Enhanced pitch angle scattering of protons at mid-latitudes during geomagnetic storms

Søraas, F.; Aarsnes, K.; Lundblad, J.Å.; Evans, David S.

doi:10.1016/s1464-1917(98)00041-5

Cited by 30 publications

(46 citation statements)

References 12 publications

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“…In contrast to Søraas et al (1999), who found the enhancement of the > 300 keV electrons associated with proton precipitation bursts only during the main phase of a geomagnetic storm, we detected the electron precipitations at energies > 30 keV in 44% of the Type 1 events (occurring mainly during the late recovery phase and quiet conditions) and in more than 80% of the Type 2 events, which occur during early recovery. It was suggested (Thorne and Kennel, 1971) that ion cyclotron waves can precipitate the relativistic electrons (E ≈ 1 MeV), but this theory is hardly applicable to the 30-keV particles. Nevertheless, the fact that proton and electron precipitation may be coincident explains the experimental result by Pikkarainen et al (1986), who found the correlation between the IPDP events and riometer absorption, which is evidently due to energetic electron precipitation.…”

Section: Discussioncontrasting

confidence: 99%

“…1 in Yahnina et al, 2000). Søraas et al (1999) concluded that localised enhancements of precipitating protons that were observed during the main phase of the geomagnetic storms occurred in the evening sector. The enhancements during the main phase were often associated with precipitation of energetic electrons.…”

Section: Discussionmentioning

confidence: 97%

“…These authors established the main morphological characteristics of the phenomenon, including the latitudinal width of the flux enhancements, their dependence on the geomagnetic storms, the MLT dependence, etc. Lunblad and Søraas (1978) and Søraas et al (1999) noted the correlation of the enhancements (mainly in the locally trapped flux) with observations of the SAR arcs, while Yahnina et al stressed the relationship between the localised energetic proton precipitation and structured Pc1 pulsations seen on the ground. Note that Yahnina et al (2000Yahnina et al ( , 2002 considered the precipitation pattern just the same as the Type 1 events described here (without precipitating low energy fluxes measured by the TED instrument, see, for example, Fig.…”

Section: Discussionmentioning

confidence: 98%

“…As mentioned in the Introduction, some features of the localised enhancements of the energetic proton flux at low altitudes have been studied by Lundblad and Søraas (1978), Søraas et al (1999), Yahnina et al (1998Yahnina et al ( , 2000Yahnina et al ( , 2002. These authors established the main morphological characteristics of the phenomenon, including the latitudinal width of the flux enhancements, their dependence on the geomagnetic storms, the MLT dependence, etc.…”

Section: Discussionmentioning

confidence: 99%

“…Some features of the localised enhancements of energetic proton fluxes (not only precipitating, but mainly locally mirroring) have been discussed by Lundblad and Søraas (1978) on the basis of the ESRO-1 satellite data and more recently by Søraas et al (1999) on the basis of the NOAA-6 satellite data. However, these authors did not correlate these enhancements with Pc1.…”

Section: Introductionmentioning

confidence: 99%

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Energetic particle counterparts for geomagnetic pulsations of Pc1 and IPDP types

Yahnina

Yahnin

Kangas³

et al. 2003

Ann. Geophys.

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Abstract. Using the low-altitude NOAA satellite particle data, we study two kinds of localised variations of energetic proton fluxes at low altitude within the anisotropic zone equatorward of the isotropy boundary. These flux variation types have a common feature, i.e. the presence of precipitating protons measured by the MEPED instrument at energies more than 30 keV, but they are distinguished by the fact of the presence or absence of the lower-energy component as measured by the TED detector on board the NOAA satellite. The localised proton precipitating without a lowenergy component occurs mostly in the morning-day sector, during quiet geomagnetic conditions, without substorm injections at geosynchronous orbit, and without any signatures of plasmaspheric plasma expansion to the geosynchronous distance. This precipitation pattern closely correlates with ground-based observations of continuous narrow-band Pc1 pulsations in the frequency range 0.1-2 Hz (hereafter Pc1). The precipitation pattern containing the low energy component occurs mostly in the evening sector, under disturbed geomagnetic conditions, and in association with energetic proton injections and significant increases of cold plasma density at geosynchronous orbit. This precipitation pattern is associated with geomagnetic pulsations called Intervals of Pulsations with Diminishing Periods (IPDP), but some minor part of the events is also related to narrow-band Pc1. Both Pc1 and IPDP pulsations are believed to be the electromagnetic ion-cyclotron waves generated by the ion-cyclotron instability in the equatorial plane. These waves scatter energetic protons in pitch angles, so we conclude that the precipitation patterns studied here are the particle counterparts of the ion-cyclotron waves.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Energetic particle counterparts for geomagnetic pulsations of Pc1 and IPDP types

Yahnina

Yahnin

Kangas³

et al. 2003

Ann. Geophys.

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The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

Borovsky

Cayton²,

Denton

et al. 2016

JGR Space Physics

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The outer proton radiation belt (OPRB) and outer electron radiation belt (OERB) at geosynchronous orbit are investigated using a reanalysis of the LANL CPA (Charged Particle Analyzer) 8‐satellite 2‐solar cycle energetic particle data set from 1976 to 1995. Statistics of the OPRB and the OERB are calculated, including local time and solar cycle trends. The number density of the OPRB is about 10 times higher than the OERB, but the 1 MeV proton flux is about 1000 times less than the 1 MeV electron flux because the proton energy spectrum is softer than the electron spectrum. Using a collection of 94 high‐speed stream‐driven storms in 1976–1995, the storm time evolutions of the OPRB and OERB are studied via superposed epoch analysis. The evolution of the OERB shows the familiar sequence (1) prestorm decay of density and flux, (2) early‐storm dropout of density and flux, (3) sudden recovery of density, and (4) steady storm time heating to high fluxes. The evolution of the OPRB shows a sudden enhancement of density and flux early in the storm. The absence of a proton dropout when there is an electron dropout is noted. The sudden recovery of the density of the OERB and the sudden density enhancement of the OPRB are both associated with the occurrence of a substorm during the early stage of the storm when the superdense plasma sheet produces a “strong stretching phase” of the storm. These storm time substorms are seen to inject electrons to 1 MeV and protons to beyond 1 MeV into geosynchronous orbit, directly producing a suddenly enhanced radiation belt population.

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Energetic Proton Spectra Measured by the Van Allen Probes

et al. 2017

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We test the hypothesis that pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves can limit ring current proton fluxes. For two chosen magnetic storms, during 17–20 March 2013 and 17–20 March 2015, we measure proton energy spectra in the region 3 ≤ L ≤ 6 using the RBSPICE‐B instrument on the Van Allen Probes. The most intense proton spectra are observed to occur during the recovery periods of the respective storms. Using proton precipitation data from the POES (NOAA and MetOp) spacecraft, we deduce that EMIC wave action was prevalent at the times and L‐shell locations of the most intense proton spectra. We calculate limiting ring current proton energy spectra from recently developed theory. Comparisons between the observed proton energy spectra and the theoretical limiting spectra show reasonable agreement. We conclude that the measurements of the most intense proton spectra are consistent with self‐limiting by EMIC wave scattering.

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Enhanced pitch angle scattering of protons at mid-latitudes during geomagnetic storms

Cited by 30 publications

References 12 publications

Energetic particle counterparts for geomagnetic pulsations of Pc1 and IPDP types

Energetic particle counterparts for geomagnetic pulsations of Pc1 and IPDP types

The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

Energetic Proton Spectra Measured by the Van Allen Probes

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