Browsing by Author "Dokgo, K."

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    Cross-Scale Processes of Magnetic Reconnection
    (Springer Nature, 2023) Hwang, K.-J.; Nakamura, R.; Eastwood, J. P.; Fuselier, S. A.; Hasegawa, H.; Nakamura, T.; Lavraud, B.; Dokgo, K.; Turner, D. L.; Ergun, R. E.; Reiff, P. H.
    Various physical processes in association with magnetic reconnection occur over multiple scales from the microscopic to macroscopic scale lengths. This paper reviews multi-scale and cross-scale aspects of magnetic reconnection revealed in the near-Earth space beyond the general global-scale features and magnetospheric circulation organized by the Dungey Cycle. Significant and novel advancements recently reported, in particular, since the launch of the Magnetospheric Multi-scale mission (MMS), are highlighted being categorized into different locations with different magnetic topologies. These potentially paradigm-shifting findings include shock and foreshock transient driven reconnection, magnetosheath turbulent reconnection, flow shear driven reconnection, multiple X-line structures generated in the dayside/flankside/nightside magnetospheric current sheets, development and evolution of reconnection-driven structures such as flux transfer events, flux ropes, and dipolarization fronts, and their interactions with ambient plasmas. The paper emphasizes key aspects of kinetic processes leading to multi-scale structures and bringing large-scale impacts of magnetic reconnection as discovered in the geospace environment. These key features can be relevant and applicable to understanding other heliospheric and astrophysical systems.
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    High‐Frequency Wave Generation in Magnetotail Reconnection: Linear Dispersion Analysis
    (Wiley, 2019) Burch, J.L.; Dokgo, K.; Hwang, K.J.; Torbert, R.B.; Graham, D.B.; Webster, J.M.; Ergun, R.E.; Giles, B.L.; Allen, R.C.; Chen, L.-J.; Wang, S.; Genestreti, K.J.; Russell, C.T.; Strangeway, R.J.; Contel, O. Le
    Plasma and wave measurements from the NASA Magnetospheric Multiscale mission are presented for magnetotail reconnection events on 3 July and 11 July 2017. Linear dispersion analyses were performed using distribution functions comprising up to six drifting bi‐Maxwellian distributions. In both events electron crescent‐shaped distributions are shown to be responsible for upper hybrid waves near the X‐line. In an adjacent location within the 3 July event a monodirectional field‐aligned electron beam drove parallel‐propagating beam‐mode waves. In the 11 July event an electron distribution consisting of a drifting core and two crescents was shown to generate upper‐hybrid and beam‐mode waves at three different frequencies, explaining the observed broadband waves. Multiple harmonics of the upper hybrid waves were observed but cannot be explained by the linear dispersion analysis since they result from nonlinear beam interactions.