応用科学研究の進歩 オープンアクセス

抽象的な

On the coexistence of ionospheric positive and negative storm phases during January – December, 2000 geomagnetic activities at East Asian Sector

ADEBESIN, B. Olufemiand and KAYODE John S.

In this paper, the analyses of the peak monthly geomagnetic storms observed between January – December 2000 had been presented. This study is based on data from a network of ionosondes stations located within the East Asian latitudinal sector of 40–65°N. It was found that the effects of ionization depletion at an F2 layer maximum observed at all stations during some of the events are as a result of rapid heating of the polar atmosphere during energy income from the magnetosphere. On the contrary, the positivestorm phases observed can be attributed partly to an eastward electric field, which will movethe mid-latitude ionospheric F region plasma to higheraltitudes with lower recombination, resulting in increases of the electron density. It is therefore suggested that this action may be responsible for the observed long-duration positive storm for the 12th February 2000 and 5th October 2000 geomagnetic activities. On the geoeffectiveness of the F2 Ionosphere with Interplanetary and Solar wind parameters,the correlation percentage between the F2 critical frequency deviation D(foF2) and IMF Bz are higher at most ionosonde stations than between D(foF2) and Dst. In relation to the flow speed V, all the stations had a good correlation (>58%) except at Petropavlovsk.The average correlation percentage for the F2 ionosphere against the Dst, flow speed V and Bz are 40.5, 60.3 and 46.4 respectively. This suggests that the plasma flow speed is the most geoeffective parameter with the F2 ionosphere; irrespective of the latitudinal position (low latitude is not considered here).For D(foF2)versus ,the high latitude station of Salekhard had the highest correlation percentage (71.4%), followed by Magadan (60.4%), Tashkent (42.3%), Novosibirk (10%), and Petropavlovsk (negligible). From these, the following were deduced: (i) the increase in percentage correlation of against D(foF2) is directly proportional to the increase in the latitudinal position of each station (ii) the stations with more occurrences of electron density enhancement are those whose altitudes are greater than 100m. (iii) an average value of 37.5% correlation for versus D(foF2) showed that V is more geoeffective, if it were to be Bz, the % value would have been ≥50%.