Ion and Electron Acoustic Bursts during Anti-Parallel Magnetic Reconnection Driven by Lasers

TL;DR

This study observes ion and electron acoustic bursts during laser-driven magnetic reconnection, revealing their role in energy dissipation and electron energization in collisionless plasmas, with implications for astrophysical phenomena.

Contribution

It provides experimental evidence and simulation insights into ion and electron acoustic dynamics during magnetic reconnection driven by lasers, highlighting their significance in plasma energy transfer.

Findings

Ion acoustic bursts observed during reconnection

Electron acoustic bursts follow ion bursts with electron heating

Simulations reproduce acoustic burst phenomena and electron energization

Abstract

Magnetic reconnection converts magnetic energy into thermal and kinetic energy in plasma. Among numerous candidate mechanisms, ion acoustic instabilities driven by the relative drift between ions and electrons, or equivalently electric current, have been suggested to play a critical role in dissipating magnetic energy in collisionless plasmas. However, their existence and effectiveness during reconnection have not been well understood due to ion Landau damping and difficulties in resolving the Debye length scale in the laboratory. Here we report a sudden onset of ion acoustic bursts measured by collective Thomson scattering in the exhaust of anti-parallel magnetically driven reconnection using high-power lasers. The ion acoustic bursts are followed by electron acoustic bursts with electron heating and bulk acceleration. We reproduce these observations with 1D and 2D particle-in-cell simulations in which electron outflow jet drives ion-acoustic instabilities, forming double layers. These layers induce electron two-stream instabilities that generate electron acoustic bursts and energize electrons. Our results demonstrate the importance of ion and electron acoustic dynamics during reconnection when ion Landau damping is ineffective, a condition applicable to a range of astrophysical plasmas including near-Earth space, stellar flares, and black hole accretion engines.