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Graduate Student Seminar - 03/09/2018

"Characterizing Ion Flows Across a Dipolarization Jet"

by Harry Arnold

Advisor:  Prof. James Drake

Friday, March 9, 2018 -- 12:00 p.m.
Large Conference Room, 1207 Energy Research Facility

Abstract: The structure of reconnection jets with finite extent in the out-of-plane (dawn-dusk) direction relevant to magnetic reconnection in the Earth's magnetotail is explored with particle-in-cell (PIC) simulations and analysis. A Riemann system is explored in which a finite North-South magnetic field is imposed on a system with an initial current layer. Spatial variations in the GSM y (dawn-dusk) and z (North-South) directions are included. The results of the PIC simulations are used to explore the dependence of the jet structure on the width of the jet in the dawn-dusk direction. The finite width of the jet leads to particle transport through the jet along the dawn-dusk direction that can have a significant impact on the magnetic field as well as the magnitude and profile of the Earthward-directed ion flow. As a result, there is a reversal in the usual Hall magnetic field near the center of the current sheet on the positive y-GSM side of larger jets. This structure is supported by a vortex in the ion flow on either side of the current sheet and causes the field to return to the usual Hall field outside of the current sheet. For small jet widths, the maximum velocity of the Earthward flow is significantly reduced below the upstream Alfvén speed, which is the expectation for jets with infinite cross-tail extent. However, the ion flow speed approaches its well-known theoretical limit once the jet width exceeds the ion Larmor radius based on the normal magnetic field Bz.

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