Ion and electron heating during magnetic reconnection in simulations
| Author(s) | Haggerty, Colby C. | |
| Date Accessioned | 2017-06-28T12:11:09Z | |
| Date Available | 2017-06-28T12:11:09Z | |
| Publication Date | 2016 | |
| Abstract | Magnetic reconnection is a fundamental plasma process that converts energy stored in magnetic fields into kinetic energy. Reconnection is believed to occur in astrophysical, heliospheric and laboratory plasma. In this thesis we examine how magnetic energy is converted into electron and ion thermal energy during collisionless magnetic reconnection using fully kinetic 2.5D particle-in-cell (PIC) simulations. We find that both ion and electron heating are reasonably well correlated with the inflowing available magnetic energy per ion electron pair, or more succinctly, to an energy associated with the upstream Alfvén speed (micAup 2). We also show that while the upstream Alfvén speed is the primary factor controlling the heating, other factors, including the strength of a guide field and the electron to ion temperature ratio, affect the heating as well. Ion heating is found to be inversely proportional to the strength of the guide field relative to the reconnecting field. In anti-parallel reconnection, ion heating is suppressed by an upstream electron to ion temperature ratio greater than unity; conversely, electron heating is found to be enhanced by these upstream parameters. It is also shown that increasing the upstream ion temperature normalized to the Alfvén speed squared (β i) reduces the reconnection outflow velocity in the exhaust for anti-parallel reconnection. The firehose instability in the exhaust limits the field line (and thus the outflow) velocity and it is shown that v0 = ⅓cAr2/√ Ti||/mi, where v 0 is the outflow velocity and Ti|| is the ion parallel temperature in the exhaust. While the upstream temperatures appear to cause the heating to deviate from scaling with mic Aup2, the total heating (ion + electron) is significantly better correlated with micAup 2, giving ΔTi + Δ Te = 0.14, micAup 2. This implies that the total fraction of magnetic energy released into thermal energy is a constant, and this constant fraction of magnetic energy is partitioned between electrons and ion. Finally, we show that parallel electric fields mediate the transfer of thermal energy between the electrons and the ions. This is achieved by slowing down inflowing ions and limiting the effectiveness of the Fermi reflection mechanism, and by trapping electrons in the reconnection exhaust to be repeatedly accelerated through the same process. | en_US |
| Advisor | Shay, Michael A. | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Physics and Astronomy | |
| Unique Identifier | 993260432 | |
| URL | http://udspace.udel.edu/handle/19716/21512 | |
| Publisher | University of Delaware | en_US |
| URI | https://search.proquest.com/docview/1883860270?accountid=10457 | |
| dc.subject.lcsh | Magnetic reconnection -- Computer simulation. | |
| dc.subject.lcsh | Ions -- Computer simulation. | |
| dc.subject.lcsh | Electrons -- Computer simulation. | |
| dc.subject.lcsh | Heating -- Computer simulation. | |
| Title | Ion and electron heating during magnetic reconnection in simulations | en_US |
| Type | Thesis | en_US |