Bibliography

On the impact of meridional wind circulation changes in the electron density distribution over the Indian equatorial and low latitude ionospheric region during a severe geomagnetic storm

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.

Ambili, K.; Choudhary, R.;

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

The investigation on daytime conjugate hemispheric asymmetry along 100°E longitude using observations and model simulations: New insights

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

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

Two different properties of ionospheric perturbations detected in the vicinity of the Korean Peninsula after the Hunga-Tonga volcanic eruption on 15 January 2022

Hong, Junseok; Kil, Hyosub; Lee, Woo; Kwak, Young-Sil; Choi, Byung-Kyu; Paxton, Larry;

Published by:       Published on:

YEAR: 2022     DOI:

Critical Dynamics in Stratospheric Potential Energy Variations Prior to Significant (M> 6.7) Earthquakes

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

Seismogenic Anomalies in Atmospheric Gravity Waves as Observed from SABER/TIMED Satellite during Large Earthquakes

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

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

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

Assessing the performance of a Northeast Asia Japan-centered 3-D ionosphere specification technique during the 2015 St. Patrick’s day geomagnetic storm

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

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

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

On the Relationship of the O(1D) 630.0 nm Dayglow Emission to the F10.7 cm Solar Flux and the Solar Zenith Angle

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

On the Relationship of the O (1D) 630.0 nm Dayglow Emission to the F10. 7 cm Solar Flux and the Solar Zenith Angle

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

Geomagnetic storm-induced plasma density enhancements in the southern polar ionospheric region: A comparative study using St. Patrick s Day storms of 2013 and 2015

order to examine if the variations in the TEC were caused by thermospheric composition changes in the southern high-latitude regions, we present O/N 2 maps obtained from the GUVI

Shreedevi, PR; Choudhary, RK; Thampi, Smitha; Yadav, Sneha; Pant, TK; Yu, Yiqun; McGranaghan, Ryan; Thomas, Evan; Bhardwaj, Anil; Sinha, AK;

Published by: Space Weather      Published on:

YEAR: 2020     DOI: 10.1029/2019SW002383

Morphological study on the ionospheric variability at Bharati, a polar cusp station in the southern hemisphere

Morphological features of the quiet/disturbed time variations in the Total Electron Content (TEC) at the polar cusp station Bharati (76.69\textdegreeS MLAT) during a period of 5 years starting from February 2013 to December 2017 has been studied using GPS TEC measurements. The TEC at Bharati follows a diurnal pattern with its peak appearing close to local noon/magnetic noon during the summer/winter months. A nighttime enhancement in the TEC is seen around the magnetic midnight during winter. The plasma density at Bharati also exhibits semi-annual variation and a strong dependence on solar activity. A comparison of the IRI 2016 model derived TEC and the GPS TEC at Bharati shows significant differences with large underestimation of TEC especially during the nighttime period of the winter months. A two fold difference in magnitude between the GPS and modeled TEC is also observed in the summer months of the high solar activity period of 2013\textendash2015. The response of the TEC to geomagnetic storms is found to depend on the onset time of the storm. We show that the morphological features in the temporal evolution of the plasma density at Bharati vary as the location of Bharati changes from being inside the polar cap, to the auroral region, and to the polar cusp in quick succession in a day. Our results highlight the fact that the dynamic nature of the location of Bharati with respect to the position of the polar cap plays an important role in deciding the plasma distribution at the polar cusp station.

Shreedevi, P.R.; Choudhary, R.K.; Yu, Yiqun; Thomas, Evan;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 10/2019

YEAR: 2019     DOI: 10.1016/j.jastp.2019.105058

Time-Dependent Response of the Terrestrial Exosphere to a Geomagnetic Storm

Recent observations of significant enhancements in exospheric hydrogen (H) emission in response to geomagnetic storms have been difficult to interpret in terms of the evolution of the underlying global, 3-D exospheric structure. In this letter, we report the first measurement of the timescales and spatial gradients associated with the exospheric response to a geomagnetic storm, which we derive from a novel, time-dependent tomographic analysis of H emission data. We find that global H density at 3 R_E begins to rise promptly, by \~15\%, after storm onset and that this perturbation appears to propagate outward with an effective speed of \~60\ m/s, a response that may be associated with enhanced thermospheric temperature and vertical neutral wind. This effective upwelling has significant implications for atmospheric escape as well as for charge exchange reaction rates, which drive important space weather effects such as plasmaspheric refilling and ring current decay.

Cucho-Padin, Gonzalo; Waldrop, Lara;

Published by: Geophysical Research Letters      Published on: 09/2019

YEAR: 2019     DOI: 10.1029/2019GL084327

Signatures of the Solar Transient Disturbances Over the Low Latitude Ionosphere During 6 to 8 September 2017

Low latitude ionospheric behavior during solar transient disturbances of solar flares and storm time penetrating electric fields comprises an important part of the Earth\textquoterights space weather. The flares enhance the electron density of the sunlit ionosphere by supplying excess solar radiation. However, the degree of these density changes is subjective if a geomagnetic storm persists simultaneously. The present case study addresses the ionospheric variations over the Indian longitudes under the combined effects of the solar flares and a geomagnetic storm during 6 to 8 September 2017 and probably the first of its kind in delineating the effects of these two over the low latitude ionosphere. The X9.3 class flare of 6 September, which occurred during non-storm conditions, produced an intense E region ionization (~500\% over the ambient). However, the total electron content response to this flare was comparatively weak. The flares on 7 and 8 September occurred during the 7\textendash8 September geomagnetic storm. Though the 8 September flare occurred with higher intensity (M8.1) and early in local time compared to the flare of 7 September (M7.3), the equatorial electrojet current enhancement was lesser on 8 September (~75\% over the ambient) than that of 7 September (~110\% over the ambient). This aspect is discussed in view of the storm time convection effects over the low latitudes during 7\textendash8 September storm. The total electron content did not respond to the flares of 7 and 8 September. This behavior is attributed to the varying center-to-limb distance of the solar active region 12673 during this period.

Bagiya, Mala; Thampi, Smitha; Hui, Debrup; Sunil, A.; Chakrabarty, D.; Choudhary, R.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 08/2018

YEAR: 2018     DOI: 10.1029/2018JA025496

The Far Ultra-Violet Imager on the Icon Mission

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N₂ ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny\textendashTurner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft.

Mende, S.; Frey, H.; Rider, K.; Chou, C.; Harris, S.; Siegmund, O.; England, S.; Wilkins, C.; Craig, W.; Immel, T.; Turin, P.; Darling, N.; Loicq, J.; Blain, P.; Syrstad, E.; Thompson, B.; Burt, R.; Champagne, J.; Sevilla, P.; Ellis, S.;

Published by: Space Science Reviews      Published on: 10/2017

YEAR: 2017     DOI: 10.1007/s11214-017-0386-0

Impact of Oscillating IMF B _z During 17 March 2013 Storm on the Distribution of Plasma Over Indian Low-Latitude and Mid-Latitude Ionospheric Regions

We show evidence of a positive ionospheric storm occurring simultaneously at the equatorial, low-latitude and mid-latitude ionospheric regions in the Indian sector in response to an intense geomagnetic storm on 17 March 2013. The storm had its onset time coinciding with the local noon. An on-site digisonde at Trivandrum (dip equator) recorded a sharp decrease in the height of F\ region peak in the afternoon, which is a signature of westward electric field associated with a counter electrojet (CEJ). Coupled with it was a simultaneous increase in total electron content (TEC) in the entire Indian region. The magnitude of increase in TEC decreased slowly northward of the dip equator and had almost no change near the anomaly crest. Farther northward of the anomaly crest, the TEC started increasing again and at Shimla, a mid-latitude station, it had a value close to 2 times its monthly mean. We surmise that the westward electric field resulting from the CEJ pushed the F\ layer at the dip equator down to the altitude regions where recombination and diffusion played minimal roles. No loss of plasma due to diffusion while photoproduction of ions was still taking place, led to an enhancement in the electron density near the equatorial/low-latitude region. The Joule heating of the thermosphere, on the other hand, gave rise to the traveling atmospheric disturbances which pushed the plasma up in altitude at the equatorial anomaly region. It supplemented the loss of plasma at the anomaly crest region resulting in no change in the TEC thereat and a marked increase in the TEC in the mid-latitude ionosphere.

Shreedevi, P.; Choudhary, R.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2017

YEAR: 2017     DOI: 10.1002/2017JA023980

Ionospheric-thermospheric UV tomography: 3. A multisensor technique for creating full-orbit reconstructions of atmospheric UV emission

We present the Volume Emission Rate Tomography (VERT) technique for inverting satellite-based, multisensor limb and nadir measurements of atmospheric ultraviolet emission to create whole-orbit reconstructions of atmospheric volume emission rate. The VERT approach is more general than previous ionospheric tomography methods because it can reconstruct the volume emission rate field irrespective of the particular excitation mechanisms (e.g., radiative recombination, photoelectron impact excitation, and energetic particle precipitation in auroras); physical models are then applied to interpret the airglow. The technique was developed and tested using data from the Special Sensor Ultraviolet Limb Imager and Special Sensor Ultraviolet Spectrographic Imager instruments aboard the Defense Meteorological Satellite Program F-18 spacecraft and planned for use with upcoming remote sensing missions. The technique incorporates several features to optimize the tomographic solutions, such as the use of a nonnegative algorithm (Richardson-Lucy, RL) that explicitly accounts for the Poisson statistics inherent in optical measurements, capability to include extinction effects due to resonant scattering and absorption of the photons from the lines of sight, a pseudodiffusion-based regularization scheme implemented between iterations of the RL code to produce smoother solutions, and the capability to estimate error bars on the solutions. Tests using simulated atmospheric emissions verify that the technique performs well in a variety of situations, including daytime, nighttime, and even in the challenging terminator regions. Lastly, we consider ionospheric nightglow and validate reconstructions of the nighttime electron density against Advanced Research Project Agency (ARPA) Long-range Tracking and Identification Radar (ALTAIR) incoherent scatter radar data.

Hei, Matthew; Budzien, Scott; Dymond, Kenneth; Nicholas, Andrew; Paxton, Larry; Schaefer, Robert; Groves, Keith;

Published by: Radio Science      Published on: 07/2017

YEAR: 2017     DOI: 10.1002/2015RS005887

Stationary depletions in thermospheric atomic oxygen concentration and mass density observed with WINDII, GUVI, GOCE and simulated by NRLMSISE-00

Impact of Oscillating IMF B z During 17 March 2013 Storm on the Distribution of Plasma Over Indian Low-Latitude and Mid-Latitude Ionospheric Regions

We show evidence of a positive ionospheric storm occurring simultaneously at the equatorial, low-latitude and mid-latitude ionospheric regions in the Indian sector in response to an intense geomagnetic storm on 17 March 2013. The storm had its onset time coinciding with the local noon. An on-site digisonde at Trivandrum (dip equator) recorded a sharp decrease in the height of F region peak in the afternoon, which is a signature of westward electric field associated with a counter electrojet (CEJ).

Shreedevi, PR; Choudhary, RK;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2017     DOI: 10.1002/2017JA023980

Direct observational evidence for disturbance dynamo on the daytime low-latitude ionosphere: A case study based on the 28 June 2013 space weather event

A case of the westward disturbance dynamo (DD) electric field, influencing the daytime equatorial and low-latitude ionosphere, during a geomagnetic storm that occurred on 28\textendash29 June 2013 is presented. The GPS total electron content (TEC) observations from a network of stations in the Indian equatorial, low and middle latitude regions along with the radio beacon TEC, ionosonde, and magnetic field observations are used to study the storm time behavior of the ionosphere. Negative ionospheric storm effects were seen over the low and middle latitudes during the storm time due to the presence of a westward DD electric field. Observations show that the suppression of the equatorial ionization anomaly (EIA) from the morning hours itself on 29 June 2013 took place due to the prevailing westward DD electric field, providing evidence for the model calculations by Balan et al. (2013). Simulations using the GITM model also agree well with our results. The present study gains importance as the direct observational evidences for disturbance dynamo effects on the daytime low-latitude ionosphere and the EIA are sparse, as it has been difficult to delineate it from the compositional disturbances.

Thampi, Smitha; Shreedevi, P.; Choudhary, R.; Pant, Tarun; Chakrabarty, D.; Sunda, S.; Mukherjee, S.; Bhardwaj, Anil;

Published by: Journal of Geophysical Research: Space Physics      Published on: 09/2016

YEAR: 2016     DOI: 10.1002/2016JA023037

On the latitudinal changes in ionospheric electrodynamics and composition based on observations over the 76--77 E meridian from both hemispheres during a geomagnetic storm

The relative contributions of the composition disturbances and the disturbance electric fields in the redistribution of ionospheric plasma is investigated in detail by taking the case of a long-duration positive ionospheric storm that occurred during 18\textendash21 February 2014. GPS total electron content (TEC) data from the Indian Antarctic station, Bharti (69.4\textdegreeS, 76.2\textdegreeE geographic), the northern midlatitude station Hanle (32.8\textdegreeN, 78.9\textdegreeE geographic), northern low-latitude station lying in the vicinity of the anomaly crest, Ahmedabad (23.04\textdegreeN, 72.54\textdegreeE geographic, dip latitude 17\textdegreeN), and the geomagnetic equatorial station, Trivandrum (8.5\textdegreeN, 77\textdegreeE geographic, dip latitude 0.01\textdegreeS) are used in the study. These are the first simultaneous observations of TEC from Bharti and Hanle during a geomagnetic storm. The impact of the intense geomagnetic storm (Dst\~-130\ nT) on the southern hemisphere high-latitude station was a drastic reduction in the TEC (negative ionospheric storm) starting from around 0330 Indian standard time (IST) on 19 February which continued till 21 February, the maximum reduction in TEC at Bharti being \~35 TEC units on 19 February. In the northern hemisphere midlatitude and equatorial stations, a positive ionospheric storm started on 19 February at around 0900 IST and lasted for 3\ days. The maximum enhancement in TEC at Hanle was about \~25 TECU on 19 February while over Trivandrum it was \~10 TECU. This long-duration positive ionospheric storm provided an opportunity to assess the relative contributions of disturbance electric fields and composition changes latitudinally. The results indicate that the negative ionospheric storm over Bharti and the positive ionospheric storm over Hanle are the effect of the changes in the global wind system and the storm-induced composition changes. At the equatorial latitudes, the positive ionospheric storm was due to the interplay of prompt penetration electric field and disturbance dynamo electric field.

Shreedevi, P.; Thampi, Smitha; Chakrabarty, D.; Choudhary, R.; Pant, Tarun; Bhardwaj, Anil; Mukherjee, S.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2016

YEAR: 2016     DOI: 10.1002/2015JA021841

Geomagnetic storms; High latitude low latitude coupling; Ionosphere; positive ionospheric storm

Thermospheric atomic oxygen concentrations from WINDII O+ (2P→ 2D) 732 nm emission: Comparisons with the NRLMSISE-00 and C-IAM models and with GUVI observations

Shepherd, Gordon; Cho, Young-Min; Fomichev, Victor; Martynenko, Oleg;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2016     DOI:

Tomographic Imaging of Thermospheric Neutral Density Using UV Limb Scanning

Dymond, K; Budzien, SA; Nicholas, AC;

Published by:       Published on:

YEAR: 2013     DOI:

Day-to-day variability of equatorial anomaly in GPS-TEC during low solar activity period

Aggarwal, Malini; Joshi, H.P.; Iyer, K.N.; Kwak, Y.-S.; Lee, J.J.; Chandra, H.; Cho, K.S.;

Published by: Advances in Space Research      Published on: Jan-06-2012

YEAR: 2012     DOI: 10.1016/j.asr.2012.03.005

Evaluation of OVATION Prime as a forecast model for visible aurorae

This study evaluates the ability of the OVATION Prime auroral precipitation model to provide operational forecasts of the visible aurora. An operational implementation would primarily provide the general public with some guidance for viewing the aurora. We evaluate the likelihood that if aurorae are predicted to be visible at a location, they will be seen there within the hour. Nighttime model forecasts were validated with Polar Ultraviolet Imager data for Kp >= 3 and for the years 1997 and 1998. The overall forecasts for a visible aurora to occur or to not occur were correct 77\% of the time. The most important prediction for public auroral viewing is that the visible aurora will occur, and these forecasts were correct 86\% of the time.

Machol, Janet; Green, Janet; Redmon, Robert; Viereck, Rodney; Newell, Patrick;

Published by: Space Weather: The International Journal of Research and Applications      Published on: 09/2012

YEAR: 2012     DOI: 10.1029/2011SW000746

AURORA; model

The Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite: A 20 year perspective

The Wind Imaging Interferometer (WINDII) was launched on the NASA\textquoterights Upper Atmosphere Research Satellite on 12 September 1991 and operated until 2003. Its role in the mission was to measure vector winds in the Earth\textquoterights atmosphere from 80 to 110 km, but its measurements extended to nearly 300 km. The approach employed was to measure Doppler shifts from a suite of visible region airglow lines emitted over this altitude range. These included atomic oxygen O(¹S) and O(¹D) lines, as well as lines in the OH Meinel (8,3) and O₂ Atmospheric (0,0) bands. The instrument employed was a Doppler Michelson Interferometer that measured the Doppler shift as a phase shift of the cosinusoidal interferogram generated by single airglow lines. An extensive validation program was conducted after launch to confirm the accuracy of the measurements. The dominant wind field, the first one observed by WINDII, was that of the migrating diurnal tide at the equator. The overall most notable WINDII contribution followed from this: determining the influence of dynamics on the transport of atmospheric species. Currently, nonmigrating tides are being studied in the thermosphere at both equatorial and high latitudes. Other aspects investigated included solar and geomagnetic influences, temperatures from atmospheric-scale heights, nitric oxide concentrations, and the occurrence of polar mesospheric clouds. The results of these observations are reviewed from a perspective of 20 years. A future perspective is then projected, involving more recently developed concepts. It is intended that this description will be helpful for those planning future missions.

Shepherd, G.; Thuillier, G.; Cho, Y.-M.; Duboin, M.-L.; Evans, W.; Gault, W.; Hersom, C.; Kendall, D.; Lathuillère, C.; Lowe, R.; McDade, I.; Rochon, Y.; Shepherd, M.; Solheim, B.; Wang, D.-Y.; Ward, W.;

Published by: Reviews of Geophysics      Published on: 06/2012

YEAR: 2012     DOI: 10.1029/2012RG000390

airglow; dynamics; interferometers; mesosphere; temperature; winds

The Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite: A 20 year perspective

The Wind Imaging Interferometer (WINDII) was launched on the NASA\textquoterights Upper Atmosphere Research Satellite on 12 September 1991 and operated until 2003. Its role in the mission was to measure vector winds in the Earth\textquoterights atmosphere from 80 to 110 km, but its measurements extended to nearly 300 km. The approach employed was to measure Doppler shifts from a suite of visible region airglow lines emitted over this altitude range. These included atomic oxygen O(¹S) and O(¹D) lines, as well as lines in the OH Meinel (8,3) and O₂ Atmospheric (0,0) bands. The instrument employed was a Doppler Michelson Interferometer that measured the Doppler shift as a phase shift of the cosinusoidal interferogram generated by single airglow lines. An extensive validation program was conducted after launch to confirm the accuracy of the measurements. The dominant wind field, the first one observed by WINDII, was that of the migrating diurnal tide at the equator. The overall most notable WINDII contribution followed from this: determining the influence of dynamics on the transport of atmospheric species. Currently, nonmigrating tides are being studied in the thermosphere at both equatorial and high latitudes. Other aspects investigated included solar and geomagnetic influences, temperatures from atmospheric-scale heights, nitric oxide concentrations, and the occurrence of polar mesospheric clouds. The results of these observations are reviewed from a perspective of 20 years. A future perspective is then projected, involving more recently developed concepts. It is intended that this description will be helpful for those planning future missions.

Shepherd, G.; Thuillier, G.; Cho, Y.-M.; Duboin, M.-L.; Evans, W.; Gault, W.; Hersom, C.; Kendall, D.; Lathuillère, C.; Lowe, R.; McDade, I.; Rochon, Y.; Shepherd, M.; Solheim, B.; Wang, D.-Y.; Ward, W.;

Published by: Reviews of Geophysics      Published on: 06/2012

YEAR: 2012     DOI: 10.1029/2012RG000390

airglow; dynamics; interferometers; mesosphere; temperature; winds

Heterogeneous Measurements for Advances in Space Science and Space Weather Forecasting

Examples of heterogenous data might include GPS radio occultation limb data and ultraviolet nadir photometry; GUVI/SSUSI cross-track O/N2 maps coupled with SSULI in-track

Budzien, Scott; Chua, Damien; Coker, Clayton; Dandenault, Patrick; Dymond, Kenneth; Nicholas, Andrew; Stephan, Andrew; Doe, Richard; Crowley, Geoff;

Published by: To emphasize that space weather forecasting with new, full-physics models requires heterogeneous datasets with complementary characteristics—not merely a higher volume of any single data type      Published on:

YEAR: 2012     DOI:

Onset conditions of bubbles and blobs: A case study on 2 March 2009

Kil, H; Choi, H-S; Heelis, RA; Paxton, LJ; Coley, WR; Miller, ES;

Published by: Geophysical Research Letters      Published on:

YEAR: 2011     DOI: 10.1029/2011GL046885

Science of opportunity: Heliophysics on the FASTSAT mission and STP-S26

The FASTSAT spacecraft, which was launched on November 19, 2010 on the DoD STP-S26 mission, carries three instruments developed in joint collaboration by NASA GSFC and the

Rowland, Douglas; Collier, Michael; Sigwarth, John; Jones, Sarah; Hill, Joanne; Benson, Robert; Choi, Michael; Chornay, Dennis; Cooper, John; Feng, Steven; , others;

Published by:       Published on:

YEAR: 2011     DOI: 10.1109/AERO.2011.5747235

Science of opportunity: Heliophysics on the FASTSAT mission and STP-S26

The FASTSAT spacecraft, which was launched on November 19, 2010 on the DoD STP-S26 mission, carries three instruments developed in joint collaboration by NASA GSFC and the

Rowland, Douglas; Collier, Michael; Sigwarth, John; Jones, Sarah; Hill, Joanne; Benson, Robert; Choi, Michael; Chornay, Dennis; Cooper, John; Feng, Steven; , others;

Published by:       Published on:

YEAR: 2011     DOI: 10.1109/AERO.2011.5747235

Evolved Tiny Ionospheric Photometer (ETIP): A sensor for ionospheric specification

Budzien, Scott; Chua, Damien; Coker, Clayton; Dandenault, Patrick; Dymond, Kenneth; Nicholas, Andrew; Doe, Richard; Crowley, Geoff;

Published by: To address the requirements for space weather sensors, and includes adequate flexibility for accommodation on a range of future flight opportunities, including microsatellite constellations      Published on:

YEAR: 2010     DOI:

Seasonal, diurnal, and solar cycle variations of the longitudinal wave structure in the low-latitude thermosphere

Kwak, Y; Kil, H; Lee, W; Cho, K;

Published by:       Published on:

YEAR: 2010     DOI:

The Armada mission: Determining the dynamic and spatial response of the thermosphere/ionosphere system to energy inputs on global and regional scales

Ridley, AJ; Forbes, JM; Cutler, J; Nicholas, AC; Thayer, JP; Fuller-Rowell, TJ; Matsuo, T; Bristow, WA; Conde, MG; Drob, DP; , others;

Published by:       Published on:

YEAR: 2010     DOI:

Extreme Enhancements in GPS TEC on 8 and 10 November 2004

Chung, Jong-Kyun; Jee, Gun-Hwa; Kim, Eo-Jin; Kim, Yong-Ha; Cho, Jung-Ho;

Published by: Bulletin of the Korean Space Science Society      Published on:

YEAR: 2010     DOI:

LONGITUDINAL VARIATION OF THE ANNUAL AND HEMISPHERIC ASYMMETRIES OF THE LOW-MIDDLE LATITUDE IONOSPHERE

Kwak, Y; Kil, H; Oh, S; Lee, W; Forbes, JM; Cho, K;

Published by:       Published on:

YEAR: 2009     DOI:

Continuous FUV/EUV Imaging of the Ionosphere from Geosynchronous Orbit

Wood, Kent; Dymond, KF; Budzien, SA; McDonald, SE; Coker, C; Nicholas, AC; Kowalski, MP;

Published by: To use new imaging systems to generate measurements in 2-dimensional formats continuously for large regions with high spatial resolution      Published on:

YEAR: 2009     DOI:

MRO/CRISM observations of Phobos and Deimos

Murchie, SL; Choo, T; Humm, D; Rivkin, AS; Bibring, J-P; Langevin, Y; Gondet, B; Roush, TL; Duxbury, T; team, CRISM; , others;

Published by:       Published on:

YEAR: 2008     DOI:

SciBox: a software library for rapid development of science operation simulation, planning, and command tools

It carries four primary instruments: GUVI (Global Ultraviolet Imager), TIDI (TIMED Doppler stations plan for simultaneous observations of the atmosphere with GUVI, TIDI, and SABER.

Choo, Teck; Skura, Joseph;

Published by: Johns Hopkins APL Technical Digest      Published on:

YEAR: 2004     DOI:

Ionospheric and dayglow responses to the radiative phase of the Bastille Day flare

Meier, RR; Warren, HP; Nicholas, AC; Bishop, J; Huba, JD; Drob, DP; Lean, JL; Picone, JM; Mariska, JT; Joyce, G; , others;

Published by: Geophysical research letters      Published on:

YEAR: 2002     DOI:

Variations in the FUV dayglow after intense auroral activity

Craven, JD; Nicholas, AC; Frank, LA; Strickland, DJ; Immel, TJ;

Published by: Geophysical research letters      Published on:

YEAR: 1994     DOI:

KARAKTERISERING VAN PERIODIEK DROOGVALLENDE BEEKJES LN HET STROOMGEBIED VAN DE LUNTERSE BEEK AAN DE HAND VAN DE MAKROFAUNA; AANZET TOT BEHEER.

LANDBOUWHOGESCHOOL, WAGENINGEN; GEBRUIK, GEGEVENS; OVERLEG, OVERNAME; DE PROJECTLEIDER, MET;

Published by:       Published on:

YEAR: 1985     DOI: