Plasma Energization in Colliding Magnetic Flux Ropes

Journal Article · Thu Oct 25 00:00:00 EDT 2018 · The Astrophysical Journal (Online)

DOI:https://doi.org/10.3847/1538-4357/aae30e· OSTI ID:1544070

Du, Senbei ^[1]; Guo, Fan ^[2]; Zank, Gary P. ^[3]; Li, Xiaocan ^[4]; Stanier, Adam ^[4]

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1. Univ. of Alabama, Huntsville, AL (United States). Dept. of Space Science; New Mexico Consortium, Los Alamos, NM (United States)
2. New Mexico Consortium, Los Alamos, NM (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Univ. of Alabama, Huntsville, AL (United States). Dept. of Space Science, and Center for Space Plasma and Aeronomic Research (CSPAR)
4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Magnetic flux ropes are commonly observed throughout the heliosphere, and recent studies suggest that interacting flux ropes are associated with some energetic particle events. In this work, we carry out 2D particle-in-cell (PIC) simulations to study the coalescence of two magnetic flux ropes (or magnetic islands), and the subsequent plasma energization processes. The simulations are initialized with two magnetic islands embedded in a reconnecting current sheet. The two islands collide and eventually merge into a single island. Particles are accelerated during this process as the magnetic energy is released and converted to the plasma energy, including bulk kinetic energy increase by the ideal electric field, and thermal energy increase by the fluid compression and the nonideal electric field. We find that contributions from these different energization mechanisms are all important and comparable with each other. Fluid shear and a nongyrotropic pressure tensor also contribute to the energy conversion process. For simulations with different box sizes ranging from $$L_x$$ ~ 25–100$$d_i$$ and ion-to-electron mass ratios $$m_i /m_e$$ = 25,100, and 400, we find that the general evolution is qualitatively the same for all runs, and the energization depends only weakly on either the system size or the mass ratio. The results may help us understand plasma energization in solar and heliospheric environments.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Nmc, Inc.; Univ. of California, Oakland, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
• Grant/Contract Number: AC02-05CH11231; SC0018240
• OSTI ID: 1544070
• Journal Information: The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 1 Vol. 867; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Astronomy & Astrophysics