SAMPEX observations of precipitation bursts in the outer radiation belt

Abstract

Abstract. The occurrence frequency of precipitation bursts of > 1 MeV electrons in the outer radiation belt is examined using data from the SAMPEX satellite. Electron burst characteristics shown in this paper include the dependence of the precipitation on magnetic local time, radial distance and geomagnetic activity. Precipitation bursts with timescales < 1 s, i.e., microbursts, are studied in detail, including their dependence on the phases of geomagnetic storms. It is found that precipitation bursts occur typically in the region between L = 4 and L = 6. Microbursts tend to occur at L lower than the bursts with timescales of several tens of seconds. The number of observed microbursts significantly increases during storms, appearing mainly in the morning sector early in the recovery phase of storms. These findings suggest that the microbursts may be due to interactions with electron whistler waves, which take place near the dawnside plasmapause in the density irregularities that are perhaps created in the "recovering" plasmasphere. The prevalence of bursty precipitation indicates that this enhanced loss component of the relativistic electron flux should be taken into account in any quantitative model of relativistic electron acceleration processes.

Science Objectives and Rationale for the Radiation Belt Storm Probes Mission

“…One of the most intriguing phenomena related to Earth's radiation belts are the so-called microbursts observed at low altitudes (Nakamura et al 2000;Lorentzen et al 2001). In the case of the features shown in Since microbursts occur in the dawn-morning quadrant (O'Brien et al 2004), where chorus/whistler waves are active (Fig.…”

The Balloon Array for RBSP Relativistic Electron Losses (BARREL)

“…Microbursts were later shown to extend to relativistic energies (Imhof et al 1992), and studied extensively with data from the SAMPEX satellite (e.g., Blake et al 1996;Nakamura et al 2000;). The top panel of Fig.…”

Short-duration Electron Precipitation Studied by Test Particle Simulation

“…The timescales of chorus waves are similar to those of electron microbursts, and the coincident occurrence of microbursts and VLF chorus waves supports the idea that microbursts are produced by resonant interactions between electrons and cyclotron waves (Rosenberg et al 1981). Imhof et al (1992) and Nakamura et al (2000) reported observations of impulsive electron precipitations with energies exceeding 1 MeV by spacecraft; these precipitations were named relativistic microbursts. However, relativistic microbursts have not been observed by balloon-borne experiments, and at this time it is unknown whether these microburst phenomena are related or originate from the same source.…”