Abstract Details
Abstracts
Author: Yanzeng Zhang
Requested Type: Poster
Submitted: 2024-04-12 13:00:30
Co-authors: Xianzhu Tang
Contact Info:
Los Alamos National Laboratory
Bikini Atoll Rd
Los Alamos, 87545
USA
Abstract Text:
Collisionless electrostatic shocks are common in space, astrophysical, and laboratory plasmas. They are known to have great
importance, e.g., in facilitating ion acceleration. Substantial
efforts have been dedicated to this area through experiments,
theories, and simulations since the 1960s. The most well-studied case resembles an explosion in which an over-pressured high-density plasma expands into the surrounding rarefied plasma with a shock front. The plasma temperature, or more specifically the electron temperature, is
initially uniform or larger in the expanding plasma (downstream of
the shock). A contrasting case, which is also ubiquitous in
astrophysical and laboratory plasmas, has a cold/dense plasma roughly in pressure balance with a background hot/dilute plasma. Such hot-cold interface is known to trigger a thermal collapse of the nearly collisionless hot background plasma (e.g. tokamak thermal quench), and an ablative mix of the cold ions with the background ions, which becomes particularly interesting if they are of different species, for example, in impurity pellet assimilation by fusion plasmas. We have found [Zhang et al EPL 141 54002 2023] that a parallel collisionless shock play an essential role in both the thermal collapse and ablative mix. Here, by employing the first-principles kinetic simulations, we show that such collisionless shock is electrostatic by nature and can be formed in hot-cold ablative mixing plasmas, even though the downstream plasma pressure is lower than that of the upstream. The shock front speed and width are shown to be affected differently by the upstream and downstream plasma temperatures. More interestingly, an intermittent emission of cold ion beams into the upstream is observed, the mechanism underlying which will be discussed.
Comments: