Observations of mirror waves and plasma depletion layer upstream of Saturn's magnetopause

Violante, L.; Cattaneo, M. B. Bavassano; Moreno, G.; Richardson, J. D.

doi:10.1029/94ja02703

Cited by 66 publications

(51 citation statements)

References 21 publications

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“…The plasma density decreases and magnetic field strength increases within it. An investigation of Cassini measurements in Saturn's magnetosheath by Masters et al (2014) found that in this case there is no difference in the plasma depletion layer for northward and southward IMF, which is contrary to the results of related Voyager measurements that indicated an IMF effect (Violante et al, 1995). Masters et al (2014) inferred that reconnection at the dayside magnetopause is not effective at Saturn.…”

Section: Southward and Northward Imfcontrasting

confidence: 44%

Open and partially closed models of the solar wind interaction with outer planet magnetospheres: the case of Saturn

et al. 2017

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Abstract. A wide variety of interactions take place between the magnetized solar wind plasma outflow from the Sun and celestial bodies within the solar system. Magnetized planets form magnetospheres in the solar wind, with the planetary field creating an obstacle in the flow. The reconnection efficiency of the solar-wind-magnetized planet interaction depends on the conditions in the magnetized plasma flow passing the planet. When the reconnection efficiency is very low, the interplanetary magnetic field (IMF) does not penetrate the magnetosphere, a condition that has been widely discussed in the recent literature for the case of Saturn. In the present paper, we study this issue for Saturn using Cassini magnetometer data, images of Saturn's ultraviolet aurora obtained by the HST, and the paraboloid model of Saturn's magnetospheric magnetic field. Two models are considered: first, an open model in which the IMF penetrates the magnetosphere, and second, a partially closed model in which field lines from the ionosphere go to the distant tail and interact with the solar wind at its end. We conclude that the open model is preferable, which is more obvious for southward IMF. For northward IMF, the model calculations do not allow us to reach definite conclusions. However, analysis of the observations available in the literature provides evidence in favor of the open model in this case too. The difference in magnetospheric structure for these two IMF orientations is due to the fact that the reconnection topology and location depend on the relative orientation of the IMF vector and the planetary dipole magnetic moment. When these vectors are parallel, two-dimensional reconnection occurs at the low-latitude neutral line. When they are antiparallel, three-dimensional reconnection takes place in the cusp regions. Different magnetospheric topologies determine different mapping of the open-closed boundary in the ionosphere, which can be considered as a proxy for the poleward edge of the auroral oval.

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Section: Southward and Northward Imfcontrasting

confidence: 44%

Open and partially closed models of the solar wind interaction with outer planet magnetospheres: the case of Saturn

et al. 2017

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“…Mirror mode structures have been detected in the magnetosheaths of the Earth, Jupiter and Saturn (Tsurutani et al, 1982(Tsurutani et al, , 1984Balogh et al, 1992;Violante et al, 1995;Bavassano Cattaneo et al, 1998;Baumjohann et al, 1999;Lucek et al, 1999;Soucek et al, 2008;Balikhin et al, 2009). They are characterized by small or no changes in the magnetic field across the structures, with scale of tens of proton gyroradii.…”

Section: Introductionmentioning

confidence: 99%

Cluster-C1 observations on the geometrical structure of linear magnetic holes in the solar wind at 1 AU

et al. 2010

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Abstract.Interplanetary linear magnetic holes (LMHs) are structures in which the magnetic field magnitude decreases with little change in the field direction. They are a 10-30% subset of all interplanetary magnetic holes (MHs). Using magnetic field and plasma measurements obtained by Cluster-C1, we surveyed the LMHs in the solar wind at 1 AU. In total 567 interplanetary LMHs are identified from the magnetic field data when Cluster-C1 was in the solar wind from 2001 to 2004. We studied the relationship between the durations and the magnetic field orientations, as well as that of the scales and the field orientations of LMHs in the solar wind. It is found that the geometrical structure of the LMHs in the solar wind at 1 AU is consistent with rotational ellipsoid and the ratio of scales along and across the magnetic field is about 1.93:1. In other words, the structure is elongated along the magnetic field at 1 AU. The occurrence rate of LMHs in the solar wind at 1 AU is about 3.7 per day. It is shown that not only the occurrence rate but also the geometrical shape of interplanetary LMHs has no significant change from 0.72 AU to 1 AU in comparison with previous studies. It is thus inferred that most of interplanetary LMHs observed at 1 AU are formed and fully developed before 0.72 AU. The present results help us to study the formation mechanism of the LMHs in the solar wind.

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“…Different mirror mode intervals with B and D pointing in different directions will yield estimates for all offset components O x , O y , and O z . Furthermore, mirror modes are not restricted to the Earth's magnetosheath but have also been observed in other solar system environments (e.g., Russell et al, 1989;Glassmeier et al, 1993;Violante et al, 1995;Schmid et al, 2014). Hence, magnetic field measurements in distant regions of the solar system may benefit from offset determinations by the mirror mode method, as well.…”

Section: Discussionmentioning

confidence: 99%

On determining fluxgate magnetometer spin axis offsets from mirror mode observations

Plaschke

Narita

2016

Ann. Geophys.

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Abstract. In-flight calibration of fluxgate magnetometers that are mounted on spacecraft involves finding their outputs in vanishing ambient fields, the so-called magnetometer offsets. If the spacecraft is spin-stabilized, then the spin plane components of these offsets can be relatively easily determined, as they modify the spin tone content in the de-spun magnetic field data. The spin axis offset, however, is more difficult to determine. Therefore, usually Alfvénic fluctuations in the solar wind are used. We propose a novel method to determine the spin axis offset: the mirror mode method. The method is based on the assumption that mirror mode fluctuations are nearly compressible such that the maximum variance direction is aligned to the mean magnetic field. Mirror mode fluctuations are typically found in the Earth's magnetosheath region. We introduce the method and provide a first estimate of its accuracy based on magnetosheath observations by the THEMIS-C spacecraft. We find that 20 h of magnetosheath measurements may already be sufficient to obtain high-accuracy spin axis offsets with uncertainties on the order of a few tenths of a nanotesla, if offset stability can be assumed.

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Observations of mirror waves and plasma depletion layer upstream of Saturn's magnetopause

Cited by 66 publications

References 21 publications

Open and partially closed models of the solar wind interaction with outer planet magnetospheres: the case of Saturn

Open and partially closed models of the solar wind interaction with outer planet magnetospheres: the case of Saturn

Cluster-C1 observations on the geometrical structure of linear magnetic holes in the solar wind at 1 AU

On determining fluxgate magnetometer spin axis offsets from mirror mode observations

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