The dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of EMIC waves observed by the Van Allen Probes

Saikin, A.; Zhang, J.-C.; Smith, Charles W.; Spence, H. E.; Torbert, R. B.; Kletzing, C.

doi:10.1002/2016ja022523

Cited by 94 publications

(199 citation statements)

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“…Thus, to some extent, results in this manuscript and those in Saikin et al [] are complementary. In addition, effects of solar wind dynamic pressure are specially checked during isolated preonset in this study, while all EMIC waves observed were categorized by solar wind dynamic pressure data in Saikin et al []. Furthermore, they identify the location of EMIC waves relative to plasmapause according to empirical models, while plasma density data are shown in this manuscript.…”

Section: Summary and Discussionsupporting

confidence: 66%

“…During the 22 geomagnetic storms under research, only 29% of EMIC waves were found in the main phase and the rest in recovery phase. Recently, with observations from Van Allen Probes, the correlation between EMIC wave occurrences in the inner magnetosphere and geomagnetic conditions and solar wind dynamic pressure is checked [ Saikin et al , ], based on their previous work [ Saikin et al , ]. Storm time EMIC waves were more often observed during recovery phase than main phase.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Summary and Discussionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Geomagnetic storms and EMIC waves: Van Allen Probe observations

Wang

Yuan

et al. 2016

JGR Space Physics

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“…This was initially thought to be a product of the larger geomagnetic storms in October and November of 2012 during which the apogee of the spacecraft was located at ∼7:00 MLT, but the fact that the Van Allen Probes have precessed orbitally to resample this region during their mission and observed similar occurrences implies that this may be a region of significance. Saikin et al [] recorded a similar enhancement of EMIC wave activity observed during geomagnetically quiet periods, which would corroborate our finding of increased pearl pulsation occurrence during quiet periods discussed in section 2.2. The late morning sector at geostationary orbit (just outside of the Van Allen Probe coverage range) has also been shown to be a concentration of azimuthally polarized standing Pc5 waves [ Takahashi and Mcpherron , ; Kokubun , ; Anderson , ], and it has been implied that the late morning and prenoon sectors are most favorable to pearl generation according to the BWP method by Mazur and Potapov [].…”

Section: Observationsmentioning

confidence: 99%

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

et al. 2017

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We present here the first in situ statistical survey of structured Pc1 pearl pulsations compared with unstructured electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes spacecraft. This data set was compiled from observations spanning 8 September 2012 through 31 August 2015 and comprises over 1630 h of total EMIC wave activity, of which 291 h exhibited pearl structure. Additionally, we have identified 29 wave events demonstrating periodically oscillating wave packets, mostly about the magnetic equator, indicated by the reversal of Poynting flux along the background magnetic field. We have found several stark differences between Pc1 pearl pulsations and unstructured EMIC waves. While unstructured EMIC waves demonstrate the predicted behavior of a higher occurrence across the dayside with enhanced wave power at dusk, pearl pulsations occur uniformly across magnetic local time, with a small enhancement in the late morning sector. Pearl pulsations were more often observed during magnetospherically quiet periods, particularly in the late recovery period of geomagnetic storms. The mean excitation frequency of pearl pulsations was observed to be independent of the local ion cyclotron frequency, and individual wave investigations indicate that the modulation period also remained constant for the duration of the event over a finite range in L. We examine three possible generation mechanisms—the bouncing wave packet model, modulation by ultralow‐frequency Pc4 and Pc5 waves, and the formation of an ion cyclotron resonator—but are unable to definitively confirm the validity of any one model.

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“…In a follow‐up study, Saikin et al . [] examined the geomagnetic condition dependence of EMIC waves. They found as AE index increases the peak of EMIC waves shifted from prenoon to afternoon sector.…”

Section: Introductionmentioning

confidence: 99%

Convective growth of electromagnetic ion cyclotron waves from realistic ring current ion distributions

Fok

Khazanov

Krivorutsky³

et al. 2016

JGR Space Physics

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It is well established that the development of pitch angle anisotropy in ring current ions provides a favorable condition for electromagnetic ion cyclotron (EMIC) wave growth. Many studies have calculated the EMIC growth rate assuming a bi‐Maxwellian or ring distribution of energetic ions in velocity space. To test the appropriateness of these assumptions, we compute the EMIC growth rate by using the realistic ion distributions output by our Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model. The CIMI model calculates energetic ion and electron distributions and many other essential quantities in the inner magnetosphere and ionosphere. We found that the ring current distributions are often very different from a bi‐Maxwellian or a ring distribution. The corresponding EMIC growth rates are likewise quite distinctive from those estimated by functional fits. In the simulation of an idealized magnetic storm, we found that much stronger EMIC growth near the dayside magnetopause was attained with realistic ring current distributions. On the other hand, with the assumption of a ring distribution, EMIC growth at the peak of the ring current pressure was overestimated. Our calculation using the realistic ion distribution function reproduces the observed occurrence of EMIC waves and demonstrates the need to use realistic ring current ion distributions when modeling EMIC wave excitation.

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The dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of EMIC waves observed by the Van Allen Probes

Cited by 94 publications

References 63 publications

Geomagnetic storms and EMIC waves: Van Allen Probe observations

Geomagnetic storms and EMIC waves: Van Allen Probe observations

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

Convective growth of electromagnetic ion cyclotron waves from realistic ring current ion distributions

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