Behavior of MeV electrons at geosynchronous orbit during last two solar cycles

Abstract

[1] A comparison of MeV electron measurements at geosynchronous orbit, GEO, with solar wind shows that the MeV electron prediction model developed for GEO using data from the declining phase of solar cycle 22 (1995-1996) works well for the declining phase of solar cycle 23 (2006-2008), indicating that the MeV electron flux has a predictable and systematic response to the solar wind. The same comparison for solar maximum (2000)(2001)(2002)(2003) shows that the model works less well partly because it does not match the high flux cutoff seen in the data and partly because it does not reproduce the sudden drops in flux that occur when the magnetopause is close to GEO. The model also reproduces the nonlinear correlation of the solar wind speed with the log of the MeV electron flux seen at GEO. An examination of 15 yr of solar wind and the MeV electron data shows that geomagnetic activity driven by a southward orientation of the interplanetary magnetic field, IMF, is a necessary condition for MeV electron enhancements at GEO and that high-speed solar wind are not necessary. The reason that high-speed solar wind is almost always associated with the enhancement of MeV electrons is mainly because high-speed solar wind almost always has some southward components of the IMF.

Science Objectives and Rationale for the Radiation Belt Storm Probes Mission

“…SAMPEX revealed that the radiation belts change dramatically over multiple time scales for reasons that are not always readily apparent (Fig. 4;Baker et al 2004;Li et al 2011).…”

“…Electron intensity (color scale) versus magnetospheric L-parameter (vertical axis) versus time (horizontal axis) for 2-6 MeV electrons as measured by the low altitude, polar orbit SAMPEX mission for over an entire ∼11-year solar cycle (Baker et al 2004; these measurements have continued for a second solar cycle; see Li et al 2011) In parallel with the new findings and interest in the radiation belts of Earth, extraterrestrial planetary probes have revealed robust radiation belts at all of strongly magnetized planets, despite the huge differences between the respective planets and despite the huge differences in how the space environments of these different planets are powered (Mauk and Fox 2010, and references therein). The creation of trapped populations of relativistic and penetrating charged particles is clearly a universal characteristic of strongly magnetized space environments and not just a characteristic of the special conditions that prevail at Earth.…”

High‐speed solar wind with southward interplanetary magnetic field causes relativistic electron flux enhancement of the outer radiation belt via enhanced condition of whistler waves

“…[4] However, HSS events do not always lead to large flux enhancement [Kim et al, 2006;Li et al, 2011;Reeves et al, 2011], suggesting the involvement of other important solar wind parameters. Miyoshi and Kataoka [2008] conducted a superposed epoch analysis of MeV electrons at geosynchronous orbit about the 179 stream interface crossing events, which are precursor of the arrival of HSS events during solar cycle 23.…”

Electron radiation belt dynamics during magnetic storms and in quiet time

“…Sufficiently convincing arguments for the mechanism of electron dropout at the magnetopause have been put forward in [Dmitriev, Chao, 2003;Shprits et al, 2006, Millan, Thorne, 2007Kim et al, 2008;Saito et al, 2010;Matsumura et al, 2011;Turner et al, 2012;Hudson et al, 2014;Lazutin, 2016]. In the quasitrapping region, drift shells are not closed; on the night side, electrons drift with adiabatic invariants remaining unchanged to the morning magnetosphere-magnetopause boundary; protons, to the evening boundary (and vice versa on the dayside); then they go from the closed field lines to the turbulent magnetosheath.…”

“…Figure 6 shows that RB gets rid of such an overpopulation for a long time. Note that strong storms may result in the formation of additional energetic electron belts in the vicinity of the slot region, which also exist for months [Vernov et al, 1965;Kuznetsov, 1966;Logachev, Lazutin, 2012].…”