Signatures of auroral potential structure extending through the
near-equatorial inner magnetosphere
Abstract
The auroral acceleration region plays an important role in the
magnetosphere-ionosphere coupling system. In this study, signatures of
an auroral U-shaped potential structure were found for the first time in
the near-equatorial inner magnetosphere by the Arase satellite at
~6.0 RE geocentric distance and 11˚ magnetic latitude.
The observed magnetic and electric field variations corresponded to the
equatorward motion of the upward field-aligned current and converging
perpendicular electric field. Examining the three-dimensional velocity
distribution function of H+ and O+
ions, we demonstrate that upflowing ion beams were significantly
deflected in an east-west direction with a perpendicular velocity up to
~80 km/s, which is consistent with the ExB drift
velocity. A simple particle drift model with the inferred auroral
perpendicular potential presents a new kink-like drift path of ions from
the magnetotail, implying that the auroral potential structure has a
great impact on particle dynamics in the near-earth plasma sheet.