Bibliography

Quantification of the vertical transport and escape of atomic hydrogen in the terrestrial upper atmosphere

Measurements of the limiting escape rate of atomic hydrogen (H) atoms at Earth, and the relative significance of thermal evaporation and non-thermal escape mechanisms, such as charge exchange and polar wind, have long been lacking. Our recent development of sophisticated radiative transport analysis techniques now enables the reliable interpretation of remotely-sensed measurements of optically-thick H emission, such as those acquired along the Earth\textquoterights limb by the Global Ultraviolet Imager (GUVI) onboard the NASA TIMED spacecraft, in terms of physical parameters such as exobase density and, crucially, vertical diffusive flux. In this work, we present results from a systematic investigation of H Ly_α emission measured by TIMED/GUVI along the Earth\textquoterights dayside limb from 2002-2007, which we use to derive the vertical H flux and associated density distribution from 250 km out to 1 earth radius. Our analysis reveals that the vertical flux of thermospheric H is nearly constant ver a large range of solar activity and typically exceeds the calculated thermal evaporative flux, suggesting that terrestrial H escape is indeed limited by its vertical diffusion. The excess supply of H atoms to the exobase associated with large observed vertical fluxes requires that non-thermal escape mechanisms be operative for steady-state continuity balance. We find that such non-thermal processes are a particularly significant component of total H escape during low solar activity, when thermal evaporation is weakest.

Joshi, P.P.; Phal, Y.D.; Waldrop, L.S.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2019

YEAR: 2019     DOI: 10.1029/2019JA027057

Parametric estimation of neutral hydrogen density under charge exchange and quantification of its effect on plasmasphere-ionosphere coupling

Joshi, Pratik; Waldrop, Lara;

Published by:       Published on:

YEAR: 2018     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

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

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