Radial distributions of equatorial phase space density for outer radiation belt electrons

Abstract

[1] We present the first direct observations of equatorial electron phase space density (PSD) as a function of the three adiabatic invariants throughout the outer radiation belt using data from the Solid State Telescopes on THEMIS-D. We estimate errors in PSD that result from data fitting and uncertainty in the calculation of the second and third invariants based on performance-weighted results from seven different magnetic field models. The PSD gradients beyond geosynchronous orbit (GEO) are energy dependent, revealing different source regions for the relativistic and non-relativistic populations. Specifically, the PSD distribution of outer belt relativistic electrons is peaked near L* ≈ 5.5. These features are typical for the outer belt, based on a survey of a two-month period from 01 Feb.-31 Mar. 2010. The results are consistent with previous studies, which were based on off-equatorial observations, but remove the high uncertainties introduced from mapping by using truly equatorial measurements (i.e., within only a few degrees of the magnetic equator) and quantifying the error in PSD. The newly calibrated THEMIS-SST dataset forms a powerful tool for exploration of the near-Earth magnetosphere, especially when combined with the upcoming RBSP mission. Citation: Turner, D. L., V.

Prompt enhancement of the Earth's outer radiation belt due to substorm electron injections

“…For the fixed K = 0.11 G 1/2 R E , the electron pitch angle range is from about 40°to 90°along the drift orbit. RBSP-A observed that the PSD for 700 MeV/G electrons at L *~5 was~1 × 10 À4 (c/MeV cm) 3 , which is comparable to that reported by Turner et al [2012a], because the radial transport process usually corresponds to the higher electron PSDs at larger radial distance. Such uncertainty was considered to produce a small difference of the electron PSDs in Figure 5.…”

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

“…(8), df A is indeed proportional to dW A although their ratio (i.e., the pre-existing PSD gradient) depends on l (or equivalently, W) at any given location. Near geosynchronous orbit, the PSD radial gradient for equatoriallymirroring electrons is statistically shown to be positive (outward) at lower l values and positive (earthward) at higher l values (Turner et al 2012). However, the PSD gradient can be highly dynamic during active geomagnetic conditions (Chen et al 2007;Turner et al 2010).…”

Electron source at the outer boundary of the radiation belts: Storm time case

“…These averaged values are considerably higher than those found in the outer radiation belt. For example, Turner et al [2012] reported the PSD at L*~5 for 700 MeV/G electrons to be~1 Â 10 À4 (c/cm-MeV)…”

“…Therefore, it is questionable to use an average magnetic field model to investigate the drift paths of energetic electrons during dipolarization. As a result, the possibility of an external source contributing to the relativistic electrons in the outer radiation belt should not be discarded outright in spite of strong evidence for the importance of an internal source [Selesnick and Blake, 2000;Green and Kivelson, 2004;Fox et al, 2006;Chen et al, 2006Chen et al, , 2007Turner and Li, 2008;Turner et al, 2010Turner et al, , 2012.…”