Speaker
Alexander A. Soloviev
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.4017.pdf
Experimental study of laser plasma expansion in presence of the strong external
magnetic field
A. Soloviev1, K. Burdonov1, S. N. Chen1,2, G. Revet2, S. Pikuz3, E. Filippov3, M.
Cerchez4, T. Gangly2, A. Sladkov1, A. Korzhimanov1, V. Ginzburg1, E. Khazanov1, A.
Kochetkov1, A. Kuzmin1, I. Shaykin1, A. Shaykin1, I. Yakovlev1, M. Starodubtsev1, and
J. Fuchs1,2
1
Institute of Applied Physics, Russian Academy of Science, Nizhny Novgorod, Russia
2
LULI, CNRS UMLR7605, Ecole Polytechnique, Palaiseau, France
3
Joint Institute for High Temperatures, Russian Academy of Science, Moscow, Russia
4
HHU, Dusseldorf, Germany
We present recent experiments, performed at PEARL laser facility (Institute of Applied
Physics), aimed at investigating the dynamic of plasma flows expending into the ambient
magnetic field. The main attention has been paid to the case when the plasma flow penetrates
across the magnetic field. Such geometry of the experiment is related to laboratory modeling
of accretion of matter into compact stars and, especially, to the processes developing at the
inner edge of the accretion disks in the region where the pressure of the magnetic field of the
star is of the order of the dynamic pressure of the accreting plasma. Using two femtosecond
interferometers, 2D snapshots of plasma flow expanding into the ambient magnetic field have
been obtained in two geometries (perpendicular and parallel to the direction of the magnetic
field lines) and in different times after the plasma flow formation. It has been found that the
plasma flow exhibits strong Rayleigh–Taylor instability in the region where the pressure of the
magnetic field is of the order of the plasma flow dynamic pressure. As a result of this instability,
the plasma flow deeply penetrates into the magnetic field forming a narrow (‘pancake-like’)
tongs of supersonic plasma streams (in practice, a thin plasma layer penetrates between the
magnetic field lines). This result, confirmed also by numerical modeling, calls into question the
generally accepted astrophysical model of matter accretion in form of ‘accretion columns’,
when the matter falls onto the star from the inner edge of the accretion disc (which is formed at
the magnetic/plasma dynamic pressures balance region) along the magnetic field lines to the
polar regions of the star. On the contrary, the results of the present experiment make it possible
to propose an alternative model for the fall of matter onto the equator of the star.
