`Self-generation of hollow current profile
and tilt instability in field-reversed configuration'
H.Ohtani, R.Horiuchi and T.Sato
Physics of Plasmas 10 145 (2003).
Two-dimensional electromagnetic particle simulation
is performed
to investigate the profile relaxation from
a magnetohydrodynamic (MHD) equilibrium
to a kinetic one
and the physical property of the kinetic equilibrium
in the field-reversed configuration.
The radial oscillation is excited
in order to relax an excess energy in the MHD equilibrium.
After this profile oscillation,
the system spontaneously relaxes toward a kinetic equilibrium,
in which
the electron current profile becomes hollow
as a result of the combined effects of
the gradient-B drift near the field-null line and
the ExB drift generated by the ion finite Larmor radius effect
near the magnetic separatrix.
On the other hand,
the ion current profile becomes peaked
due to the effect of the ion meandering orbit
near the field-null line.
The stability of the obtained kinetic equilibrium
against the tilt mode is also studied
by means of three-dimensional full electromagnetic particle simulation.
It is found that
the growth rate of the tilt instability
in the case of the hollow current profile and high separatrix beta value
is smaller than that in the case of the peaked current profile.
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2003/01/29