Flux pile-up and plasma depletion at the high latitude dayside magnetopause during southward interplanetary magnetic field: a cluster event study

Moretto, T.; Sibeck, D. G.; Lavraud, B.; Trattner, K. J.; Rème, H.; Balogh, A.

doi:10.5194/angeo-23-2259-2005

Cited by 6 publications

(6 citation statements)

References 27 publications

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“…Maynard et al (2004) reported that the layer shifts to the region behind the quasi-perpendicular bow shock. Finally, a pronounced depletion layer has indeed been observed on the high latitude magnetopause during an interval of southward IMF orientation (Moretto et al 2005). Contrary to model predictions, the depletion layer may become less prominent for small IMF cone angles (Anderson and Fuselier 1993).…”

Section: Earth's Magnetosheathmentioning

confidence: 85%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

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Section: Earth's Magnetosheathmentioning

confidence: 85%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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“…Earth's PDL has been the subject of many past studies, which have shown that the level of the terrestrial PDL is highly variable [ Paschmann et al ., , ; Crooker et al ., ; Song et al ., , ; Fuselier et al ., ; Hall et al ., ; Anderson and Fuselier , ; Anderson et al ., , ; Phan et al ., ; Farrugia et al ., , ; Wang et al ., , ; Moretto et al ., ; Erkaev et al ., ]. A dominant response of the terrestrial PDL to the magnetic shear across the low‐latitude magnetopause has been established, where the PDL level is lower at higher magnetic shear [ Anderson and Fuselier , ; Phan et al ., ; Anderson et al ., ].…”

Section: Introductionmentioning

confidence: 98%

The plasma depletion layer in Saturn's magnetosheath

et al. 2014

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A plasma depletion layer (PDL) of reduced plasma density and enhanced magnetic field strength can form in the magnetosheath (shocked solar wind) adjacent to the magnetopause boundary of a planetary magnetosphere. The dominant factor controlling the level of plasma depletion and field enhancement in Earth's PDL is the magnetic shear across the magnetopause, due to the influence of this parameter on magnetic reconnection at the boundary. Here we examine the PDL in Saturn's magnetosheath using Cassini spacecraft observations. For most Cassini magnetosheath intervals analyzed, there is some level of both plasma depletion and magnetic field enhancement approaching Saturn's magnetopause, consistent with the presence of a PDL. We find some evidence that the Saturnian PDL responds to the solar wind dynamic pressure, in the same sense as Earth's PDL. However, we find no evidence for a response of Saturn's PDL to the magnetic shear across the magnetopause, in contrast with the terrestrial case. Our results thus suggest that the rate of magnetic flux transport due to reconnection at Saturn's magnetopause is generally small in comparison to the rate of magnetic flux advection by the solar wind and are consistent with the expectation that conditions at Saturn's magnetopause are less favorable for magnetopause reconnection than those at Earth's magnetopause.

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“…PDLs have long been observed at Earth [ Cummings and Coleman , ; Crooker et al ., ; Fuselier et al ., ; Anderson and Fuselier , ; Paschmann et al ., ; Song et al ., ; Anderson et al ., , ; Phan et al ., , ; Farrugia et al ., ; Moretto et al ., ] leading to updated theoretical predictions [ Southwood and Kivelson , , ] and the successful reproduction of the phenomena with magnetohydrodynamic (MHD) simulations that take into account both magnetic field and hydrodynamic effects [ Lyon , ; Denton and Lyon , ; Siscoe et al ., ; Erkaev et al ., ; Wang et al ., , ; Nabert et al ., ]. Plasma depletion is a general process and occurs any time that magnetic flux is draped and compressed against an obstacle as demonstrated in studies of flux pileup and plasma depletion at Venus [ Luhmann , ; Zhang et al ., ], Mars [ Bertucci et al ., ; Øieroset et al ., ], Saturn [ Slavin et al ., ; Violante et al ., ], and even in the sheath of interplanetary coronal mass ejections [ Liu et al ., ].…”

Section: Introductionmentioning

confidence: 99%

“…At Earth, these layers typically form during periods of extended northward interplanetary magnetic field (IMF) [ Song et al ., ; Phan et al ., ; Anderson et al ., ]. They have also been observed, however, during periods of southward IMF with high upstream Alfvénic Mach numbers (~8–10) [ Anderson et al ., ] or high plasma density [ Moretto et al ., ] in which the high plasma β inhibits reconnection despite a thin magnetic barrier. Flux pileup and plasma depletion have rarely been studied in the low M A (3–5) regime.…”

Section: Introductionmentioning

confidence: 99%

Magnetic flux pileup and plasma depletion in Mercury's subsolar magnetosheath

et al. 2013

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Measurements from the Fast Imaging Plasma Spectrometer (FIPS) and Magnetometer (MAG) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft during 40 orbits about Mercury are used to characterize the plasma depletion layer just exterior to the planet's dayside magnetopause. A plasma depletion layer forms at Mercury as a result of piled‐up magnetic flux that is draped around the magnetosphere. The low average upstream Alfvénic Mach number (MA ~3–5) in the solar wind at Mercury often results in large‐scale plasma depletion in the magnetosheath between the subsolar magnetopause and the bow shock. Flux pileup is observed to occur downstream under both quasi‐perpendicular and quasi‐parallel shock geometries for all orientations of the interplanetary magnetic field (IMF). Furthermore, little to no plasma depletion is seen during some periods with stable northward IMF. The consistently low value of plasma β, the ratio of plasma pressure to magnetic pressure, at the magnetopause associated with the low average upstream MA is believed to be the cause for the high average reconnection rate at Mercury, reported to be nearly 3 times that observed at Earth. Finally, a characteristic depletion length outward from the subsolar magnetopause of ~300 km is found for Mercury. This value scales among planetary bodies as the average standoff distance of the magnetopause.

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Flux pile-up and plasma depletion at the high latitude dayside magnetopause during southward interplanetary magnetic field: a cluster event study

Cited by 6 publications

References 27 publications

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

The plasma depletion layer in Saturn's magnetosheath

Magnetic flux pileup and plasma depletion in Mercury's subsolar magnetosheath

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