X ray microbursts and VLF chorus

Roeder, J. L.; Benbrook, J. R.; Bering, E. A.; Sheldon, W. R.

doi:10.1029/ja090ia11p10975

Cited by 16 publications

(8 citation statements)

References 20 publications

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“…It is well established that subrelativistic microbursts are accompanied by chorus, although chorus can occur without generating microbursts [ Oliven and Gurnett , 1968; Parks , 1978; Rosenberg et al , 1981, 1990; Roeder et al , 1985; Torkar et al , 1987]. For electrons with energy of ∼100 keV, cyclotron resonant interactions with chorus can readily occur near the magnetic equator, with resonant energy increasing off the equator.…”

Section: Microburst Observationsmentioning

confidence: 99%

Energization of relativistic electrons in the presence of ULF power and MeV microbursts: Evidence for dual ULF and VLF acceleration

et al. 2003

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[1] We examine signatures of two types of waves that may be involved in the acceleration of energetic electrons in Earth's outer radiation belts. We have compiled a database of ULF wave power from SAMNET and IMAGE ground magnetometer stations for 1987-2001. Long-duration, comprehensive, in situ VLF/ELF chorus wave observations are not available, so we infer chorus wave activity from low-altitude SAMPEX observations of MeV electron microbursts for 1996-2001 since microbursts are thought to be caused by interactions between chorus and trapped electrons. We compare the ULF and microburst observations to in situ trapped electrons observed by high-altitude satellites from 1989-2001. We find that electron acceleration at low L shells is closely associated with both ULF activity and MeV microbursts and thereby probably also with chorus activity. Electron flux enhancements across the outer radiation belt are, in general, related to both ULF and VLF/ELF activity. However, we suggest that electron flux peaks observed at L $ 4.5 are likely caused by VLF/ELF wave acceleration, while ULF activity probably produces the dominant electron acceleration at geosynchronous orbit and beyond.

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Section: Microburst Observationsmentioning

confidence: 99%

Energization of relativistic electrons in the presence of ULF power and MeV microbursts: Evidence for dual ULF and VLF acceleration

et al. 2003

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“…The overlap of chorus and REP microburst maxima in the morning sector suggests the need for a detailed examination of chorus as the precipitating agent for at least some of the observed microburst REP events. Chorus has long been associated with lower-energy X-ray and electron microbursts through wave-particle interactions near the equator [Oliven and Gurnett, 1968;Parks, 1978;Rosenberg et al, 1981Rosenberg et al, , 1990Roeder et al, 1985;Torkar et al, 1987]. Other observations of higher-energy relativistic electron precipitation from balloon-borne X-ray detectors have also been associated with wave activity, although these observations did not display temporal structure with timescales as short as the typical microburst and found no correlation with ground-based chorus observations.…”

Section: Introduction Orbiting Satellites Bands Last > 1 S and Micrmentioning

confidence: 96%

Observations of relativistic electron microbursts in association with VLF chorus

Lorentzen¹,

Blake²,

Inan³

et al. 2001

J. Geophys. Res.

244

307

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Abstract.The Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite frequently observes relativistic (> 1 MeV) electron precipitation in the radiation belts at oe shells of 4-6 with bursty temporal structure lasting < 1 s. This phenomenon can occur at all local times but is most often seen between 0200 and 1000 magnetic local time. VLF chorus is also observed to occur preferentially at these same local times. Using electron observations from the SAMPEX satellite Heavy Ion Large Telescope and data from the Polar satellite plasma wave instrument, we show correlation between observations of relativistic electron microbursts and VLF chorus with frequencies <2 kHz. In addition, the duration of the individual rising frequency chorus elements is comparable to the duration of the relativistic electron microbursts. It has been speculated that relativistic electron microbursts are caused by wave-particle interactions, which strongly scatter electrons into the loss cone for a short period. Lower-energy electron microbursts in the range from tens to hundreds of keV have long been associated with chorus waves, since these lower-energy electrons can resonate at the equator with whistler-mode waves at chorus frequencies. Electrons of MeV energies do not satisfy the first-order cyclotron resonance condition with chorus wave frequencies at the equator. However, MeV electrons may interact with chorus through higher-order resonances or off-equatorial interactions.

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“…1,2 Apparently, it is the most important type of electromagnetic emssions in the magnetosphere, providing precipitation of bulk energetic electrons from radiation belts 3,4 and essentially contributing to the acceleration of MeV electrons. 5 At the same time, chorus emissions remain the most intriguing signals among natural ELF/VLF radiation.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of Cluster data on chorus emissions using the backward wave oscillator model

et al. 2004

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The measurements of chorus emissions by four closely separated Cluster spacecraft provide important information concerning the chorus generation mechanism. They confirm such properties of the wave source as their strong localization near the equatorial cross section of a magnetic flux tube, an almost parallel average wave-vector direction with respect to the geomagnetic field, and an energy flux direction pointing outward from the generation region. Inside this region, Cluster discovered strong temporal and spatial variations in the amplitude with correlation scale lengths of the order of 100 km across the magnetic flux. The wave electric field reached 30 mV/m, and the maximum growth and damping rates are of the order of a few hundreds of s−1. These and other properties of the detected chorus emissions are discussed here in relation with the backward wave oscillator mechanism. According to this mechanism, a succession of whistler wave packets is generated in a small near-equatorial region with temporal and spatial characteristics close to the Cluster data. Amplitudes and frequency spectra, as well as dynamical features of the Poynting flux of chorus are estimated and compared with the Cluster measurements.

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X ray microbursts and VLF chorus

Cited by 16 publications

References 20 publications

Energization of relativistic electrons in the presence of ULF power and MeV microbursts: Evidence for dual ULF and VLF acceleration

Energization of relativistic electrons in the presence of ULF power and MeV microbursts: Evidence for dual ULF and VLF acceleration

Observations of relativistic electron microbursts in association with VLF chorus

Interpretation of Cluster data on chorus emissions using the backward wave oscillator model

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