Real-time monitor of geomagnetic field in the near-pole regions as an index of magnetospheric electric field

Abstract

Solar wind electric field that penetrates into the magnetosphere is an important key for causes of magnetospheric disturbances. Since PC (Polar Cap) index, produced from the variation of the magnetic field in the near-pole regions is known to be good indicator of magnetospheric electric field, monitoring the magnetic activity in the near-pole regions in the real-time is useful for nowcasting/forcasting space weather. From the comparison of horizontal components of the magnetic field data between two stations, Eureka and Thule, it is found that the correlation between these two stations are quite high except for the summer months. This result suggests that magnetic field variations in the near-pole region are uniform, and the index can be produced throughout the year using magnetic field data in the northern and southern near-pole region.

磁気圏に浸透する太陽風電場は磁気圏擾乱原因の重要な手がかりである。極近傍領域での磁場変動から生じるPC(極冠)指数は、磁気圏電場のよい指標となることが知られているので、極近傍域の磁気活動をモニタすることは、宇宙天気の現報や予報に有益である。2つの観測所EuekaとThuleにおける磁場データ水平成分の比較から、夏期を除いてこの2観測所の測定データ間には非常に相関がよいことが判った。この結果は極近傍領域での磁場変化は一様であり、北極および南極近傍境域での磁場のデータを用いて年間を通じて指標をつくることができることを示している。