Electron Demagnetization in a Magnetically Expanding Plasma

Electron demagnetization in a magnetically expanding plasma, a fundamental process for plasma flow and detachment in magnetic nozzles, is experimentally investigated using a rf plasma source and magnetic nozzle (MN). Measurements of the plasma potential spatial profile reveal an ion-confining potent...

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Bibliographic Details
Published in:Physical review letters 2019-10, Vol.123 (14), p.145001-145001, Article 145001
Main Authors: Little, Justin M., Choueiri, Edgar Y.
Format: Article
Language:English
Subjects:
Demagnetization
Divergence
Electrons
Expanding plasmas
Field strength
Larmor radius
Magnetic flux
Magnetic nozzles
Magnetism
Plasma
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Summary:Electron demagnetization in a magnetically expanding plasma, a fundamental process for plasma flow and detachment in magnetic nozzles, is experimentally investigated using a rf plasma source and magnetic nozzle (MN). Measurements of the plasma potential spatial profile reveal an ion-confining potential surface, indicative of the edge of a magnetized plasma, that extends along the outermost magnetic flux surface. The downstream extent of the potential surface scales inversely with a characteristic electron Larmor radius, which agrees with an existing theory [E. Ahedo and M. Merino, Phys. Plasmas 19, 083501 (2012)] for electron demagnetization via finite electron Larmor radius (FELR) effects. These results represent the first experimental evidence of FELR demagnetization, and provide an empirical metric for the significance of FELR effects based on the degree of separation between electron and magnetic flux surfaces. With this metric, a critical magnetic field strength is found that ensures electrons remain magnetized through the MN turning point, thus avoiding the rapid plume divergence associated with premature demagnetization.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.123.145001