Occurrence features of simultaneous H+- and He+-band EMIC emissions in the outer radiation belt

Fu, Song; He, Fazhi; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Liu, Jiang

doi:10.1016/j.asr.2018.01.041

Cited by 12 publications

(10 citation statements)

References 31 publications

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“…Apparently, the count of ‘H + ‐MS’ waves is much larger than the other two types of cases. By contrast, the previous statistic studies of EMIC waves (e.g., Fu, He, et al., 2018; Saikin et al., 2015; Zhang et al., 2016) have demonstrated that He + band EMIC are the most prevalent in the inner magnetosphere among the three wave bands of H + , He + , and O + .…”

Section: Statistical Resultsmentioning

confidence: 79%

Global Distribution of Concurrent EMIC Waves and Magnetosonic Waves: A Survey of Van Allen Probes Observations

Zhou

et al. 2022

JGR Space Physics

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Electromagnetic ions cyclotron (EMIC) waves and magnetosonic (MS) waves are electromagnetic emissions that can be frequently observed over a broad range of L-shell and magnetic local time (MTL) in the Earth's magnetosphere, owing to the free energy provided by the magnetospheric ion instabilities. Numerous studies have demonstrated that EMIC waves can be excited by the Alfven cyclotron instability during enhancements of ring current protons (e.g.

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Section: Statistical Resultsmentioning

confidence: 79%

Global Distribution of Concurrent EMIC Waves and Magnetosonic Waves: A Survey of Van Allen Probes Observations

Zhou

et al. 2022

JGR Space Physics

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“…Recent study using Van Allen Probe observations suggests that the majority of the EMIC waves are located in the afternoon (12-18 MLT) sector (Noh et al 2018). Fu et al (2018) have looked into the multi-band EMIC waves observed by Van Allen Probe and reported the enhanced EMIC wave activity in the dayside magnetosphere. Park et al (2016) used a higher resolution data of GOES and showed that the peak occurrence of EMIC waves is at 15-16 MLT.…”

Section: Seasonal and Local Time Dependencementioning

confidence: 99%

“…The ions responsible for the wave generation can be proton H + , helium He + , and oxygen O + and they determine the stop band frequency for the EMIC waves. These waves are transverse plasma waves, and can be observed in the Earth's magnetosphere by various satellites, like AMPTE/ CCE (Anderson et al 1990), Viking (Erlandson et al 1990), Cluster (Pickett et al 2010), THEMIS (Usanova et al 2012), Polar (Carson et al 2013), GOES (Park et al 2016), Arase (Shoji et al 2018), and Van Allen Probe (Fu et al 2018). The Cluster and THEMIS observations have reported the EMIC-triggered coherent emissions having rising tone frequencies (Pickett et al 2010;Nakamura et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Occurrence characteristics of electromagnetic ion cyclotron waves at sub-auroral Antarctic station Maitri during solar cycle 24

Upadhyay

Kakad

et al. 2020

Earth Planets Space

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We present a statistical study of electromagnetic ion cyclotron (EMIC) waves observed at Antarctic station (geographic 70.7 • S , 11.8 • E , L = 5) on quiet and disturbed days during 2011-2017. The data span a fairly good period of both ascending and descending phases of the solar cycle 24, which has witnessed extremely low activity. We noted EMIC wave occurrence by examining wave power in different frequency ranges in the spectrogram. EMIC wave occurrence during ascending and descending phases of solar cycle 24, its local time, seasonal dependence and durations have been examined. There are total 2367 days for which data are available. Overall, EMIC waves are observed for 3166.5 h (≈ 5.57% of total duration) which has contributions from 1263 days. We find a significantly higher EMIC wave occurrence during the descending phase (≈ 6.83%) as compared to the ascending phase (≈ 4.08%) of the solar cycle, which implies nearly a twofold increase in EMIC wave occurrence. This feature is attributed to the higher solar wind dynamic pressure during descending phase of solar activity. There is no evident difference in the percentage occurrence of EMIC waves on magnetically disturbed and quiet days. On ground, EMIC waves show marginally higher occurrence during winter as compared to summer. This seasonal tendency is attributed to lower electron densities and conductivities in the ionosphere, which can affect the propagation of EMIC waves through ionospheric ducts. In local time, the probability distribution function of EMIC wave occurrence shows enhancement during 11.7-20.7 LT (i.e., afternoon-dusk sector). Daily durations of EMIC waves are in the range of 5-1015 min and it is noted that the longer duration (240-1015 min) events are prevalent on quiet days and are mostly seen during the descending phase of solar cycle.

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“…In the postnoon (approximately 13:00 < MLT < 17:00) sector, peaks of wave occurrence possibility have been observed in the outer radiation belt ( L ∼ 4–6; Saikin et al, ) and in regions of higher L ‐shell ( L ∼ 8–12; Allen et al, ; Min et al, ). These postnoon waves ( L >4) mainly propagate with small wave normal angles, being left‐handed polarized and dominated by He + band emissions (Allen et al, ; Fu et al, ; Min et al, ; Saikin et al, ). The He + band waves are suggested to be related to the substorm injection: Tens of kiloelectron volt hot H + ions (Elkington et al, ) carry the free energy and drift from midnight to postnoon sector, and waves will be excited once the background plasma conditions are suitable for wave growth (Clausen et al, ).…”

Section: Introductionmentioning

confidence: 99%

Propagation of EMIC Waves Inside the Plasmasphere: A Two‐Event Study

et al. 2019

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Electromagnetic ion cyclotron (EMIC) waves are important for the loss of high-energy electrons in the radiation belt. Based on the measurements of Van Allen Probes, two events during the same storm period are presented to study the propagation of EMIC waves. In the first event, left-handed polarized EMIC waves were observed near the plasmapause, while right-handed waves were observed in the inner plasmasphere. The Poynting flux of the right-hand waves was mainly directed inward and equatorward, and no positive growth rates were obtained in the region of these right-hand waves, indicating the inward propagation of the waves from a higher L-shell. In the second event, the wave vectors were quasi-perpendicular to the background magnetic field inside the plasmaspheric plume but became quasi-parallel outside. This phenomenon can be explained by the refraction of the large density gradient, which qualitatively satisfies Snell's law. These observations provide indirect evidence of the inward propagation of the EMIC waves and give a new insight on how density gradients may modify wave properties.

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Occurrence features of simultaneous H+- and He+-band EMIC emissions in the outer radiation belt

Cited by 12 publications

References 31 publications

Global Distribution of Concurrent EMIC Waves and Magnetosonic Waves: A Survey of Van Allen Probes Observations

Global Distribution of Concurrent EMIC Waves and Magnetosonic Waves: A Survey of Van Allen Probes Observations

Occurrence characteristics of electromagnetic ion cyclotron waves at sub-auroral Antarctic station Maitri during solar cycle 24

Propagation of EMIC Waves Inside the Plasmasphere: A Two‐Event Study

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