In situ statistical observations of Pc1 pearl pulsations and unstructured EMIC waves by the Van Allen Probes

Paulson, K. W.; Smith, Charles W.; Lessard, M.; Torbert, R. B.; Kletzing, C. A.; Wygant, J. R.

doi:10.1002/2016ja023160

Cited by 28 publications

(40 citation statements)

References 56 publications

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“…The frequency range of the fine‐structured EMIC wave is observed to be approximately constant and is not confined between the equatorial ion cyclotron frequencies. This is consistent with that observed in previous reports (e.g., Paulson et al, ) and indicates that the waves are generated by a mechanism that is different from that of local ion cyclotron instability. The wave intensity was about 10 −3 mV 2 /m 2 /Hz, which is relatively small compared to typical EMIC waves observed in the inner magnetosphere.…”

Section: Observationssupporting

confidence: 93%

“…Paulson et al () also discriminated the observed EMIC waves based on the structures of their spectra, and they found that the local‐time distributions of unstructured and fine‐structured EMIC waves are different. They pointed out that the observed fine‐structured EMIC waves have no distinct local‐time dependence in the equatorial plane.…”

Section: Introductionmentioning

confidence: 99%

“…Comparing these statistical results shows that the distribution of EMIC waves in the inner magnetosphere depends on the L shell and the magnetic local time (MLT) as well as on the magnetic latitude (MLAT). Paulson et al (2017) also discriminated the observed EMIC waves based on the structures of their spectra, and they found that the local-time distributions of unstructured and fine-structured EMIC waves are different. They pointed out that the observed fine-structured EMIC waves have no distinct local-time dependence in the equatorial plane.…”

Section: Introductionmentioning

confidence: 99%

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Spatial Distribution of Fine‐Structured and Unstructured EMIC Waves Observed by the Arase Satellite

Matsuda

Kasahara

Miyoshi

et al. 2018

Geophysical Research Letters

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We surveyed 378 electromagnetic ion cyclotron (EMIC) wave events using Arase during the first 12 months. We discriminated the observed EMIC waves into two types (fine‐structured EMIC waves and unstructured EMIC waves), according to whether or not they exhibited clear periodic amplitude modulations. We found a clear afternoon peak in the occurrence probability of unstructured EMIC waves in the region of L = 5–9. Fine‐structured EMIC waves were mainly distributed in the off‐equatorial region, and their occurrence probability was clearly high around the noon sector. Such noon sector EMIC wave peaks had not been found in the THEMIS, AMPTE, or Cluster measurements, due to their limited L shell coverages. The Van Allen probes, too, were not able to measure the major region of fine‐structured EMIC waves because of their limited latitudinal coverage. Our unique statistical results demonstrate the importance of discriminating the wave structures as well as of performing observations over a wide range of latitudes.

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Section: Observationssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial Distribution of Fine‐Structured and Unstructured EMIC Waves Observed by the Arase Satellite

Matsuda

Kasahara

Miyoshi

et al. 2018

Geophysical Research Letters

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“…Figures c and d present structured H + band EMIC waves from 1118 to 1210 UT, representing a long duration event. These structured EMIC waves are called “pearl structures” (e.g., Jun et al, , ; Paulson et al, ) that have often been observed during quiet geomagnetic conditions in the morning sector within the inner magnetosphere (Paulson et al, ). During this EMIC event, we can see a clear H + flux enhancement at 0.1–1 keV (Figure e).…”

Section: Observationsmentioning

confidence: 99%

A Statistical Study of EMIC Waves Associated With and Without Energetic Particle Injection From the Magnetotail

et al. 2019

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To understand the relationship between generation of electromagnetic ion cyclotron (EMIC) waves and energetic particle injections, we performed a statistical study of EMIC waves associated with and without injections based on the Van Allen Probes (Radiation Belt Storm Probes) and Geostationary Operational Environmental Satellite (GOES; GOES‐13 and GOES‐15) observations. Using 47 months of observations, we identified wave events seen by the Van Allen Probes relative to the plasmapause and to energetic particle injections seen by GOES‐13 and GOES‐15 on the nightside. We separated the events into four categories: EMIC waves with (without) injections inside (outside) the plasmasphere. We found that He+ EMIC waves have higher occurrence rate inside the plasmasphere, while H+ EMIC waves predominantly occur outside the plasmasphere. Meanwhile, the time duration and peak occurrence rate of EMIC waves associated with injections are shorter and limited to a narrower magnetic local time region than those without injections, indicating that these waves have localized source regions. He+ EMIC waves inside the plasmasphere associated with injection are usually accompanied by an increase in H+ flux within energies of 1–50 keV through all magnetic local time regions, while most wave events outside the plasmasphere show less relationship with H+ flux increase. From these observations, we suggest that injected hot ions are the major driver of He+ EMIC waves inside the plasmasphere during active time. Expanding plasmasphere during quiet times can provide broad wave source regions for He+ EMIC waves on the dayside. However, H+ EMIC waves outside the plasmasphere show different characteristics, suggesting that these waves are generated by other processes.

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“…This event does not belong to the class of “pearl” events identified by Paulson et al . [, ] in that it does not show any periodic temporal modulation. Nevertheless, it is similar to them in that those events at times exhibited a nearly constant frequency across L shells.…”

Section: Examples Sorted By Storm Phasementioning

confidence: 99%

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

et al. 2017

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We have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from −1 to +2 RE relative to the PP. Very few events occurred only within 0.1 RE of the PP, and events with a width in L of < 0.2 RE occurred both inside and outside the PP. Wave occurrence was always associated with high densities of ring current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and compressions of the magnetosphere were more evenly distributed both inside and outside the PP. Superposed epoch analyses of the dependence of wave onset on solar wind dynamic pressure (Psw), the SME (SuperMAG auroral electrojet) index, and the SYM‐H index showed that substorm injections and solar wind compressions were temporally closely associated with EMIC wave onset but to an extent that varied with frequency band, magnetic local time, and storm phase, and location relative to the PP. The fact that increases in SME and Psw were less strongly correlated with events at the PP than with other events might suggest that the occurrence of those events was affected by the density gradient.

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In situ statistical observations of Pc1 pearl pulsations and unstructured EMIC waves by the Van Allen Probes

Cited by 28 publications

References 56 publications

Spatial Distribution of Fine‐Structured and Unstructured EMIC Waves Observed by the Arase Satellite

Spatial Distribution of Fine‐Structured and Unstructured EMIC Waves Observed by the Arase Satellite

A Statistical Study of EMIC Waves Associated With and Without Energetic Particle Injection From the Magnetotail

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

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