Magnetic Perturbation Events (MPEs) that cause GICs: Investigating their
Interhemispheric Conjugacy and Control by IMF Orientation
Abstract
Nearly all studies of impulsive magnetic perturbation events (MPEs) that
can produce dangerous geomagnetically induced currents (GICs) have used
data from the northern hemisphere. In this study we investigated MPE
occurrences during the first 6 months of 2016 at four magnetically
conjugate high latitude station pairs using data from the Greenland West
Coast magnetometer chain and from Antarctic stations in the conjugate
AAL-PIP magnetometer chain. Events for statistical analysis and four
case studies were selected from Greenland/AAL-PIP data by detecting the
presence of >6 nT/s derivatives of any component of the
magnetic field at any of the station pairs. For case studies, these
chains were supplemented by data from the BAS-LPM chain in Antarctica as
well as Pangnirtung and South Pole in order to extend longitudinal
coverage to the west. Amplitude comparisons between hemispheres showed
a) a seasonal dependence (larger in the winter hemisphere), and b) a
dependence on the sign of the By component of the interplanetary
magnetic field (IMF): MPEs were larger in the north (south) when IMF
By was > 0 (< 0). A majority of events
occurred nearly simultaneously (to within ± 3 min) independent of the
sign of By as long as |By| ≤ 2
|Bz|. As has been found in earlier studies, IMF
Bz was < 0 prior to most events. When IMF data from
Geotail, Themis-B, and/or Themis C in the near-Earth solar wind were
used to supplement the time-shifted OMNI IMF data, the consistency of
these IMF orientations was improved.