Plasmapause location under quiet geomagnetic conditions (Kp≤1): THEMIS observations

Abstract

We statistically examined the plasmapause location (<em>L</em>pp) under quiet geomagnetic conditions (Kp ≤ 1) using the electron density inferred from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft potential for 2 year period (2008 and 2009). Five hundred forty-three <em>L</em>pp samples were identified under steady quiet conditions with Kp values ≤ 1 during 12 h prior to the plasmapause crossing. From our large data set, we determined the medians and means of Lpp in <em>L</em> and magnetic local time (MLT). They are located near geosynchronous orbit and nearly circular. The <em>L</em><em>p</em>p medians show a slight bulge located in postdusk sector. Comparing with previous models, our median or mean Lpp is extended ∼1-2<em> L</em> from the Earth than the model <em>L</em><em>p</em>p along the local time from 0800 to 2400 MLT. That is, <em>L</em>pp locations in the previous models are underestimated during quiet geomagnetic conditions.