[IGPP Everyone] Space Physics Seminar, Fri. 2/15, 3:30pm: "Spiky Electric and Magnetic Field Structures in Flux Rope Experiments" (W. Gekelman, UCLA Physics)

[Emmanuel V. Masongsong]

SPACE PHYSICS SEMINAR 
DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES 
DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES 
UNIVERSITY OF CALIFORNIA, LOS ANGELES 
(AOS M275C, EPSS M288C) 

Spiky Electric and Magnetic Field Structures in Flux Rope Experiments 

Walter Gekelman 
UCLA Physics 

Magnetic flux ropes are bundles of twisted magnetic fields and their associated currents. They are common on the surface of the sun (and presumably all other stars) and are observed to have a large range of sizes and lifetimes. One or more flux ropes are routinely generated in the Large Plasma Device at UCLA. The ropes are kink unstable and when they collide fully 3D magnetic reconnection occurs. The time dependent magnetic field, plasma flow, electron temperature, plasma density, and the space charge and inductive electric fields were measured at over 42,000 spatial positions throughout the plasma volume over several million rope collisions. Magnetic field lines are followed and used to derive quasi-seperatrix layers, locations where reconnection occurs. The complete data set was used to evaluate all the terms in Ohm’s law, which resulted in unphysical plasma resistivity. It was then determined that in this situation Ohm’s law is non-local. The resistively was properly evaluated using the fluctuation dissipation theorem (Kubo resistivity). Time domain structures (TDS) , sharp pulses in potential and magnetic field are generated during reconnection events and subsequent move from the reconnection region into the rope currents. The probability distribution function of the spike amplitudes is log-normal, the same as the fold of crumpled paper. A amplitude counting method is used to create a vector map of the magnetic field of the spikes. TDS observed by satellites are ubiquitous in the plasma surrounding the earth. 

Friday, February 15 , 2019 
Room 6704 Geology 
3:30 - 5:00 PM 

In Charge: 
V. Angelopoulos 

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