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

Hietala, Heli; Partamies, Noora; Laitinen, T. V.; Clausen, L. B. N.; Facskó, G.; Vaivads, A.; Koskinen, H.; Dandouras, I.; Rème, H.; Lucek, E.

doi:10.5194/angeo-30-33-2012

Cited by 116 publications

(263 citation statements)

References 54 publications

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“…A substantial fraction of jets is believed to originate from bow shock ripples or undulations , which are common at the reforming, patchy, quasi-parallel bow shock (Schwartz and Burgess, 1991;Omidi et al, 2005). At inclined shock surfaces, the solar wind plasma is compressed, but less decelerated and thermalized, leading to entities of dense and fast plasma inside the magnetosheath (Hietala et al, 2009(Hietala et al, , 2012. Other generation mechanisms are related to IMF discontinuities, discontinuity-related hot flow anomalies (HFAs), and spontaneous HFAs originating from foreshock cavitons (Lin et al, 1996a, b;Savin et al, 2012;Zhang et al, 2013;Kajdič et al, 2013;Omidi et al, 2013;Archer et al, 2014;Chu et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, large-scale jets with a cross-sectional diameter of over 2 R E (Earth radii) have been found to impact the subsolar magnetopause at relatively high rates (with respect to other transients) of once every 21 min, on average, and once every 6 min when the IMF cone angle is low (under 30 • ). These impact rates are even more remarkable when taking into account that jets of smaller scale occur more often and that typical jet scales are on the order of 1 R E (Karlsson et al, 2012;Archer et al, 2012;Hietala et al, 2012;Plaschke et al, 2013Plaschke et al, , 2016Gunell et al, 2014). When jets impact the magnetopause, the consequences can be substantial.…”

Section: Introductionmentioning

confidence: 99%

“…Due to their excess dynamic pressure, they will indent the magnetopause locally, generating surface waves on the boundary and inner magnetospheric compressional waves (Glassmeier and Heppner, 1992;Plaschke et al, 2009;Shue et al, 2009;Amata et al, 2011;Plaschke and Glassmeier, 2011;Archer et al, F. Plaschke and H. Hietala: Jet flow patterns 2013a, b). In addition, local reconnection may perhaps be triggered at the magnetopause (Hietala et al, 2012). In the magnetosphere, the radiation belt electron population may be modified by magnetopause shadowing (Elkington et al, 2003;Turner et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…In the magnetosphere, the radiation belt electron population may be modified by magnetopause shadowing (Elkington et al, 2003;Turner et al, 2012). Consequences may even be seen on the ground, in the form of increased ionospheric convection, geomagnetic field variations, and possibly "throat" aurora observations (Hietala et al, 2012;Dmitriev and Suvorova, 2012;Archer et al, 2013b;Han et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Plasma flow patterns in and around magnetosheath jets

Plaschke¹,

Hietala²

2018

Ann. Geophys.

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Abstract. The magnetosheath is commonly permeated by localized high-speed jets downstream of the quasi-parallel bow shock. These jets are much faster than the ambient magnetosheath plasma, thus raising the question of how that latter plasma reacts to incoming jets. We have performed a statistical analysis based on 662 cases of one THEMIS spacecraft observing a jet and another (second) THEMIS spacecraft providing context observations of nearby plasma to uncover the flow patterns in and around jets. The following results are found: along the jet's path, slower plasma is accelerated and pushed aside ahead of the fastest core jet plasma. Behind the jet core, plasma flows into the path to fill the wake. This evasive plasma motion affects the ambient magnetosheath, close to the jet's path. Diverging and converging plasma flows ahead and behind the jet are complemented by plasma flows opposite to the jet's propagation direction, in the vicinity of the jet. This vortical plasma motion results in a deceleration of ambient plasma when a jet passes nearby.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Plasma flow patterns in and around magnetosheath jets

Plaschke¹,

Hietala²

2018

Ann. Geophys.

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“…Therefore, it is plausible that during Alfvénic solar wind, the IMF directions change Figure 6. In addition to HFAs and FBs, there are other types of density or dynamic pressure perturbations created in association with the quasi-parallel bow shock, such as spontaneous HFAs [Zhang et al, 2013], magnetosheath filamentary structures [Omidi et al, 2014], transient flux enhancements or jets [e.g., Němeček et al, 1998;Hietala et al, 2012], or large-scale low-frequency electromagnetic wavefronts [Karimabadi et al, 2014]. But these perturbations can occur without IMF discontinuities.…”

Section: The Bow Shock Perturbationsmentioning

confidence: 99%

Dawn‐dusk asymmetry in bursty hot electron enhancements in the midtail magnetosheath

et al. 2015

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Bursty (a few minutes) enhancements of hot electrons (1–10 keV) in the tail magnetosheath, which we name hot electron enhancements (HEEs), are sometimes observed. To understand the processes leading to HEEs, we have used 4 years of measurements from Acceleration Reconnection Turbulence and Electrodynamics of Moon's Interaction with the Sun mission to statistically investigate the dawn‐dusk asymmetry of HEEs in the midtail (x from −30 to −70 RE) magnetosheath and their correlations with the solar wind/interplanetary magnetic field (IMF) conditions. We find two strong dawn‐dusk asymmetries associated with HEEs: (1) they occur about 3 to 4 times more frequently on the dawnside. (2) Their fluxes on the dawnside are about twice as large as those on the duskside. The magnitudes of HEE fluxes are similar to those of the magnetosphere fluxes near the magnetopause, which are also a factor of 2 higher on the dawnside, indicating that the magnetosphere electrons are likely the source for HEEs and the cause for the HEE flux asymmetry. HEEs occur preferentially during higher solar wind speed, and the majority of HEEs are associated with sharp IMF direction changes and are accompanied by large and transient magnetosheath density changes. These correlations are stronger on the dawnside, suggesting that perturbations created near the quasi‐parallel bow shock, which is most of the time on the dawnside, associated with IMF discontinuities is a possible process leading to HEEs and could account for the higher HEE occurrence on the dawnside.

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On the generation of magnetosheath high‒speed jets by bow shock ripples

Hietala

Plaschke

2013

JGR Space Physics

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[1]The terrestrial magnetosheath is embedded with coherent high-speed jets of about 1RE in scale, predominantly during quasi-radial interplanetary magnetic field (IMF). When these high dynamic pressure (Pdyn) jets hit the magnetopause, they cause large indentations and further magnetospheric effects. The source of these jets has remained controversial. One of the proposed mechanisms is based on ripples of the quasi-parallel bow shock. In this paper, we combine for the first time, 4 years of subsolar magnetosheath observations from the Time History of Events and Macroscale Interactions during Substorms mission and corresponding NASA/OMNI solar wind conditions with model calculations of a rippled bow shock. Concentrating on the magnetosheath close to the shock during intervals when the angle between the IMF and the Sun-Earth line was small, we find that (1) 97% of the observed jets can be produced by local ripples of the shock under the observed upstream conditions; (2) the coherent jets form a significant fraction of the high Pdyn tail of the magnetosheath flow distribution; (3) the magnetosheath Pdyn distribution matches the flow from a bow shock with ripples that have a dominant amplitude to wavelength ratio of about 9% (∼0.1RE/1RE) and are present ∼12% of the time at any given location.

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

Cited by 116 publications

References 54 publications

Plasma flow patterns in and around magnetosheath jets

Plasma flow patterns in and around magnetosheath jets

Dawn‐dusk asymmetry in bursty hot electron enhancements in the midtail magnetosheath

On the generation of magnetosheath high‒speed jets by bow shock ripples

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