Solar flare effects on the geomagnetic elements during normal and counter electrojet periods

Abstract

The paper describes the study of solar flare effects (sfe) on horizontal (H ), eastward (Y ) and vertical (Z ) components of the geomagnetic field at the Indo-USSR chain of magnetic observatories extending from the magnetic latitudes 0• to 45• N, a network not available any where else in the world. Events are selected when strong, normal and reversed (counter) equatorial electrojet are in existence as well as when only a partial counter electrojet is present.During a strong and normal electrojet event time, sfe consists of a positive impulse in H at all stations, the amplitude of H following the latitudinal variation similar to that of the quiet day monthly mean, Sq (H ). The sfe in Y is negative at all the stations. Sfe in Z shows positive impulse at the four-electrojet stations and negative at other stations. During a counter electrojet period the effect of solar flare on H field is negative impulse at electrojet stations, positive at low latitude and again negative at stations north of Sq focus. Sfe in Y is small at all the equatorial and negative at higher latitude stations. However, sfe (Z ) is negative at the equatorial latitudes.During a partial counter electrojet period the observed effect is the combination of an increase of the planetary current component and the decrease of the electrojet component, giving rise to a negative impulse in H at equatorial stations and a positive impulse in H , increasing with increasing distance from the equator. These results are presented and discussed.

Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 – a case study

“…These studies have shown that SFE (H) amplitude is lower at equator and higher for stations outside the jet due to the counter electrojet related decreasing effect on H . The characteristics of the electrojet response, to solar flares, under conditions of counter electrojet, have been described by Rastogi et al (1999). They have also confirmed the existence of zonal and meridional components of the ionospheric currents over the equatorial latitudes, which in combination with S q currents produce complex effects (as seen during flares occurring at the time of partial CEJ events).…”

“…They have explained the observed irregular variations of Z components at different stations in terms of possible distortions in the altitude profile of the ionospheric currents at low latitudes. Several studies have reported the effects of solar flares during counter electrojet events (Srivastava, 1974;Sastri, 1975;Rastogi et al, 1975Rastogi et al, , 1999Rangarajan and Rastogi, 1981;Manju and Viswanathan, 2005). These studies have shown that SFE (H) amplitude is lower at equator and higher for stations outside the jet due to the counter electrojet related decreasing effect on H .…”

Latitude-dependent delay in the responses of the equatorial electrojet and <i>S</i><sub><i>q</i></sub> currents to X-class solar flares

“…In response to flare enhancement in the X-ray flux, the H component shows a strong and rapid increase at all the stations. This sudden intensification in the H component is a signature of the response of the global ionospheric S q and the EEJ current systems to the sudden conductivity enhancement, caused by the flare X-ray ionization (Richmond and Venkateswaran, 1971;Rastogi et al, 1999). The red arrows mark the time of the peaks in H intensification at each of the stations.…”

“…The EEJ response under solar flare events has been extensively investigated and documented in the literature. Besides the sudden increase in the ionization density by the flare radiation, the EEJ enhancement is also shaped by the background electric field (Abdu et al, 2017;Zhang et al, 2017;Rastogi et al, 1999). In the present work, we analyze the responses of the ionospheric current system during two solar flare events that occurred near midday on 13 May 2013 and 11 March 2015; both events occur during geomagnetic quiet days.…”

“…The increase in the solar radiation during a solar flare events produces geomagnetic field disturbances, due to the sudden intensification in the global ionospheric current system caused by the flare-induced enhanced ionospheric conductivity (Rastogi et al, 1999;Moldavanov, 2002). The EEJ response under solar flare events has been extensively investigated and documented in the literature.…”