Interplanetary phenomenon, geomagnetic and ionospheric response associated with the storm of January 10-11, 1976

Abstract

This paper attempts to investigate the intense (Dst = -158 nT) magnetic storm of January 10-11, 1976; in regards to the appearance of positive storm before the beginning of a geomagnetic storm in the mid latitudes and the occurrence of strong negative phase at the equator, and also to confirm whether the storm event will agree with earlier results of the very intense geomagnetic storm (D_st = -600nT) of March 12- 14, 1989, and April 12-14, 1981 (D_st = -311nT), which shows that the depletion of foF2 was simultaneously worldwide and extended to very low latitudes. The analysis of the D(foF2) plots appear to show that the storm event is characterized by (i) the occurrence of positive ionospheric storm at the high latitudes and mid latitude stations of Khabarovsk, Yamagawa and Okinawa stations before the beginning of the storm event (ii) Presence of strong negative phase at Manila, a low latitude station before the beginning of a geomagnetic storm (iii). Simultaneous existence of negative storm at all latitudes during January 10-11, 1976 storm event between 0600UT-0900UT, January 10, before storm commencement; as well as between 1200UT-1400UT during storm main phase on January 10, and (iv) appearance of strong positive storm at the mid latitude stations of Kokubunji and Yamagawa between 0000UT-2200UT, January 11; and Okinawa between 1200UT-2300UT, January 11. The simultaneous depletion of foF2 during the storm event occurs at all latitudes between the time intervals in (iii) above. This shows that the F2 regional structure response is simultaneous, and in agreement with the aforementioned intense storm events. However, this observed simultaneous depletion of foF2 at all latitudes revealed that the depletion of F2 region plasma density is due to particle precipitation and not only changes in neutral composition resulting from neutral wind. Moreover, it was observed that this storm event is caused as a result of shock generated by magnetic clouds which are characterized by low beta plasma, high IMF magnitude, and large scale coherent field rotations often including large and steady north-south components. Also, the positive storm experienced at some of the high and mid latitude stations after storm commencement appear to be caused by the short duration southward turning of Bz giving äBz = -12nT between 0600UT and 0800UT on January 10.

Keywords: beta plasma, Depletion of foF2, plasma density, magnetic clouds, geomagnetic storm.