Study of energy conversion and partitioning in the magnetic reconnection layer of a laboratory plasma

While the most important feature of magnetic reconnection is that it energizes plasma particles by converting magnetic energy to particle energy, the exact mechanisms by which this happens are yet to be determined despite a long history of reconnection research. Recently, we have reported our result...

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Bibliographic Details
Published in:Physics of plasmas 2015-05, Vol.22 (5)
Main Authors: Yamada, Masaaki, Yoo, Jongsoo, Jara-Almonte, Jonathan, Ji, Hantao, Kulsrud, Russell M., Myers, Clayton E., Daughton, William
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOUNDARY CONDITIONS
COMPUTERIZED SIMULATION
DATASETS
DIFFUSION
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ENERGY CONVERSION
MAGNETIC RECONNECTION
MAGNETIZATION
MONITORING
PARTICLES
PARTITION
PLASMA
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Summary:While the most important feature of magnetic reconnection is that it energizes plasma particles by converting magnetic energy to particle energy, the exact mechanisms by which this happens are yet to be determined despite a long history of reconnection research. Recently, we have reported our results on the energy conversion and partitioning in a laboratory reconnection layer in a short communication [Yamada et al., Nat. Commun. 5, 4474 (2014)]. The present paper is a detailed elaboration of this report together with an additional dataset with different boundary sizes. Our experimental study of the reconnection layer is carried out in the two-fluid physics regime where ions and electrons move quite differently. We have observed that the conversion of magnetic energy occurs across a region significantly larger than the narrow electron diffusion region. A saddle shaped electrostatic potential profile exists in the reconnection plane, and ions are accelerated by the resulting electric field at the separatrices. These accelerated ions are then thermalized by re-magnetization in the downstream region. A quantitative inventory of the converted energy is presented in a reconnection layer with a well-defined, variable boundary. We have also carried out a systematic study of the effects of boundary conditions on the energy inventory. This study concludes that about 50% of the inflowing magnetic energy is converted to particle energy, 2/3 of which is ultimately transferred to ions and 1/3 to electrons. Assisted by another set of magnetic reconnection experiment data and numerical simulations with different sizes of monitoring box, it is also observed that the observed features of energy conversion and partitioning do not depend on the size of monitoring boundary across the range of sizes tested from 1.5 to 4 ion skin depths.
ISSN:1070-664X
1089-7674