Antisunward Streaming Westward Sub‐Auroral Ion Drifts (SAID) Developed in the Postmidnight (1–4) Magnetic Local Time Sector During 2013

Abstract

AbstractIn this study, we have surveyed the Defense Meteorological Satellite Program F15 plots of horizontal ion velocity measurements for the calendar year of 2013 and specified 15 antisunward (westward) sub‐auroral ion drifts (SAID) detections taken in the 1–4 magnetic local time (MLT) sector based on their respective underlying polar convections. We find that during these 15 SAID events, the strong duskside westward polar plasma convection extended across the midnight meridian into the postmidnight 1–4 MLT sector making there the westward SAID flows streaming antisunward. These antisunward (westward) SAID flows were observed only once as a northern‐southern conjugate pair over the Mid Pacific and repeatedly in the South American longitude sector's wider region. We could correlate six antisunward (westward) SAID flows with their respective nearby outward SAID E fields observed by one of the Van Allen Probe (VAP) satellites in the inner magnetosphere. These provided two strong correlations depicting inner‐magnetosphere—topside‐ionosphere conjugate observations and four weak correlations. The VAP observations illustrate (a) the newly‐formed outward SAID E field and (b) its plasma environment still showing (c) the signatures of short‐circuiting across (d) the newly‐formed plasmapause appearing with (e) the hot zone on the earthward/tailward side and sometimes with (f) a localized heat source. Implying different underlying heating mechanisms, the hot zone and the heat source were associated with energetic plasma particles accelerated by plasma turbulence, low‐frequency waves including electromagnetic ion cyclotron waves, and/or auroral kilometric radiation bursts.