Impacts of cold ionospheric ions in magnetic reconnection at the Earth's
magnetopause and magnetotail
Abstract
The Earth’s magnetosphere is filled by particles from two sources: the
solar wind and the ionosphere. Ionospheric ions are initially cold and
contain He+ and O+, in addition to
to H+. Depending on their initial magnetic latitude
and local time, and the state of the magnetosphere, they may contribute
to the plasmasphere, the plasma sheet, the ring current, the warm plasma
cloak etc. Depending on which path they follow in the magnetosphere,
some of these ionospheric ions remain cold when they reach the two key
reconnection regions: the Earth’s magnetopause and the plasma sheet in
the tail. In this presentation, we will first review previous
statistical works that quantify the number of cold/ionospheric ions near
these two regions. Several works have attempted to quantify these
populations, but they are inherently difficult to characterize due to
their low energy, often below the spacecraft potential. We will also
discuss the impacts they have on the magnetic reconnection process.
Ionospheric ions mass-load the regions where reconnection takes place
and change the characteristic Alfven speed, resulting in a smaller
reconnection electric field. They also take a portion of the energy that
is imparted to particles, affecting the energy budget of magnetic
reconnection. Finally, they introduce new length and time scales,
associated to their gyroradius and gyroperiod. We will discuss what are
the implications of these impacts for the evolution of the magnetosphere
– solar wind interactions.