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2014_bellan_epr_madison_v2b-1.pdf2014-08-11 12:10:58Paul Bellan
2014_bellan_epr_madison_v2b.pdf2014-08-11 12:09:22Paul Bellan

Fast collisionless reconnection intrinsic to construction & destruction of Caltech MHD-driven plasma jet

Author: Paul M. Bellan
Requested Type: Consider for Invited
Submitted: 2014-05-29 14:02:27

Co-authors:

Contact Info:
Caltech
MC 128-95 Caltech
Pasadena, CA   91125
USA

Abstract Text:
The Caltech MHD-driven plasma jet forms from the merging of the inner segments of eight arched, plasma-filled magnetic flux tubes collectively having a spider-leg morphology. After formation, the jet kinks when it attains a critical length (Hsu/Bellan, PRL 2003). Extreme, kink-driven lateral acceleration of the jet can spawn a fast Rayleigh-Taylor instability (RTI) which can lead to the jet breaking off near its source electrodes (Moser/Bellan, Nature 2012). Two distinct, short-lived rf bursts in the whistler frequency range are measured by an electrostatic probe. The first burst occurs when the spider legs merge and the second when the RTI causes the jet to break off. Since both spider-leg merging and jet breaking off involve magnetic reconnection, the two distinct whistler-regime rf bursts are presumed to be associated with magnetic reconnection. Measurements indicate that reconnection occurs when the RTI ripples choke the jet radius to be smaller than the ion skin depth, the characteristic scale at which Hall physics becomes important. Since whistler waves result from Hall physics, the observed association of whistler-regime rf bursts with reconnection suggests that Hall physics is transiently coming into play. Theoretical investigation of collisionless reconnection dynamics at the sub-ion-skin-depth scale shows that inclusion of both finite electron inertia and Hall physics leads to a 4th-order differential equation in x, the direction of initial magnetic field inhomogeneity. The eigenvalue of this equation prescribes a purely-growing magnetic reconnection mode with exponential growth rate scaling with the whistler frequency. However, if finite electron inertia is not included, the resulting equation is only 2nd-order and has a non-physical mathematical singularity at the reconnection X-point and no ability to predict a well-defined exponential growth rate.
–Supported by DOE.

Characterization: 1.3,4.0

Comments:
If not chosen for oral, please group Caltech posters as follows:1. Bellan, 2.Zhai, 3. Chai, 4. Chaplin, 5. Haw

Workshop on Exploratory Topics in Plasma and Fusion Research (EPR) and US-Japan Compact Torus (CT) Workshop
August 5-8, 2014
Madison, Wisconsin

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