Van Allen Probe measurements of the electric drift E \texttimes B/B2 at Arecibo\textquoterights L = 1.4 field line coordinate

We have used electric and magnetic measurements by Van Allen Probe B from 2013 to 2014 to examine the equatorial electric drift E \texttimes B/B2 at one field line coordinate set to Arecibo\textquoterights incoherent scatter radar location (L = 1.43). We report on departures from the traditional picture of corotational motion with the Earth in two ways: (1) the rotational angular speed is found to be 10\% smaller than the rotational angular speed of the Earth, in agreement with previous works on plasmaspheric notches, and (2) the equatorial electric drift displays a dependence in magnetic local time, with a pattern consistent with the mapping of the Arecibo ionosphere dynamo electric fields along equipotential magnetic field lines. The electric fields due to the ionosphere dynamo are therefore expected to play a significant role when discussing, for instance, the structure and dynamics of the plasmasphere or the transport of trapped particles in the inner belt.