Spatial localization and ducting of EMIC waves: Van Allen Probes and ground‐based observations

Mann, I. R.; Usanova, Maria; Murphy, K. R.; Robertson, Matthew; Milling, D. K.; Kale, A.; Kletzing, C. A.; Wygant, J. R.; Thaller, S. A.; Raita, Tero

doi:10.1002/2013gl058581

Cited by 45 publications

(57 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The precipitation spikes in the POES data are very narrowly defined in IGRF L with each event typically occurring across an L shell range of around 0.3 L, consistent with previously published case studies, e.g., Mann et al []. We are therefore able to use the L shell location of the POES‐observed precipitation spikes to calculate the ion gyrofrequencies at the IGRF‐determined geomagnetic equator for the POES trigger locations.…”

Section: Database Analysissupporting

confidence: 84%

Confirmation of EMIC wave‐driven relativistic electron precipitation

et al. 2016

View full text Add to dashboard Cite

Electromagnetic ion cyclotron (EMIC) waves are believed to be an important source of pitch angle scattering driven relativistic electron loss from the radiation belts. To date, investigations of this precipitation have been largely theoretical in nature, limited to calculations of precipitation characteristics based on wave observations and small‐scale studies. Large‐scale investigation of EMIC wave‐driven electron precipitation has been hindered by a lack of combined wave and precipitation measurements. Analysis of electron flux data from the POES (Polar Orbiting Environmental Satellites) spacecraft has been suggested as a means of investigating EMIC wave‐driven electron precipitation characteristics, using a precipitation signature particular to EMIC waves. Until now the lack of supporting wave measurements for these POES‐detected precipitation events has resulted in uncertainty regarding the driver of the precipitation. In this paper we complete a statistical study comparing POES precipitation measurements with wave data from several ground‐based search coil magnetometers; we further present a case study examining the global nature of this precipitation. We show that a significant proportion of the precipitation events correspond with EMIC wave detections on the ground; for precipitation events that occur directly over the magnetometers, this detection rate can be as high as 90%. Our results demonstrate that the precipitation region is often stationary in magnetic local time, narrow in L, and close to the expected plasmapause position. Predominantly, the precipitation is associated with helium band rising tone Pc1 waves on the ground. The success of this study proves the viability of POES precipitation data for investigating EMIC wave‐driven electron precipitation.

show abstract

Section: Database Analysissupporting

confidence: 84%

Confirmation of EMIC wave‐driven relativistic electron precipitation

et al. 2016

View full text Add to dashboard Cite

show abstract

“…We examine a long-lasting EMIC wave event from 11 October 2012, which occurred in the recovery of a moderate geomagnetic storm (with minimum Dst = À111 nT on 9 October). Continuous EMIC activity was observed on the ground by multiple CARISMA stations for more than 18 h (see accompanying paper by Mann et al [2014] for more details).…”

Section: Long-lasting Emic Wave Event On 11 October 2012mentioning

confidence: 99%

“…Continuous EMIC activity was observed on the ground by multiple CARISMA stations for more than 18 h (see accompanying paper by Mann et al . [] for more details).…”

Section: Observationsmentioning

confidence: 99%

Effect of EMIC waves on relativistic and ultrarelativistic electron populations: Ground‐based and Van Allen Probes observations

Usanova

Drozdov

Orlova

et al. 2014

Geophysical Research Letters

Self Cite

331

405

View full text Add to dashboard Cite

We study the effect of electromagnetic ion cyclotron (EMIC) waves on the loss and pitch angle scattering of relativistic and ultrarelativistic electrons during the recovery phase of a moderate geomagnetic storm on 11 October 2012. The EMIC wave activity was observed in situ on the Van Allen Probes and conjugately on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity throughout an extended 18 h interval. However, neither enhanced precipitation of >0.7 MeV electrons nor reductions in Van Allen Probe 90°pitch angle ultrarelativistic electron flux were observed. Computed radiation belt electron pitch angle diffusion rates demonstrate that rapid pitch angle diffusion is confined to low pitch angles and cannot reach 90°. For the first time, from both observational and modeling perspectives, we show evidence of EMIC waves triggering ultrarelativistic (~2-8 MeV) electron loss but which is confined to pitch angles below around 45°and not affecting the core distribution.

show abstract

“…Relatively high amplitude chorus whistler mode waves are pervasive at GEO, which should generally make their resonant scattering of electrons one of the dominant processes. EMIC waves are most frequently observed during disturbed periods (such as the main phase of storms), near the plasmapause, or in regions of strongly decreasing plasma density less than one Earth radius away from the compressed plasmasphere, or (but seemingly more rarely) near the edge of plasmaspheric plumes formed during storms [e.g., see Thorne and Kennel, 1971;Carson et al, 2013;Usanova et al, 2013;Mann et al, 2014;Usanova et al, 2014, and references therein]. In contrast, our flux decays are measured only during rather moderately disturbed periods (recovery phase) at GEO.…”

Section: Comparison With Analytical Lifetimes For Chorus-induced Lossesmentioning

confidence: 99%

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus‐driven losses

2014

View full text Add to dashboard Cite

The population of electrons in the Earth's outer radiation belt increases when the magnetosphere is exposed to high-speed streams of solar wind, coronal mass ejections, magnetic clouds, or other disturbances. After this increase, the number of electrons decays back to approximately the initial population. This study statistically analyzes the lifetimes of the electron at Geostationary Earth Orbit (GEO) from Los Alamos National Laboratory electron flux data. The decay rate of the electron fluxes are calculated for 14 energies ranging from 24 keV to 3.5 MeV to identify a relationship between the lifetime and energy of the electrons. The statistical data show that electron lifetimes increase with energy. Also, the statistical results show a good agreement up to ∼1 MeV with an analytical model of lifetimes, where electron losses are caused by their resonant interaction with oblique chorus waves, using average wave intensities obtained from Cluster statistics. However, above 500 keV, the measured lifetimes increase with energy becomes less steep, almost stopping. This could partly stem from the difficultly of identifying lifetimes larger than 10 days, for high energy, with the methods and instruments of the present study at GEO. It could also result from the departure of the actual geomagnetic field from a dipolar shape, since a compressed field on the dayside should preferentially increase chorus-induced losses at high energies. However, during nearly quiet geomagnetic conditions corresponding to lifetime measurement periods, it is more probably an indication that outward radial diffusion imposes some kind of upper limit on lifetimes of high-energy electrons near geostationary orbit.

show abstract

Spatial localization and ducting of EMIC waves: Van Allen Probes and ground‐based observations

Cited by 45 publications

References 36 publications

Confirmation of EMIC wave‐driven relativistic electron precipitation

Confirmation of EMIC wave‐driven relativistic electron precipitation

Effect of EMIC waves on relativistic and ultrarelativistic electron populations: Ground‐based and Van Allen Probes observations

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus‐driven losses

Contact Info

Product

Resources

About