Abstract
A laboratory plasma experiment was built to explore the eruptive behavior of arched magnetized plasmas with dimensionless parameters relevant to the Sun’s photosphere (β ≈ 10−3, Lundquist number ≈104, plasma radius/ion gyroradius ≈20, ion-neutral collision frequency ≫ion cyclotron frequency). Dynamic formation of a transient plasma jet was observed in the presence of the strapping magnetic field. The eruption leading to the jet is unintuitive because the arched plasma is both kink- and torus-stable. The jet structure erupts within a few Alfvén transit times from the formation of the arched plasma. Extensive measurements of plasma temperature, density, magnetic field, and flows are presented. In its early stages, the jet plasma flows away from the arch with supersonic speeds (Mach 1.5). This high-speed flow persists up to the resistive diffusion time in the arched plasma and is driven by large gradients in the magnetic and thermal pressures near the birthplace of jets. There are two distinct electric current channels within the jet, one consisting of outgoing electrons and another composed of electrons returning to the anode footpoint. Significant current density around the jet is a consequence of the diamagnetic current produced by a large thermal pressure gradient in the jet. Ion-neutral charge-exchange collisions provide an efficient mechanism to produce the cross-field current and control the dynamics of the complex current channels of the jet.
Original language | English |
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Article number | 5 |
Journal | Astrophysical Journal |
Volume | 953 |
Issue number | 1 |
DOIs | |
State | Published - Aug 1 2023 |
Externally published | Yes |
Funding
This research was primarily supported by the US Department of Energy under award number DE-SC0022153. Support from National Science Foundation under award number 1619551 is also acknowledged. The experiment is conducted at the Basic Plasma Science Facility (BaPSF) at UCLA, which is supported by US DOE under Contract No. DE-FC02-07ER54918 and the NSF under Award No. PHY1561912.