Oscillations of energetic ions flux near the Earth's bow shock

Петрукович, А. А.; Inamori, Takaya; Baláž, J.; Kudela, K.; Slivka, M.; Strharsky, I.; Gladyshev, V. A.; Sarris, T. E.; Sarris, E. T.

doi:10.1002/2015ja021077

Cited by 3 publications

(5 citation statements)

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“…This is most visible between t = 460 s and t = 490 s in panel (f), corresponding to a period of about 30 s, but a modulation at a shorter period, around 10 s, may also be present in panel (h). This variation in the flux of suprathermal ions is similar to that reported by Petrukovich et al (; see in particular Figure 4 of their paper) and is therefore likely caused by the foreshock ULF waves.…”

Section: Resultssupporting

confidence: 90%

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

et al. 2018

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In this paper, we present a detailed study of the effects of the interplanetary magnetic field (IMF) strength on the foreshock properties at small and large scales. Two simulation runs performed with the hybrid‐Vlasov code Vlasiator with identical setup but with different IMF strengths, namely, 5 and 10 nT, are compared. We find that the bow shock position and shape are roughly identical in both runs, due to the quasi‐radial IMF orientation, in agreement with previous magnetohydrodynamic simulations and theory. Foreshock waves develop in a broader region in the higher IMF strength run, which we attribute to the larger growth rate of the waves. The velocity of field‐aligned beams remains essentially the same, but their density is generally lower when the IMF strength increases, due to the lower Mach number. Also, we identify in the regular IMF strength run ridges of suprathermal ions which disappear at higher IMF strength. These structures may be a new signature of the foreshock compressional boundary. The foreshock wave field is structured over smaller scales in higher IMF conditions, due to both the period of the foreshock waves and the transverse extent of the wave fronts being smaller. While the foreshock is mostly permeated by monochromatic waves at typical IMF strength, we find that magnetosonic waves at different frequencies coexist in the other run. They are generated by multiple beams of suprathermal ions, while only a single beam is observed at typical IMF strength. The consequences of these differences for solar wind‐magnetosphere coupling are discussed.

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Section: Resultssupporting

confidence: 90%

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

et al. 2018

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“…This investigation confirms and extends analysis of our previous publication [ Petrukovich et al , ], presenting oscillations of foreshock energetic ion flux in a wide energy range from 4 keV to the first hundreds of keV. The spatial scale of correlations and the frequency dependence on local magnetic field suggest that these oscillations correspond to previously described 30 s magnetic waves [ Greenstadt et al , ; Le and Russell , ].…”

Section: Discussionsupporting

confidence: 91%

“…Magnetic waves in our data set, although rather intense, do not fit the criteria of Hsieh and Shue [], especially that of high ratio of intermediate to minimal eigenvalue of covariance matrix, which determines the quality of a planar elliptically polarized wave. Magnetic variations in our events look nonlinear (Figure ) [ Petrukovich et al , , Figure 3] and often similar to the shocklet type [ Greenstadt et al , ]. Regi et al [] also suggested that waves are “less monochromatic” (more noisy), when solar wind speed is higher.…”

Section: Discussionsupporting

confidence: 52%

“…Recently, with better time resolution of the energetic particle instruments attention was brought to oscillations of energetic ion fluxes around 30 s range, which were almost never described before [ Petrukovich et al , , hereafter P15]. Spectr‐R Russian spacecraft with the energetic particle instrument Monitor of Electrons and protons (MEP) [ Baláž et al , ] allowed to see them up to 50 R E away from Earth, while on a larger statistics and closer to Earth they were confirmed with Time History of Events and Macroscale Interactions during Substorms (THEMIS) solid state telescope (SST) data.…”

Section: Introductionmentioning

confidence: 96%

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Foreshock waves as observed in energetic ion flux

et al. 2017

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Oscillations of energetic ion fluxes with periods 10–100 s are often present in the Earth's foreshock. Detailed analysis of wave properties with Time History of Events and Macroscale Interactions during Substorms data and comparisons with other data sets confirm that these oscillations are the previously unnoticed part of well‐known “30 s” waves but are observed mainly for higher‐speed solar wind. Simultaneous magnetic oscillations have similar periods, large amplitudes, and nonharmonic unstable waveforms or shocklet‐type appearance, suggesting their nonlinearity, also typical for high solar wind speed. Analysis of the general foreshock data set of Interball project shows that the average flux of the backstreaming energetic ions increases more than 1 order of magnitude, when solar wind speed increases from 400 to 500 km/s.

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“…The modulation was visible both in the distribution core and in fluxes of suprathermal reflected ions. Such oscillations of enhanced energetic ion fluxes in foreshock observations were also reported by Petrukovich et al (),Petrukovich et al (). The authors discussed the coupling of magnetic field and particle oscillations and suggested that it may be caused by the foreshock ULF waves.…”

Section: Discussionsupporting

confidence: 83%

Solar Wind Deflection in the Foreshock: Model‐Data Comparison

et al. 2020

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We present the results of a 2.5‐D (2‐D in space and 3‐D in currents and electromagnetic fields) electromagnetic hybrid simulation run for foreshock wave activity during an interval of a radial interplanetary magnetic field (IMF). The simulation predicts nonlinear waves and foreshock expansion in connection with the development of cavitons and the formation of the foreshock compressional boundary. Fluctuations of the ion velocity VY component are associated with wave fronts corresponding to small wave normal angles and oscillate around 0 in the far upstream region. At distances closer to the bow shock, these fluctuations become asymmetric with duskward flow perturbations dominating at dusk and dawnward flow perturbations at dawn. We compare this simulation with THEMIS observations of large‐amplitude quasi‐monochromatic variations of ion velocity in the foreshock under radial IMF. A case study of simultaneous dual observations of unipolar VY fluctuations is followed by a statistical study of similar solar wind deflections in the foreshock. The observations that confirm the simulation predictions indicate that, in addition to ion heating, ultralow‐frequency waves participate in the magnetosheath‐like plasma flow deflection in the foreshock during periods of small IMF cone angles.

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Oscillations of energetic ions flux near the Earth's bow shock

Cited by 3 publications

References 34 publications

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

Foreshock Properties at Typical and Enhanced Interplanetary Magnetic Field Strengths: Results From Hybrid‐Vlasov Simulations

Foreshock waves as observed in energetic ion flux

Solar Wind Deflection in the Foreshock: Model‐Data Comparison

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