The collisionless deceleration of an ionized cloud dispersing in a uniform plasma in a magnetic field

Hybrid simulations of debris‐ambient ion interactions in astrophysical explosions

“…Simulations have also been applied to model the super‐Alfvenic expansion of debris in a uniform magnetized plasma, where the debris is stopped by the ambient plasma, a regime that is not as well documented with experimental results. An early two‐dimensional (2‐D) hybrid simulation model by Bashurin et al [1983] was used to model the debris expansion, similar to the calculations presented in this paper. More generally, simulations have been done in both one spatial dimension [ Golubev et al , 1978; Lembege and Simonet , 2001; Yamauchi and Ohsawa , 2007] and two spatial dimensions [ Thomas and Brecht , 1985, 1987] to model super‐Alfvenic debris expansions to understand how collisionless shocks in magnetized plasmas are formed.…”

Collisionless momentum transfer in space and astrophysical explosions

“…One of its most significant findings was the unanticipated displacement of the barium ion 'comet head' (and an oppositely directed deflection of the streaming hydrogen ions) transverse to both the solar wind flow and the interplanetary magnetic field, defying the conventional expectation that the barium ions would simply move downwind 4 . While subsequent theoretical and computational e orts [5][6][7] to understand the cause of the transverse motion reached di ering conclusions, several authors 5 attributed the observations to Larmor coupling 8,9 , a collisionless momentum exchange mechanism believed to occur in various astrophysical and space-plasma environments 10,11 and to participate in cosmic magnetized collisionless shock formation [12][13][14] . Here we present the detection of Larmor coupling in a reproducible laboratory experiment that combines an explosive laser-produced plasma cloud with preformed, magnetized ambient plasma in a parameter regime relevant to the AMPTE barium releases.…”

“…This interaction, termed Larmor coupling, thus allows the moving debris cloud to pick up the swept-over ambient ions. Larmor coupling has received extensive theoretical and numerical investigation over the past few decades, both as a basic plasma process 8,9 and as a key mechanism in the evolution of various astrophysical and space phenomena, including man-made ionospheric explosions 11 , the AMPTE artificial comets 5 , and the formation of cosmic magnetized collisionless shocks [12][13][14] . However, this process has never before been observed in a laboratory setting.…”

Collisionless interaction of an energetic laser produced plasma with a large magnetoplasma

“…The parameter d will be determined in principle by the size of the expanding diamagnetic cavity formed by the laser plasma (see details in Bashurin et al 1984). In the perpendicular case the cavity radius is given by the equal-charge radius:…”

“…Another key parameter to be considered in the shock formation is the Larmor-coupling efficiency (Bashurin et al 1984;Golubev et al 1978;Winske and Gary 2007) that depends strongly on the magnetic laminar mechanism (MLM) criterion: δ = R 2 /(R L · R L * ) must be greater than 1, where R L is the Larmor radius of the laser-plasma ions, which is proportional to the laser-plasma front speed v lp , and R L * is the directed Larmor radius of the background ions, also proportional to v lp (Zakharov 2003).…”