ORCID Profile
0000-0002-2463-4716
Current Organisations
University of Colorado at Boulder
,
University of Texas at Arlington
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Astronomical Society
Date: 31-07-2023
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: 05-2017
DOI: 10.1002/2017JA024062
Publisher: American Geophysical Union (AGU)
Date: 09-04-2017
DOI: 10.1002/2016GL072493
Publisher: American Geophysical Union (AGU)
Date: 06-2018
DOI: 10.1029/2018JA025245
Publisher: American Geophysical Union (AGU)
Date: 10-02-2018
DOI: 10.1002/2017GL076809
Publisher: American Geophysical Union (AGU)
Date: 03-2018
DOI: 10.1002/2017JA024537
Publisher: American Geophysical Union (AGU)
Date: 02-2018
DOI: 10.1002/2017JA024789
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.
Publisher: American Geophysical Union (AGU)
Date: 2018
DOI: 10.1002/2017JA024551
Abstract: Mirror mode waves are ubiquitous in the Earth's magnetosheath, in particular behind the quasi‐perpendicular shock. Embedded in these nonlinear structures, intense lion roars are often observed. Lion roars are characterized by whistler wave packets at a frequency ∼100 Hz, which are thought to be generated in the magnetic field minima. In this study, we make use of the high time resolution instruments on board the Magnetospheric MultiScale mission to investigate these waves and the associated electron dynamics in the quasi‐perpendicular magnetosheath on 22 January 2016. We show that despite a core electron parallel anisotropy, lion roars can be generated locally in the range 0.05–0.2 f ce by the perpendicular anisotropy of electrons in a particular energy range. We also show that intense lion roars can be observed up to higher frequencies due to the sharp nonlinear peaks of the signal, which appear as sharp spikes in the dynamic spectra. As a result, a high s ling rate is needed to estimate correctly their litude, and the latter might have been underestimated in previous studies using lower time resolution instruments. We also present for the first‐time 3‐D high time resolution electron velocity distribution functions in mirror modes. We demonstrate that the dynamics of electrons trapped in the mirror mode structures are consistent with the Kivelson and Southwood (1996) model. However, these electrons can also interact with the embedded lion roars: first signatures of electron quasi‐linear pitch angle diffusion and possible signatures of nonlinear interaction with high‐ litude wave packets are presented. These processes can lead to electron untrapping from mirror modes.
Publisher: American Geophysical Union (AGU)
Date: 12-2017
DOI: 10.1002/2017JA024550
Publisher: Wiley
Date: 04-2018
DOI: 10.1002/2017JA025034
No related grants have been discovered for FREDERICK WILDER.