Occurrence rate of magnetic holes between 0.72 and 1 AU: comparative study of Cluster and VEX data

Amariutei, O. A.; Walker, S. N.; Zhang, T. L.

doi:10.5194/angeo-29-717-2011

Cited by 11 publications

(8 citation statements)

References 30 publications

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“…In spite of their closeness to THEMIS D these significant magnetic depressions are not evident in the data of THEMIS A and E which led Ge et al [2011] to conclude that none of the structures was observed by multiple spacecraft. The magnetic profile of these magnetic depressions does indeed look very similar to the mirror structures commonly observed in magnetosheath [e.g., Chisham et al, 1999;Amariutei et al, 2011] or in the solar wind [Zhang et al, 2009]. It must be noted that even though the magnetic depressions are most evident in the GSM B z component their effect can also be observed in the two other components of the magnetic field.…”

Section: Instrumentation and Datasupporting

confidence: 74%

Magnetic holes in the vicinity of dipolarization fronts: Mirror or tearing structures?

et al. 2012

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[1] Magnetic holes filled with isotropic energetic electrons (up to a few 10 5 eV) have been observed by THEMIS in the vicinity of dipolarization fronts. These structures can partially contribute to the initial seed population of energetic electrons within the magnetosphere; therefore finding their nature is important for understanding of the population of high energy electrons within the magnetosphere. Previously, these structures have been interpreted as the result of the mirror instability due to the similarity in their appearance with mirror dips observed in the terrestrial magnetosheath and solar wind. The THEMIS data shown here prove that the measured properties of these structures contradict to the interpretation as mirror waves. In the present study it is shown that these waves do not exhibit the effects on the ion population that are expected due to mirror wave structures. However, they do have a pronounced effect on the high energy electron population. The evolution of the high energy electron population within these structures is investigated. It is then argued that the tearing instability can be responsible for their generation.

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Section: Instrumentation and Datasupporting

confidence: 74%

Magnetic holes in the vicinity of dipolarization fronts: Mirror or tearing structures?

et al. 2012

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“…The most commonly invoked formation mechanism of linear magnetic holes is the mirror-mode instability, where in thermally dominated (i.e., high β) plasmas, strong temperature anisotropy can give rise to "hole-like" signatures in the density [Winterhalter et al, 1994]. Because the temperature anisotropy observed inside these structures is nearly always mirror stable, it is often suggested that the structures have formed elsewhere and evolved to their as-measured form [Stevens and Kasper, 2007;Russell et al, 2008;Amariutei et al, 2011]. An alternative proposed formation mechanism is from solitary waves, where steepened magnetohydrodynamic waves generate large-scale depletions in the magnetic field [Buti et al, 2001;Tsurutani et al, 2002].…”

Section: Introductionmentioning

confidence: 99%

Electron dynamics in a subproton‐gyroscale magnetic hole

Gershman

Dorelli

Viñas

et al. 2016

Geophysical Research Letters

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Magnetic holes are ubiquitous in space plasmas, occurring in the solar wind, downstream of planetary bow shocks, and inside the magnetosphere. Recently, kinetic‐scale magnetic holes have been observed near Earth's central plasma sheet. The Fast Plasma Investigation on NASA's Magnetospheric Multiscale (MMS) mission enables measurement of both ions and electrons with 2 orders of magnitude increased temporal resolution over previous magnetospheric instruments. Here we present data from MMS taken in Earth's nightside plasma sheet and use high‐resolution particle and magnetometer data to characterize the structure of a subproton‐scale magnetic hole. Electrons with gyroradii above the thermal gyroradius but below the current layer thickness carry a current sufficient to account for a ~10–20% depression in magnetic field magnitude. These observations suggest that the size and magnetic depth of kinetic‐scale magnetic holes is strongly dependent on the background plasma conditions.

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“…As such, our observation demonstrates properties of another form of current sheet referred to as a magnetic hole or magnetic bubble and would be the first time such a structure has been found in the ionosphere of Mars. Such structures have been identified in the solar wind (Turner et al, 1977;Fitzenreiter and Burlaga, 1978;Stevens and Kasper, 2007;Zhang et al, 2008a,b;Amariutei et al, 2011), in the Earth's magnetosheath (Kaufmann et al, 1970;Tsurutani et al, 1982;Hubert et al, 1989;Fazakerley and Southwood, 1994;Schwartz et al, 1996;Lucek et al, 1999) in the magnetosheath of Jupiter (Tsurutani et al, 1993;Balogh et al, 1992;Erd} os and Balogh, 1996) in cometary plasma (Russell et al, 1987) and at the borders of the heliosphere (Tsurutani et al, 1992).…”

Section: Summary and Discussionmentioning

confidence: 96%

Properties of a large-scale flux rope and current sheet region on the dayside of Mars: MGS MAG/ER and MEX ASPERA-3 ELS observations

Soobiah

Wild

Beharrell

et al. 2014

Icarus

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a b s t r a c tWe present dual spacecraft observations by MGS MAG/ER and MEX ASPERA-3 ELS of a large-scale magnetic flux rope on the dayside of Mars that occurs in close proximity to the crustal magnetic fields and a dayside current sheet region. A current sheet (including the large-scale flux rope) was observed on repeated MGS orbits when the draped solar wind magnetic field present in the ionosphere had a þB y component (in MSO). Minimum Variance Analysis (MVA) of the large-scale flux rope and two current sheet crossings that occur after show a common peak in magnetic field along the intermediate variance direction, indicating the normal component of a reconnecting current sheet. All repeated orbits demonstrated evidence of a plasma boundary by the decrease in electron differential flux above 100 eV when moving into regions dominated by the crustal magnetic field, and coincided with the measured magnetic field strength being double the undisturbed crustal magnetic field. We argue this forms evidence of magnetic reconnection between crustal magnetic fields and draped solar wind magnetic field (from ionosphere or magnetosheath) at a ''mini-magnetopause'' type boundary on the dayside of Mars. Similar electron pitch angle distributions observed during the large-scale flux rope, current sheet crossings, and regions of radial crustal magnetic field, suggest these regions share a common magnetic field topology for the trapping of magnetosheath particles on open crustal magnetic fields on the dayside of Mars. As such, indicates a trapping quadrupole magnetic field exist either at the magnetic reconnection X-line region or where open crustal magnetic fields meet oppositely directed solar wind magnetic field. At a time when the draped solar wind magnetic field present in the ionosphere was weaker in strength, the current sheet crossing was observed over an extended region of 2000 km. The extended current sheet demonstrated properties of a hot diamagnetic region and features of a mirror mode structure or magnetic hole, the first time such a structure has been found in the ionosphere of Mars. Observations suggests lower energy electrons could be accelerated by a local process of perpendicular heating/pitch angle diffusion and supports similar results at the Earth's polar cusp reported by Nykyri et al. (Nykyri et al. [2012]. J. Atmos. Sol-Terr. Phys. 87, 70). Such large scale and energetic structures are usually associated with regions beyond a planet's ionosphere, and the occurrence within the ionosphere of Mars may have an important impact on escape processes and the evolution of the martian atmosphere.

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Occurrence rate of magnetic holes between 0.72 and 1 AU: comparative study of Cluster and VEX data

Cited by 11 publications

References 30 publications

Magnetic holes in the vicinity of dipolarization fronts: Mirror or tearing structures?

Magnetic holes in the vicinity of dipolarization fronts: Mirror or tearing structures?

Electron dynamics in a subproton‐gyroscale magnetic hole

Properties of a large-scale flux rope and current sheet region on the dayside of Mars: MGS MAG/ER and MEX ASPERA-3 ELS observations

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