Astrophysical Jet and Solar Coronal Loop Experiments

P. M. Bellan, S. You, G. Yun, and S. K. P. Tripathi

Both Taylor relaxation and magnetic reconnection theory focus on magnetic field 
behavior and say little or nothing about plasma flow, density/pressure gradients, or 
sequencing of the dynamics. However, results from our astrophysical jet and solar 
coronal loop simulation experiments show these effects are critical. These experiments 
indicate that the fundamental element is a plasma-filled, current-carrying magnetic flux 
tube laterally bounded by low-density, current-free plasma and having its ends intercept a 
conducting, mass-source boundary. Behaviors of such a flux tube include: strong MHD-
driven plasma ingestion from one or both ends, jet-like axial lengthening, bending of the 
axis, kinking, and merging with other similar flux tubes via magnetic reconnection. These 
effects have a definite sequence and do not occur simultaneously. Plasma ingestion 
occurs where the current-carrying flux tube diameter is smallest; the ingested plasma is 
accelerated in the direction of increasing flux tube diameter. Flow stagnation in the 
plasma frame (i.e., a negative velocity divergence) increases both the plasma density and 
the density of the frozen-in azimuthal magnetic flux convected with the plasma -- the 
latter effect amplifies the local azimuthal magnetic field, thereby increasing the local 
pinch force, and collimating the flux tube. Energetic particles can develop in the 
stagnation region.