Exploring Reconnection - Guide Field Off

One of the aspects of magnetic reconnection which makes it a difficult process to fully understand is the complex interactions between charged particles and the electromagnetic fields that dominate their motion. The electromagnetic fields determine the motion of the particles, but the motion of the particles changes the configuration of the electromagnetic fields.

In the visualizations below, we illustrate the magnetic field (cyan line structures) surrounding a reconnection region, sometimes called the X-line region, because the field lines form an X-like structure with most of the reconnection physics taking place in the center of the 'X'. In this case, the reconnection layer, sometimes called the diffusion region, lies in a thin region above and below the grey grid.

Inside this reconnection layer, there is an electric field that accelerates the charged particle along the y-axis, causing the particle to bounce back and forth between the regions above and below the reconnection layer. In those regions, there is a small magnetic field that is directed in opposite directions above and below the layer. This causes the charged particle to move in a curve, that bounces above and below the layer, creating the sinusiodal motion of the particle as moves along the y-axis. This is the guide-field off configuration.

But if there is a little bit of magnetic field parallel to the electric field (also in the y-direction) - the particle moves in the guide-field on configuration. In this case, the particle picks up a little extra gyro motion, perpendicular to the sinusoidal motion. This creates the loops which appear in the motion when looking along the y-axis. This additional motion pumps additional energy into the charged particle, until its trajectory slips outside the reconnection layer current sheet, and takes a little energy out of the field with it.

Additional References
Particle Trajectories in Model Current Sheets. 1. Analytical Solutions
T. W. Speiser
Journal of Geophysical Research, Volume 70, pp 4219-4226 (1965)

See the following sources:

• NASA.gov
• NASA.gov