The Season Dependent Distortions of the Ring Current

Abstract

The seasonal variations of the plasma dynamics have been investigated using Mead-Fairfield model. It is shown that shifts in the mirror points and meridional drifts are introduced as a result of the season dependent tilt of the dipole axis with the earth-sun line. Other parameters like radial and azimuthal drifts and the bounce periods are free from seasonal variations. The maximum shift in the mirror points and latitudinal drifts are produced in particles bouncing close to the equator but the former peaks in the mid-night meridian while the latter maximises (in magnitude) in the dawn and dusk sectors. A theoretical estimate has been obtained for the seasonal geomagnetic variation associated with these distortions of the ring current. It is shown that the seasonal variations in the declination can be accounted for if the ring current radius is taken as 7 earth radii. © 1982, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.