THEMIS observations of mirror structures: Magnetic holes and instability threshold

Balikhin, M. A.; Sagdeev, R. Z.; Walker, S. N.; Pokhotelov, O. A.; Sibeck, D. G.; Beloff, Natalia; Dudnikova, G. I.

doi:10.1029/2008gl036923

Cited by 64 publications

(76 citation statements)

References 21 publications

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“…We point out that the concept of a MM train is less important when MMs are dip-like; an individual dip-like MM forms a magnetic bottle and is stable by itself. In the case of peak-like MMs, in turn, a train of at least two MMs are required to create a structure between which ions are trapped (e.g., Balikhin et al, 2009Balikhin et al, , 2010. Thus, two dip-like MMs in the same MVA test interval are not necessarily related in any way.…”

Section: Summary and Discussionmentioning

confidence: 99%

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

et al. 2018

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Abstract. We present a comprehensive statistical analysis of mirror mode waves and the properties of their plasma surroundings in sheath regions driven by interplanetary coronal mass ejection (ICME). We have constructed a semiautomated method to identify mirror modes from the magnetic field data. We analyze 91 ICME sheath regions from January 1997 to April 2015 using data from the Wind spacecraft. The results imply that similarly to planetary magnetosheaths, mirror modes are also common structures in ICME sheaths. However, they occur almost exclusively as dip-like structures and in mirror stable plasma. We observe mirror modes throughout the sheath, from the bow shock to the ICME leading edge, but their amplitudes are largest closest to the shock. We also find that the shock strength (measured by Alfvén Mach number) is the most important parameter in controlling the occurrence of mirror modes. Our findings suggest that in ICME sheaths the dominant source of free energy for mirror mode generation is the shock compression. We also suggest that mirror modes that are found deeper in the sheath are remnants from earlier times of the sheath evolution, generated also in the vicinity of the shock.

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Section: Summary and Discussionmentioning

confidence: 99%

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

et al. 2018

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“…Recent studies (Balikhin et al, 2009 demonstrate the increase in plasma temperatures associated with magnetic troughs and argue that adiabatic invariants are not conserved in this process and that trapped particle dynamics needs to be considered to explain the observations. Our study is consistent with this qualitative statement: the increase in both temperatures is also seen in our example and it is at least partly due to the enhancement in particle populations at intermediate pitchangles.…”

Section: Discussionmentioning

confidence: 99%

Cluster observations of trapped ions interacting with magnetosheath mirror modes

Souček

Escoubet

2011

Ann. Geophys.

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Abstract. Mirror modes are among the most intense low frequency plasma wave phenomena observed in the magnetosheaths of magnetized planets. They appear as large amplitude non-propagating fluctuations in the magnetic field magnitude and plasma density. These structures are widely accepted to represent a non-linear stage of the mirror instability, dominant in plasmas with large ion beta and a significant ion temperature anisotropy T ⊥ /T > 1. It has long been recognized that the mirror instability both in the linear and non-linear stage is a kinetic process and that the behavior of resonant particles at small parallel velocities is crucial for its development and saturation. While the dynamics of the instability and the effect of trapped particles have been studied extensively in theoretical models and numerical simulations, only spurious observations of the trapped ions were published to date. In this work we used data from the Cluster spacecraft to perform the first detailed experimental study of ion velocity distribution associated with mirror mode oscillations. We show a conclusive evidence for the predicted cooling of resonant ions at small parallel velocities and heating of trapped ions at intermediate pitch angles.

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“…Pokhotelov (o.a.pokhotelov@sheffield.ac.uk) century these observations have also raised a number of intriguing conundrums such as the occurrence of mirror dips in regions of mirror stable plasma, the lack of mirror modes between peak structures even though the plasma is mirror unstable or the violation of adiabaticity in the ion temperatures. Recently the data from the THEMIS satellites were used to resolve these dilemmas in terms of the global structure of mirror modes and the role of the trapped particles in their dynamics (Balikhin et al, 2009(Balikhin et al, , 2010.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Mirror and Weibel modes: peculiarities of quasi-linear dynamics

et al. 2010

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Abstract.A theory for nonlinear evolution of the mirror modes near the instability threshold is developed. It is shown that during initial stage the major instability saturation is provided by the flattening of the velocity distribution function in the vicinity of small parallel ion velocities. The relaxation scenario in this case is accompanied by rapid attenuation of resonant particle interaction which is replaced by a weaker adiabatic interaction with mirror modes. The saturated plasma state can be considered as a magnetic counterpart to electrostatic BGK modes. After quasi-linear saturation a further nonlinear scenario is controlled by the mode coupling effects and nonlinear variation of the ion Larmor radius. Our analytical model is verified by relevant numerical simulations. Test particle and PIC simulations indeed show that it is a modification of distribution function at small parallel velocities that results in fading away of free energy driving the mirror mode. The similarity with resonant Weibel instability is discussed.

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THEMIS observations of mirror structures: Magnetic holes and instability threshold

Cited by 64 publications

References 21 publications

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

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

Cluster observations of trapped ions interacting with magnetosheath mirror modes

Nonlinear Mirror and Weibel modes: peculiarities of quasi-linear dynamics

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