Bibliography

Aspects related to variability of radiative cooling by NO in lower thermosphere, TEC and O/N2 correlation, and diffusion of NO into mesosphere during the Halloween storms

Nitric Oxide is a very important trace species which plays a significant role acting as a natural thermostat in Earth’s thermosphere during strong geomagnetic activity. In this paper, we present various aspects related to the variation in the NO Infrared radiative flux (IRF) exiting the thermosphere by utilizing the TIMED/SABER (Thermosphere Ionosphere Mesosphere Energetics and Dynamics/ Sounding of the Atmosphere using Broadband Emission Radiometry) observational data during the Halloween storm which occurred in late October 2003. The Halloween storm comprised of three intense-geomagnetic storms. The variability of NO infrared flux during these storm events and its connection to the strength of the geomagnetic storms were found to be different in contrast to similar super storms.

Ranjan, Alok; Krishna, MV; Kumar, Akash; Sarkhel, Sumanta; Bharti, Gaurav; Bender, Stefan; Sinnhuber, Miriam;

Published by: Advances in Space Research      Published on:

YEAR: 2022     DOI: 10.1016/j.asr.2022.07.035

Responses of the Indian Equatorial Ionization Anomaly to two CME-induced geomagnetic storms during the peak phase of solar cycle 24

This work analyzes the geo-effectiveness of Coronal Mass Ejection- (CME-) induced storms by investigating the responses of ionospheric Vertical Total Electron Content (VTEC) and the Equatorial Ionization Anomaly (EIA) over the Indian sector to two storms. One of the storms occurred on February 19, 2014 (SYM-H: −120 nT), while the other occurred on June 23, 2015 (SYM-H: −204 nT). Both storms were driven by full halo CMEs. Global TEC maps were used to characterize VTEC variations during the storms. June 23, 2015 storm was characterized with stronger solar progenitors, right from its origin, although the VTEC response to the storm was not influenced by their strong progenitors. The CMEs that caused the selected storms are large (Halo CMEs). We inferred that irrespective of the strength of solar origin of a storm, the response of ionization distribution over equatorial and low-latitude regions to it depends on the season of storm occurrence, local time of the storm onset, and PPEF orientation. From the VTEC variations for the three Indian stations namely, Trivandrum (geographic latitude: 8.52°N, geographic longitude: 76.94°E, magnetic latitude: 0.37°N), Hyderabad (17.39°N, 78.49°E, 10.15°N) and Delhi (28.70°N, 77.10°E, 22.70°N), we observed that EIA disturbances were more prominent over Hyderabad than over Delhi. The February 19, 2014 storm was characterized by a localized EIA crest at latitude a little above Hyderabad, while in June 23, 2015 storm localized EIA crest was observed directly on Hyderabad. IRI-2016 model generally underestimated VTEC at the three Indian equatorial and low-latitude locations. Solar cycle 24 was characterized with low heliospheric pressure due to its weak polar field strength. The lower pressure allowed CMEs to expand greatly as they transit through space. As they expand, the strengths of the magnetic field inside them decrease, and such lower-strength magnetic fields cause geomagnetic storms that are less geoeffective, even when their solar/interplanetary progenitors are strong and healthy. This associated weak polar field strength of solar cycle 24 caused weak fountain effect with the attendant inability to exhibit storm-time super-fountain effect in the dayside of the equatorial/low-latitude regions.

Simi, K.; Akala, A.; Krishna, Siva; Amaechi, Paul; Ogwala, Aghogho; Ratnam, Venkata; Oyedokun, O.;

Published by: Advances in Space Research      Published on: oct

YEAR: 2021     DOI: 10.1016/j.asr.2021.06.013

Coronal mass ejection; Disturbance dynamo electric field; geomagnetic storm; prompt penetration electric field; total electron content

The impact of a stealth CME on the Martian topside ionosphere

Solar cycle 24 is one of the weakest solar cycles recorded, but surprisingly the declining phase of it had a slow coronal mass ejection (CME) that evolved without any low coronal

Thampi, Smitha; Krishnaprasad, C; Nampoothiri, Govind; Pant, Tarun;

Published by: Monthly Notices of the Royal Astronomical Society      Published on:

YEAR: 2021     DOI: 10.1093/mnras/stab494

Radiative cooling due to NO at 5.3

The effect of geomagnetic storms on the peak emission of NO Volume Emission Rate (NO VER) at 5.3 m, in mesosphere and lower thermosphere (MLT) region, is studied over the Asian sector during 26\textendash29 September 2011 (storm 1) and 18\textendash21 February 2014 (storm 2). The data for peak emission of NO VER is obtained from SABER instrument onboard the NASA\textquoterights TIMED satellite. The SABER retrieved data along with the neutral densities obtained from NRLMSISE-00 model have been used to study the latitudinal and longitudinal variation of peak NO VER during the storm period. The variations induced in the peak emission of NO VER is understood with the help of fluctuations in neutral species and the resulting changes in chemistry. It has been found that the peak emission of NO VER is strongly influenced by the storm conditions. The peak emission of NO VER at 5.3 m is found to be maximum at higher latitudes during the storms. However, the magnitude of peak NO VER gradually decreases towards the equator during the storms. The modeled atomic oxygen number density shows depletion at the higher latitudes corresponding to peak altitude of NO VER. There is a negative correlation between the peak emission of NO VER and Dst index during the main phase of the storm. The peak emission of NO VER and modeled atomic oxygen number density shows the positive correlation at the equator region, while negative correlation at the higher latitudes. At higher latitudes modeled atomic oxygen number density shows positive correlation with Dst index, while negative correlation at the equator. The correlation factors obtained between various parameters related to the storm time radiative cooling strongly support the existing understanding of the variation of NO VER during extreme space weather events.

Bharti, Gaurav; Krishna, M.V.; Singh, Vir;

Published by: Advances in Space Research      Published on: 11/2019

YEAR: 2019     DOI: 10.1016/j.asr.2019.07.016

Radiative cooling due to NO at 5.3 $\mu$m emission as observed by TIMED/SABER over Asian sector

The effect of geomagnetic storms on the peak emission of NO Volume Emission Rate (NO VER) at 5.3 μ m, in mesosphere and lower thermosphere (MLT) region, is studied over the

Bharti, Gaurav; Krishna, MV; Singh, Vir;

Published by: Advances in Space Research      Published on:

YEAR: 2019     DOI: 10.1016/j.asr.2019.07.016

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

Variation of radiative cooling and Nitric Oxide abundance during intense geomagnetic storms as observed by TIMED-SABER and GUVI

Krishna, MV; Bharti, Gaurav;

Published by: 42nd COSPAR Scientific Assembly      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:

Radiative cooling by NO emission observed by TIMED/SABER over Asian sector

Bharti, Gaurav; Krishna, MV;

Published by:       Published on:

YEAR: 2015     DOI:

GPS-TEC variations during low solar activity period (2007--2009) at Indian low latitude stations

The paper is based on the ionospheric variations in terms of vertical total electron content (VTEC) for the low solar activity period from May 2007 to April 2009 based on the analysis of dual frequency signals from the Global Positioning System (GPS) satellites recorded at ground stations Varanasi (Geographic latitude 25\textdegree16 \ N, Longitude 82\textdegree59 \ E), situated near the equatorial ionization anomaly crest and other two International GNSS Service (IGS) stations Hyderabad (Geographic latitude 17\textdegree20 \ N, longitude 78\textdegree30 \ E) and Bangalore (Geographic latitude 12\textdegree58 \ N, longitude 77\textdegree33 \ E) in India. We describe the diurnal and seasonal variations of total electron content (TEC), and the effects of a space weather related event i.e. a geomagnetic storm on TEC. The mean diurnal variation during different seasons is brought out. It is found that TEC at all the three stations is maximum during equinoctial months (March, April, September and October), and minimum during the winter months (November, December, January and February), while obtaining intermediate values during summer months (May, June, July and August). TEC shows a semi-annual variation. TEC variation during geomagnetic quiet as well as disturbed days of each month and hence for each season from May 2007 to April 2008 at Varanasi is examined and is found to be more during disturbed period compared to that in the quiet period. Monthly, seasonal and annual variability of GPS-TEC has been compared with those derived from International Reference Ionosphere (IRI)-2007 with three different options of topside electron density, NeQuick, IRI01-corr and IRI 2001. A good agreement is found between the GPS-TEC and IRI model TEC at all the three stations.

Kumar, Sanjay; Priyadarshi, S.; Krishna, Gopi; Singh, A.;

Published by: Astrophysics and Space Science      Published on: 05/2012

YEAR: 2012     DOI: 10.1007/s10509-011-0973-6

geomagnetic storm; GPS; Ionospheric total electron contents; IRI model