Simulation of low‐latitude ionospheric response to 2015 St. Patrick's Day super geomagnetic storm using ionosonde‐derived PRE vertical drifts over Indian region

Abstract

In this paper, we present low‐latitude ionospheric response over Indian longitude to the recent super geomagnetic storm of 17 March 2015, using the Sami2 is Another Model of the Ionosphere (SAMI2) model which incorporates ionosonde‐derived vertical drift impacted by prompt penetration eastward electric field occurring during the evening prereversal enhancement (PRE) in the vertical drift. The importance of this storm is that (1) Dst reaches as low as −228 nT and (2) prompt penetration of eastward electric field coincided with evening hours PRE. The daytime vertical E × B drifts in the SAMI2 model are, however, considered based on Scherliess‐Fejer model. The simulations indicate a significant enhancement in F layer height and equatorial ionization anomaly (EIA) in the post sunset hours on 17 March 2015 vis‐a‐vis quiet day. The model simulations during recovery phase, considering disturbance dynamo vertical E × B drift along with equatorward disturbance wind, indicate suppression of the daytime EIA. SAMI2 simulations considering the disturbance wind during the recovery phase suggest that equatorward wind enhances the ionospheric density in the low latitude; however, its role in the formation of the EIA depends on the polarity of the zonal electric field. Comparison of model derived total electron content (TEC) with the TEC from ground GPS receivers indicates that model does reproduce enhancement of the EIA during the main phase and suppression of the EIA during the recovery phase of the superstorm. However, peculiarities pertaining to the ionospheric response to prompt penetration electric field in the Indian sector vis‐a‐vis earlier reports from American sector have been discussed.

Ionosphere data assimilation modeling of 2015 St. Patrick's Day geomagnetic storm

“…The effect of the vertical drift in modification of the EIA crests during quiet and storm periods have been reported by several observational, statistical, and theoretical studies [e.g., Rastogi and Klobuchar, 1990;Chen et al, 2008;Lin et al, 2009;Stoneback et al, 2013]. The feature of strong vertical drift in this assimilation model around Indian sector at 1400 UT on 17 March 2015 has been confirmed by the observational results reported by Joshi et al [2016]. Our results suggest that the estimated electric fields in the ionospheric assimilation system have good agreement with the observations, even we only assimilate the GPSTEC observations.…”

“…The feature of strong vertical drift in this assimilation model around Indian sector at 1400 UT on 17 March 2015 has been confirmed by the observational results reported by Joshi et al . []. Our results suggest that the estimated electric fields in the ionospheric assimilation system have good agreement with the observations, even we only assimilate the GPSTEC observations.…”

Equatorial Ionospheric Response to Different Estimated Disturbed Electric Fields as Investigated Using Sheffield University Plasmasphere Ionosphere Model at INPE

“…Simulations for the St. Patrick superstorm (17–18 March 2015) using SAMI2 (Sami2 is Another Model of the Ionosphere) over the Indian region are reported by Joshi et al (). They use a composite vertical drift model: for 18–21 IST (UT + 5:30) a vertical drift derived from HF Doppler observations (Tirunelveli; 8.5°N, 78.2°E; 0.5° geomagnetic latitude) of F layer height at 7 MHz in association with standard ionogram h ′ F and f o F 2 determinations is used; for all other times the quiet time S‐F model applies.…”

“…Many authors used numerical models in an attempt to reproduce the observed ionospheric effects of geomagnetic storms (e.g., Balan et al, , , ; Batista et al, , ; Fang et al, ; Fuller‐Rowell et al, , ; Joshi et al, ; Lin et al, ; Lin, Richmond, Liu, et al, ; Lin, Richmond, Bailey, et al, ; Lu et al, ; Maruyama et al, , ; Pincheira et al, ; Retterer & Kelley, ; Richmond et al, , among others). Specifically, if we want to mainly model the storm equatorial ionosphere dynamics, we must modify its quiet zonal electric field input.…”

“…It is necessary to find alternatives to cover the lack of measurement. Alternative measurements and models could be the Jicamarca Unattended Long-Term studies of the Ionosphere and Atmosphere (JULIA) measurements at 150 km height (Chau & Woodman, 2004), the drift deduced from magnetometer measurements (Anderson et al, 2002(Anderson et al, , 2004 and the drift calculated from the time variations of the ionosonde determined F layer height (Bittencourt & Abdu, 1981) or from HF Doppler observations of that height (Joshi et al, 2016). All these alternatives have some time limitations.…”