Abstract
Abstract. Within the last two solar cycles (from 2001 to 2018), the location of the outer radiation belt (ORB) was determined using NOAA/Polar-orbiting Operational Environmental Satellite (POES) observations of energetic electrons with energies above 30 keV. It was found that the ORB was shifted a little (∼1∘) in the European and North American sectors, while in the Siberian sector the ORB was displaced equatorward by more than 3∘. The displacements corresponded qualitatively to the change in the geomagnetic field predicted by the IGRF-12 model. However, in the Siberian sector, the model has a tendency to underestimate the equatorward shift of the ORB. The shift became prominent after 2012, which might have been related to a geomagnetic “jerk” that occurred in 2012–2013. The displacement of the ORB to lower latitudes in the Siberian sector can contribute to an increase in the occurrence rate of midlatitude auroras observed in the Eastern Hemisphere.
Highlights
The outer radiation belt (ORB) is populated by energetic and relativistic electrons trapped in the magnetosphere at drift shells above L ∼ 3 (e.g., Ebihara and Miyoshi, 2011)
Magnetic storms are produced by interplanetary coronal mass ejecta (ICME) and high-speed streams (HSS) of the solar wind from coronal holes
Energetic electrons in energy ranges > 30, > 100 and > 300 keV are measured at lowearth orbit (LEO) by the Medium Energy Proton and Electron Detector (MEPED) instruments on board the NOAA/Polar-orbiting Operational Environmental Satellite (POES) satellites (Evans and Greer, 2004; Asikainen and Mursula, 2013)
Summary
The outer radiation belt (ORB) is populated by energetic and relativistic electrons trapped in the magnetosphere at drift shells above L ∼ 3 (e.g., Ebihara and Miyoshi, 2011). The ORB is very dynamic and exhibits variations in a wide temporal range: short-term storm-time and local-time variations, 27 d solar rotation, and seasonal and solar cycle variations (e.g., Li et al, 2001; Baker and Kanekal, 2008; Miyoshi and Kataoka, 2011). The ORB manifests prominent variations with the solar cycle (Fung et al, 2006; Baker and Kanekal, 2008): it has been shown that the ORB maximum is mostly distant from the Earth during solar minima (Miyoshi et al, 2004) and is closest to the Earth during solar maxima (Glauert et al, 2018)
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