Bibliography

Local-time, seasonal and solar cycle variation of Nitric Oxide radiative emission over Indian longitude sector

We study the local-time, seasonal and solar cycle variations of Nitric Oxide (NO) infrared radiative emission, as observed by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the NASA’s Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, over Indian longitude sector. It covers nineteen (January 2002-December 2020) years of NO radiative emission data in the altitude region of 100–155 km. The NO volume emission rate (VER) shows a strong local-time variation with maximum and minimum, respectively, during local-noon and local-midnight. The peak altitude of NO VER decreases by about 18 km from the midnight to the lowest altitude of 117 km at noon. The mean NO VER also undergoes a significant change between the day and night. The mean daytime NO VER is more than double the night-time counterpart. The seasonal variation of peak NO VER shows a maximum during the month of December and a minimum during March. The peak altitude is maximum during September and minimum during June unlike the peak NO VER. The lowest peak altitude, maximum VER and maximum intensity are observed during winter. The relative change in NO VER between the winter and the summer seasons, peaks around 116 km, increases with altitude above 108 km. The long-term trend of NO VER/intensity shows a clear solar cycle variation with higher values during the higher solar activity periods. The NO intensity exhibits a strong correlation with sunspot number (SSN), F10.7 solar index and Lyman-α during both 23rd and 24th solar cycles, although the peak VER does not coincide with the peak SSN.

Bag, Tikemani;

Published by: Advances in Space Research      Published on: sep

YEAR: 2021     DOI: 10.1016/j.asr.2021.05.003

Indian longitude; Nitric Oxide Radiative Emission; TIMED-SABER satellite observation

Ionospheric Response Over Brazil to the August 2018 Geomagnetic Storm as Probed by CSES-01 and Swarm Satellites and by Local Ground-Based Observations

The geomagnetic storm that occurred on 25 August 25 2018, that is, during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo-Electromagnetic Satellite (CSES-01). By integrating the in situ measurements provided by CSES-01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca., 460 km) with ground-based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower- and mid-latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the equatorial electrojet (EEJ). Our proposed multisensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between prompt penetrating electric fields and disturbance dynamo electric fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES-01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter-EEJ during both 25 and 26 August at Braziliian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES-01/Swarm altitudes integrated with the ground-based observation recorded signatures of equatorial ionospheric anomaly crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude.

Spogli, L.; Sabbagh, D.; Regi, M.; Cesaroni, C.; Perrone, L.; Alfonsi, L.; Di Mauro, D.; Lepidi, S.; Campuzano, S.; Marchetti, D.; De Santis, A.; Malagnini, A.; Scotto, C.; Cianchini, G.; Shen, Xu; Piscini, A.; Ippolito, A.;

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

YEAR: 2021     DOI: 10.1029/2020JA028368

Geomagnetic storms; Equatorial Electrojet; in situ plasma density; ionospheric elctroduamics; Ionospheric storms; low-latitude ionosphere

SABER Observation of Storm-Time Hemispheric Asymmetry in Nitric Oxide Radiative Emission

The nitric oxide (NO) 5.3 μm radiative emission is the dominating and most efficient cooling agent in the thermosphere above 100 km. The NO 5.3 μm radiative cooling is an important

Bag, Tikemani; Li, Zheng; Rout, Diptiranjan;

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

YEAR: 2021     DOI: 10.1029/2020JA028849

Unprecedented hemispheric asymmetries during a surprise ionospheric storm: A game of drivers

Astafyeva, Elvira; Bagiya, Mala; Förster, Matthias; Nishitani, Nozomu;

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

YEAR: 2020     DOI:

Game of drivers and a surprise ionospheric storm

For this purpose, we use a set of space-borne (the Swarm constellation, GUVI/TIMED) and ground-based (GPS receivers, magnetometers, SuperDARN) instruments. In the

Astafyeva, Elvira; Bagiya, Mala;

Published by:       Published on:

YEAR: 2019     DOI:

Local Time Hemispheric Asymmetry in Nitric Oxide Radiative Emission During Geomagnetic Activity

The nitric oxide (NO) radiative emission at 5.3\ μm cools the thermosphere by conversion of solar energy into infrared radiation subsequently exiting thermosphere. It correctly serves as a natural thermostat. The NO 5.3-μm emission is even more important during geomagnetic storm events due to huge deposition of heat energy and momentum in the Earth\textquoterights atmosphere. The Thermosphere, Ionosphere, Mesosphere Energetics, and Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry observation of NO 5.3-μm radiative emission is studied between \textpm55\textdegree geographic latitudes during eight geomagnetic storm events. Two events that occurred during 7\textendash12 November 2004 (Dst\ =\ -374\ nT) and 23\textendash28 August 2005 (Dst\ =\ -184\ nT) are analyzed in details. The variation of NO emission during other six storms is also presented. The NO volume emission rate (NO VER) shows an enhancement during storm events. The enhanced NO VER illustrates an equatorward movement with descending peak altitude as one moves toward the equator. The NO infrared radiative flux is calculated by integrating NO VER from altitude of 100 to 155\ km. A local time hemispheric asymmetry in both NO VER and NO infrared radiative flux is observed during all geomagnetic storm events.

Bag, Tikemani;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2018

YEAR: 2018     DOI: 10.1029/2018JA025731

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

Storm Time Variation of Radiative Cooling by Nitric Oxide as Observed by TIMED-SABER and GUVI

The variation of O/N₂ (reference to N₂ column density 10¹⁷\ cm^-2) and nitric oxide radiative emission flux exiting the thermosphere have been studied over the Northern Hemisphere during the superstorm event of 7\textendash12 November 2004. The data have been obtained from Global Ultraviolet Imager (GUVI) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on board the National Aeronautics and Space Administration (NASA)\textquoterights Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. The NO radiative flux is observed to show an anti-correlation with O/N₂ on a global scale. Both NO radiative flux and O/N₂ ratio show equatorward motion with maximum penetration in western longitude sectors. A local variation of O, O₂, and N₂ densities have been calculated using NRLMSISE-00 model over a midlatitude location (55\textdegreeN,180\textdegreeE). On a local scale, model calculated O/O₂ and O/N₂ ratios are found to follow the observations made by GUVI. The collisional excitation of NO with atomic oxygen is the most dominant process for the total cooling rate. The SABER-retrieved NO cooling rate (CR) at a local site suggests an enhancement during the storm period with the peak emission rate closely correlated to the progression of the storm. The peak emission altitude of NO CR moves upward during the main phase of the storm. The NO abundance has been calculated by using cooling rate and Nitric Oxide Empirical Model (NOEM) model. Both these suggest a vary large (3\textendash15 times) increase in NO density during the storm, which is required to account the changes in NO radiative flux. A similar kind of enhancement in NO abundance is also noticed in Student Nitric Oxide Explorer observations during intense geomagnetic storms.

Bharti, Gaurav; Sunil~Krishna, M.; Bag, T.; Jain, Puneet;

Published by: Journal of Geophysical Research: Space Physics      Published on: 01/2018

YEAR: 2018     DOI: 10.1002/2017JA024576

Planetary Magnetospheres 60 years after Explorer 1

Paxton, LJ; Bagenal, F;

Published by:       Published on:

YEAR: 2018     DOI:

Storm-time variation of radiative cooling by Nitric Oxide as observed by TIMED-SABER and GUVI

Krishna, Sunil; Bharti, Gaurav; Bag, Tikemani;

Published by:       Published on:

YEAR: 2017     DOI:

Storm time variation of radiative cooling of thermosphere by nitric oxide emission

Krishna, MV; Bag, Tikemani; Bharti, Gaurav;

Published by: 41st COSPAR Scientific Assembly      Published on:

YEAR: 2016     DOI:

Effects of prolonged southward interplanetary magnetic field on low-latitude ionospheric electron density

The present work describes the low-latitude ionospheric variability during an unusually prolonged (~33 h) geomagnetically disturbed condition that prevailed during 15\textendash16 July 2012. The low-latitude electron density in summer hemisphere, investigated using ground- and satellite-based observations, responded to this by generating strong negative ionospheric storm on 16 July. The maximum electron density on 16 July over Indian low latitudes was reduced by more than 50\% compared to that on a geomagnetically quiet day (14 July 2012). In contrast to the extreme reduction in total electron content (TEC) in the Northern Hemisphere, TEC from a winter hemispheric station revealed substantial (~23 total electron content unit, 1 TECU = 10¹⁶ el m^-2) enhancements on the same day. This contrasting hemispherical response in TEC is suggested to be due to the combined effects of strong interhemispheric and solar-driven day-night winds. Further, very weak equatorial electrojet (EEJ) strength on 16 July indicated that the westward electric field perturbations in the low-latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes. Interestingly, despite reduction in the integrated EEJ strength on 15 July, the low-latitude electron density showed substantial enhancement, highlighting the significant effect of the positive ionospheric storm on the low-latitude ionosphere. The roles of electrodynamical/neutral-dynamical and compositional disturbances are discussed in view of these observations to understand low-latitude ionospheric response when geomagnetic disturbance persists for longer duration.

Bagiya, Mala; Hazarika, Rumajyoti; Laskar, Fazlul; Sunda, Surendra; Gurubaran, S.; Chakrabarty, D.; Bhuyan, P.; Sridharan, R.; Veenadhari, B.; Pallamraju, D.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 07/2014

YEAR: 2014     DOI: 10.1002/2014JA020156

low-latitude ionosphere; neutral winds; prolonged southward IMF Bz; thermospheric neutral composition

Low-latitude ionospheric-thermospheric response to storm time electrodynamical coupling between high and low latitudes

Bagiya, Mala; Iyer, K.; Joshi, H.; Thampi, Smitha; Tsugawa, Takuya; Ravindran, Sudha; Sridharan, R.; Pathan, B.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2011

YEAR: 2011     DOI: 10.1029/2010JA015845

Multitechnique studies of ionospheric phenomena

The ionospheric plasma density shows temporal variability (with time of the day, season and solar cycle), latitudinal variability and variations during geomagnetic disturbances. In

Bagiya, Mala;

Published by:       Published on:

YEAR: 2010     DOI:

TEC variations during low solar activity period (2005--2007) near the Equatorial Ionospheric Anomaly Crest region in India

The dual frequency signals from the GPS satellites recorded at Rajkot (22.29 N, 70.74 E, Geographic, 14.03 N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst=−216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated.

Bagiya, Mala; Joshi, H.; Iyer, K.; Aggarwal, M.; Ravindran, S.; Pathan, B.;

Published by: Annales Geophysicae      Published on: Jan-01-2009

YEAR: 2009     DOI: 10.5194/angeo-27-1047-2009