Response of equatorial ionosphere during the super geomagnetic storm of April 2000
The effects of the super geomagnetic storm of 6 April 2000 on E and F-regions of the ionosphere at Thumba, India and at Jicamarca, Peru are studied. The geomagnetic storm started at 1630 UT on 6 April 2000 with sudden increase in solar wind speed and ion density and southward turning of IMF-Bz from 0 to -25 nT. The event was unique with IMF-Bz steady southward for about 6 hours and later turning from -30 nT at 2300 UT to 10 nT at 02 UT and large fluctuations around 1200 UT on 7 April 2000. The southward turning of IMF-Bz on the night of 06-07 April inhibited the development of spread-F irregularities at Thumba. The large excursions of IMF-Bz on 7 April 2000 inhibited the Es-q at Thumba. At Jicamarca the southward turning of IMF-Bz on 6 April caused a very large enhancement of EEJ current and generated very strong Es-q. The northward turning of IMF-Bz on 7 April 2000 is associated with large rise of F-layer around midnight and ESF was seen at 0100 LT however later the F-layer descended and inhibited ESF irregularities. The results confirm the earlier suggestion of Rastogi and Patel (1975) that northward (southward) turning of IMF-Bz generates an eastward (westward) electric field in night side of ionosphere and westward (eastward) electric field in the dayside of ionosphere. The effect of a solar weather event on the equatorial ionosphere at different longitudes depends on the local solar time of the event.
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