A statistical study of the cross‐shock electric potential at low Mach number, quasi‐perpendicular bow shock crossings using Cluster data

Dimmock, A. P.; Balikhin, M. A.; Krasnoselskikh, V.; Walker, S. N.; Bale, S. D.; Hobara, Y.

doi:10.1029/2011ja017089

Cited by 45 publications

(66 citation statements)

References 47 publications

(50 reference statements)

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“…Previous observational [e.g., Wilson et al, 2007Wilson et al, , 2012 and simulation [e.g., Matsukiyo and Scholer, 2006;Muschietti and Lembège, 2013] studies only infer but do not quantify the importance of wave-particle interactions in the energy dissipation of collisionless shock waves. Other studies have focused on the effects due to quasi-static fields [e.g., Dimmock et al, 2012;Eastwood et al, 2007;Hull et al, 2001;Mitchell et al, 2012;Mitchell and Schwartz, 2014], arguing that wave-particle interactions are only of secondary importance. However, we have quantitatively shown that microscopic wave-particle interactions can regulate the macroscopic structure of low-to-mid Mach number collisionless shocks.…”

Section: Discussionmentioning

confidence: 99%

Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation

et al. 2014

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Key Points:• Microscopic wave-particle interactions can regulate macroscopic shock structure • High-frequency large-amplitude waves are ubiquitous in collisionless shocks • Wave-particle interactions are the end result of nearly all dissipation pathways AbstractWe present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collisionless bow shock using data from the Time History of Events and Macroscale Interactions during Substorms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collisionless shocks. In every bow shock crossing examined, we observed both low-frequency (<10 Hz) and high-frequency (≳10 Hz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding B ∼ 10 nT and E ∼ 300 mV/m, though more typical values were B ∼ 0.1-1.0 nT and E ∼ 10-50 mV/m; (2) Poynting fluxes in excess of 2000 μW m −2 (typical values were ∼ 1-10 μW m −2 ); (3) resistivities > 9000 Ω m; and (4) associated energy dissipation rates > 10 μW m −3 . The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for ∼90% of the wave burst durations. For ∼22% of these times, the wave-particle interactions needed to only be ≤ 0.1% efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave-particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collisionless shocks.

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Section: Discussionmentioning

confidence: 99%

Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation

et al. 2014

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“…The value of the cross‐shock potential determines the energy loss by the directly transmitted ions and their eventual heating [ Gedalin , ]. It is of interest to compare the numerically found potential with the widely used model approximation [see, e.g., Dimmock et al ., ]

φ = φ_{max} \frac{B - B_{normalu}}{B_{max} - B_{normalu}} .

The comparison is shown in Figure . The adopted model appears to be very good at ion scales (larger than the electron ones).…”

Section: Numerical Modelingmentioning

confidence: 99%

Two‐dimensional hybrid simulations of quasi‐perpendicular collisionless shock dynamics: Gyrating downstream ion distributions

Ofman

Gedalin

2013

JGR Space Physics

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[1] Quasi-perpendicular collisionless shocks undergo structural changes with the increase of the Mach number. These changes are related to the increasing role of the reflected ions, which have a highly nongyrotropic distribution. Eventually, it is expected that the shock front becomes nonstationary. At low and moderate Mach numbers, the fraction of reflected ions is small, yet recent observations show the existence of a well-pronounced structure of the postshock magnetic field in the close vicinity of the transition layer. Large amplitude oscillations were earlier interpreted as waves generated by the shock front or passing through the shock in the downstream direction. Here we show, using two-dimensional hybrid simulations of quasi-perpendicular shocks, that the gyration of the directly transmitted ions downstream of the ramp produces the spatial pressure variations, which are accompanied with the observed magnetic oscillations due to the momentum conservation. In a wide range of the upstream ion temperatures, the low and moderate-Mach-number shocks remain stationary and one-dimensional, so that the magnetic and electric field depend only on the coordinate along the shock normal. The downstream ion distributions gradually gyrotropize due to the collisionless mixing of gyrophases. Nonstationary effects in these shocks do not affect noticeably the ion dynamics. However, we find that with the increase of the Mach number, shocks form rippled fronts in the low-b and moderate-b regimes.Citation: Ofman, L., and M. Gedalin (2013), Two-dimensional hybrid simulations of quasi-perpendicular collisionless shock dynamics: Gyrating downstream ion distributions,

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“…A majority of these bursts occur at the shock ramp (when a clear ramp is identifiable). Though the waves are bursty, their amplitudes usually far exceed the typical few tens of mV/m quasi-static electric field component [Eastwood et al, 2007;Dimmock et al, 2012].…”

Section: Stereo and Wind Survey And Event Analysismentioning

confidence: 99%

STEREO and Wind observations of intense cyclotron harmonic waves at the Earth's bow shock and inside the magnetosheath

et al. 2013

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[1] We present the first observations of electron cyclotron harmonic waves at the Earth's bow shock from STEREO and Wind burst waveform captures. These waves are observed at magnetic field gradients at a variety of shock geometries ranging from quasi-parallel to nearly perpendicular along with whistler mode waves, ion acoustic waves, and electrostatic solitary waves. Large amplitude cyclotron harmonic waveforms are also observed in the magnetosheath in association with magnetic field gradients convected past the bow shock. Amplitudes of the cyclotron harmonic waves range from a few tens to more than 500 mV/m peak-peak. A comparison between the short (15 m) and long (100 m) Wind spin plane antennas shows a similar response at low harmonics and a stronger response on the short antenna at higher harmonics. This indicates that wavelengths are not significantly larger than 100 m, consistent with the electron cyclotron radius. Waveforms are broadband and polarizations are distinctively comma-shaped with significant power both perpendicular and parallel to the magnetic field. Harmonics tend to be more prominent in the perpendicular directions. These observations indicate that the waves consist of a combination of perpendicular Bernstein waves and field-aligned waves without harmonics. A likely source is the electron cyclotron drift instability which is a coupling between Bernstein and ion acoustic waves. These waves are the most common type of high-frequency wave seen by STEREO during bow shock crossings and magnetosheath traversals and our observations suggest that they are an important component of the high-frequency turbulent spectrum in these regions.

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A statistical study of the cross‐shock electric potential at low Mach number, quasi‐perpendicular bow shock crossings using Cluster data

Cited by 45 publications

References 47 publications

Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation

Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation

Two‐dimensional hybrid simulations of quasi‐perpendicular collisionless shock dynamics: Gyrating downstream ion distributions

STEREO and Wind observations of intense cyclotron harmonic waves at the Earth's bow shock and inside the magnetosheath

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