English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present a statistical study of Polarelectric field observations using auroral oval passes over Scandinavia above theacceleration region. We are especially interested in seeing whether we can findlarge perpendicular electric fields associated with an upward extended classicalU-shaped potential drop for these passes, during which Polar is in the northernhemisphere usually at about 4 RE altitude. We also use Polarmagnetic field data to infer the existence of a field-aligned current (FAC) andconjugate ground-based magnetometers (the IMAGE magnetometer network) to checkwhether the event is substorm-related or not. We find several events with a FACbut only weak perpendicular electric fields at Polar. In those rare cases wherethe Polar electric field was large, its direction was mostly found to beincompatible with the U-shaped potential model, or it was associated withdisturbed conditions (substorms), where one cannot easily distinguish betweeninductive and static perpendicular electric fields. We found only two caseswhich are compatible with the upward extended U-shaped potential picture, andeven in those cases the potential value is quite small (1-2 kV). To check thevalidity of the analysis method we also estimate the perpendicular electricfield on the southern hemisphere, where Polar flies within or below theacceleration region, and we found a large number of inverted-V-type signaturesas expected from previous studies. To explain the lack of perpendicular electricfields at high altitudes we suggest an O-shaped potential model instead of theU-shaped one. Key words. Ionosphere (particle acceleration) ·Magnetospheric physics (auroral phenomena; magnetosphere · ionosphereinteractions

How does the U-shaped potential close above the acceleration region? A study using Polar data