nouveau bandeau du PNST 2022

Magnetospheric MultiScale Measurements of Energy Balance in Collisionless Plasma
Souhail Dahani  1@  , Benoit Lavraud  1, 2  , Vincent Génot  1  , Sergio Toledo-Redondo  3  , Rungployphan Kieokaew  1  , Naïs Fargette  4  , Gershman Daniel  5  , Barbara Giles  5  , Roy Torbert  6  , James Burch  7  
1 : Institut de recherche en astrophysique et planétologie
Institut National des Sciences de l'Univers : UMR5277, Université Toulouse III - Paul Sabatier, Observatoire Midi-Pyrénées, Centre National de la Recherche Scientifique : UMR5277, Institut National des Sciences de l'Univers, Centre National de la Recherche Scientifique
2 : Laboratoire d'Astrophysique de Bordeaux [Pessac]
Université de Bordeaux, Institut National des Sciences de l'Univers, Centre National de la Recherche Scientifique
3 : Department of Electromagnetism and Electronics, University of Murcia
4 : Blackett Laboratory, Imperial College London
5 : NASA Goddard Space Flight Center
6 : UNH Space Science Center [Durham]
7 : Southwest Research Institute [San Antonio]

The study of energy conversion in collisionless plasmas has remained largely inaccessible until recently thanks to the high-resolution, multi-spacecraft Magnetospheric MutliScale (MMS) observations. Direct derivation from the Vlasov-Maxwell equation provides a set of equations that describe the temporal evolution of the kinetic and internal energies. In this work, we investigate, in a multifluid framework, the terms that quantify the transfer to and from kinetic energy, i.e., pressure-gradient force term, and the electromagnetic energy term. The former accounts for plasma acceleration/deceleration from a pressure-gradient, while the latter accounts for plasma acceleration/deceleration from an electric field. We use in-situ observations from MMS to understand the relationship between the pressure-gradient force term and the electromagnetic energy term. We perform a statistical analysis of those parameters in different regions, i.e., regular magnetosheath regions, electron diffusion regions and bow shock crossings. The analysis reveals a weak but observable anti-correlation between the two terms for ions, implying energy balance. However, the expected relationship is less clear for electrons. Overall, the signs of the two terms are opposite, as expected. Possible explanations lie in the uncertainty associated with gradient measurements in pressure-gradient terms. In an approach aimed at understanding errors arising directly from gradient measurements, we modeled a pressure gradient from a regular magnetopause crossing. We measured the gradient using a 4 spacecraft technique and compared it to the analytical derivative. The analysis indicates that gradient values are underestimated when spacecraft separation is either comparable to the gradient scale or greater than the gradient scale. A more comprehensive analysis is underway to investigate the factors influencing gradient measurements, particularly the impact of signal noise on these measurements.


Personnes connectées : 4 Vie privée
Chargement...