First Detection of Extremely Enhanced Solar Wind Helium-3 Originated
from the Lunar
Abstract
The first observations of 3He2+
density extremely enhanced to thousand times of average solar wind by
SWID/Chang’E-2 is reported in this paper. The two events occurred near
the lunar and the Lagrange L2 point respectively. The synchronized
energetic electrons increasing can induce the lunar surface charging to
a large negative voltage and produce the electron-impact double
ionization of helium-3 in the exosphere.
3He2+ will converge to the lunar
surface by the negative potentials, and fully pick up via non-resonance
stochastic heating process by Alfvén wave of the solar wind. It
indicates 3He2+ in the events can
originate from the lunar and transport to L2. Besides SEP (solar
energetic events), the increasing of energetic electrons occurs
frequently in quiet time, so the loss of the lunar exosphere will be
recurrent, and the ionosphere ion void may be formed.