Statistical analysis of mirror mode waves in sheath regions driven by interplanetary coronal mass ejection

Ala‐Lahti, Matti; Kilpua, Emilia; Dimmock, A. P.; Osmane, Adnane; Pulkkinen, Tuija; Souček, J.

doi:10.5194/angeo-36-793-2018

Cited by 34 publications

(53 citation statements)

References 67 publications

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“…It has been shown that a typical magnetic hole at 0.72 AU has an asymmetrical shape in the form of a rotational ellipsoid with major to minor axes ratio of 2.45:1 (Zhang, Russell, Baumjohann, et al, 2008). A separate analysis at 1 AU showed a consistent shape with the elongation ratio of 1.84:1, suggesting that MHs develop inside 0.72 AU and their shape is preserved in the solar wind (Xiao et al, 2010;Ala-Lahti et al, 2018;Baumgärtel, 1999). While Burlaga et al (2007) showed that the normalized size of MHs in the heliosheath is of the same order of magnitude as their size at 1 AU.…”

Section: Statistical Analysis Of Magnetic Holesmentioning

confidence: 93%

Magnetic Holes Upstream of the Martian Bow Shock: MAVEN Observations

Madanian

Halekas

Mazelle

et al. 2019

Preprint

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Magnetic holes (MHs) are pressure‐balanced structures characterized by distinct decreases in the interplanetary magnetic field strength in otherwise unperturbed solar wind. In this paper we present an analysis of MHs upstream of the Martian bow shock based on 3 months of observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Plasma properties within and around these structures as well as their shape characteristics are examined. We find an occurrence rate of around 2.1 events per day. About 51% of all events are of linear type with magnetic field rotation across the hole less than 10°. We observe linear MHs both as isolated events and as part of a train of MHs. The proton temperature anisotropy inside MHs increases, while alpha particles remain mostly isotropic. The average electron temperature inside MHs modestly increases with increasing hole depth. The duration of linear holes at 1.5 AU shows an increase compared to durations at smaller heliocentric distances, but the structures remain asymmetrical and ellipsoid. A case study of MHs accompanied by a population of heavy pickup ions is also discussed.

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Section: Statistical Analysis Of Magnetic Holesmentioning

confidence: 93%

Magnetic Holes Upstream of the Martian Bow Shock: MAVEN Observations

Madanian

Halekas

Mazelle

et al. 2019

Preprint

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“…Here n denotes the proton number density, k B the Boltzmann constant, B the local magnetic field strength and 0 the permeability of free space (Hasegawa, 1969). We note that a temperature anisotropy is the only likely generation mechanism for MM waves, and the interest in MM wave observations is less the mechanism of their generation but rather the origin of the generating temperature anisotropy (Ala-Lahti et al, 2018).…”

Section: Wave Generationmentioning

confidence: 99%

Proton Temperature Anisotropies in the Plasma Environment of Venus

et al. 2019

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Velocity distribution functions (VDFs) are a key to understanding the interplay between particles and waves in a plasma. Any deviation from an isotropic Maxwellian distribution may be unstable and result in wave generation. Using data from the ion mass spectrometer IMA (Ion Mass Analyzer) and the magnetometer (MAG) onboard Venus Express, we study proton distributions in the plasma environment of Venus. We focus on the temperature anisotropy, that is, the ratio between the proton temperature perpendicular (T⊥) and parallel (T‖) to the background magnetic field. We calculate average values of T⊥ and T‖ for different spatial areas around Venus. In addition we present spatial maps of the average of the two temperatures and of their average ratio. Our results show that the proton distributions in the solar wind are quite isotropic, while at the bow shock stronger perpendicular than parallel heating makes the downstream VDFs slightly anisotropic (T⊥/T‖ > 1) and possibly unstable to generation of proton cyclotron waves or mirror mode waves. Both wave modes have previously been observed in Venus's magnetosheath. The perpendicular heating is strongest in the near‐subsolar magnetosheath (T⊥/T‖≈3/2), which is also where mirror mode waves are most frequently observed. We believe that the mirror mode waves observed here are indeed generated by the anisotropy. In the magnetotail we observe planetary protons with largely isotropic VDFs, originating from Venus's ionosphere.

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“…ICME sheaths also share some general properties of the fast solar wind (e.g., high fluctuation amplitudes) and slow wind (e.g., lower Alfvénicity). Plasma fluctuations found in ICME sheaths may comprise pre-existing fluctuations from the swept-up solar wind and fluctuations generated locally within the sheath, and may include a broad range of wave activity (e.g., Liu et al 2006;Ala-Lahti et al 2018;Ala-Lahti et al 2019). Global properties of the sheaths such as bulk flow speed can modify sheath turbulence properties, particularly in the kinetic range (Riazantseva et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Good

Ala‐Lahti

Palmerio

et al. 2020

ApJ

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The sheaths of compressed solar wind that precede interplanetary coronal mass ejections (ICMEs) commonly display large-amplitude magnetic field fluctuations. As ICMEs propagate radially from the Sun, the properties of these fluctuations may evolve significantly. We have analyzed magnetic field fluctuations in an ICME sheath observed by MESSENGER at 0.47 au and subsequently by STEREO-B at 1.08 au while the spacecraft were close to radial alignment. Radial changes in fluctuation amplitude, compressibility, inertial-range spectral slope, permutation entropy, Jensen-Shannon complexity, and planar structuring are characterized. These changes are discussed in relation to the evolving turbulent properties of the upstream solar wind, the shock bounding the front of the sheath changing from a quasi-parallel to quasi-perpendicular geometry, and the development of complex structures in the sheath plasma.

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Statistical analysis of mirror mode waves in sheath regions driven by interplanetary coronal mass ejection

Cited by 34 publications

References 67 publications

Magnetic Holes Upstream of the Martian Bow Shock: MAVEN Observations

Magnetic Holes Upstream of the Martian Bow Shock: MAVEN Observations

Proton Temperature Anisotropies in the Plasma Environment of Venus

Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

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