Properties of saturated bi-stable magnetosheath mirror structures

0452255 - ÚFA 2016 IT eng A - Abstrakt
Souček, Jan - Escoubet, C. P.
Properties of saturated bi-stable magnetosheath mirror structures.
Cluster 15th and Double Star 10th anniversary workshop. Venice: CAA - ESA, 2015. s. 13-14.
[Cluster Workshop /25./. 12.10.2015–16.10.2015, Venice]
Institucionální podpora: RVO:68378289
Klíčová slova: magnetospheric physics * plasma waves and instabilities * magnetosheath
Kód oboru RIV: BL - Fyzika plazmatu a výboje v plynech
http://caa.estec.esa.int/images/cluster_workshops/25/Cluster25_abstract_book4.pdf

Mirror mode structures in the magnetosheath are characterized by non-periodic low frequency field and plasma oscillations, where magnetic field magnitude alternates between two meta-stable values (high and low field level). This property of fully saturated mirror modes is often referred to as bi-stability in the literature. We investigated mirror structures of this form using two years of Cluster observations focusing on the width of the structures and magnitudes of the low field and high field areas. In the statistical study it was observed that the plasma in the high field areas is usually stable or marginally stable with respect to mirror instability, but plasma corresponding to the low field level is unstable. The relative width of the low and high field areas is thus proportional to the degree of instability of the plasma consistently with the previously described association between mirror mode shape (magnetic peaks or dips) and distance to mirror instability threshold. It is shown that the areas of low magnetic field level and unstable plasma are usually comparable or smaller than the mirror mode wavelength, indicating fully saturated state where the mirror instability is no longer efficient. The observed values were compared with low field saturation level predicted from particle trapping theory and high field level calculated from a marginal stability condition.
Trvalý link: http://hdl.handle.net/11104/0253283