Title: Asymmetric magnetic reconnection during coronal mass ejections|
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
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
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 , 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 .
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
 Savage, S. L., McKenzie, D. E., Reeves, K. K., Forbes, T. G., &
Longcope, D. W., Astrophys. J, 722, 329, 2010.
 Landi, E., Raymond, J. C., Miralles, M. P., & Hara, H., Astrophys. J.,
711, 75, 2010.
 Cassak, P. A., & Shay, M. A., Phys. Plasmas, 14, 102114, 2007.