Plasma wave interactions with energetic ions near the magnetic equator

Gurnett, D. A.

doi:10.1029/ja081i016p02765

Cited by 181 publications

(197 citation statements)

References 17 publications

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“…Our results suggest an analogy with natural emissions of whistler-mode chorus (generally observed above f lh ), which are also very intense, and which are believed to significantly influence the dynamics of the energetic electrons in the Earth's outer radiation belt (Meredith et al, 2003;Horne et al, 2003;Horne and Thorne, 2003). According to the most accepted generation mechanism of equatorial noise (Gurnett, 1976;Perraut et al, 1982), its amplification is fed by the free energy in the distribution functions of energetic ions, which may be significantly influenced by interactions with these waves.…”

Section: Discussionmentioning

confidence: 83%

“…Later observations (Gurnett, 1976;Perraut et al, 1982;Laakso et al, 1990;Kasahara et al, 1994;André et al, 2002) revealed that the equatorial noise occurs at radial distances between 2 and 7 R E , and at latitudes within 10 • from the magnetic equator, and that its lowest frequency could go down to the fundamental f H + . Detailed time-frequency spectrograms (Gurnett, 1976) also showed that, what appears as a noise band in the low resolution data, is in fact a superposition of many spectral lines with different frequency spacings.…”

Section: Introductionmentioning

confidence: 99%

“…The term "equatorial noise" is, however, still used even for these discrete wave phenomena, to indicate the connection to the original observations of Russell et al (1970). The generation mechanism of these waves is most probably connected to the ion-cyclotron harmonic interaction (Gurnett, 1976), with energetic protons having ring-like distribution functions at a pitch angle of 90 • (Perraut et al, 1982). After being generated at the ion Bernstein wave-mode branches, the waves subsequently propagate in the electromagnetic whistler mode (also known as the extraordinary or fast magnetosonic mode).…”

Section: Introductionmentioning

confidence: 99%

“…Detailed time-frequency spectrograms (Gurnett, 1976) also showed that, what appears as a noise band in the low resolution data, is in fact a superposition of many spectral lines with different frequency spacings. The term "equatorial noise" is, however, still used even for these discrete wave phenomena, to indicate the connection to the original observations of Russell et al (1970).…”

Section: Introductionmentioning

confidence: 99%

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Systematic analysis of equatorial noise below the lower hybrid frequency

et al. 2004

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Abstract.We report results of a systematic analysis of a large number of observations of equatorial noise between the local proton cyclotron frequency and the local lower hybrid frequency. The analysis is based on the data collected by the STAFF-SA instruments on board the four Cluster spacecraft. The data set covers their first two years of measurement in the equatorial magnetosphere at radial distances between 3.9 and 5 Earth radii. Inspection of 781 perigee passages shows that the occurrence rate of equatorial noise is approximately 60%. We identify equatorial noise by selecting data with nearly linearly polarized magnetic field fluctuations. These waves are found within 10 • of the geomagnetic equator, consistent with the published past observations. Our results show that equatorial noise has the most intense magnetic field fluctuations among all the natural emissions in the given interval of frequencies and latitudes. Electric field fluctuations of equatorial noise are also more intense compared to the average of all detected waves. Equatorial noise thus can play a non-negligible role in the dynamics of the internal magnetosphere.

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Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Systematic analysis of equatorial noise below the lower hybrid frequency

et al. 2004

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“…Gurnett [1976] analyzed equatorial crossings in the region 2 < L < 3.5 and found that the waves were largely confined to within 5°of the magnetic equatorial plane. These waves are excluded from our survey by excluding emissions observed within ±5°of the magnetic equator.…”

Section: Identification Of Plasmaspheric Hiss and Lightning Generatedmentioning

confidence: 99%

Slot region electron loss timescales due to plasmaspheric hiss and lightning‐generated whistlers

et al. 2007

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[1] Energetic electrons (E > 100 keV) in the Earth's radiation belts undergo Dopplershifted cyclotron resonant interactions with a variety of whistler mode waves leading to pitch angle scattering and subsequent loss to the atmosphere. In this study we assess the relative importance of plasmaspheric hiss and lightning-generated whistlers in the slot region and beyond. Electron loss timescales are determined using the Pitch Angle and energy Diffusion of Ions and Electrons (PADIE) code with global models of the spectral distributions of the wave power based on CRRES observations. Our results show that plasmaspheric hiss propagating at small and intermediate wave normal angles is a significant scattering agent in the slot region and beyond. In contrast, plasmaspheric hiss propagating at large wave normal angles and lightning-generated whistlers do not contribute significantly to radiation belt loss. The loss timescale of 2 MeV electrons due to plasmaspheric hiss propagating at small and intermediate wave normal angles in the center of the slot region (L = 2.5) lies in the range 1-10 days, consistent with recent Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) observations. Wave turbulence in space, which is responsible for the generation plasmaspheric hiss, thus leads to the formation of the slot region. During active periods, losses due to plasmaspheric hiss may occur on a timescale of 1 day or less for a wide range of energies, 200 keV < E < 1 MeV, in the region 3.5 < L < 4.0. Plasmaspheric hiss may thus also be a significant loss process in the inner region of the outer radiation belt during magnetically disturbed periods.Citation: Meredith, N. P., R. B. Horne, S. A. Glauert, and R. R. Anderson (2007), Slot region electron loss timescales due to plasmaspheric hiss and lightning-generated whistlers,

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Extremely intense ELF magnetosonic waves: A survey of polar observations

et al. 2014

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A Polar magnetosonic wave (MSW) study was conducted using 1 year of 1996-1997 data (during solar minimum). Waves at and inside the plasmasphere were detected at all local times with a slight preference for occurrence in the midnight-postmidnight sector. Wave occurrence (and intensities) peaked within~±5°of the magnetic equator, with half maxima at~±10°. However, MSWs were also detected as far from the equator as +20°and 60°MLAT but with lower intensities. An extreme MSW intensity event of amplitude B w =~± 1 nT and E w =~± 25 mV/m was detected. This event occurred near local midnight, at the plasmapause, at the magnetic equator, during an intense substorm event, e.g., a perfect occurrence. These results support the idea of generation by protons injected from the plasma sheet into the midnight sector magnetosphere by substorm electric fields. MSWs were also detected near noon (1259 MLT) during relative geomagnetic quiet (low AE). A possible generation mechanism is a recovering/expanding plasmasphere engulfing preexisting energetic ions, in turn leading to ion instability. The wave magnetic field components are aligned along the ambient magnetic field direction, with the wave electric components orthogonal, indicating linear wave polarization. The MSW amplitudes decreased at locations further from the magnetic equator, while transverse whistler mode wave amplitudes (hiss) increased. We argue that intense MSWs are always present somewhere in the magnetosphere during strong substorm/convection events. We thus suggest that modelers use dynamic particle tracing codes and the maximum (rather than average) wave amplitudes to simulate wave-particle interactions.

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Plasma wave interactions with energetic ions near the magnetic equator

Cited by 181 publications

References 17 publications

Systematic analysis of equatorial noise below the lower hybrid frequency

Systematic analysis of equatorial noise below the lower hybrid frequency

Slot region electron loss timescales due to plasmaspheric hiss and lightning‐generated whistlers

Extremely intense ELF magnetosonic waves: A survey of polar observations

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