Lower‐Hybrid Wave Structures and Interactions With Electrons Observed in Magnetotail Reconnection Diffusion Regions. Issue 5 (29th April 2022)

• Record Type: Journal Article
• Authors: Wang, Shan; Chen, Li‐Jen; Bessho, Naoki; Ng, Jonathan; Hesse, Michael; Graham, Daniel B.; Le Contel, Olivia; Gershman, Daniel; Giles, Barbara
• Is Part Of: Journal of geophysical research. Volume 127:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-29
• Subjects: magnetic reconnection -- lower‐hybrid wave -- electron heating; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA030109
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We investigate waves close to the lower‐hybrid frequency in 12 magnetotail reconnection electron diffusion region (EDR) events with guide field levels of near‐zero to 30%. In about half of the events, the wave vector has a small component along the current sheet normal, consistent with known lower‐hybrid drift wave properties, but the perpendicular magnetic field fluctuations can be comparable or greater than the parallel component, a feature unique to the waves inside and adjacent to EDRs. Another new wave property is that the wave vector has a significant component along the current sheet normal in some events and completely along the normal for one event. In 1/4 of the events, the ∇ · P e $\nabla \cdot {\boldsymbol{P}}_{e}$ term has a significant contribution to the wave electric field, possibly a feature of lower‐hybrid waves more likely to exist in the diffusion region than further away from the X‐line. Electron temperature variations are correlated with the wave potential, due to wave electric field acceleration and crossings at the corrugated separatrix region with different amounts of mixing between reconnection inflowing and outflowing populations. The latter also leads to the anti‐correlation between parallel and perpendicular temperature components. Using four‐spacecraft measurements, the magnetic field line twisting is demonstrated by the correlated fluctuations in ∇ × V E × B | | ${\left(\nabla \times {\boldsymbol{V}}_{E\times B}\right)}_{\vert \vert }$ and ( ∇ × B ) | | ${(\nabla \times \mathbf{B})}_{\vert \vert }$ . The lower‐hybrid wave in the EDR of weak guide field reconnection may be generated near separatrices and penetrate to the mid‐plane or locally generated, and the latter possibility is beyond the prediction of previous reconnection simulations. Key Points: A dozen of magnetotail electron diffusion region with near‐zero to 30% guide field are analyzed to establish lower‐hybrid wave properties therein Electron temperature fluctuations due to electron acceleration and current sheet corrugation are correlated with the wave potential The electron pressure gradient contribution to the wavefield and electron vortices correlated with field line twisting are demonstrated