On the edge of the foreshock: model-data comparisons

Sibeck, D. G.; Omidi, N.; Dandouras, I.; Lucek, E.

doi:10.5194/angeo-26-1539-2008

Cited by 46 publications

(81 citation statements)

References 15 publications

(19 reference statements)

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“…Since the magnetic field is aligned with the solar wind flow, the turbulent foreshock of the quasi-parallel bow shock covers the whole dayside. The effects of radial IMF are displayed most vividly in the 2.5D hybrid simulations by Sibeck et al (2008), Blanco-Cano et al (2009) Omidi et al (2009). There are also observations that show that during radial IMF the bow shock is closer to the Earth than predicted by the models (see Merka et al, 2003, and references therein).…”

Section: Discussionmentioning

confidence: 82%

“…2. The Advanced Composition Explorer (ACE) (Stone et al, 1998) and Wind (Acuña et al, 1995) spacecraft, acting as the solar wind monitors, were located near the Lagrangian point L1 at (X,Y,Z) GSE = (237, 36.4, −18.6) R E and (198.7, −33, −18.7) R E . Geotail (Nishida, 1994) was in the turbulent foreshock region near the subsolar point.…”

Section: Discussionmentioning

confidence: 99%

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Supermagnetosonic subsolar magnetosheath jets and their effects: from the solar wind to the ionospheric convection

et al. 2012

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Abstract. It has recently been proposed that ripples inherent to the bow shock during radial interplanetary magnetic field (IMF) may produce local high speed flows in the magnetosheath. These jets can have a dynamic pressure much larger than the dynamic pressure of the solar wind. On 17 March 2007, several jets of this type were observed by the Cluster spacecraft. We study in detail these jets and their effects on the magnetopause, the magnetosphere, and the ionospheric convection. We find that (1) the jets could have a scale size of up to a few R E but less than ∼6 R E transverse to the X GSE axis; (2) the jets caused significant local magnetopause perturbations due to their high dynamic pressure; (3) during the period when the jets were observed, irregular pulsations at the geostationary orbit and localised flow enhancements in the ionosphere were detected. We suggest that these inner magnetospheric phenomena were caused by the magnetosheath jets.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Supermagnetosonic subsolar magnetosheath jets and their effects: from the solar wind to the ionospheric convection

et al. 2012

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“…Thus foreshock cavitons in our simulations do not correspond to the signatures identified in the past as foreshock cavities. In a recent paper Sibeck et al [2008] compare observations of isolated foreshock cavities with hybrid simulation results for a day with a small cone angle. They conclude that isolated foreshock cavities are associated with changes in the IMF orientation which causes the spacecraft to go in and out of the foreshock.…”

Section: Cavitonsmentioning

confidence: 99%

“…Most previous works related to foreshock cavities held the common view that cavities are distinct structures inside the foreshock. However, in a recent study Sibeck et al [2008] showed that previously identified isolated cavities can be interpreted as crossings of the foreshock boundary. This raises the question of whether all cavities are foreshock boundary encounters or if some of the observed density depressions can be structures within the foreshock.…”

Section: Introductionmentioning

confidence: 99%

Global hybrid simulations: Foreshock waves and cavitons under radial interplanetary magnetic field geometry

2009

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[1] We use global hybrid (kinetic ions and fluid electrons) simulations to study the solar wind interaction with the magnetosphere for a radial (q vB = 0) interplanetary magnetic field (IMF) geometry. Global hybrid simulations provide a collective picture of processes taking place in the foreshock, bow shock, and magnetosheath. Because ions are treated as particles, these codes also give information on ion-scale microphysics. Under radial IMF geometry, the foreshock forms in front of the dayside magnetosphere, and the plasma convecting downstream is very perturbed. The foreshock is permeated by weakly compressive ultralow frequency (ULF) waves that propagate at angles up to 30°to the ambient field. These weakly compressive waves are generated by field-aligned ions. Wave-Particle interaction results in ion scattering, while wave amplitude grows and fluctuations become compressive as they approach the shock. While weakly compressive waves are dominant far from the shock, a second population of ULF fluctuations arises close to it. These fast magnetosonic waves propagate at large angles to the magnetic field and are linearly polarized. We find that, in addition to the ULF waves, large depressions in density and magnetic field magnitude form near the shock. These density cavitons or depressions are bounded by enhanced magnetic fields, and inside them, hot diffuse ions are present. Foreshock density cavitons in our simulations are embedded in regions with ULF activity, which is in contrast to the isolated character of ''foreshock cavities'' reported previously. We show that density cavitons form due to the nonlinear interaction of the two types of waves present in the foreshock. Wave interaction also modifies the characteristics of weakly compressive waves. A comparison of our results with Cluster observations reveals that the characteristics of weakly compressive waves in our simulation resemble the properties of right-handed 30-s waves found in the terrestrial foreshock. Likewise, we show the existence of density cavitons, or depressions, in regions of Earth's foreshock permeated by ULF waves. The properties of these observed Cluster cavitons are similar to the ones we find in the simulations.Citation: Blanco-Cano, X., N. Omidi, and C. T. Russell (2009), Global hybrid simulations: Foreshock waves and cavitons under radial interplanetary magnetic field geometry,

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“…Once the ions have escaped from the bow shock, their field-aligned velocities do not change as long as the IMF is uniform because the Lorentz force does not act in the field-aligned direction. Depending on the ratio of the beam's field-aligned velocity (V ) and the solar wind velocity component perpendicular to the magnetic field (V SW⊥ ), these ions experience a so-called velocity filter effect to either completely escape from the bow shock within the magnetically-connected foreshock region or return back to the bow shock (Eastwood et al, 2005;Sibeck et al, 2008). To diagnose whether the ions will escape or return, it is useful to obtain the field-aligned velocity in the de Hoffman-Teller frame (Miao et al, 2009, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars

et al. 2011

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Abstract. Foreshock ions are compared between Venus andMars at energies of 0.6∼20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2∼6 times the solar wind energy) that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a fieldaligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward inCorrespondence to: M. Yamauchi (m.yamauchi@irf.se) terplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and effects of cold ion abundance in the bow shock are discussed.

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On the edge of the foreshock: model-data comparisons

Cited by 46 publications

References 15 publications

Supermagnetosonic subsolar magnetosheath jets and their effects: from the solar wind to the ionospheric convection

Supermagnetosonic subsolar magnetosheath jets and their effects: from the solar wind to the ionospheric convection

Global hybrid simulations: Foreshock waves and cavitons under radial interplanetary magnetic field geometry

Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars

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