations, related processes in the thermosphere–ionosphere system were analyzed in the period from June 20 to July 21, 2014. There is a clear reaction to the daytime electron concentration Ne in the ionosphere for 27-day variations of the solar radiation flux (index F10.7). Using comparative and correlational analyses, we revealed the delay in the variations of the daytime electron concentration values calculated in the Ne model at different heights, including at the maximum of the F2-layer of the ionosphere (NmF2) and the total electron content and global electron content regarding changes F10.7. It is shown that changes in the O/N2 ratio are the main possible reasons for the delay. The revealed two-day lag in the global electron content is consistent with the results obtained earlier from the observational data. The height structure of the delay Ne relative to F10.7 is discussed. The results of the calculations over the ionospheric stations of the Northern Hemisphere showed that the maximum delay of variations Ne relative to F10.7 is obtained in high and low latitudes, and less at the subauroral and middle latitudes. It is shown that the lag of variations in the total electron content relative to F10.7 is always less than in the case of NmF2. Klimenko, M.; Klimenko, V.; Ratovsky, K.; Yasyukevich, A.; Published by: Russian Journal of Physical Chemistry B Published on: may YEAR: 2021 DOI: 10.1134/S1990793121030052 Ionosphere; global electron content; neutral composition of the thermosphere; solar activity |
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The Global Positioning System (GPS) cycle slip has a marked impact on the application of communication and navigation systems and therefore is one of the main concerns of the user and designer of terminal systems. In this study, we analyzed the temporal and spatial characteristics of cycle slip events using the GPS data detected from 260 observations in the China sector during the period of the year 2015–2018. The results show that the temporal variations of cycle slips are dependent on the local time, seasons, and solar activity. It occurs from 20:00 LT to midnight and more frequently in the equinox months, especially in solar maximum years. The spatial distribution occurs mainly at southern sector below 25°N, which should be associated with the solar condition and ionospheric irregularities in the equatorial region, and the case analyses reveal that the variation of cycle slips has a similar tendency with the ionospheric scintillation monitored at low-latitude station Guangzhou explaining this relationship. Our results reflect the performance of the GPS signals monitored in the China area during the declining period of solar activity to some degree. Geng, Wei; Huang, Wengeng; Liu, Guoqi; Liu, Siqing; Luo, Binxian; Chen, Yanhong; Published by: Radio Science Published on: may YEAR: 2021 DOI: 10.1029/2020RS007196 Monitoring; Delays; Global positioning system; Indexes; Receivers; Satellite broadcasting; Signal to noise ratio |
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Inferring thermospheric composition from ionogram profiles: a calibration with the TIMED spacecraft \textlessp\textgreater\textlessstrong class="journal-contentHeaderColor"\textgreaterAbstract.\textless/strong\textgreater We present a method for augmenting spacecraft measurements of thermospheric composition with quantitative estimates of daytime thermospheric composition below 200 \textlessspan class="inline-formula"\textgreaterkm\textless/span\textgreater, inferred from ionospheric data, for which there is a global network of ground-based stations. Measurements of thermospheric composition via ground-based instrumentation are challenging to make, and so details about this important region of the upper atmosphere are currently sparse. The visibility of the F1 peak in ionospheric soundings from ground-based instrumentation is a sensitive function of thermospheric composition. The ionospheric profile in the transition region between F1 and F2 peaks can be expressed by the “\textlessspan class="inline-formula"\textgreater\textitG\textless/span\textgreater” factor, a function of ion production rate and loss rates via ion–atom interchange reactions and dissociative recombination of molecular ions. This in turn can be expressed as the square of the ratio of ions lost via these processes. We compare estimates of the \textlessspan class="inline-formula"\textgreater\textitG\textless/span\textgreater factor obtained from ionograms recorded at Kwajalein (9\textlessspan class="inline-formula"\textgreater$^\textrm∘$\textless/span\textgreater N, 167.2\textlessspan class="inline-formula"\textgreater$^\textrm∘$\textless/span\textgreater E) for 25 times during which the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) spacecraft recorded approximately co-located measurements of the neutral thermosphere. We find a linear relationship between \textlessspan class="inline-formula"\textgreater\textlessmath xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"\textgreater\textlessmsqrt\textgreater\textlessmi\textgreaterG\textless/mi\textgreater\textless/msqrt\textgreater\textless/math\textgreater\textlessspan\textgreater\textlesssvg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="fe020e378fd223a5491b91deb815e309"\textgreater\textlesssvg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-39-309-2021-ie00001.svg" width="21pt" height="12pt" src="angeo-39-309-2021-ie00001.png"/\textgreater\textless/svg:svg\textgreater\textless/span\textgreater\textless/span\textgreater and the molecular-to-atomic composition ratio, with a gradient of \textlessspan class="inline-formula"\textgreater2.55±0.40\textless/span\textgreater. Alternatively, using hmF1 values obtained by ionogram inversion, this gradient was found to be \textlessspan class="inline-formula"\textgreater4.75±0.4\textless/span\textgreater. Further, accounting for equal ionisation in molecular and atomic species yielded a gradient of \textlessspan class="inline-formula"\textgreater4.20±0.8\textless/span\textgreater. This relationship has potential for using ground-based ionospheric measurements to infer quantitative variations in the composition of the neutral thermosphere via a relatively simple model. This has applications in understanding long-term change and the efficacy of the upper atmosphere on satellite drag.\textless/p\textgreater Scott, Christopher; Jones, Shannon; Barnard, Luke; Published by: Annales Geophysicae Published on: mar YEAR: 2021 DOI: 10.5194/angeo-39-309-2021 |
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Features of the Ionospheric Storm on December 21--24, 2016 The purpose of this work is to investigate the response of the F region and topside ionosphere to the moderate geomagnetic storm on December 21, 2016 (Kp max = 6). The subject of the study is the height–time variations in the parameters of the ionospheric plasma over Kharkiv. Experimental data were obtained using vertical sounding and incoherent scatter methods by the ionosonde and incoherent scatter radar. The presented results are based on the correlation analysis of the incoherent scattered signal. The ion and electron temperatures, as well as the ionospheric plasma velocity, were determined from a set of measured correlation functions of the incoherently scattered signal. The electron density was calculated using the following parameters measured for a number of ionospheric heights: power of the incoherent scatter signal, ion and electron temperatures, and the electron density at the ionospheric F2 layer peak, which is calculated from the critical frequency measured by the ionosonde. The moderate geomagnetic storm was accompanied by an ionospheric storm over Kharkiv with sign-variable phases (first positive and second negative). The peak increase in the electron density was 1.8 times and decrease was 3.4 times. The negative phase was accompanied by a slight rise of the F2 layer (by 20–28 km), which could be due to a decrease in the vertical component of the plasma velocity and an increase in the electron temperature by 600–800 K and ion temperature by 100–160 K. Effects of strong negative ionospheric disturbances were registered during the subsequent magnetospheric disturbance of December 22–24, 2016, with a decrease in electron density at the F2 layer peak up to 2.5–4.9 times. The effects of negative disturbances manifested themselves in the variations of temperatures of electrons and ions. In general, the moderate magnetic storm caused significant changes in the electron density in the ionospheric F2 layer peak, which were accompanied by heating of the ionospheric plasma as well as changes in variations of the vertical component of the ionospheric plasma velocity and the height of ionization during the main phase of the magnetic storm. Katsko, S.; Emelyanov, Ya.; Chernogor, L.; Published by: Kinematics and Physics of Celestial Bodies Published on: mar YEAR: 2021 DOI: 10.3103/S0884591321020045 geomagnetic storm; Electron density; Ionospheric storm; space weather; ionosonde; electron and ion temperatures; incoherent scatter radar; plasma velocity; positive and negative storm phases |
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In this paper, echo occurrence rates for the Dome C East (DCE) and the new Dome C North (DCN) radars are studied. We report the ionospheric and ground scatter echo occurrence rates for selected periods around equinoxes and solstices in the final part of the solar cycle XXIV. The occurrence maps built in Altitude Adjusted Corrected Geomagnetic latitude and Magnetic Local Time coordinates show peculiar patterns highly variable with season. The comparisons of the radar observations with the International Reference Ionosphere model electron density and with ray tracing simulations allow us to explain the major features of observed patterns in terms of electron density variations. The study shows the great potential of the DCE and DCN radar combination to the Super Dual Auroral Radar Network (SuperDARN) convection mapping in terms of monitoring key regions of the high-latitude ionosphere critical for understanding of the magnetospheric dynamics. Marcucci, Maria; Coco, Igino; Massetti, Stefano; Pignalberi, Alessio; Forsythe, Victoriya; Pezzopane, Michael; Koustov, Alexander; Longo, Simona; Biondi, David; Simeoli, Enrico; Consolini, Giuseppe; Laurenza, Monica; Marchaudon, Aurélie; Satta, Andrea; Cirioni, Alessandro; De Simone, Angelo; Olivieri, Angelo; Baù, Alessandro; Salvati, Alberto; Published by: Polar Science Published on: jun YEAR: 2021 DOI: 10.1016/j.polar.2021.100684 |
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Spatial structures in solar wind superthermal electrons and polar rain aurora We report a special polar rain aurora case around 11:24 UT on October 27, 2003, where intense polar rain electrons produced observable polar rain auroral emission with the shape of a roughly dawn-dusk aligned bar. Associated solar wind speed and density observations during the event were around 450 km/s and 2.5 cm−3 respectively. The interplanetary magnetic field (IMF) components Bx, By, and Bz were \textasciitilde5, −3, and 5 nT respectively. The negative By condition likely caused the dawnside shift and slight tilt of the polar rain aurora bar. Furthermore, although Kelvin-Helmholtz waves on the high latitude magnetopause have been previously reported to induce dawn-dusk aligned auroral bars (Zhang et al., 2007), the solar wind and IMF conditions of the event are not favorable for generating them (Zhang et al., 2013) and are therefore not a likely cause. Instead, coincident observations by the Geotail satellite show enhanced anti-sunward flux in the solar wind superthermal electrons (7 eV–42 keV) around the time of the auroral bar. The solar wind superthermal electron spatial size, when mapped into the polar ionosphere, is consistent with the width of the auroral bar, confirming a connection between the two. Herschbach, Dennis; Zhang, Yongliang; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: jul YEAR: 2021 DOI: 10.1016/j.jastp.2021.105633 Magnetosphere interaction; Polar rain aurora; Polar rain electrons; solar wind; Solar wind superthermal electrons |
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Quantifying the Impact of Dynamic Storm-Time Exospheric Density on Plasmaspheric Refilling As soon as the outer plasmasphere gets eroded during geomagnetic storms, the greatly depleted plasmasphere is replenished by cold, dense plasma from the ionosphere. A strong correlation has been revealed between plasmaspheric refilling rates and ambient densities in the topside ionosphere and exosphere, particularly that of atomic hydrogen (H). Although measurements of H airglow emission at plasmaspheric altitudes exhibit storm-time response, temporally static distributions have typically been assumed in the H density in plasmasphere modeling. In this presentation, we evaluate the impact of a realistic distribution of the dynamic H density on the plasmaspheric refilling rate during the geomagnetic storm on March 17, 2013. The temporal and spatial evolution of the plasmaspheric density is calculated by using the Ionosphere-Plasmasphere Electrodynamics (IPE) model, which is driven by a global, 3-D, and time-dependent H density distribution reconstructed from the exospheric remote sensing measurements by NASA’s TWINS and TIMED missions. We quantify the spatial and temporal scales of the refilling rate and its correlation with H densities. Waldrop, Lara; Cucho-Padin, Gonzalo; site, this; Maruyama, Naomi; site, this; Published by: Earth and Space Science Open Archive ESSOAr Published on: jan YEAR: 2021 DOI: 10.1002/essoar.10505771.1 Atmospheric Sciences; Atmospheric Sciences / Magnetospheric Particles |
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Understanding the role of exospheric density in the ring current recovery rate Atomic Hydrogen (H) is the most abundant constituent of the terrestrial exosphere. Its charge exchange interaction with ring current ions (H+ and O+) serves to dissipate magnetospheric energy during geomagnetic storms, resulting in the generation of energetic neutral atoms (ENAs). Determination of ring current ion distributions through modeling depends critically on the specification of the exospheric H density distribution. Furthermore, theoretical studies have demonstrated that ring current recovery rate after the storm onset directly correlates with the H density. Although measurements of H airglow emission at altitudes [3,6] Re exhibit storm-time variations, the H density distributions used in ring current modeling are typically assumed to be temporally static during storms. In this presentation, we will describe the temporal and spatial evolution of ring current ion densities in response to a realistically dynamic exospheric H density distribution using the Comprehensive Inner Magnetosphere-Ionosphere Model (CIMI). The exospheric densities used as input to the model are fully data-driven, derived as global, 3D, and time-dependent tomographic reconstructions of H emission data acquired from Lyman-alpha detectors onboard the NASA TWINS satellites during the geomagnetic storm that occurred on March 17, 2013. We will examine modeled ring current recovery rates using both dynamic and static reconstructions and evaluate the impact of realistic storm-time exospheric variability on the simulations. Cucho-Padin, Gonzalo; site, this; Ferradas, Cristian; Waldrop, Lara; Fok, Mei-Ching; site, this; Published by: Earth and Space Science Open Archive ESSOAr Published on: jan YEAR: 2021 DOI: 10.1002/essoar.10505770.1 Atmospheric Sciences; Atmospheric Sciences / Magnetospheric Particles |
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A new method to remove the dayglow components for auroral observations from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) aboard the Defense Meteorological Satellite Program (DMSP) F16 in Lyman-Birge-Hopfield (LBH) ranges based on the improved Atmospheric Ultraviolet Radiance Integrated Code (AURIC) algorithm is proposed in this study. This method is developed by determining the coefficients between the dayglow intensities calculated by the improved AURIC algorithm and the dayglow components from SSUSI in the whole 2005. The least-square polynomials are used to fit the calculations to the observations and the coefficients of the polynomials are divided by Ap indices and solar zenith angles (SZA). This algorithm can be used to simulate the dayglow intensity in the northern polar region at an altitude of 110 Km. Three examples with Ap indices 5, 27, 154 are tested to verify the effectiveness of the algorithm. The consistency between the original AURIC and the improved AURIC at nadir direction, the derived auroral images and the simulated dayglow images, also the fitting precisions and deviations between the dayglow intensities from improved AURIC and the dayglow intensities from SSUSI, demonstrate that this method is feasible and reliable. The proposed method provides us with a useful tool to separate the dayglow and aurora for space FUV observation. Wang, JiaKe; Ding, GuangXing; Yu, Miao; Wang, HaiFeng; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: jan YEAR: 2021 DOI: 10.1016/j.jastp.2020.105517 |
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The ionospheric responses to High-Intensity Long Duration Continuous Auroral Electrojet Activity (HILDCAA) event which happened following the CIR-driven storm were studied over the southern hemisphere mid-latitude in the African sector. The 13–15 April 2005 event was analysed to understand some of the mechanisms responsible for the ionospheric changes during HILDCAA event. The ionosonde critical frequency of F2 layer (foF2) and Global Navigation Satellite System (GNSS) Total Electron Content (TEC) were used to analyse the ionospheric responses. The daytime increase in foF2 and TEC values were observed on 13 April 2005. The TEC and foF2 enhancement could be attributed to Large Scale Traveling Ionospheric Disturbances (LSTIDs), increase in thermospheric neutral composition changes, Prompt Penetration Electric Field (PPEF) and an expansion of Equatorial Ionization Anomaly (EIA) to the mid-latitude. Matamba, Tshimangadzo; Habarulema, John; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.034 |
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We present a joint analysis of longitude-temporal variations of ionospheric and geomagnetic parameters at middle and high latitudes in the Northern Hemisphere during the two severe magnetic storms in March and June 2015 by using data from the chains of magnetometers, ionosondes and GPS/GLONASS receivers. We identify the fixed longitudinal zones where the variability of the magnetic field is consistently high or low under quiet and disturbed geomagnetic conditions. The revealed longitudinal structure of the geomagnetic field variability in quiet geomagnetic conditions is caused by the discrepancy of the geographic and magnetic poles and by the spatial anomalies of different scales in the main magnetic field of the Earth. Variations of ionospheric parameters are shown to exhibit a pronounced longitudinal inhomogeneity with changing geomagnetic conditions. This inhomogeneity is associated with the longitudinal features of background and disturbed structure of the geomagnetic field. During the recovery phase of a storm, important role in dynamics of the mid-latitude ionosphere may belong to wave-like thermospheric disturbances of molecular gas, propagating westward for several days. Therefore, it is necessary to extend the time interval for studying the ionospheric effects of strong magnetic storms by a few days after the end of the magnetospheric source influence, while the disturbed regions in the thermosphere continues moving westward and causes the electron density decrease along the trajectories of propagation. Chernigovskaya, M.; Shpynev, B.; Yasyukevich, A.; Khabituev, D.; Ratovsky, K.; Belinskaya, Yu.; Stepanov, A.; Bychkov, V.; Grigorieva, S.; Panchenko, V.; Kouba, D.; Mielich, J.; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.028 Chain of GPS/GLONASS receivers; Geomagnetic field variations; geomagnetic storm; Ionosonde chain; ionospheric disturbances |
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\textlessp\textgreater\textlessstrong class="journal-contentHeaderColor"\textgreaterAbstract.\textless/strong\textgreater Coincident auroral far-ultraviolet (FUV) and ground-based ionosonde observations are compared for the purpose of determining whether auroral FUV remote sensing algorithms that assume pure electron precipitation are biased in the presence of proton precipitation. Auroral particle transport and optical emission models, such as the Boltzmann 3-Constituent (B3C) model, predict that maximum E region electron density (NmE) values derived from auroral Lyman–Birge–Hopfield (LBH) emissions, assuming electron precipitation, will be biased by up to \textlessspan class="inline-formula"\textgreater∼20\textless/span\textgreater \% (high) for pure proton aurora, while comparisons between LBH radiances and radiances derived from in situ particle flux observations (i.e., Knight et al., 2008, 2012) indicate that the bias associated with proton aurora should be much larger. Surprisingly, in the comparisons with ionosonde observations described here, no bias associated with proton aurora is found in FUV-derived auroral NmE, which means that auroral FUV remote sensing methods for NmE are more accurate in the presence of proton precipitation than was suggested in the aforementioned earlier works. Possible explanations for the discrepancy with the earlier results are discussed.\textless/p\textgreater Published by: Annales Geophysicae Published on: jan YEAR: 2021 DOI: 10.5194/angeo-39-105-2021 |
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A ROTI-Aided Equatorial Plasma Bubbles Detection Method In this study, we present a Rate of Total Electron Content Index (ROTI)-aided equatorial plasma bubbles (EPBs) detection method based on a Global Navigation Satellite System (GNSS) ionospheric Total Electron Content (TEC). This technique seeks the EPBs occurrence time according to the ROTI values and then extracts the detrended ionospheric TEC series, which include EPBs signals using a low-order, partial polynomial fitting strategy. The EPBs over the Hong Kong area during the year of 2014 were detected using this technique. The results show that the temporal distribution and occurrence of EPBs over the Hong Kong area are consistent with that of previous reports, and most of the TEC depletion error is smaller than 1.5 TECU (average is 0.63 TECU), suggesting that the detection method is feasible and highly accurate. Furthermore, this technique can extract the TEC depletion series more effectively, especially for those with a long duration, compared to previous method. Tang, Long; Louis, Osei-Poku; Chen, Wu; Chen, Mingli; Published by: Remote Sensing Published on: jan YEAR: 2021 DOI: 10.3390/rs13214356 Ionosphere; detection method; equatorial plasma bubbles; GNSS; ROTI |
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We present an analysis of the ionosphere and thermosphere response to Solar Proton Events (SPE) and magnetospheric proton precipitation in January 2005, which was carried out using the model of the entire atmosphere EAGLE. The ionization rates for the considered period were acquired from the AIMOS (Atmospheric Ionization Module Osnabrück) dataset. For numerical experiments, we applied only the proton-induced ionization rates of that period, while all the other model input parameters, including the electron precipitations, corresponded to the quiet conditions. In January 2005, two major solar proton events with different energy spectra and proton fluxes occurred on January 17 and January 20. Since two geomagnetic storms and several sub-storms took place during the considered period, not only solar protons but also less energetic magnetospheric protons contributed to the calculated ionization rates. Despite the relative transparency of the thermosphere for high-energy protons, an ionospheric response to the SPE and proton precipitation from the magnetotail was obtained in numerical experiments. In the ionospheric E layer, the maximum increase in the electron concentration is localized at high latitudes, and at heights of the ionospheric F2 layer, the positive perturbations were formed in the near-equatorial region. An analysis of the model-derived results showed that changes in the ionospheric F2 layer were caused by a change in the neutral composition of the thermosphere. We found that in the recovery phase after both solar proton events and the enhancement of magnetospheric proton precipitations associated with geomagnetic disturbances, the TEC and electron density in the F region and in topside ionosphere/plasmasphere increase at low- and mid-latitudes due to an enhancement of atomic oxygen concentration. Our results demonstrate an important role of magnetospheric protons in the formation of negative F-region ionospheric storms. According to our results, the topside ionosphere/plasmasphere and bottom-side ionosphere can react to solar and magnetospheric protons both with the same sign of disturbances or in different way. The same statement is true for TEC and foF2 disturbances. Different disturbances of foF2 and TEC at high and low latitudes can be explained by topside electron temperature disturbances. Bessarab, F.; Sukhodolov, T.; Klimenko, M.; Klimenko, V.; Korenkov, Yu.; Funke, B.; Zakharenkova, I.; Wissing, J.; Rozanov, E.; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.026 Ionosphere; Proton precipitations; Solar proton events; thermosphere; Whole atmosphere model |
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By using the data of GNSS (Global Navigation Satellite System) observation from Crustal Movement Observation Network of China (CMONOC), ionospheric electron density (IED) distributions reconstructed by using computerized ionospheric tomography (CIT) technique are used to investigate the ionospheric storm effects over Wuhan region during 17 March and 22 June 2015 geomagnetic storm periods. F-region critical frequency (foF2) at Wuhan ionosonde station shows an obvious decrease during recovery phase of the St. Patrick’s Day geomagnetic storm. Moreover, tomographic results present that the decrease in electron density begins at 12:00 UT on 17 March during the storm main phase. Also, foF2 shows a long-lasting negative storm effect during the recovery phase of the 22 June 2015 geomagnetic storm. Electron density chromatography presents the evident decrease during the storm day in accordance with the ionosonde observation. These ionospheric negative storm effects are probably associated with changes of chemical composition, PPEF and DDEF from high latitudes. Feng, Jian; Zhou, Yufeng; Zhou, Yan; Gao, Shuaihe; Zhou, Chen; Tang, Qiong; Liu, Yi; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.008 Ionospheric electron density distributions; ionospheric storm effects; Multiplication algebraic reconstruction technique |
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In this study, an algorithm to identify the maneuvers of a satellite is developed by comparing the Keplerian elements acquired from the two-line elements (TLEs) and Keplerian elements propagated from simplified perturbation models. TLEs contain a specific set of orbital elements, whereas the simplified perturbation models are used to propagate the state vectors at a given time. By comparing the corresponding Keplerian elements derived from both methods, a satellite’s maneuver is identified. This article provides an outline of the working methodology and efficacy of the method. The function of this approach is evaluated in two case studies, i.e., TOPEX/Poseidon and Envisat, whose maneuver histories are available. The same method is implemented to identify the station-keeping maneuvers for TDRS-3, whose maneuver history is not available. Results derived from the analysis indicate that maneuvers with a magnitude of even as low as cm/s are detected when the detection parameters are calibrated properly. Mukundan, Arvind; Wang, Hsiang-Chen; Published by: Applied Sciences Published on: jan YEAR: 2021 DOI: 10.3390/app112110181 Keplarian elements; simplified perturbation models; trial \& error and maneuver detection; two-line elements |
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Effects of the 12 May 2021 Geomagnetic Storm on Georeferencing Precision In this work, we present the positioning error analysis of the 12 May 2021 moderate geomagnetic storm. The storm happened during spring in the northern hemisphere (fall in the south). We selected 868 GNSS stations around the globe to study the ionospheric and the apparent position variations. We compared the day of the storm with the three previous days. The analysis shows the global impact of the storm. In the quiet days, 93\% of the stations had 3D errors less than 10 cm, while during the storm, only 41\% kept this level of accuracy. The higher impact was over the Up component. Although the stations have algorithms to correct ionospheric disturbances, the inaccuracies lasted for nine hours. The most severe effects on the positioning errors were noticed in the South American sector. More than 60\% of the perturbed stations were located in this region. We also studied the effects produced by two other similar geomagnetic storms that occurred on 27 March 2017 and on 5 August 2019. The comparison of the storms shows that the effects on position inaccuracies are not directly deductible neither from the characteristics of geomagnetic storms nor from enhancement and/or variations of the ionospheric plasma. Valdés-Abreu, Juan; Díaz, Marcos; Báez, Juan; Stable-Sánchez, Yohadne; Published by: Remote Sensing Published on: jan YEAR: 2021 DOI: 10.3390/rs14010038 Geomagnetic storms; total electron content; global navigation satellite system; Global positioning system; precise point positioning; rate of change of the tec index |
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B2 Thickness Parameter Response to Equinoctial Geomagnetic Storms The thickness parameters that most empirical models use are generally defined by empirical relations related to ionogram characteristics. This is the case with the NeQuick model that uses an inflection point below the F2 layer peak to define a thickness parameter of the F2 bottomside of the electron density profile, which is named B2. This study is focused on the effects of geomagnetic storms on the thickness parameter B2. We selected three equinoctial storms, namely 17 March 2013, 2 October 2013 and 17 March 2015. To investigate the behavior of the B2 parameter before, during and after those events, we have analyzed variations of GNSS derived vertical TEC (VTEC) and maximum electron density (NmF2) obtained from manually scaled ionograms over 20 stations at middle and low latitudes of Asian, Euro-African and American longitude sectors. The results show two main kinds of responses after the onset of the geomagnetic events: a peak of B2 parameter prior to the increase in VTEC and NmF2 (in \textasciitilde60\% of the cases) and a fluctuation in B2 associated with a decrease in VTEC and NmF2 (\textasciitilde25\% of the cases). The behavior observed has been related to the dominant factor acting after the CME shocks associated with positive and negative storm effects. Investigation into the time delay of the different measurements according to location showed that B2 reacts before NmF2 and VTEC after the onset of the storms in all the cases. The sensitivity shown by B2 during the studied storms might indicate that experimentally derived thickness parameter B2 could be incorporated into the empirical models such as NeQuick in order to adapt them to storm situations that represent extreme cases of ionospheric weather-like conditions. Migoya-Orué, Yenca; Alazo-Cuartas, Katy; Kashcheyev, Anton; Amory-Mazaudier, Christine; Radicella, Sandro; Nava, Bruno; Fleury, Rolland; Ezquer, Rodolfo; Published by: Sensors Published on: jan YEAR: 2021 DOI: 10.3390/s21217369 Geomagnetic storms; total electron content; ionospheric empirical models; NeQuick model; thickness parameter |
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Proton Aurora and Optical Emissions in the Subauroral Region Optical structures located equatorward of the main auroral oval often exhibit different morphologies and dynamics than structures at higher latitudes. In some cases, questions arise regarding the formation mechanisms of these photon-emitting phenomena. New developments in space and ground-based instruments have enabled us to acquire a clearer view of the processes playing a role in the formation of subauroral structures. In addition, the discovery of new optical structures helps us improve our understanding of the latitudinal and altitudinal coupling that takes place in the subauroral region. However, several questions remain unanswered, requiring the development of new instruments and analysis techniques. We discuss optical phenomena in the subauroral region, summarize observational results, present conclusions about their origin, and pose a number of open questions that warrant further investigation of proton aurora, detached subauroral arcs and spots, stable auroral red (SAR) arcs, and STEVE (Strong Thermal Emission Velocity Enhancement). Gallardo-Lacourt, B.; Frey, H.; Martinis, C.; Published by: Space Science Reviews Published on: jan YEAR: 2021 DOI: 10.1007/s11214-020-00776-6 |
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This study investigates the morphology of the GPS TEC responses in the African Equatorial Ionization Anomaly (EIA) region to intense geomagnetic storms during the ascending and maximum phases of solar cycle 24 (2012–2014). Specifically, eight intense geomagnetic storms with Dst ≤ −100 nT were considered in this investigation using TEC data obtained from 13 GNSS receivers in the East African region within 36–42°E geographic longitude; 29°N–10°S geographic latitude; ± 20°N magnetic latitude. The storm-time behavior of TEC shows clear positive and negative phases relative to the non-storm (median) behavior, with amplitudes being dependent on the time of sudden commencement of the storm and location. When a storm starts in the morning period, total electron content increases for all stations while a decrease in total electron content is manifested for a storm that had its sudden commencement in the afternoon period. The TEC and the EIA crest during the main phase of the storm is significantly impacted by the geomagnetic storm, which experiences an increase in the intensity of TEC while the location and spread of the crest usually manifest a poleward expansion. Oyedokun, O.; Akala, A.; Oyeyemi, E.; Published by: Advances in Space Research Published on: feb YEAR: 2021 DOI: 10.1016/j.asr.2020.11.020 African equatorial ionization anomaly; geomagnetic storm; GNSS; Ionosphere |