On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

Lobzin, V. V.; Krasnoselskikh, V.; Musatenko, K.; Wit, T. Dudok de

doi:10.5194/angeo-26-2899-2008

Cited by 21 publications

(27 citation statements)

References 39 publications

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“…Later, rippling on similar scales was found by Lowe and Burgess []; Burgess and Scholer [] using 2‐D hybrid simulations and attributed to the surface waves developing due to the instability associated with reflected ions. Observations by [ Moullard et al , ; Lobzin et al , ] confirmed the existence of this type of rippling. Large‐scale rippling with the wavelength of about 20 ion inertial lengths was found in numerical simulations by Yuan et al [].…”

Section: Introductionmentioning

confidence: 80%

Rippled quasi‐perpendicular collisionless shocks: Local and global normals

Ofman

Gedalin

2013

JGR Space Physics

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[1] Proper determination of the shock normal is necessary for reliable determination of observed heliospheric shock parameters and comparison of observations with theory. The existing methods work sufficiently well for low and moderate Mach numbers one-dimensional stationary shocks. Higher-Mach-number shocks are no longer planar at the scales of the ion convective gyroradius or smaller. In rippled shock fronts, the local shock normal may differ substantially from the global normal. The former is determined by the local direction of the fastest variation of the magnetic field, while the latter is determined by the far upstream and far downstream plasma conditions. Here we use 2-D hybrid modeling of quasi-perpendicular collisionless shocks with moderate and high Mach numbers to quantify the difference between the directions of the two normals. We find that the angle between the local normal and the global normal may be as large as 40 ı within the front of a rippled heliospheric shock. The coplanarity method of the shock normal determination is sensitive to the choice of the region for the magnetic field averaging. We also find that the usage of the sliding averaging region in the close vicinity of the shock transition provides satisfactory estimates of the global normal.Citation: Ofman, L., and M. Gedalin (2013), Rippled quasi-perpendicular collisionless shocks: Local and global normals,

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Section: Introductionmentioning

confidence: 80%

Rippled quasi‐perpendicular collisionless shocks: Local and global normals

Ofman

Gedalin

2013

JGR Space Physics

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“…Shock ripples and their importance for particle acceleration and for formation of downstream phenomena have been the subject of several works [i.e., Gedalin, 2001, Hao et al, 2016, Hietala et al, 2009, Yang et al, 2011, 2018. Rippling was observed at the Earth's bow-shock by several authors by using multi-spacecraft data from Cluster [Horbury et al, 2002, 2001, Lobzin et al, 2008, Moullard et al, 2006 and Magnetospheric Multiscale (MMS) mission [Gingell et al, 2017, Johlander et al, 2016. As for the IP shocks, several authors [i.e., Kajdič et al, 2017, Koval & Szabo, 2010, Pulupa & Bale, 2008, Russell & Alexander, 1984, Russell et al, 2000, Szabo, 2005 discussed and/or observed their non-planar structure at scales of several tens of Earth radii (R E ), but never at ion scales.…”

Section: Introductionmentioning

confidence: 99%

First Observations of Irregular Surface of Interplanetary Shocks at Ion Scales by Cluster

Kajdič

Preisser

Blanco‐Cano

et al. 2019

ApJL

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We present the first observational evidence of the irregular surface of interplanetary (IP) shocks by using multi-spacecraft observations of the Cluster mission. In total we discuss observations of four IP shocks that exhibit moderate Alfvénic Mach numbers (M A ≤6.5). Three of them are high-β shocks with upstream β = 2.2-3.7. During the times when these shocks were observed, the Cluster spacecraft formed constellations with inter-spacecraft separations ranging from less than one upstream ion inertial length (d i ) up to 100 d i . Expressed in kilometers, the distances ranged between 38 km and ∼10 4 km. We show that magnetic field profiles and the local shock normals of observed shocks are very similar when the spacecraft are of the order of one d i apart, but are strikingly different when the distances increase to ten or more d i . We interpret these differences to be due to the irregular surface of IP shocks and discuss possible causes for such irregularity. We strengthen our interpretation by comparing observed shock profiles with profiles of simulated shocks. The latter had similar characteristics (M A , θ BN , upstream ion β) as observed shocks and the profiles were obtained at separations across the simulation domain equivalent to the Cluster inter-spacecraft distances.

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“…Indeed recent simulation studies using hybrid and PIC code showed that the shock front has nonstationarity (known as self‐reformation and shock rippling) in the quasi‐perpendicular regime where the loss cone–shaped energetic ions are detected [ Lembège and Dawson , 1987; Krasnoselskikh et al , 2002; Scholer et al , 2003; Hada et al , 2003; Lowe and Burgess , 2003]. The evidence of the shock nonstationarity was also found in Cluster observations [ Horbury et al , 2001; Moullard et al , 2006; Lobzin et al , 2007, 2008]. By noting that the upstream energetic ion characteristics changed dramatically at the transition shock angle Θ t , the idea that we pursue is that the loss cone–shaped ions are produced by nonstationary structure that starts to appear above Θ t (∼75°).…”

Section: Discussionmentioning

confidence: 85%

“…Recently, the nonstationary structures began to be detected from multipoint measurements by Cluster [ Moullard et al , 2006; Lobzin et al , 2007, 2008]. The characteristics of the upstream energetic particles produced at the bow shock should strongly depend on the shock front structures.…”

Section: Discussionmentioning

confidence: 99%

Observations of loss cone–shaped back streaming energetic protons upstream of the Earth's bow shock

et al. 2009

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[1] Energetic ions are at times observed in the upstream region of the Earth's bow shock, and their origin is considered to be in the interaction with the shock front. While the energy of the solar wind ions is a few keV at most, the energy of the back streaming ions ranges from $5 keV to several MeV. In the present study we investigate back streaming energetic ions in the upstream of the Earth's bow shock observed by Geotail during two coronal mass ejection events. The observed local magnetic field rotated significantly during the events. Using the bow shock model and the observed magnetic field data, we found that the energetic ions appeared only when the upstream magnetic field was connected to the bow shock. The energetic ions showed two distinct distribution function characteristics, namely, the field-aligned beam (FAB) and the loss cone-shaped distribution. While the former is occasionally detected, the latter having higher energies (30 keV to several hundred keV, compared to <18 keV for FAB) has not been reported before. Using a bow shock model, we can also estimate the shock angle at the point on the shock surface that the upstream field line is connected to and find that the distribution function shape transits from the FAB to the loss cone-shaped distribution as the shock angle becomes larger (transition at Q Bn = 70°-80°). We discuss the possible mechanisms responsible for the production of the newly found member of the energetic upstream ion family.

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On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

Cited by 21 publications

References 39 publications

Rippled quasi‐perpendicular collisionless shocks: Local and global normals

Rippled quasi‐perpendicular collisionless shocks: Local and global normals

First Observations of Irregular Surface of Interplanetary Shocks at Ion Scales by Cluster

Observations of loss cone–shaped back streaming energetic protons upstream of the Earth's bow shock

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