Statistical relations between the probability of occurrence of Pc3-4 pulsations at high latitudes in the Antarctic regions and the solar wind and IMF parameters

Geomagnetic pulsation in the Pc3–4 bands have been studied at high Antarctic latitudes during the local summer. The statistical relation between the occurrence probability of Pc3 and Pc4 pulsations and the solar wind (SW) and IMF parameters has been revealed by verifying the hypothesis that an indication is identical in two distributions. Different dependences of the occurrence probability of high-latitude Pc3 and Pc4 pulsations on the IMF value and orientation and SW density and velocity have been found out. It has been indicated that these dependences remain unchanged in the range of geomagnetic latitudes from 66 to 87. It has been established that the Pc3 observation probability at small (2050) IMF cone angles ( = cos1(Bx/B)) is a factor of 1.5 higher than the average statistical probability and depends on the IMF value, which confirms the hypothesis that the Pc3 source is the turbulent region upstream of the magnetospheric quasiparallel low shock. On the contrary, the probability of occurrence of Pc4 weakly depends on the IMF cone angle and is maximal at ~ 0 and ~90. With increasing negative Bz values, the generation probability increases in the Pc4 band and tends to decrease in the Pc3 band. It has been found out for the first time that the dependence of the Pc4 occurrence probability on the IMF clock angle ( = /Bz) is identical in the regions of projections of closed and open field lines, whereas this dependence is different for Pc3. In the region of projections of closed field lines, the Pc3 occurrence probability increases at Bz 0 (the condition under which the cusp shifts on the dawn side) and at By 0 (which is typical of the formation of the low-latitude boundary plasma sheet). In the region of projections of open field lines such a probability increases at By < 0 and Bz < 0 (which results in the formation of the high-latitude boundary plasma sheet). Based on the discovered regularities, the conclusion has been made that the sources of generation of high-latitude Pc3 and Pc4 pulsations are different.


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Authors: Chugunova, O.M., Pilipenko, V.A., Engebretson, M., Rodger, A.

1 January, 2007
Geomagnetism and Aeronomy / 47
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