Explicit IMF By Dependence in Geomagnetic Activity: Modulation of Precipitating Electrons
Lauri Holappa, Timo Asikainen, К. Мурсула
Abstract
Abstract The most important driver of geomagnetic activity is the north–south ( ) component of the interplanetary magnetic field (IMF), which dominates the solar wind‐magnetosphere coupling and all solar wind coupling functions. While the east–west ( ) IMF component is also included in most coupling functions, its effect is always assumed to be symmetric with respect of its sign. However, recent studies have shown that, for a fixed value of any coupling function, geomagnetic activity is stronger for than for in Northern Hemisphere winter. In Southern Hemisphere winter, the dependence on the sign is reversed. In this paper, we use measurements of National Oceanic and Atmospheric Administration Polar‐Orbiting Operational Environmental Satellites to show that the flux of magnetospheric electrons precipitating into the atmosphere also exhibits an explicit dependence. This dependence is strong in the midnight and dawn sectors where it causes a related effect in the westward electrojet and geomagnetic activity by modulating ionospheric conductivity.