Magnetic storm effects at equatorial electrojet stations

Abstract

It is shown that there are distinctly two different mechanisms for the interaction of solar wind with the earth's magnetosphere to produce electric field in the ionospheric heights at low and middle latitudes. A persistent or slowly varying southward Interplanetary magnetic field i.e. negative IMF-B z generates dawn to dusk electric field at polar latitudes and a westward (dusk to dawn) electric field at dayside electrojet region which is anti-Sq in direction. A rapid increase of IMF-B z (northward turning) imposes a westward (dusk to dawn) electric field at all latitudes of the dayside hemisphere. The process involved is the imposition of −V × B z electric field at the magnetosphere transmitted instantaneously to the magnetic equator through the polar latitudes. The changes in the H field at ground are largest at stations close to the magnetic equator and the midday longitudes. During magnetic storms, associated with the southward IMF-B z , there are definite enhancements in the decrease of H field at the dayside equatorial electrojet stations. These changes may be coincident with the development of auroral or magnetospheric ring currents. These enhancements may be observed during the main phase as well as during the recovery phase of the magnetic storm, but the essential condition is that the IMF-B z has to be steadily significant southward. Sometimes during the storm period abnormally large changes in H field at day side equatorial electrojet regions are observed associated with large sudden changes in IMF-B z following the second mechanism of solar wind magnetospheric interaction. Thus the equatorial magnetic storm effects are due to combined effects of disturbance ring current, slow and steady IMF-B z as well as due to sudden large changes in IMF-B z .

Extended study of extreme geoelectric field event scenarios for geomagnetically induced current applications

“…This feature is considered to be a consequence of penetration of electric fields associated with the rapid changes in the magnetospheric convection due to the sudden reversal of the IMF Bz, before shielding by the ring current becomes effective. Therefore, the convection electric field penetrated into low‐latitude ionosphere, drives global DP2 currents, which at the dayside EEJ region are composed of the ionospheric Pedersen currents amplified by the Cowling effect [e.g., Rastogi , ; Tsuji et al , , and references therein].…”

Study of the Equatorial and Low‐Latitude Electrodynamic and Ionospheric Disturbances During the 22–23 June 2015 Geomagnetic Storm Using Ground‐Based and Spaceborne Techniques

“…The storm time EF strongly affect the low‐latitude ionosphere, by strengthening the equatorial fountain effect on the dayside and in the postsunset region and by causing an overall enhancement of the low‐latitude electron density (Astafyeva, , ; Astafyeva, Zakharenkova, & Doornbos, ; Mannucci et al, ; Tsurutani et al, ). At the magnetic equator, the disturbed EF may alter the direction of the EEJ causing a counter electrojet (CEJ) (Kikuchi et al, ; Rastogi, ; Yamazaki & Kosch, ), and they also may influence the behavior of the ionospheric Es layer, causing development or disruption of the Es layer (Abdu et al, ; Rastogi et al, ; Singh & Sripathi, ).…”

Characteristics of the equatorial electrojet current in the central region of South America

“…Studying the magnetic storm effects in the H field at the chain of 13 stations along Indo-USSR longitudes, Rastogi (1999) showed that the maximum depression in the H field during the main phase showed larger values over the magnetic equator than was expected from the D st index. Rastogi (2006) recently showed that additional westward electric field is imposed on the equatorial latitudes in the sunlit hemisphere during the storm period when there is steady southward IMF. This additional storm-time effect maximizes over the dip equator at the midday hour sector.…”