A Comparison of the Location of the Mid-Latitude Trough and Plasmapause Boundary

We have compared the location of the mid-latitude trough observed in two dimensional vertical total electron content (vTEC) maps with four plasmapause boundary models, Radiation Belt Storm Probes (RBSP) observations, and IMAGE extreme ultraviolet (EUV) observations all mapped to the ionosphere pierce point using the Tsyganenko (1996) magnetic field line model. For this study, we examine four events over North America: one just after the October 13, 2012 storm, one during the April 20, 2002 double storm, another during a large substorm on January 26, 2013, and one quiet event on May 19, 2001. We have found that in general, the equatorward edge of the mid-latitude trough is within several degrees in geographic latitude of the mapped model plasmapause boundary location, the plasmapause boundary identified with IMAGE EUV, and the location identified by the RBSP spacecraft. When the mid-latitude trough is mapped to the inner magnetosphere, the observed boundary agrees with the plasmapause boundary models within two Earth Radii at nearly all local times in the nightside and the observed mid-latitude boundary is within the uncertainty of the observations at most local times in the nightside. Furthermore, during dynamic solar wind conditions of April 20, 2002, the mid-latitude trough observed in the vTEC maps propagates equatorward as the plasmapause boundary identified with IMAGE EUV moves earthward. Our results indicate that the mid-latitude trough observed within the vTEC maps represents an additional means of identifying the plasmapause boundary location, which could result in improved plasmapause boundary models. Plain Language Summary The equatorward edge of the mid-latitude trough as observed in TEC maps indicates the location of the plasmapause boundary. We compare the location of the midlatitude trough for four events over a range of geomagnetic conditions with plasmapause boundary identified by IMAGE extreme ultraviolet and Radiation Belt Storm Probes and the plasmapause location as indicated by four different models. We find a good agreement between some the methods even under dynamics conditions. The mid-latitude trough can supply the location for the plasmapause boundary during periods when no spacecraft are available to identify the boundary.

Automated summary

This study compared the location of the mid-latitude trough with plasmapause boundaries using various methods and found good agreement in most cases, especially under dynamic conditions. The mid-latitude trough can serve as an additional means of identifying the plasmapause boundary, providing valuable information during periods when spacecraft observations are not available.