5 research outputs found
Role of electron inertia and reconnection dynamics in a stressed X-point collapse with a guide-field
In previous simulations of collisionless 2D magnetic reconnection it was
consistently found that the term in the generalised Ohm's law that breaks the
frozen-in condition is the divergence of the electron pressure tensor's
non-gyrotropic components. A fully relativistic particle-in-cell (PIC) code was
used to model -point collapse with a guide-field in two and three spatial
dimensions. We show that in a 2D -point collapse with a guide-field close to
the strength of the in-plane field, the increased induced shear flows along the
diffusion region lead to a new reconnection regime in which electron inertial
terms play a dominant role at the -point. This transition is marked by the
emergence of a magnetic island - and hence a second reconnection site - as well
as electron flow vortices moving along the current sheet. The reconnection
electric field at the -point is shown to exceed all lower guide-field cases
for a brief period, indicating a strong burst in reconnection. By extending the
simulation to three spatial dimensions it is shown that the locations of
vortices along the current sheet (visualised by their -value) vary in the
out-of-plane direction, producing tilted vortex tubes. The vortex tubes on
opposite sides of the diffusion region are tilted in opposite directions,
similarly to bifurcated current sheets in oblique tearing-mode reconnection.
The tilt angles of vortex tubes were compared to a theoretical estimation and
were found to be a good match. Particle velocity distribution functions for
different guide-field runs, for 2.5D and 3D simulations, are analysed and
compared.Comment: A&A, Forthcoming articl