Solar Flares (2) ...
The adjacent right animation shows about a three-hour sequence of extreme UV
(171 Angstrom) imagery for a small portion of the solar surface in a flare region.
The images were obtained by the TRACE satellite and the Sun has been turned on its side with north to
the right.
Origin of Flares
Although the cause of flares is not totally understood, they are
known to be associated with
the Sun's magnetic field. One favored theory is that they occur when
sets of solar magnetic field lines rearrange suddenly into a lower energy
state. This is called a reconnection event, and is somewhat
analogous to a twisted and stretched
rubber band suddenly unwinding or snapping. The snapping of a
rubber band can transfer energy stored in the stretched band to your hand
(Ouch!). In a similar way,
reconnection of magnetic field lines can suddenly
transfer large amounts of energy stored in the magnetic
field to particles at the solar surface, accelerating them to high velocities and
producing a flare.
Solar Activity and Reconnections
Conditions favoring a reconnection can be brought about by the churning motion of solar
material near the surface, which is more likely during periods of the active Sun.
Thus, there is a correlation between the frequency of flares and the
number of
sunspots.
