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/

Zendy Plus

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

Zendy Tools

Zendy Open

We investigate the characteristics of rapid geomagnetic variations at highlatitudes based on the occurrence of large time derivatives of the horizontalmagnetic field (dH/dt exceeding 1 nT s−1). Analysis of IMAGEmagnetometer data from North Europe in 1983–2010, covering more than twosolar cycles, confirms and specifies several previous findings. We show thatdH/dt activity is high around the midnight and early morninghours, and nearly vanishes at noon and early afternoon. This happens duringall seasons, although the midnight maximum is nearly invisible during summer.As indicated by modelled ionospheric equivalent currents, largedH/dt values occur predominantly during westward ionosphericelectrojets. Before and around midnight, dH/dt tends to benorth-south oriented, whereas in the morning hours, its direction is morewest-east directed. dH/dt tends to be more strictly north-southoriented during winter than other seasons. The seasonal occurrence of largedH/dt values is similar to the variation of the maximum amplitudeof westward equivalent currents. The yearly fraction of east-west directedlarge dH/dt vectors at the Kilpisjärvi station (MLAT 65.88) variesfrom 31 to 47 % without any clear correlation with the general geomagneticactivity nor with the yearly averages of solar wind parameters

Climatology of rapid geomagnetic variations at high latitudes over two solar cycles