Bibliography

Quantification of the role of gravity wave induced TIDs in modulating ESF day to day variability during geomagnetically disturbed periods

The control of magnetic disturbance induced seed perturbations on the daily variation in night-time ionization irregularity occurrence is studied using ionosonde data and TIMED/GUVI neutral density data at the magnetic equatorial region, Trivandrum. The study reveals that there is a requisite threshold seed amplitude for ESF to occur at a particular altitude and this requisite seed increases as the altitude decreases. This dependence of requisite seed perturbation on altitude for multiple years, which incorporates the electrodynamical effects also, is used as the basis for developing an empirical model to hind-cast ESF. Using the model, the threshold seed perturbation for any day of vernal equinox (ve) season of any year can be delineated if the solar flux index (F10.7) is known. The empirical model is also validated using the data for high and low solar activity periods. The model is able to hind-cast ESF with 92\% success for low solar activity while the success rate for high solar activity is 50\%. Further, the dependence of the threshold curves on neutral density is brought out, thereby confirming the role of ion-neutral coupling processes in modulating the same for magnetically disturbed periods. The geomagnetically disturbed period requisite seed amplitudes are higher than those for quiet periods at a given altitude. This study underlines the importance of disturbance induced seed perturbations and neutral density in controlling ESF occurrence.

Sruthi, T.; Manju, G.;

Published by: Advances in Space Research      Published on: mar

YEAR: 2022     DOI: 10.1016/j.asr.2021.11.038

Equatorial ionosphere; Equatorial Spread F; Geomagnetically disturbed period; neutral density

Modeling the Impact of Metallic Ion Layers on Equatorial Spread With SAMI3/ESF

The impact of region metal ion layers on the development of equatorial plasma bubbles is investigated using the SAMI3/ESF model. We find that metal ion layers reduce the growth rate of the generalized Rayleigh-Taylor instability (GRTI) and act to suppress the development of equatorial plasma bubbles. This is consistent with theoretical expectations and observations and is attributed to the increase in both the Pedersen and Hall conductances. Additionally, inhomogeneities in the region metal ion layer can map into the layer and alter the morphology of equatorial spread (ESF) bubble evolution. Lastly, we find that if EFS bubbles develop in the presence of a metal ion layer, then the electric fields generated by the instability can lift the metal ions into the region. This is consistent with observations of Fe in the region during equatorial spread .

Huba, J.; Krall, J.; Drob, D.;

Published by: Geophysical Research Letters      Published on: 02/2020

YEAR: 2020     DOI: 10.1029/2020GL087224

Equatorial ionosphere; Equatorial Spread F; metal ions; sporadic E

First observational evidence of the modulation of the threshold height h'Fc for the occurrence of equatorial spread F by neutral composition changes

[1]\ In the present study, the seasonal and solar activity variations of the threshold height for equatorial spread F occurrence irrespective of the polarity of the meridional winds during magnetically disturbed period are presented for the first time. The modulation of the seasonal pattern of the threshold height by the seasonal mean O/N₂ values is also examined. The Ionosonde data of magnetic equatorial location Trivandrum (8.5\textdegreeN, 76.5\textdegreeE) and low latitude station SHAR (13.7\textdegreeN, 80.2\textdegreeE) in the Indian longitude sector during equinoxes, winter, and summer seasons of 2002 to 2006 and the corresponding Thermosphere Ionosphere Mesosphere Energetics and Dynamics/GUVI (Global Ultra Violet Imager) O/N₂ data are used for the study. The important findings that have emerged from this study are (i) the substantial increase of threshold height with magnetic activity for all the seasons and (ii) the modulation of h\textquoterightF_c by neutral density changes, irrespective of season, solar, or magnetic activity.

Haridas, M.; Manju, G.; Pant, Tarun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1002/jgra.50331

Equatorial Spread F; O/N2; solar activity; Threshold height