ORCID Profile
0000-0002-5414-8604
Current Organisation
Los Alamos National Laboratory
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Publisher: American Geophysical Union (AGU)
Date: 12-2019
DOI: 10.1029/2019JA027228
Abstract: Magnetic reconnection at the subsolar magnetopause is persistently accompanied by strong fluctuations of the magnetic field ( B ), plasma density ( n ), and all components of the electric field ( E ) and current ( J ). The strongest fluctuations are at frequencies below the lower hybrid frequency and observed in a thin, intense current sheet adjacent to the electron diffusion region. In this current sheet, the background magnitudes of B and n are changing considerably, creating an inhomogeneous plasma environment. We show that the fluctuations in B and n are consistent with an oscillatory displacement of the current sheet in the surface normal direction. The displacement is propagating parallel to the magnetic reconnection X line. Wavelengths are on the order of or longer than the thickness of the current sheet to which they are confined, so we label these waves electromagnetic drift waves. E and J fluctuations are more complex than a simple displacement. They have significant variations in the component along B , which suggest that the drift waves also may be confined along B . The current sheet is supported by an electron drift driven by normal electric field, which, in turn, is balanced by an ion pressure gradient. We suggest that wave growth comes from an instability related to the drift between the electrons and ions. We discuss the possibility that drift waves can displace or penetrate into the electron diffusion region giving magnetic reconnection three‐dimensional structure. Drift waves may corrugate the X line, possibly breaking the X line and generating turbulence.
Publisher: American Geophysical Union (AGU)
Date: 09-04-2017
DOI: 10.1002/2016GL072493
Publisher: American Astronomical Society
Date: 09-10-2020
Publisher: American Geophysical Union (AGU)
Date: 09-2020
DOI: 10.1029/2020JA027854
Abstract: Spacecraft potential has often been used to infer electron density with much higher time resolution than is typically possible with plasma instruments. However, recently, two studies by Torkar et al. (2017, 0.1002/2017JA024724 ) and Graham, Vaivads, Khotyaintsev, Eriksson, et al. (2018, 0.1029/2018JA025874 ) have shown that external electric fields can also have an effect on the spacecraft potential by enhancing photoelectron escape from the surface. Consequently, should the electron density derived from the spacecraft potential be used during an event with a large electric field, the estimation would be contaminated and the user would see the effects of the electric field rather than density perturbations. The goal of this paper is to propose a method to remove the electric field effects to allow the density derived from spacecraft potential to be used even during large‐ litude wave events such as Langmuir waves or upper hybrid waves.
Publisher: American Geophysical Union (AGU)
Date: 12-2019
DOI: 10.1029/2019JA027275
Abstract: We present a model of electromagnetic drift waves in the current sheet adjacent to magnetic reconnection at the subsolar magnetopause. These drift waves are potentially important in governing 3‐D structure of subsolar magnetic reconnection and in generating turbulence. The drift waves propagate nearly parallel to the X line and are confined to a thin current sheet. The scale size normal to the current sheet is significantly less than the ion gyroradius and can be less than or on the order of the wavelength. The waves also have a limited extent along the magnetic field ( B ), making them a three‐dimensional eigenmode structure. In the current sheet, the background magnitudes of B and plasma density change significantly, calling for a treatment that incorporates an inhomogeneous plasma environment. Using detailed examination of Magnetospheric Multiscale observations, we find that the waves are best represented by series of electron vortices, superimposed on a primary electron drift, that propagate along the current sheet (parallel to the X line). The waves displace or corrugate the current sheet, which also potentially displaces the electron diffusion region. The model is based on fluid behavior of electrons, but ion motion must be treated kinetically. The strong electron drift along the X line is likely responsible for wave growth, similar to a lower hybrid drift instability. Contrary to a classical lower hybrid drift instability, however, the strong changes in the background B and n o , the normal confinement to the current sheet, and the confinement along B are critical to the wave description.
Location: United States of America
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