Abstract
AbstractDropouts in electron fluxes at L ∼ 4.2 were investigated for a broad range of energies from 120 keV to 10 MeV, using 16 years of electron flux data from Combined X‐ray Dosimeter on board Global Positioning System (GPS) satellites. Dropouts were defined as flux decreases by at least a factor 4 in 12 h, or 24 h during which a decrease by at least a factor of 1.5 must occur during each 12 h time bin. Such fast and strong dropouts were automatically identified from the GPS electron flux data and statistics of dropout magnitudes, and occurrences were compiled as a function of electron energy. Moreover, the Error Reduction Ratio analysis was employed to search for nonlinear relationships between electron flux dropouts and various solar wind and geomagnetic activity indices, in order to identify potential external causes of dropouts. At L ∼ 4.2, the main driving factor for the more numerous and stronger 1–10 MeV electron dropouts turns out to be the southward interplanetary magnetic field Bs, suggesting an important effect from precipitation loss due to combined electromagnetic ion cyclotron and whistler mode waves in a significant fraction of these events, supplementing magnetopause shadowing and outward radial diffusion which are also effective at lower energies.
Highlights
The outer radiation belt environment of the Earth consists of energetic electrons from ∼100 keV to ∼10 MeV, with flux levels that can vary by several orders of magnitude within a few hours and pose various threats to satellites (Welling, 2010; Wrenn, 1995)
Such fast and strong dropouts were automatically identified from the Global Positioning System (GPS) electron flux data and statistics of dropout magnitudes, and occurrences were compiled as a function of electron energy
The Error Reduction Ratio analysis was employed to search for nonlinear relationships between electron flux dropouts and various solar wind and geomagnetic activity indices, in order to identify potential external causes of dropouts
Summary
The outer radiation belt environment of the Earth consists of energetic electrons from ∼100 keV to ∼10 MeV, with flux levels that can vary by several orders of magnitude within a few hours (e.g., see Baker et al, 1986; Li et al, 2017; Turner et al, 2013) and pose various threats to satellites (Welling, 2010; Wrenn, 1995). Once the magnetopause recovers to the precompression shape, there will be a higher electron Phase Space Density (PSD) closer to the Earth than farther away, where the electrons have just been lost. This spatial gradient in PSD leads to a fast outward radial diffusion of electrons from the region of high PSD to the region where electrons have just been lost. This results in a loss of electrons coming progressively closer to the Earth as electrons diffuse radially toward higher Ls (Shprits et al, 2006; Turner et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
