Equilibrium Equation: The forces
of gravity and gas pressure can be neglected in the equilibrium equation
of the coronal magnetic structure. This means that J and B are collinear.
Ampere's Law: Neglecting the electric
field, the curl of B is proportional to the current density.
Alpha: The curl of B is just B times
a scalar value alpha. Alpha is a measure of the helicity of of the magnetic
field.
Mean Alpha: Alpha is calculated at each pixel, and the mean value of the alpha distribution is found. This alpha histogram at time 18:01 on AR8210 shows that alpha is centered closely around zero.
Linear Fit Alpha: Alpha is also calculated by plotting Jz, the vertical current density, versus Bz, the vertical magnetic field, and fitting a line to the plot. Alpha is equal to the slope of the line. Bz and Bt uncertaintiesthresholds were set to minimize noise.
