T. Tokunaga

A new index to monitor temporal and long-term variations of the equatorial electrojet by MAGDAS/CPMN real-time data: EE -Index

A new index, EE-index (EDst, EU, and EL), is proposed to monitor temporal and long-term variations of the equatorial electrojet by using theMAGDAS/CPMN real-time data. The mean value of the H component magnetic variations observed at the nightside (LT = 18–06) MAGDAS/CPMN stations along the magnetic equatorial region is found to show variations similar to those of Dst; we defined this quantity as EDst. The EDst can be used as a proxy of Dst for the real-time and long-term geospace monitoring. By subtracting EDst from the H component data of each equatorial station, it is possible to extract the Equatorial Electrojet and Counter Electrojet components, which are defined as EU and EL, respectively.

Annual and semi-annual Sq variations at 96° MM MAGDAS I and II stations in Africa

The quiet daily variations of the geomagnetic field (Sq) have been studied by using the geomagnetic data of the 10 International Quietest Days. Geomagnetic data from MAGDAS I and II stations—ten stations were selected around the 96° magnetic meridian (MM)—over Africa have been analyzed from September 2008 to August 2009. The analysis of this unique data set clarifies the characteristics of the Sq variations over the African sector for the first time by observational geomagnetic data. In this paper, we found that Sq(H) and Sq(D) show a predominantly annual variation. The most interesting result, and a new finding in the African sector, is the appearance of two vortices in the day lit southern hemisphere during spring. Further data analysis also revealed many other interesting characteristics for the Sq over the African sector.