Speaker
Description
Magnetic reconnection serves as a crucial mechanism for generating various sources of free energy for waves and instabilities, including pressure gradients, temperature anisotropies, and large electric currents. In this talk, we focus on recent observations of waves in laboratory reconnection experiments, particularly in the Magnetic Reconnection Experiment (MRX).
Whistler waves, originating from electron temperature anisotropy, have been detected near the separatrix on the low-density (magnetosphere) side [Yoo et al., 2018]. The presence of these waves is attributed to the loss of electrons with high parallel speeds, leading to local temperature anisotropy and subsequent whistler wave generation. Additionally, enhanced electron transport with high parallel speed is likely associated with lower hybrid drift instabilities near the separatrix [Yoo et al., 2019].
Ion acoustic waves, triggered by large local currents, have been observed during low-beta reconnection in high-energy-density plasmas generated by high-power lasers [Zhang et al., 2023]. In these laser-generated plasmas, the condition where ion temperature normalized to charge state (Z) is smaller than the electron temperature is met, such that ion acoustic waves are not strongly Landau damped. The onset of ion acoustic wave instability results in the emergence of electron acoustic waves and electron heating. Moreover, ion acoustic waves are effective in inducing anomalous drag between electrons and ions.
Finally, quasi-electrostatic lower hybrid drift waves (ES-LHDW) have been observed during guide field reconnection in the electron diffusion region of MRX. ES-LHDW contributes significantly (~20% of the reconnection electric field) to anomalous resistivity by inducing fluctuations in density and the out-of-plane component of the electric field. The observed small phase difference (30 degrees) between two fluctuations aligns with results from a linear model [Yoo et al., 2022]. Through quasilinear analysis, we confirm that ES-LHDW can generate anomalous electron heating surpassing classical Ohmic heating in laboratory plasmas [Yoo et al., 2024]. Observations in space show that LHDW can be either quasi-electrostatic and electromagnetic, depending on the local condition [Yoo et al. 2021]. Only ES-LHDW is capable of generating a significant anomalous drag term [Yoo et al. 2021, Graham et al. 2022].
