Solar Wind Energy Input: The Primary Control Factor of Magnetotail
Reconnection Site
Abstract
In this paper, we examine the solar wind energy input (expressed by −Vx
× Bs, where Vx is the x component of the solar wind velocity and Bs is
the southward component of the interplanetary magnetic field IMF Bz) for
an onset of magnetic reconnection in the near-Earth magnetotail. There
are 41 events in which in situ observations of magnetic reconnection
were made by Geotail. Magnetic reconnection in the postmidnight
(premidnight) sector of the plasma sheet occurred under strong (weak)
solar wind energy input conditions. Furthermore, we study temporal
variations in the solar wind energy input with two different approaches
using ground magnetic field observations and proton injections at
geosynchronous altitude. These two analyses confirmed the preference of
the postmidnight sector for the onset of magnetic reconnection under the
strong solar wind energy input conditions. It is also found that the
medium and weak solar wind energy input moves the onset location to
earlier magnetic local times. The onset location of magnetic
reconnection in the near-Earth magnetotail is controlled by the solar
wind energy input through the global magnetospheric dynamics during the
loading period.