EMIC wave activity during geomagnetic storm and nonstorm periods: CRRES results

Halford, A. J.; Fraser, B. J.; Morley, S.

doi:10.1029/2010ja015716

Cited by 137 publications

(264 citation statements)

References 73 publications

(166 reference statements)

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“…Although EMIC waves have been intensively investigated [e.g, Kennel and Petschek, 1966;Young et al, 1981;Rauch and Roux, 1982;Roux et al, 1982;Anderson et al, 1996;Fraser and Nguyen, 2001;Halford et al, 2010;Pickett et al, 2010;Zhang et al, 2010Zhang et al, , 2011Min et al, 2012;Allen et al, 2013;Lin et al, 2014], plasma properties relevant to EMIC wave excitation have not been fully understood in the magnetosphere due to the wide spatial extent of EMIC wave generation and propagation. For example, Lin et al [2014] recently found that the correlation of positive A hp events, EMIC instability threshold (Σ h > S h ), and EMIC waves observed by the polar-orbiting Cluster spacecraft is low.…”

Section: Discussionmentioning

confidence: 99%

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Zhang

Saikin

Kistler

et al. 2014

Geophysical Research Letters

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We report the wave observations, associated plasma measurements, and linear theory testing of electromagnetic ion cyclotron (EMIC) wave events observed by the Van Allen Probes on 28 April 2013. The wave events are detected in their generation regions as three individual events in two consecutive orbits of Van Allen Probe-A, while the other spacecraft, B, does not detect any significant EMIC wave activity during this period. Three overlapping H + populations are observed around the plasmapause when the waves are excited. The difference between the observational EMIC wave growth parameter (Σ h ) and the theoretical EMIC instability parameter (S h ) is significantly raised, on average, to 0.10 ± 0.01, 0.15 ± 0.02, and 0.07 ± 0.02 during the three wave events, respectively. On Van Allen Probe-B, this difference never exceeds 0. Compared to linear theory (Σ h > S h ), the waves are only excited for elevated thresholds.

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Section: Discussionmentioning

confidence: 99%

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Zhang

Saikin

Kistler

et al. 2014

Geophysical Research Letters

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“…The rate of the electron loss is not simply controlled by the wave intensity but crucially depends on the wave spectral distribution [Glauert and Horne, 2005], and a properly specified global distribution of the EMIC wave power spectral density (PSD) is needed to accurately describe wave-particle interactions on the global magnetospheric scale throughout the 10.1002/2014JA020032 different storm phases. However, despite a number of statistical and case studies of EMIC waves [e.g., Anderson et al, 1992aAnderson et al, , 1992bFraser et al, 2010;Halford et al, 2010;Clausen et al, 2011;Usanova et al, 2012;Min et al, 2012], there is still no reliable global and dynamic model of the EMIC wave PSD that could be incorporated in the model of relativistic electrons in the outer RB. Currently, the EMIC wave PSD is poorly specified in all models of the outer RB relativistic electrons.…”

Section: Introductionmentioning

confidence: 99%

Model of electromagnetic ion cyclotron waves in the inner magnetosphere

et al. 2014

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Citation:Gamayunov, K. V., M. J. Engebretson, M. Zhang, and H. K. Rassoul (2014) Abstract The evolution of He + -mode electromagnetic ion cyclotron (EMIC) waves is studied inside the geostationary orbit using our global model of ring current (RC) ions, electric field, plasmasphere, and EMIC waves. In contrast to the approach previously used by Gamayunov et al. (2009), however, we do not use the bounce-averaged wave kinetic equation but instead use a complete, nonbounce-averaged, equation to model the evolution of EMIC wave power spectral density, including off-equatorial wave dynamics. The major results of our study can be summarized as follows. (1) The thermal background level for EMIC waves is too low to allow waves to grow up to the observable level during one pass between the "bi-ion latitudes" (the latitudes where the given wave frequency is equal to the O + -He + bi-ion frequency) in conjugate hemispheres. As a consequence, quasi-field-aligned EMIC waves are not typically produced in the model if the thermal background level is used, but routinely observed in the Earth's magnetosphere. To overcome this model-observation discrepancy we suggest a nonlinear energy cascade from the lower frequency range of ultralow frequency waves into the frequency range of EMIC wave generation as a possible mechanism supplying the needed level of seed fluctuations that guarantees growth of EMIC waves during one pass through the near equatorial region. The EMIC wave development from a suprathermal background level shows that EMIC waves are quasi field aligned near the equator, while they are oblique at high latitudes, and the Poynting flux is predominantly directed away from the near equatorial source region in agreement with observations. (2) An abundance of O + strongly controls the energy of oblique He + -mode EMIC waves that propagate to the equator after their reflection at bi-ion latitudes, and so it controls a fraction of wave energy in the oblique normals. waves generated by RC O + in the region L ≈ 2-3 may have an implication to the energetic particle loss in the inner radiation belt.

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“…However, the authors found higher occurrence during the recovery phase than during the main phase. Halford et al (2010) indeed found that the majority of EMIC waves occur during the main phase but most of the events were observed in the dusk-noon sector and relatively few were observed for MLT > 18 h, whereas there were no anomalous IB dispersions observed for MLT < 19 h. It is also unclear why higher energy IBs never exhibit anomalous dispersion (Fig. 5c).…”

Section: Discussionmentioning

confidence: 77%

“…There are many observations supporting a wave-scattering scenario. Mostly, these are magnetospheric and low-altitude observations of the EMIC wave activity in the inner magnetosphere region (Bräysy et al, 1998;Erlandson and Ukhorskiy, 2001;Halford et al, 2010). Gvozdevsky et al (1997) investigated the intense proton precipitation equatorward of the IB which were called LLPP (low-latitude proton precipitation).…”

Section: Discussionmentioning

confidence: 99%

Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations

et al. 2013

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We present the results of a coordinated study of the moderate magnetic storm on 22 July 2009. The THEMIS and GOES observations of magnetic field in the inner magnetosphere were complemented by energetic particle observations at low altitude by the six NOAA POES satellites. Observations in the vicinity of geosynchronous orbit revealed a relatively thin (half-thickness of less than 1 R_E) and intense current sheet in the dusk MLT sector during the main phase of the storm. The total westward current (integrated along the z-direction) on the duskside at r ~ 6.6 R_E was comparable to that in the midnight sector. Such a configuration cannot be adequately described by existing magnetic field models with predefined current systems (error in B > 60 nT). At the same time, low-altitude isotropic boundaries (IB) of > 80 keV protons in the dusk sector were shifted ~ 4° equatorward relative to the IBs in the midnight sector. Both the equatorward IB shift and the current strength on the duskside correlate with the Sym-H* index. These findings imply a close relation between the current intensification and equatorward IB shift in the dusk sector. The analysis of IB dispersion revealed that high-energy IBs (E > 100 keV) always exhibit normal dispersion (i.e., that for pitch angle scattering on curved field lines). Anomalous dispersion is sometimes observed in the low-energy channels (~ 30–100 keV). The maximum occurrence rate of anomalous dispersion was observed during the main phase of the storm in the dusk sector

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EMIC wave activity during geomagnetic storm and nonstorm periods: CRRES results

Cited by 137 publications

References 73 publications

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

Model of electromagnetic ion cyclotron waves in the inner magnetosphere

Geometry of duskside equatorial current during magnetic storm main phase as deduced from magnetospheric and low-altitude observations

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