Magnetic reconnection in solar atmosphere: three-dimensional evolution and fine structures

H. Isobe

The University of Tokyo

Clarifying the similarities and differences in magnetic reconnection in solar, interplanetary, magnetospheric and laboratory plasmas will be of great benefit to understand its basic physics. Keeping this in mind, I will discuss a few issues on global dynamics of solar reconnection.

First one is related to 3D evolution of reconnection. Many eruptive events (namely flare/filament eruption/CME events) shows systematic propagation of reconnection site (as inferred from propagation of chromospheric brightenings) along the neutral line. By examining the observational data of many filament eruption events, we found that such systematic motion was closely related to the dynamics of plasmoids/flux ropes/filaments. In fact the original motivation of this work was searching for solar analogy of dawn-dusk asymmetry in substorms.

Second issue is related to the fine structures in reconnection. The flare emissions often exhibit fine structures both in time and space, indicating that reconnection is bursty and spatially intermittent. High resolution images show many small-scale plasma ejections corresponding to elementary peaks of flare emissions. We present the result of a 3D MHD simulations of an emerging flux region that actually shows the formation of many plasmoid and patchy reconnection. This is due to the interchanging of the current sheet by the magnetic Rayleigh-Taylor instability. We suggest that similar interchange-type instability and resultant patchy reconnection may occur if reconnection occurs when the system is dynamically evolving, which may be the case in some reconnection events in interplanetary and magnetosphere.