Bibliography
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Found 243 entries in the Bibliography.
Showing entries from 1 through 50
| 2022 |
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Using a suite of instruments, which included a chain of ground-based dual-frequency GPS receivers, and magnetometers, we have studied the importance of thermospheric meridional wind circulation in controlling the distribution of plasma over the Indian low latitude ionospheric regions during the period of a severe geomagnetic storm. The storm on 15 May 2005, which had its onset coinciding with the local noon time sector for the Indian ionospheric zone, was a severe geomagnetic storm with symH ∼ - 305 nT. A steep increase in the Total Electron Content (TEC) of the ionosphere over the entire Indian ionospheric region was observed on May 15. The enhancement in the TEC was well correlated with the increase in ΔH at the dip-equator due to the prompt penetration of the convection electric field associated with the storm. However, contrary to the previous studies on the storm impact over low latitude regions, a clear signature of disturbance dynamo was absent on the day after the storm. Enhancements in the TEC were observed on May 16, a day after the storm, as well, though the ΔH at the dip-equator was quite below the quite-time mean. The TEC remained well above its monthly mean over the entire Indian ionospheric region during the storm recovery period. We suggest that the TEC enhancement on May 16, even though it looked like due to a prompt penetration effect, was directly related to the compositional disturbances as given by the O/N2 ratio. We conclude that the meridional wind circulation plays an important role in the distribution of electron density over the equatorial and low latitudinal region during the period of a geomagnetic storm. Published by: Advances in Space Research Published on: oct YEAR: 2022 DOI: 10.1016/j.asr.2022.06.027 Compositional disturbances; Equatorial ionosphere; geomagnetic storm; total electron content |
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The hemispherical asymmetry of the low latitude region along 100°E ± 5°E is scrutinized for the year 2015 at magnetically conjugate points on seasonal and intra-seasonal time scales. Two conjugate Ionosonde station pairs are selected- one pair in the inner valley (from SEALION) and the other in the outer edges of the EIA region. The anomaly in the stations is estimated using the difference of low latitude NmF2 from the dip equatorial NmF2 in the same meridian. A monthly average scheme is used instead of a seasonal mean, as the month-to-month variations are found to provide intricate details. The anomaly at the conjugate stations is highly asymmetric even during the equinoctial months of March and October, whereas it is nearly symmetric during April. During June/July, the morning time hemispheric asymmetry (larger on the winter side) temporarily reduces in the midday period and then reverses sign (larger in summer) in the afternoon. The NmF2 observations suggest a close relation of hemispheric symmetry to the position of the subsolar point with respect to the dip equator and a shift/expansion of the trough region of the EIA towards the summer hemisphere. The inter-hemispheric comparison of the hmF2 suggests a strong modulating influence of meridional winds at both the inner and outer stations which depend strongly on the relative position of the subsolar point with respect to the field line geometry. Theoretical (SAMI3/SAMI2) and empirical model (IRI) simulations show a meridional movement of the EIA region with the subsolar point. The winter to summer hemisphere movement of the EIA trough and crest region is also reproduced in the GIM-TEC along 100°E for 2015. This shifting or tailoring of the trough and the crest region is attributed primarily to the meridional wind field, which varies with the shifting position of subsolar point relative to the field line geometry. The seasonal and intra-seasonal difference in the NmF2 hemispheric asymmetry is attributed to the misalignment of the two centers of power viz., the thermospheric/neutral processes and the electromagnetic forces, due to the geographic-geomagnetic offset in this longitude. Kalita, B.; Bhuyan, P.; Nath, S.; Choudhury, M.; Chakrabarty, D.; Wang, K.; Hozumi, K.; Supnithi, P.; Komolmis, T.; . Y. Yatini, C; Le Huy, M.; Published by: Advances in Space Research Published on: may YEAR: 2022 DOI: 10.1016/j.asr.2022.02.058 NmF2; asymmetry; Conjugate; EIA; model; Hemisphere; hmF2; Subsolar |
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The hemispherical asymmetry of the low latitude region along 100°E ± 5°E is scrutinized for the year 2015 at magnetically conjugate points on seasonal and intra-seasonal time scales. Two conjugate Ionosonde station pairs are selected- one pair in the inner valley (from SEALION) and the other in the outer edges of the EIA region. The anomaly in the stations is estimated using the difference of low latitude NmF2 from the dip equatorial NmF2 in the same meridian. A monthly average scheme is used instead of a seasonal mean, as the month-to-month variations are found to provide intricate details. The anomaly at the conjugate stations is highly asymmetric even during the equinoctial months of March and October, whereas it is nearly symmetric during April. During June/July, the morning time hemispheric asymmetry (larger on the winter side) temporarily reduces in the midday period and then reverses sign (larger in summer) in the afternoon. The NmF2 observations suggest a close relation of hemispheric symmetry to the position of the subsolar point with respect to the dip equator and a shift/expansion of the trough region of the EIA towards the summer hemisphere. The inter-hemispheric comparison of the hmF2 suggests a strong modulating influence of meridional winds at both the inner and outer stations which depend strongly on the relative position of the subsolar point with respect to the field line geometry. Theoretical (SAMI3/SAMI2) and empirical model (IRI) simulations show a meridional movement of the EIA region with the subsolar point. The winter to summer hemisphere movement of the EIA trough and crest region is also reproduced in the GIM-TEC along 100°E for 2015. This shifting or tailoring of the trough and the crest region is attributed primarily to the meridional wind field, which varies with the shifting position of subsolar point relative to the field line geometry. The seasonal and intra-seasonal difference in the NmF2 hemispheric asymmetry is attributed to the misalignment of the two centers of power viz., the thermospheric/neutral processes and the electromagnetic forces, due to the geographic-geomagnetic offset in this longitude. Kalita, B.; Bhuyan, P.; Nath, S.; Choudhury, M.; Chakrabarty, D.; Wang, K.; Hozumi, K.; Supnithi, P.; Komolmis, T.; . Y. Yatini, C; Le Huy, M.; Published by: Advances in Space Research Published on: may YEAR: 2022 DOI: 10.1016/j.asr.2022.02.058 NmF2; asymmetry; Conjugate; EIA; model; Hemisphere; hmF2; Subsolar |
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Total Electron Content Variations during an HSS/CIR driven storm at high and middle latitudes Geethakumari, Gopika; Aikio, Anita; Cai, Lei; Vanhamaki, Heikki; Pedersen, Marcus; Coster, Anthea; Marchaudon, Aurélie; Blelly, Pierre-Louis; Haberle, Veronika; Maute, Astrid; Ellahouny, Nada; Virtanen, Ilkka; Norberg, Johannes; Soyama, Shin-Ichiro; Grandin, Maxime; Published by: Published on: mar YEAR: 2022 DOI: 10.5194/egusphere-egu22-8194 |
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We present the ionospheric disturbance responses over low-latitude regions by using total electron content from Geostationary Earth Orbit (GEO) satellites of the BeiDou Navigation Satellite System (BDS), ionosonde data and Swarm satellite data, during the geomagnetic storm in August 2018. The results show that a prominent total electron content (TEC) enhancement over low-latitude regions is observed during the main phase of the storm. There is a persistent TEC increase lasting for about 1–2 days and a moderately positive disturbance response during the recovery phase on 27–28 August, which distinguishes from the general performance of ionospheric TEC in the previous storms. We also find that this phenomenon is a unique local-area disturbance of the ionosphere during the recovery phase of the storm. The enhanced foF2 and hmF2 of the ionospheric F2 layer is observed by SANYA and LEARMONTH ionosonde stations during the recovery phase. The electron density from Swarm satellites shows a strong equatorial ionization anomaly (EIA) crest over the low-latitude area during the main phase of storm, which is simultaneous with the uplift of the ionospheric F2 layer from the SANYA ionosonde. Meanwhile, the thermosphere O/N2 ratio shows a local increase on 27–28 August over low-latitude regions. From the above results, this study suggests that the uplift of F layer height and the enhanced O/N2 ratio are possibly main factors causing the local-area positive disturbance responses during the recovery phase of the storm in August 2018. Tang, Jun; Gao, Xin; Yang, Dengpan; Zhong, Zhengyu; Huo, Xingliang; Wu, Xuequn; Published by: Remote Sensing Published on: jan YEAR: 2022 DOI: 10.3390/rs14092272 BDS-GEO; differential code biases; geomagnetic storm; Ionospheric disturbance; TEC |
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Chapter 4 - Energetic particle dynamics, precipitation, and conductivity This chapter reviews cross-scale coupling and energy transfer in the magnetosphere-ionosphere-thermosphere system via convection, precipitation, and conductance. It begins with an introduction into Earth’s plasma sheet characteristics including particles, plasma moments, and magnetic fields, and their dependence on solar wind and interplanetary magnetic field parameters. Section 4.2 transitions to observations of the magnetosphere convection, precipitation, and coupling with the ionosphere on multiple scales, with Section 4.3 focusing on related global modeling efforts for particle precipitation. This chapter describes basic concepts and principles of major pitch angle scattering processes—wave-particle interactions and field-line curvature scattering—as well as the resulting precipitation and conductance. Section 4.4 continues the discussion started in 4.2 Observations of multiscale convection, precipitation, and conductivity, 4.3 Simulating particle precipitation of magnetospheric origin in global models regarding the resulting ionosphere conductance, delving more deeply into empirical and data assimilative techniques. This chapter describes techniques used over the years to observe and model precipitation and conductance on multiple scales. Gabrielse, Christine; Kaeppler, Stephen; Lu, Gang; Wang, Chih-Ping; Yu, Yiqun; Nishimura, Yukitoshi; Verkhoglyadova, Olga; Deng, Yue; Zhang, Shun-Rong; Published by: Published on: jan YEAR: 2022 DOI: 10.1016/B978-0-12-821366-7.00002-0 Conductance; Conductivity; Convection; particle precipitation |
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Line-of-sight integration of emissions from planetary and cometary atmospheres is the Abel transform of the emission rate, under the spherical symmetry assumption. Indefinite integrals constructed from the Abel transform integral are useful for implementing remote sensing data analysis methods, such as the numerical inverse Abel transform. We propose analytical expressions obtained by a suitable, non-alternating, series development to compute those indefinite integrals. We establish expressions allowing absolute accuracy control of the convergence of these series and illustrate how this accuracy depends on the number of terms involved in the series computation. We compare the analytical method with numerical computation techniques, which are found to be sufficiently accurate as well. Inverse Abel transform fitting is then tested in order to establish that the expected emission rate profiles can be retrieved from the observation of both planetary and cometary atmospheres. We show that the method is robust, i.e. that it can be applied even when the properties of the observed atmosphere depart from the assumed ones, especially when Tikhonov regularization is included. A first application is conducted over observation of comet 46P/Wirtanen, showing some variability, possibly attributable to an evolution of the contamination by dust and icy grains. Hubert, B.; Munhoven, G.; Moulane, Y.; Hutsemekers, D.; Manfroid, J.; Opitom, C.; Jehin, E.; Published by: Icarus Published on: jan YEAR: 2022 DOI: 10.1016/j.icarus.2021.114654 Abel transform; Aeronomy; Coma; Cometary atmospheres; Comets; Data reduction techniques; Planetary atmospheres. |
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Validation of in-situ ionospheric density using FORMOSAT-7/COSMIC-2 IVM and ICON IVM We investigate the validation of in-situ ion density measurements by the ion velocity meter (IVM) onboard F7/C2 and ICON, respectively, during the solar minimum condition of Choi, Jong-Min; Lin, Charles; Rajesh, PK; Park, Jaeheung; Kwak, Young-Sil; Chen, Shih-Ping; Lin, Jia-Ting; Published by: Published on: YEAR: 2022 DOI: 10.21203/rs.3.rs-1758637/v1 |
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Disappearance of the Polar Cap Ionosphere During Geomagnetic Storm on 11 May 2019 Multi-instrument data from Jang Bogo Station (JBS) in Antarctica were utilized to study ionospheric responses to the 11 May 2019 moderate geomagnetic storm. These include Vertical Incident Pulsed Ionospheric Radar (VIPIR)/Dynasonde, Fabry-Perot Interferometer (FPI), GPS vertical total electron content (vTEC), and magnetometer. The VIPIR/Dynasonde observed long-lasting (\textgreater11 hr) severe depletion of the electron density in the F-region ionosphere over JBS. During the depletion interval, GPS TEC also correspondingly decreased, FPI neutral temperature was significantly enhanced, and the polar magnetic field variations showed positive and negative excursions in the Y (east) and Z (vertical) components, respectively. GK-2 A satellite, located ∼2.5 hr west of JBS, observed negative magnetic field perturbations in the azimuthal BD component at geosynchronous orbit during the depletion of ionospheric plasma. Such a BD perturbation at geosynchronous orbit is due to the field-aligned currents flowing out of the ionosphere. From these observations we suggest that transpolar ionospheric currents connected to the field-aligned currents flowing on a substorm wedge-shaped circuit act as a source of polar atmospheric heating during the moderate geomagnetic storm interval and that elevated heavy molecular gases (O2 and N2) by atmospheric heating contribute to the electron density depletion via increased recombination rate. Kwon, H.-J.; Kim, K.-H.; Jee, G.; Seon, J.; Lee, C.; Ham, Y.-B.; Hong, J.; Kim, E.; Bullett, T.; Auster, H.-U.; Magnes, W.; Kraft, S.; Published by: Space Weather Published on: YEAR: 2022 DOI: 10.1029/2022SW003054 |
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The latitudinal and temporal variation of atomic oxygen (O) is opposite between the empirical model, NRLMSISE-00 (MSIS) and the whole atmosphere model, whole atmosphere community climate model with thermosphere and ionosphere extension (WACCM-X) at 97–100 km. Atomic Oxygen from WACCM-X has maxima at solstices and summer mid-high latitudes, similar to [O] from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). We use the densities and dynamics from WACCM-X to drive the Global Ionosphere Thermosphere Model (GITM) at its lower boundary and compare it with the MSIS driven GITM. We focus on the differences in the modeling of the thermospheric and ionospheric semiannual oscillation (T-I SAO). Our results reveal that driving GITM with WACCM-X causes the T-I SAO to maximize around solstices, opposite to when MSIS is used. This is because the global mixing in GITM during solstices is not strong enough to decrease the solstitial [O] densities below the equinoctial values between mesosphere and lower thermosphere (MLT) and upper thermosphere. Larger summer [O] in the MLT leads to the accumulation of [O] at lower latitudes in the thermosphere due to weaker meridional transport, which further increases the amplitude of the oppositely phased SAO. WACCM-X itself has the right phase of SAO in the upper thermosphere but wrong at lower altitudes. The exact mechanisms that can correct the phase of T-I SAO in GITM while using SABER-like [O] in the MLT are currently unknown and warrant further investigation. We suggest mechanisms that can reduce the solstitial maxima in the lower thermosphere, for example, stronger interhemispheric meridional winds, stronger residual circulation, seasonal variations in eddy diffusion, and momentum from breaking gravity waves. Malhotra, Garima; Ridley, Aaron; , Jones; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2021JA029320 global ionosphere thermosphere modeling; semiannual oscillation; thermospheric and ionospheric SAO; thermospheric spoon mechanism; vertical coupling of thermosphere with lower atmosphere; whole atmosphere community climate model with thermosphere and ionosphere extension (WACCM-X) |
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Hong, Junseok; Kil, Hyosub; Lee, Woo; Kwak, Young-Sil; Choi, Byung-Kyu; Paxton, Larry; Published by: Published on: |
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Hong, Junseok; Kil, Hyosub; Lee, Woo; Kwak, Young-Sil; Choi, Byung-Kyu; Paxton, Larry; Published by: Published on: |
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Correlations Between Giant Undulations and Plasmapause Configurations In this letter, we report the correlations between giant undulations (GUs) and plasmapause (PP) configurations based on GUs images and corresponding PP crossings of satellites between 2005 and 2019. Typically, GUs occur when the plasmasphere is eroded to form a thin and sharp PP during the storm main phase and early recovery phase. The thicknesses of the PP are usually comparable with the azimuthal wavelengths of the GUs and are smaller than the radial amplitudes of the GUs. The amplitudes and wavelengths are quasi-proportional to the thicknesses of the PP and are inversely quasi-proportional to the ion density gradients around the PP. The radial centers of GUs are typically aligned with the PP surfaces and their radial geocentric locations show positive correlations for different geomagnetic storms. These results would provide both physical insights and model constrains on the magnetosphere-plasmasphere-ionosphere energy coupling and the generation mechanisms of the GUs and plasmapause surface waves. Zhou, Yi-Jia; He, Fei; Yao, Zhong-Hua; Wei, Yong; Zhang, Xiao-Xin; Zhang, Yong-Liang; Published by: Geophysical Research Letters Published on: YEAR: 2022 DOI: 10.1029/2022GL098627 Ionosphere; Giant Undulations; plasmapause; plasmapause surface waves |
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By using Wuhan VHF radar, we show the morphological features of E-region field-aligned irregularity (FAI) occurrence at Wuhan during 2015–2020. Statistical results present that E-region FAI occurrence reaches a maximum after sunset in summer season. According to Doppler spectrum features, type-2 irregularity is predominantly observed at Wuhan. In addition, we observed a remarkable correlation between E-region FAI occurrence and geomagnetic activity, which includes periods of positive correlation and negative correlation depending on different geomagnetic conditions. The strong negative correlation also exists between E-region FAI occurrence and solar activity. In our observed results, we find that E-region FAI occurrence shows a strong linkage with local sporadic E (ES) layer. A quantitative analysis of linear theory of plasma instability in the E-region at midlatitudes is also presented in our study. The calculated results of linear growth rate indicate the importance of plasma density gradient of local ES layer and field-line-integrated Pedersen conductivity on the generation of E-region FAI. The geomagnetic and solar variations of E-region FAI occurrence are also discussed in this study, which show a dependence on the geomagnetic and solar variations of both meteor rate and medium-scale traveling ionospheric disturbance occurrence. Liu, Yi; Zhou, Chen; Xu, Tong; Deng, Zhongxin; Du, Zhitao; Lan, Ting; Tang, Qiong; Zhu, Yunzhou; Wang, Zhuangkai; Zhao, Zhengyu; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2021JA029597 |
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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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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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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 |
| 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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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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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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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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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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This paper demonstrates and assesses the capability of the advanced three-dimensional (3-D) ionosphere tomography technique, during severe conditions. The study area is northeast Asia and quasi-Japan-centred. Reconstructions are based on total electron content data from a dense ground-based global navigation satellite system receiver network and parameters from operational ionosondes. We used observations from ionosondes, Swarm satellites and radio occultation (RO) to assess the 3-D picture. Specifically, we focus on St. Patrick’s day geomagnetic storm (17–19 March 2015), the most intense in solar cycle 24. During this event, the energy ingested into the ionosphere resulted in Dst and Kp and reaching values \textasciitilde − 223 nT and 8, respectively, and the region of interest, the East Asian sector, was characterized by a \textasciitilde 60\% reduction in electron densities. Results show that the reconstructed densities follow the physical dynamics previously discussed in earlier publications about storm events. Moreover, even when ionosonde data were not available, the technique could still provide a consistent picture of the ionosphere vertical structure. Furthermore, analyses show that there is a profound agreement between the RO profiles/in-situ densities and the reconstructions. Therefore, the technique is a potential candidate for applications that are sensitive to ionospheric corrections. Nicholas, Ssessanga; Mamoru, Yamamoto; Susumu, Saito; Published by: Earth, Planets and Space (Online) Published on: dec YEAR: 2021 DOI: 10.1186/s40623-021-01447-8 geomagnetic storm; Ground-GNSS-STEC tomography; Ionosonde data assimilation |
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The results presented in this paper are obtained from low-latitude ionospheric total electron content (TEC) variation during the chosen geomagnetic storm events happening during the solar cycle 24. We include the four intense geomagnetic storms that occurred on 26 September 2011, 15 July 2012, 19 February 2014 and 20 December 2015, depending upon the availability of TEC data. For this, we have used the TEC data from low-latitude station Varanasi (geographic latitude 25°, 16′N, geographic longitude 82°, 59′E and geomagnetic latitude 16°, 24′N) and an equatorial station Bengaluru (geographic latitude 13°, 02′N, geographic longitude 77°, 34′E and geomagnetic latitude 04°, 68′N). The storm-induced TEC changes at chosen stations have been discussed in terms of local time, storm wind effect, neutral wind, composition changes and variation in the dawn–dusk component of the interplanetary electric field (IEF Ey). Singh, Abha; Rathore, Vishnu; Kumar, Sanjay; Rao, S.; Singh, Sudesh; Singh, A.; Published by: Journal of Astrophysics and Astronomy Published on: aug YEAR: 2021 DOI: 10.1007/s12036-021-09774-8 geomagnetic storm; Global positioning system; low latitude; total electron contents |
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We present an investigation of the F-region electron temperature to an intense geomagnetic storm that occurred on 5 August 2011. The investigation is based on the incoherent scatter radar measurements at Arecibo Observatory, Puerto Rico (18.3°N, 66.7°W). The electron temperature exhibits a rapid and intensive enhancement after the commencement of the geomagnetic storm. The electron temperature increases by ∼800 K within an hour, which is seldomly reported at Arecibo. At the same time, a depletion of the electron density is also observed. The daytime perturbations of electron density and temperature are anticorrelated with the correlation coefficient, which is −0.88 and −0.91 on the day and the following day of the geomagnetic storm, respectively. According to the Global Ultraviolet Imager measurements, the ratio of atomic oxygen to molecular nitrogen concentration () decreases dramatically during the storm. Our analysis suggests that the enhancement of the electron temperature is due to the depletion of the electron density, which is likely associated with the decrease of . The reduction of maybe caused by a prompt upward plasma motion after the commencement of the geomagnetic storm. Lv, Xiedong; Gong, Yun; Zhang, ShaoDong; Zhou, Qihou; Ma, Zheng; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029836 Arecibo; F-region electron temperature; geomagnetic storm; incoherent scatter radar |
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The Earth’s Ionosphere and Thermosphere (IT) is a highly dynamic system persistently driven by variable forcings both from above (Solar EUV and the magnetosphere) and the lower atmosphere. The forcing from below accounts for the majority of the variability at low- and mid-latitude IT region during geomagnetic quiet times. The IT region is particularly sensitive to the composition, winds, and temperature of the Mesosphere and Lower Thermosphere (MLT) state. The goal of this dissertation is to help understand how the MLT region controls the upper atmosphere. This is achieved by using the IT model, Global Ionosphere Thermosphere Model (GITM) and altering its lower boundary (which is in the MLT) to allow a more accurate representation of the lower atmospheric physics within the model. At the beginning of this thesis, it is identified that recent solstitial observations of MLT atomic oxygen (O) from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument show larger densities in the summer hemisphere than in the winter hemisphere. This is opposite to what has been previously known and specified in the IT models, and its cause is still under investigation. The first study focuses on understanding the influence of this latitudinal distribution by using a more realistic specification of MLT [O] from the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X), in GITM. This study shows that despite being a minor species throughout the lower thermosphere, reversing the [O] distribution affects the pressure gradients, winds, temperature, and N2 in the lower thermosphere. These changes then map to higher altitudes through diffusive equilibrium, improving the agreement between GITM O/N2 and Global Ultraviolet Imager (GUVI) measurements. Secondly, the importance of MLT variations on the thermospheric and ionospheric semiannual variation (T-I SAO) is investigated. This is done by analyzing the sensitivity of T-I SAO in GITM to different lower boundary assumptions. This study reveals that the primary driver of T-I SAO is the thermospheric spoon mechanism, as a significant T-I SAO is reproduced in GITM without an SAO variation in the MLT. However, using a more realistic MLT [O] from WACCM-X produces an oppositely-phased T-I SAO, maximizing at solstices, disagreeing with the observations. Since the MLT [O] distribution is correct in WACCM-X, the results hint at incomplete specification/physics for lower thermospheric dynamics in GITM that can drive the transition of the SAO to its correct phase. These mechanisms warrant further investigation and may include stronger winter-to-summer winds, and lower thermospheric residual circulation. The goal of the last study is to examine the effects of spatially non-uniform turbulent mixing in the MLT on the IT system. This is achieved by introducing latitudinal variation in the eddy diffusion parameter (Kzz) in GITM. The results reveal larger spatial variability in O/N2 and TEC. However, the net effect is small (within 2-4\%) on the globally averaged quantities and depends on the area of the turbulent patch. The results also show a different response between the summer and the winter IT region, with winter exhibiting larger changes. Overall, this thesis has highlighted some of the outstanding questions in the domain of lower atmosphere-IT coupling and have answered them through exhaustive comparisons of GITM simulations with different satellite observations, and extensive term analyses of the GITM equations, while laying out a framework for coupling of GITM with WACCM-X. Published by: Published on: YEAR: 2021 DOI: 10.7302/2811 |
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Near Real-Time Global Plasma Irregularity Monitoring by FORMOSAT-7/COSMIC-2 This study presents initial results of the ionospheric scintillation in the F layer using the S4 index derived from the radio occultation experiment (RO-S4) on FORMOSAT-7/COSMIC-2 (F7/C2). With the sufficiently dense RO-S4 observations at low latitudes, it is possible to construct hourly, global scintillation maps to monitor equatorial plasma bubbles (EPBs). The preliminary F7/C2 RO-S4 during August 2019 to April 2020 show clear scintillation distributions around American and the Atlantic Ocean longitudes. The RO-S4 near Jicamarca are compared with range-time-intensity (RTI) maps of the 50 MHz radar, and the results show that the occurrence of intense RO-S4 in the range 0.125–0.5 are co-located with the bottomside of the spread-F patterns. Increases in RO-S4 at the upward phase of bottom-side oscillations is theoretically consistent with large-scale wave seeding of the EPBs. The locations and occurrences of the RO-S4 greater than 0.5 are consistent with airglows depletions from the NASA GOLD mission. Climatology analyses show that monthly occurrences of RO-S4 \textgreater 0.5 agree well with the monthly EPB occurrences in GOLD 135.6 nm image, and show a similar longitudinal distribution to that of DMSP and C/NOFS in-situ measurements. The results suggest that the RO-S4 intensities can be utilized to identify EPBs of specific scales. Chen, Shih-Ping; Lin, Charles; Rajesh, Panthalingal; Liu, Jann-Yenq; Eastes, Richard; Chou, Min-Yang; Choi, Jong-Min; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028339 equatorial plasma bubbles; FORMOSAT-7/COSMIC-2; global observation of limb and disk; GNSS scintillation; radio occultation; S4 index |
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Near Real-Time Global Plasma Irregularity Monitoring by FORMOSAT-7/COSMIC-2 This study presents initial results of the ionospheric scintillation in the F layer using the S4 index derived from the radio occultation experiment (RO-S4) on FORMOSAT-7/COSMIC-2 (F7/C2). With the sufficiently dense RO-S4 observations at low latitudes, it is possible to construct hourly, global scintillation maps to monitor equatorial plasma bubbles (EPBs). The preliminary F7/C2 RO-S4 during August 2019 to April 2020 show clear scintillation distributions around American and the Atlantic Ocean longitudes. The RO-S4 near Jicamarca are compared with range-time-intensity (RTI) maps of the 50 MHz radar, and the results show that the occurrence of intense RO-S4 in the range 0.125–0.5 are co-located with the bottomside of the spread-F patterns. Increases in RO-S4 at the upward phase of bottom-side oscillations is theoretically consistent with large-scale wave seeding of the EPBs. The locations and occurrences of the RO-S4 greater than 0.5 are consistent with airglows depletions from the NASA GOLD mission. Climatology analyses show that monthly occurrences of RO-S4 \textgreater 0.5 agree well with the monthly EPB occurrences in GOLD 135.6 nm image, and show a similar longitudinal distribution to that of DMSP and C/NOFS in-situ measurements. The results suggest that the RO-S4 intensities can be utilized to identify EPBs of specific scales. Chen, Shih-Ping; Lin, Charles; Rajesh, Panthalingal; Liu, Jann-Yenq; Eastes, Richard; Chou, Min-Yang; Choi, Jong-Min; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028339 equatorial plasma bubbles; FORMOSAT-7/COSMIC-2; global observation of limb and disk; GNSS scintillation; radio occultation; S4 index |
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The Ionosphere at Middle and Low Latitudes Under Geomagnetic Quiet Time of December 2019 The ionospheric electron density shows remarkable day-to-day variability due to solar radiance, geomagnetic activity and lower atmosphere forcing. In this report, we investigated the ionospheric variations at middle and low latitudes during a period under geomagnetic quiet time (Kpmax = 1.7) from November 30 to December 8, 2019. During the quiescent period, the ionosphere is not undisturbed as expected in the Asian-Australian and the American sectors. Total electron content (TEC) has multiple prominent enhancements at middle and low latitudes in the two sectors, and TEC depletions also occur repeatedly in the Asian-Australian sector. The low-latitude electric fields vary significantly, which is likely to be modulated by the notably changing tides in the mesosphere and lower thermosphere region. It is worth noting that the variations of TEC and the electric fields are not consistent in the two sectors, particularly on December 4–6. Further investigation reveals that the increase in TEC depends on altitude. The TEC enhancements are mainly contributed by the altitude below 500 km in both two sectors, which indirectly reflects that the driving sources may come from the lower atmosphere. Especially, a mid-latitude band structure continuously appears at all local times in the North American sector on December 6–8, which is also mainly contributed by the altitude below 500 km. Kuai, Jiawei; Li, Qiaoling; Zhong, Jiahao; Zhou, Xu; Liu, Libo; Yoshikawa, Akimasa; Hu, Lianhuan; Xie, Haiyong; Huang, Chaoyan; Yu, Xumin; Wan, Xin; Cui, Jun; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028964 low-latitude electric fields; the ionosphere variations in solar minimum; the ionospheric day-to-day variations; the ionospheric disturbance; the ionospheric variations; topside ionosphere |
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The Ionosphere at Middle and Low Latitudes Under Geomagnetic Quiet Time of December 2019 The ionospheric electron density shows remarkable day-to-day variability due to solar radiance, geomagnetic activity and lower atmosphere forcing. In this report, we investigated the ionospheric variations at middle and low latitudes during a period under geomagnetic quiet time (Kpmax = 1.7) from November 30 to December 8, 2019. During the quiescent period, the ionosphere is not undisturbed as expected in the Asian-Australian and the American sectors. Total electron content (TEC) has multiple prominent enhancements at middle and low latitudes in the two sectors, and TEC depletions also occur repeatedly in the Asian-Australian sector. The low-latitude electric fields vary significantly, which is likely to be modulated by the notably changing tides in the mesosphere and lower thermosphere region. It is worth noting that the variations of TEC and the electric fields are not consistent in the two sectors, particularly on December 4–6. Further investigation reveals that the increase in TEC depends on altitude. The TEC enhancements are mainly contributed by the altitude below 500 km in both two sectors, which indirectly reflects that the driving sources may come from the lower atmosphere. Especially, a mid-latitude band structure continuously appears at all local times in the North American sector on December 6–8, which is also mainly contributed by the altitude below 500 km. Kuai, Jiawei; Li, Qiaoling; Zhong, Jiahao; Zhou, Xu; Liu, Libo; Yoshikawa, Akimasa; Hu, Lianhuan; Xie, Haiyong; Huang, Chaoyan; Yu, Xumin; Wan, Xin; Cui, Jun; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028964 low-latitude electric fields; the ionosphere variations in solar minimum; the ionospheric day-to-day variations; the ionospheric disturbance; the ionospheric variations; topside ionosphere |
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Subauroral Flow Channel Structures and Auroral Undulations Triggered by Kelvin-Helmholtz Waves We investigate Kelvin-Helmholtz (K-H) waves on/near the magnetopause and surface waves near the plasmapause—in the outer region of the plasmasphere: in the hot zone—by utilizing multi-instrument/satellite observations. Our main aim is to study how the K-H waves and the K-H instability mechanisms impacted the subauroral and auroral regions during the geomagnetic storms of May 27–29 and July 16, 2017. For the subauroral region, we specify the structured flows as Sub-Auroral Polarization Streams Wave Structures (SAPS-WS) and the combined flows—created by Abnormal Sub-Auroral Ion Drifts (ASAID) and SAID or SAPS—as a complex equatorward-poleward ASAID-SAID or SAPS-ASAID. For the auroral zone, we identify the large auroral undulations appearing inside the auroral zone. The correlated observations of the K-H waves, the structured or complex subauroral flows and large auroral undulations, and the local geomagnetic field oscillations confirm the connections of both the subauroral flows and the auroral undulations with the K-H waves via the eigenfrequency of the Near-Earth Plasma Sheet (NEPS) resonator activated by the K-H waves. For the first time, we demonstrate the simultaneous detections of K-H waves near the magnetopause and surface waves near the plasmapause in the hot zone on July 16, 2017, and conclude their coupling via the NEPS resonator s eigenfrequency. Thus, the surface waves near the plasmapause were the manifestation of the undulating (or rippled) earthward inner boundary of the NEPS that led to the development of ASAID-SAID/SAPS-ASAID or SAPS-WS in the subauroral region and to the large auroral undulation inside the auroral zone. Horvath, Ildiko; Lovell, Brian; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029144 ASAID/SAPS/SAPS-WS; auroral undulations; hot zone; K-H instability |
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The Wind Imaging Interferometer (WINDII) Empirical Model, which provides the characteristics of the O(1D) 630.0 nm atomic oxygen dayglow emission from the upper atmosphere has been reviewed and updated. It now includes the Integrated Emission Rate, the peak Volume Emission Rate, the Altitude of that peak and the Full Width at Half Maximum as functions of the F10.7 cm Solar Radio Flux and the solar zenith angle (SZA). The model employs 98,617 WINDII observations obtained between the years 1992 and 1996, and the model and observations of the Integrated Emission Rate agree well with one another within 2 standard deviations of 588.7 Rayleigh (R) (106 photons cm−2 sec−1). It is also demonstrated that the impact of latitude, longitude and day of year, independently of their contribution to the SZA, is very small. The WINDII Empirical Model is also shown to agree with results from the TRANSCAR photochemical model. The dayglow is challenging to measure with ground-based instruments, as the solar scattered light from the daytime sky must be accurately subtracted from the data. Ground-based measurements of the integrated emission rate have been made by others, with good agreement for observations from Hyderabad during the 2015 summer and winter, but mixed agreement with measurements made over Boston in 2003. The latter results are reviewed and assessed. Shepherd, Gordon; Cho, Young-Min; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028715 dayglow; empirical model; O(1D) Emission; solar radio flux; solar zenith angle; upper atmosphere |
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Inhibition of F3 Layer at Low Latitude Station Sanya During Recovery Phase of Geomagnetic Storms A special F2 layer stratification structure named F3 layer occurs frequently in equatorial and low latitude ionosphere during summer daytime. In this study, a new phenomenon of decreasing occurrence of the F3 layer, and narrowing differences of virtual heights between the F3 and F2 layers in the recovery phase of geomagnetic storms is reported. We named this phenomenon as the inhibition of F3 layer event (IFLE). Using the ionosonde observations during summer of 2012–2015 at Sanya (18.3°N, 109.6°E, dip latitude 12.6°N), we found that IFLE occurred during 14 geomagnetic storms (−127 nT ≤ Dstmin ≤ −22 nT), which was accompanied by the thinning and lowering bottom ionosphere, and decreasing the crest-to-trough ratio of total electron content (TEC). Together with the ion drift data measured by Defense Meteorological Satellite Program F18, we suggest that the IFLE is mainly caused by the westward disturbance dynamo electric field (DDEF; downward drift velocity), taking disadvantage of the formation of the F3 layer. The observed decrease in the crest-to-trough ratio of TEC also indicates that the westward DDEF should prompt IFLE by providing less plasma from the equatorial region to the low latitude. Hence, IFLE then can be a good indicator to show how the magnetosphere-ionospheric coupling process affects the low and equatorial ionosphere. Notably, the results also indicate that even a very weak geomagnetic storm can generate significant changes in ionospheric state at low latitude. Jin, Yuyan; Zhao, Biqiang; Li, Guozhu; Li, Zishen; Zhou, Xu; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029850 F3 layer; Geomagnetic storms; westward disturbance dynamo electric field |
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Recently, citizen scientist photographs led to the discovery of a new auroral form called “the dune aurora” which exhibits parallel stripes of brighter emission in the green diffuse aurora at about 100 km altitude. This discovery raised several questions, such as (i) whether the dunes are associated with particle precipitation, (ii) whether their structure arises from spatial inhomogeneities in the precipitating fluxes or in the underlying neutral atmosphere, and (iii) whether they are the auroral manifestation of an atmospheric wave called a mesospheric bore. This study investigates a large-scale dune aurora event on 20 January 2016 above Northern Europe. The dunes were observed from Finland to Scotland, spanning over 1,500 km for at least 4 h. Spacecraft observations indicate that the dunes are associated with particle precipitation and reveal the presence of a temperature inversion layer below the mesopause during the event, creating suitable conditions for mesospheric bore formation. The analysis of a time lapse of pictures by a citizen scientist from Scotland leads to the estimate that, during this event, the dunes propagate toward the west-southwest direction at about 200 m s−1, presumably indicating strong horizontal winds near the mesopause. These results show that citizen science and dune aurora studies can fill observational gaps and be powerful tools to investigate the least-known region of near-Earth space at altitudes near 100 km. Grandin, Maxime; Palmroth, Minna; Whipps, Graeme; Kalliokoski, Milla; Ferrier, Mark; Paxton, Larry; Mlynczak, Martin; Hilska, Jukka; Holmseth, Knut; Vinorum, Kjetil; , others; Published by: AGU Advances Published on: YEAR: 2021 DOI: https://doi.org/10.1029/2020AV000338 |
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Smith, Todd; Hacala, Ryan; Hohlfeld, Erik; Edens, Weston; Hibbitts, Charles; Paxton, Larry; Arnold, Steven; Westlake, Joseph; Rymer, Abigail; Chacos, Al; , others; Published by: Gravitational and Space Research Published on: |
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Ionospheric day-to-day variability is essential for understanding the space environment, while it is still challenging to properly quantify and forecast. In the present work, the day-to-day variability of F2 layer peak electron densities (NmF2) is examined from both observational and modeling perspectives. Ionosonde data over Wuhan station (30.5°N, 114.5°E; 19.3°N magnetic latitude) are compared with simulations from the specific dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (SD-WACCM-X) and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) in 2009 and 2012. Both SD-WACCM-X and TIEGCM are driven by the realistic 3 h geomagnetic index and daily solar input, and the former includes self-consistently solved physics and chemistry in the lower atmosphere. The correlation coefficient between observations and SD-WACCM-X simulations is much larger than that of the TIEGCM simulations, especially during dusk in 2009 and nighttime in 2012. Both the observed and SD-WACCM-X simulated day-to-day variability of NmF2 reveal a similar day-night dependence in 2012 that increases large during the nighttime and decreases during the daytime, and shows favorable consistency of daytime variability in 2009. Both the observations and SD-WACCM-X simulations also display semiannual variations in nighttime NmF2 variability, although the month with maximum variability is slightly different. However, TIEGCM does not reproduce the day-night dependence or the semiannual variations well. The results emphasize the necessity for realistic lower atmospheric perturbations to characterize ionospheric day-to-day variability. This work also provides a validation of the SD-WACCM-X in terms of ionospheric day-to-day variability. Zhou, Xu; Yue, Xinan; Liu, Han-Li; Lu, Xian; Wu, Haonan; Zhao, Xiukuan; He, Jianhui; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028589 Ionosphere; day-to-day variability; ionosonde; NmF2; TIEGCM; WACCM-X |
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Development of a NIR camera for the BALBOA mission More than 500 years ago, when Vasco Núñez de Balboa traveled to the New World, he must not have realized that his legacy would not only be cast in currency, but branded for space Zhou, Xiaoyan; Rafol, Don; Michell, Robert; Hampton, Don; Geach, Christopher; Published by: 43rd COSPAR Scientific Assembly. Held 28 January-4 February Published on: |
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explanation, that the lower summer measurements were the result of atmospheric composition change, based on the change of [O/N2] observed during the Boston summer by the GUVI Shepherd, Gordon; Cho, Young-Min; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028715 |
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Explicit IMF By-Dependence in Geomagnetic Activity: Quantifying Ionospheric Electrodynamics Geomagnetic activity is mainly driven by the southward (Bz) component of the interplanetary magnetic field (IMF), which dominates all solar wind coupling functions. Coupling functions also depend on the absolute value of the dawn-dusk (By) component of the IMF, but not on its sign. However, recent studies have shown that for a fixed level of solar wind driving, auroral electrojets in the Northern Hemisphere (NH) are stronger for By \textgreater 0 than for By \textless 0 during NH winter. In NH summer, the dependence on the By sign is reversed. While this By sign dependence, also called the explicit By-dependence, is very strong in the winter hemisphere, it is weak in the summer hemisphere. Moreover, the explicit By-dependence is much stronger in the westward electrojet than in the eastward electrojet. In this study, we study how the explicit IMF By-dependence is coupled with large-scale field-aligned currents (FACs) by using FAC measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and an empirical ionospheric conductance model. We model the complete ionospheric electrodynamics by solving the current continuity equation, and show that during periods of elevated solar wind driving (Bz \textless 0), the IMF By component modulates Regions 1 and 2 FACs in the dawn sector of the winter hemisphere. This leads to an explicit By-dependence in ionospheric conductance and the westward electrojet. We also show that the By-dependence of FACs and conductance is weak in the dusk sector, which explains the earlier observation of the weak By-dependence of the eastward electrojet. Holappa, L.; Robinson, R.; Pulkkinen, A.; Asikainen, T.; Mursula, K.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029202 space weather; magnetosphere-ionosphere coupling; field-aligned currents; geomagnetic activity |
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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 Bessarab, Fedor; Sukhodolov, Timofei; Klimenko, Maxim; Klimenko, Vladimir; Korenkov, Yu; Funke, Bernd; Zakharenkova, Irina; Wissing, Jan; Rozanov, EV; Published by: Advances in Space Research Published on: YEAR: 2021 DOI: 10.1016/j.asr.2020.10.026 |
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Aurora in the Polar Cap: A Review This paper reviews our current understanding of auroral features that appear poleward of the main auroral oval within the polar cap, especially those that are known as Sun-aligned arcs, transpolar arcs, or theta auroras. They tend to appear predominantly during periods of quiet geomagnetic activity or northwards directed interplanetary magnetic field (IMF). We also introduce polar rain aurora which has been considered as a phenomenon on open field lines. We describe the morphology of such auroras, their development and dynamics in response to solar wind-magnetosphere coupling processes, and the models that have been developed to explain them. Hosokawa, Keisuke; Kullen, Anita; Milan, Steve; Reidy, Jade; Zou, Ying; Frey, Harald; Maggiolo, Romain; Fear, Robert; Published by: Space Science Reviews Published on: 02/2020 YEAR: 2020 DOI: 10.1007/s11214-020-0637-3 |
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In this study, we investigate the shock-sheath driven 7\textendash8 November 2004 superstorm for its flux transfer events and resultant flow channel (FC) events and associated neutral (DN) and electron (Ne) density features in order to understand better the underlying coupled magnetosphere (M) and ionosphere (I) processes and responses in the thermosphere (T). We focus on the (i) subauroral, auroral, and polar cap regions, (ii) localized DN increases and associated Ne features and FCs developed, and (iii) energy deposition occurred. Results show the development of localized DN increases (1) within/over FCs and associated enhanced small-scale field aligned currents suggesting Joule heating driving upwelling during forward and reverse polar convections, (2) appearing with Ne increases during storm-enhanced density (SED) events suggesting strong M-I-T coupling and with Ne depletions during plasmaspheric erosion events suggesting weak M-I-T coupling, and (3) in the thermosphere\textquoterights increasing NO and continuously low O/N2 composition regions. During erosion events, strong storm-time subauroral polarization streams (SAPS) E fields developed. Meanwhile the well-developed plasmapause appeared with decreased total electron content (TEC) on its poleward side and with increased TEC and Ne (appearing as a shoulder feature that is the signature of SED) on its equatorward side. From these we conclude that although strong M-I-T coupling was apparent during SED events, M-I-T coupling was also strong during erosion events when the combination of strong convection E field and large storm-time SAPS E fields eroded the high-latitude region and thus decreased the high-latitude Ne and TEC. Horvath, Ildiko; Lovell, Brian; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2020 YEAR: 2020 DOI: 10.1029/2019JA027484 flow channels; large-scale FACs; localized neutral density increases; nitric oxide (NO); Poynting flux; type-1 and type-2 aurorae |
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A case study of isolated auroral spots based on DMSP data This study employed ultraviolet images and particle data to investigate isolated auroral spots away from the Earth\textquoterights auroral oval. Data from SSUSI (Special Sensor Ultraviolet Spectrographic Imager) and SSJ (Special Sensor J) mounted on the DMSP (Defence Meteorological Satellite Program) spacecraft were examined. The isolated auroral spots were observed by DMSP F16/SSUSI and F17/SSUSI on 29 May 2010 during the recovery phase of a moderate geomagnetic storm with a minimum SYM-H index of -70 nT. The auroral spots were observed between 18:00\textendash21:00 MLT and corotated with the Earth, but stayed almost at the same magnetic latitude (MLAT) of -60\textdegree. It is found that the isolated auroral spots were produced mainly by energetic ring current ions at energies above ~10\ keV. The enhancement in the electron flux with energy below ~200\ eV was also observed for the isolated auroral spots. The MLAT of the electron flux was nearly 2\textdegreehigher than that for the precipitating ions. Zhou, Su; Chen, Yuqing; Zhang, Jin; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 01/2020 YEAR: 2020 DOI: 10.1016/j.jastp.2019.105176 Isolated auroral spots; Proton aurora; Subauroral electron precipitation |
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Comparison of Reference Heights of O/N 2 and ∑O/N 2 Based on GUVI Dayside Limb Measurement We define a new thermospheric concept, the reference heights of O/N2, referring to a series of thermospheric heights corresponding to the fixed ratios of O to N2 number density. Here, based on Global Ultraviolet Imager (GUVI) limb measurement, we compare O/N2 column density ratio (∑O/N2) and the reference heights of O/N2. We choose the transition height of O and N2 (transition height hereafter), a special reference height at which O number density is equal to N2 number density, to verify the connection with ∑O/N2 during geomagnetically quiet periods. It is found that transition height and ∑O/N2 have noticeable negative correlation with correlation coefficient of -0.887. An empirical model of transition height (O/N2 model hereafter) is established based on nonlinear least-squares-fitting method. The considerable correlation (greater than 0.96), insignificant errors (less than 4\%) and the great influencing weight of ∑O/N2 to reference heights indicate the validity of O/N2 model and the existence of quantitative relation between ∑O/N2 and transition height. Besides, it is verified that the similar quantitative relation also exists between ∑O/N2 and reference heights of other O/N2 values. Namely, using the O/N2 model coefficients, we can roughly get the whole altitude profiles of O/N2 within 6\% precision for any given ∑O/N2. Yu, Tingting; Ren, Zhipeng; Yu, You; Yue, Xinan; Zhou, Xu; Wan, Weixing; Published by: Space Weather Published on: 01/2020 YEAR: 2020 DOI: 10.1029/2019SW002391 |
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This chapter reviews fundamental properties and recent advances of diffuse and pulsating aurora. Diffuse and pulsating aurora often occurs on closed field lines and involves energetic electron precipitation by wave-particle interaction. After summarizing the definition, large-scale morphology, types of pulsation, and driving processes, we review observation techniques, occurrence, duration, altitude, evolution, small-scale structures, fast modulation, relation to high-energy precipitation, the role of ECH waves, reflected and secondary electrons, ionosphere dynamics, and simulation of wave-particle interaction. Finally we discuss open questions of diffuse and pulsating aurora. Nishimura, Yukitoshi; Lessard, Marc; Katoh, Yuto; Miyoshi, Yoshizumi; Grono, Eric; Partamies, Noora; Sivadas, Nithin; Hosokawa, Keisuke; Fukizawa, Mizuki; Samara, Marilia; Michell, Robert; Kataoka, Ryuho; Sakanoi, Takeshi; Whiter, Daniel; Oyama, Shin-ichiro; Ogawa, Yasunobu; Kurita, Satoshi; Published by: Space Science Reviews Published on: 01/2020 YEAR: 2020 DOI: 10.1007/s11214-019-0629-3 |
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Malhotra, Garima; Ridley, Aaron; Marsh, Daniel; Wu, Chen; Paxton, Larry; Mlynczak, Martin; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Comparison of reference heights of O/N2 and∑ O/N2 based on GUVI dayside limb measurement Yu, Tingting; Ren, Zhipeng; Yu, You; Yue, Xinan; Zhou, Xu; Wan, Weixing; Published by: Space weather Published on: |