Twist, Kink, and other Contortions

K. D. Leka and Y. Fan

Determining the amount of twist in active region magnetic
fields is crucial to testing proposed trigger mechanisms
for solar energetic events.  We discuss the use of
photospheric vector magnetic field data, specifically as
related to the kink instability.  It is demonstrated that
an average twist calculated using solely the boundary-layer
magnetic field information can underestimate the amount
of twist present, in part because the interpretation
is model-dependent.  Additionally, an analysis of the
lower-boundary slice of the numerical simulation of
a kink-unstable flux rope (Fan and Gibson 2003, 2004)
produces inferred magnetic twist results comparable to that
derived from photospheric vector magnetic field data in
active regions.  Thus, we propose that the kink instability
is a contender for initiating solar energetic events.

This work is supported by AFOSR contract F49620-02-C-0191.