Why is a current sheet of the distant magnetotail of the earth
to be thinned and why is a large amount of energy to be released ?
This is typically observed as magnetic reconnection. There were
many theories for the reconnection including from classical
Dungey's theory to nuclear-fusion oriented anomalous resistivity.
It is noted that Dr. Speicer paid attention as a hypothesis of
inertia resistivity to thinning the current sheet.
Much later by a particle-in-cell simulation, it was clearly proven
that inertia of ions and electrons is the mechanism for magnetic
reconnection, resulting in the large energy release of earth's
magnetotail (Ref.3).
> Particle simulation code
An electromagnetic particle simulation code is utilized for solar
and magnetospheric space physics (Ref. 3-5). Both electric and
magnetic fields are solved at low frequencies by a slightly backward
time decentering technique. The backward de-centering does not
affect low frequency phenomena \omega*Dt << 1 (JCP, 1993).
Magnetic reconnection and the solar wind-earth magnetic field
coupling are quite suitable for applying this simulation code.
Article: Macro‐particle simulations of collisionless magnetic reconnection
M. Tanaka, Phys.Plasmas, 2, 2920-2930 (1995)
The basic process of collisionless reconnection is studied in terms of
coalescence of two flux bundles using an implicit particle simulation of
two‐dimensions. As the toroidal electric field is generated by magnetic
induction, an elongated current sheet whose width is a few electron
skin depths is formed. Sub‐Alfvénic plasma outflow off the reconnection
region is generated in the poloidal plane which spreads within the
dual fans originating at the X‐point. Significant toroidal acceleration
and streaming of the electrons without direct thermalization is observed
in the current sheet. The electron parallel transport is proved to enhance
the reconnection rate by comparing the implicit and hybrid‐particle
simulations; in the latter the electrons are spatially frozen to the ions.
The reconnection rate is insensitive to finite Larmor radii of the ions
in the regime where the magnetic flux merges constantly in time.
The simulation results support that the collisionless reconnection
is mediated by the electron inertia.
Reference
1. M. Tanaka, A simulation of low-frequency electromagnetic phenomena in
kinetic plasmas of three dimensions, J.Comput. Phys., 107, 124-145 (1993).
2. M. Tanaka, Macro-EM particle simulation method and a study of collisionless
magnetic reconnection, Comput.Phys.Commun., 87, 117-138 (1995)
3.. MTanaka, Macro-particle simulations of collisionless magnetic reconnection,
Phys.Plasmas, 2, 2920-2930 (1995).
4. M. Tanaka, Asymmetry and thermal effects due to parallel motion of electrons
in collisionless magnetic reconnection, Phys.Plasmas, 3, 4010-4017 (1996).
5. H. Shimazu, M. Tanaka, and S. Machida, The behavior of heavy ions in
collisionless parallel shocks generated by the solar wind and planetary
plasma
interactions, J.Geophys.Res., 101, 27565-27571 (1996).