On the response of quasi-adiabatic ions to magnetotail reconfigurationsстатья
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Дата последнего поиска статьи во внешних источниках: 11 марта 2017 г.
Аннотация:We investigate the response of quasi-adiabatic particles to short-lived
reconfigurations of the magnetotail field lines. Although they travel through a sharp field
reversal with characteristic length scale smaller than their Larmor radii, these quasi-adiabatic
(Speiser-type) particles experience negligible net changes of magnetic moment. We examine
the robustness of these quasi-adiabatic particles in the presence of a large surging electric
field induced by a magnetic field line reconfiguration. We demonstrate that, although this
short-lived electric field can lead to significant nonadiabatic heating, quasi-adiabaticity may
be, at least partially, conserved for particles with initial velocities larger than the peak ExB
drift speed. Because of the time-varying character of the magnetic field, it is not possible to
make use of the traditional adiabaticity parameter ? to characterize the particle behavior. Still, we demonstrate that particles that intercept the field reversal in the early stage of the
reconfiguration may experience prominent energization (several keVs) and enhanced
oscillating motion in the direction normal to the midplane. On the other hand, particles
interacting with the field reversal in the late stage of the reconfiguration exhibit weaker
energization and slower oscillations about the midplane. We show that, as a result of the
surging electric field, quasi-adiabatic particles that originate from regions of strong magnetic
field can travel down to low altitudes where they lead to characteristic energy-time dispersion
signatures as observed in the plasma sheet boundary layer.