Density and temperature of energetic electrons in the Earth's magnetotail derived from high-latitude GPS observations during the declining phase of the solar cycle

Abstract

Abstract. Single relativistic-Maxwellian fits are made to high-latitude GPS-satellite observations of energetic electrons for the period January 2006-November 2010; a constellation of 12 GPS space vehicles provides the observations. The derived fit parameters (for energies ∼0.1-1.0 MeV), in combination with field-line mapping on the nightside of the magnetosphere, provide a survey of the energetic electron density and temperature distribution in the magnetotail between McIlwain L-values of L = 6 and L = 22. Analysis reveals the characteristics of the density-temperature distribution of energetic electrons and its variation as a function of solar wind speed and the Kp index. The density-temperature characteristics of the magnetotail energetic electrons are very similar to those found in the outer electron radiation belt as measured at geosynchronous orbit. The energetic electron density in the magnetotail is much greater during increased geomagnetic activity and during fast solar wind. The total electron density in the magnetotail is found to be strongly correlated with solar wind speed and is at least a factor of two greater for high-speed solar wind (V SW = 500-1000 km s −1 ) compared to low-speed solar wind (V SW = 100-400 km s −1 ). These results have important implications for understanding (a) how the solar wind may modulate entry into the magnetosphere during fast and slow solar wind, and (b) if the magnetotail is a source or a sink for the outer electron radiation belt.

Quantifying the effect of magnetopause shadowing on electron radiation belt dropouts

“…Energetic electrons are measured by two subsystems: the low-energy particle (LEP) subsystem resolves 0.14 to > 1.25 MeV electrons into five energy channels; the highenergy X-ray and particle (HXP) subsystem resolves 1.3 to > 5.8 MeV electrons into six energy channels (see also Denton and Cayton, 2011). The CXD electron count rates are inverted to obtain the omni-directional differential number flux, j , by solving the spectral inversion function (Ginet et al, 2013) …”

Inner magnetospheric heavy ion composition during high‐speed stream‐driven storms

“…The number density of O + ions could only be calculated using ions above energy 54.6 keV as O + ions below this energy could not penetrate the surface barrier of the solid state detector. Hence, all “density” measurements discussed below are more correctly “partial densities.” However, examination of the partial number density of electrons in the outer radiation belt and magnetotail, as opposed to simply observing the flux, have previously provided an alternative view of the dropout phenomena, and subsequent recovery [ Cayton et al ., ; Denton et al ., ; Borovsky and Cayton , ; Denton and Cayton , ; D. P. Hartley et al, Case studies of dropouts in the electron radiation belt: Flux, magnetic field, and phase space density, submitted to J. Geophys. Res ., 2013].…”

Energetic Particle Data From the Global Positioning System Constellation

“…Though the LANL‐GPS electron data have not been widely available until now, electron data from GPS have previously been used by several authors [see Friedel et al , ; Morley et al , , for further details]. These data have been used to examine substorm injections [ Lugo‐Solis et al , ], radiation belt dropouts [ Morley et al , , ; Yu et al , ], magnetotail plasma properties [ Borovsky and Cayton , ; Denton and Cayton , ], and for data assimilative modeling of the radiation belts [ Bourdarie et al , ; Reeves et al , ]. These topics show the broad range of potential applications for the newly available energetic electron data.…”