EMIC waves observed at geosynchronous orbit under quiet geomagnetic conditions (<i>Kp</i> ≤ 1)

Park, J.‐S.; Kim, Khan‐Hyuk; Shiokawa, K.; Lee, D.-H.; Lee, E.; Kwon, Hyuck Jin; Jin, Ho; Jee, Geonhwa

doi:10.1002/2015ja021968

Cited by 44 publications

(97 citation statements)

References 40 publications

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“…For C3 category, He + band EMIC waves are predominantly observed with wide spatial coverage at 3–14 MLT and at L ∼4–6.5, while there are significantly lower H + band EMIC wave occurrence rates (Figure c). The peak occurrence rate of C3 near the noon sector is consistent with previous studies of EMIC wave occurrence rates during steady quiet geomagnetic conditions at geosynchronous orbit (e.g., Kim et al, ; Park et al, ). The wider L shell coverage of He + band wave might be related to the influence of the expanding plasmasphere during quiet geomagnetic conditions (Kwon et al, 2015).…”

Section: Statistical Resultssupporting

confidence: 90%

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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Section: Statistical Resultssupporting

confidence: 90%

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

et al. 2019

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“…This distribution characteristic is consistent with results from Park et al []. The reason for this kind of distribution is suggested to be related to dawn‐dusk asymmetric response to enhancement of solar wind dynamics [ Park et al , , ].…”

Section: Summary and Discussionsupporting

confidence: 91%

Geomagnetic storms and EMIC waves: Van Allen Probe observations

Wang

Yuan

et al. 2016

JGR Space Physics

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Utilizing the data from magnetometer instrument of Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) suite on board Van Allen Probe A, the occurrences of electromagnetic ion cyclotron (EMIC) waves during geomagnetic storms and nonstorm periods are investigated. The 270 EMIC wave events and 76 geomagnetic storms were identified during the period under research, from 8 September 2012 to 30 April 2014, when the apogee of Van Allen Probe A covered all the magnetic local time (MLT) sectors. Fifty of the 76 storms observed 124 EMIC wave events, of which 80 are found in the recovery phase, more than those observed in the main phase. Majority EMIC wave events (~54%) were observed during the nonstorm periods. Occurrence rates of EMIC waves as a function of L and MLT during different geomagnetic conditions are also examined, whose peaks in main phase are higher than those in recovery phase. However, occurrences of EMIC waves in recovery phase distribute more uniformly than those do in main phase. Evolution of the distribution characteristics of EMIC waves respect to L and MLT in different geomagnetic phases is investigated, consistent with that of the plasmasphere during geomagnetic storms, implying that the cold and dense plasma in the plasmasphere or plasmaspheric plume play a significant role in the generation of EMIC waves in the inner magnetosphere. Few EMIC waves in the dayside sector during the preonset periods are observed, suggesting that the effect of solar wind dynamic pressure on the generation of EMIC waves in the inner magnetosphere in those periods is not so significant as expected.

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“…Park et al . [] found a similar pattern in their study of EMIC waves observed during geomagnetically quiet conditions at geosynchronous orbit: the mean and 75th percentile values of Psw increased shortly before wave onset but not the 25th percentile values.…”

Section: Superposed Epoch Analysismentioning

confidence: 98%

“…This local time range is consistent with the observations of Park et al . [] at geosynchronous orbit that quiet time EMIC waves (including those during isolated compressions) mostly occurred on the dayside with a peak occurrence near noon.…”

Section: Statistical Studymentioning

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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EMIC waves observed at geosynchronous orbit under quiet geomagnetic conditions (Kp ≤ 1)

Cited by 44 publications

References 40 publications

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

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

Geomagnetic storms and EMIC waves: Van Allen Probe observations

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

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