Transmission of large‐amplitude ULF waves through a quasi‐parallel shock at Venus

Lun, Shan; Lu, Quanming; Wu, Mingyu; Gao, Xinliang; Huang, Can; Zhang, Tielong; Wang, Shui

doi:10.1002/2013ja019396

Cited by 31 publications

(36 citation statements)

References 62 publications

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“…In that study, it was shown that the reformation of a quasi-parallel shock can drive strong magnetosheath and magnetospheric wave activity at Mercury. Similar observations have since then also been made at Venus, where Shan et al [2014] observed a transmission of ULF waves from the upstream to the downstream region. Approximately half of the wave events also show pulsations immediately upstream of the shock in a similar frequency span, but at much lower amplitudes, which is also indicative of an upstream source for this wave mode.…”

Section: Large-amplitude Wavessupporting

confidence: 76%

Coherent wave activity in Mercury's magnetosheath

et al. 2015

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This study presents a statistical overview of coherent wave activity in Mercury's magnetosheath. Left‐handed electromagnetic ion cyclotron waves are commonly found behind the quasi‐perpendicular section of the bow shock, where they are present in ~50% of the spacecraft crossings of the magnetosheath. Their occurrence distribution maximizes within the magnetosheath, approximately halfway between the bow shock and the magnetopause, and the waves are generally strongly Doppler shifted up to frequencies above the local ion cyclotron frequency. Downstream of the quasi‐parallel shock, the magnetosheath often exhibits large‐amplitude pulsations with wave periods around 10 s and peak‐to‐peak amplitudes of up to 100 nT that dominate the magnetic field structure. These waves are circularly left‐hand polarized with wave vectors in the direction of the local shock normal. The data suggest that they have been generated upstream of the shock and transmitted into the downstream region. Their occurrence rates maximize at the near‐parallel shock, where they are present approximately 10% of the time, and where they also show their largest wave powers. Some evidence is also found of waves with a right‐handed polarization in the spacecraft frame. These consist of both whistler waves above the local ion cyclotron frequency and ion cyclotron waves propagating against the magnetosheath flow with Doppler shifts exceeding the intrinsic wave frequency, which results in a change in their apparent polarization. These waves are in minority compared to the left‐handed observations, which indicates a preference for ion cyclotron waves propagating in the direction of the plasma flow.

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Section: Large-amplitude Wavessupporting

confidence: 76%

Coherent wave activity in Mercury's magnetosheath

et al. 2015

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“…Earlier reports revealed the existence of ULF waves upstream of the Venus bow shock [ Russell and Hoppe , ; Orlowski et al ., ; Shan et al ., ]. For the present work, a statistical study of Venusian foreshock ULF wave properties is undertaken using 1 Hz VEX‐MAG data.…”

Section: Discussionmentioning

confidence: 99%

“…Near the Venusian bow shock, Shan et al . [] identified five quasi‐monochromatic ULF wave events originating from the upstream of the quasi‐parallel shock and which seem to have been transmitted downstream. These waves were found to have similar properties in the foreshock and magnetosheath: frequency 0.04–0.05 Hz in spacecraft frame, an average oblique propagation angle of ~32°, left‐handed elliptical polarization, and large amplitude, indicating that the waves are magnetosonic waves, which are blown from upstream to downstream by the solar wind.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of quasi‐monochromatic ULF waves in the Venusian foreshock

et al. 2016

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The statistical properties of ULF waves observed upstream of Venus foreshock are investigated. The study is restricted to waves which are observed well below the local proton cyclotron frequency. Using the magnetic field observations from Venus Express between May 2006 and February 2012, 115 quasi‐monochromatic ULF wave trains have been identified. Statistical results show that the wave periods are mainly from 20 to 30 s in the spacecraft frame, which is about 2–3 times of the local proton cyclotron period. The transverse power dominates the power spectrum, and most of the waves display nearly circular or slightly elliptical polarization in the spacecraft frame. Moreover, these ULF waves mainly have small relative amplitudes with respect to the ambient field magnitude B0 for parallel component (δB||/B0 less than 0.3), while the range of relative amplitudes for perpendicular component δB⊥/B0 is from ~0.1 to ~1.0. Wave propagation angles are mainly less than 30° with respect to the mean magnetic field direction. The obtained results are very similar to the wave properties seen for ULF waves present in the terrestrial foreshock, which suggests that backstreaming ions in the Venusian foreshock form an important energy source for the generation of the waves.

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“…A recent study compared detailed wave diagnostics in both upstream and downstream regions of the Venusian bow shock and concluded that the downstream waves are transmitted ULF waves. 33 In cases where the steepened fronts are nearly parallel to the quasi-parallel region of the bow shock surface, they can significantly modify the shock structure and the magnetosheath thickness. This is shown in Fig.…”

Section: Transmission Of the Foreshock Turbulencementioning

confidence: 99%

The link between shocks, turbulence, and magnetic reconnection in collisionless plasmas

et al. 2014

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Global hybrid (electron fluid, kinetic ions) and fully kinetic simulations of the magnetosphere have been used to show surprising interconnection between shocks, turbulence, and magnetic reconnection. In particular, collisionless shocks with their reflected ions that can get upstream before retransmission can generate previously unforeseen phenomena in the post shocked flows: (i) formation of reconnecting current sheets and magnetic islands with sizes up to tens of ion inertial length. (ii) Generation of large scale low frequency electromagnetic waves that are compressed and amplified as they cross the shock. These "wavefronts" maintain their integrity for tens of ion cyclotron times but eventually disrupt and dissipate their energy. (iii) Rippling of the shock front, which can in turn lead to formation of fast collimated jets extending to hundreds of ion inertial lengths downstream of the shock. The jets, which have high dynamical pressure, "stir" the downstream region, creating large scale disturbances such as vortices, sunward flows, and can trigger flux ropes along the magnetopause. This phenomenology closes the loop between shocks, turbulence, and magnetic reconnection in ways previously unrealized. These interconnections appear generic for the collisionless plasmas typical of space and are expected even at planar shocks, although they will also occur at curved shocks as occur at planets or around ejecta. V C 2014 AIP Publishing LLC. [http://dx.

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Transmission of large‐amplitude ULF waves through a quasi‐parallel shock at Venus

Cited by 31 publications

References 62 publications

Coherent wave activity in Mercury's magnetosheath

Coherent wave activity in Mercury's magnetosheath

Characteristics of quasi‐monochromatic ULF waves in the Venusian foreshock

The link between shocks, turbulence, and magnetic reconnection in collisionless plasmas

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