Type of Project: Numerical modeling and data analysis

Skills/Interest Required: Interest in plasma astrophysics or the numerical modeling of plasmas. Some knowledge of intermediate electromagnetism and/or fluid mechanics is required. The data analysis will be performed primarily using IDL.

Mentors: Dr. Nick Murphy and Dr. Mari Paz Miralles

Email: namurphy_at_cfa.harvard.edu mmiralles _at_ cfa.harvard.edu

Website: http://www.cfa.harvard.edu/~namurphy/

Background:

Magnetic reconnection is one of the most important processes in the solar corona. Reconnection occurs when the magnetic field lines of a highly conducting plasma are broken and rejoined, thus changing the magnetic connectivity of the system. This process is responsible for explosive energy release and particle acceleration during solar flares. Magnetic reconnection is also responsible for loss of confinement in tokamaks and other fusion devices and for energizing the electrons responsible for aurorae. During coronal mass ejections (CMEs), a reconnecting current sheet is thought to form behind the rising flux rope. Such current sheets have been observed in the wakes behind several CMEs, including the `Cartwheel CME' observed by Hinode/XRT [1,2]. During this event, the CME current sheet appeared to drift with time. While this current sheet motion was consistent with a geometric/projection effect [1], another possibility is that the drifting is due to asymmetry in the reconnection process itself. During magnetic reconnection with asymmetric inflow, the reconnection layer usually drifts in the direction of the stronger magnetic field [3].

Project:

The goal of this project will be to test this hypothesis: that the drifting of the Cartwheel CME current sheet could be caused by asymmetry in the reconnection process. The first component of this project will be to measure the rate of apparent current sheet drifting and correct it for solar rotation. This will require using IDL to analyze Hinode/XRT images taken during this event. The second component of this project will be to analyze already-performed resistive magnetohydrodynamic simulations of magnetic reconnection with asymmetric magnetic field, where the magnetic field in one outflow region is line-tied (anchored) to the boundary representing the solar photosphere. By tying these results together, it will be possible to determine limits on the reconnection asymmetry during this CME current sheet.

Figure: April 9 2008 Cartwheel CME

[1] Savage, S. L., McKenzie, D. E., Reeves, K. K., Forbes, T. G., & Longcope, D. W., Astrophys. J, 722, 329, 2010.
[2] Landi, E., Raymond, J. C., Miralles, M. P., & Hara, H., Astrophys. J., 711, 75, 2010.
[3] Cassak, P. A., & Shay, M. A., Phys. Plasmas, 14, 102114, 2007.