J. Woch

The low‐latitude boundary layer at mid‐altitudes: Relation to large‐scale Birkeland currents

In this work the authors seek to test a projected relationship between the low latitude boundary layer (LLBL) and field aligned currents (FAC), or Birkeland currents. They use the procedure developed by Woch and Lundin for identifying LLBL boundaries. They look for correlations between properties of the FAC and properties of the LLBL. Their results show that in most cases the FAC observed are totally inside the region which exhibits LLBL plasma precipitation. The authors argue that within the biases to their data because of its source, and relative sensitivities, their conclusions support earlier work which argues for the LLBL acting as a source region for FAC features.

The low‐latitude boundary layer at mid‐altitudes: Identification based on Viking hot plasma data

On passes through the pre-dawn to pre-noon auroral oval the Viking spacecraft (apogee at 13,400 km) encounters often a generally well-defined precipitation region of ions with characteristic energies of several hundred eV, with neither cusp nor plasma mantle characteristics. Furthermore, these ions are clearly separable from ions originating from the plasma sheet. Partial ion number densities in this plasma precipitation region strongly correlate with solar wind densities, supporting the view that it constitutes the mid-altitude projection of the magnetospheric low-latitude boundary layer (LLBL). The LLBL projection thus identified is observed with high probability in the MLT range from near-noon to at least 6 MLT but occasionally extends toward 4 to 3 MLT. In the dawn to pre-noon local time sector auroral ion precipitation pattern can be divided into precipitation originating from the plasma sheet and LLBL, i.e. generally no region was encountered with properties suggesting that it projects to the magnetospheric plasma sheet boundary layer (PSBL).

An ionospheric travelling convection vortex event observed by ground-based magnetometers and by VIKING

A transient ionospheric travelling convection vortex (ITCV) event was recorded by the EISCAT magnetometer cross in northern Scandinavia on April 21, 1986 around 8:40 MLT. Simultaneously, the near-c ...