Nicholas A. Murphy, Clare E. Parnell, and Andrew L. Haynes, "The appearance, motion, and disappearance of three-dimensional magnetic null points," Physics of Plasmas, 22, 102117 (2015) (article, journal link)
Most models of magnetic reconnection assume that the process is symmetric: that the reconnecting magnetic fields are of equal strength and that the outflow jets propagate into regions with similar properties. However, reconnection in space, laboratory, and astrophysical plasmas is in general asymmetric. For example, reconnection between the Earth's magnetic field and the solar wind involves asymmetric inflow; and reconnection outflow jets during solar flares propagate into plasmas with substantially different properties. Importantly, asymmetry in the outflow direction can drastically affect where the energy released by reconnection can go. I am using a combination of numerical simulations and analytic theory to investigate the role asymmetry has in the reconnection process.
Nicholas A. Murphy, Aleida K. Young, Chengcai Shen, Jun Lin, and Lei Ni, "The plasmoid instability during asymmetric inflow magnetic reconnection," Physics of Plasmas, 20, 061211 (2013) (article, journal link, ADS)
N. A. Murphy, M. P. Miralles, C. L. Pope, J. C. Raymond, H. D. Winter, K. K. Reeves, D. B. Seaton, A. A. van Ballegooijen, and J. Lin, "Asymmetric Magnetic Reconnection in Solar Flare and Coronal Mass Ejection Current Sheets," Astrophysical Journal, 751, 56 (2012) (article, journal link, ADS)
N. A. Murphy, C. R. Sovinec, and P. A. Cassak, "Magnetic Reconnection with Asymmetry in the Outflow Direction," Journal of Geophysical Research, 115, A09206, doi:10.1029/2009JA015183 (2010) (article, journal link, ADS)
Coronal mass ejections (CMEs) are explosive events often associated with solar flares that expel huge amounts of plasma into the solar wind. Several recent observational results suggest that the cumulative heating energy during the eruption is comparable to or greater than the kinetic energy of the ejecta. We are using observations by SDO/AIA, Hinode/XRT, and SOHO/UVCS to provide constraints on plasma heating during these events. Because the ionization and recombination time scales are comparable to the expansion time scales, we use non-equilibrium ionization models to determine how much heating is necessary and where the heating occurs. The physical mechanisms responsible for the heating have not been unambiguously identified. However, candidate mechanisms include: (1) upflow from the current sheet that forms in the wake behind the rising plasmoid, (2) small-scale relaxation and reconnection during flux rope expansion and propagation, and (3) collisions between the thermal plasma and energetic particles.
N. A. Murphy, J. C. Raymond, and K. E. Korreck, "Plasma Heating During a Coronal Mass Ejection Observed by the Solar and Heliospheric Observatory," Astrophysical Journal, 735, 17 (2011) (article, journal link, ADS)
My past and present research has been supported by NASA grants NNX09AB17G, NNX11AB61G, NNX12AB25G, and NNX15AF43G; NASA contract NNM07AB07C; NSF SHINE grants AGS-1156076 and AGS-1358342; DOE grant DE-SX00163063; and subcontract S014981-F from the Princeton Plasma Physics Laboratory to the Smithsonian Astrophysical Observatory.