Spicules
dominate
the chromospheres in
non-active
regions
and
have
been
studied exhaustively.
They
are
barely
visible, last only about
15 minutes, and resemble a "burning prarie". Some jets
can be seen shooting 10,000 km up from the Sun's limb at velocities of
about 30km/sec. Studied exhaustively, they present a number of
observing challenges, as they are too small to resolve and move so
quickly as to present wing-shift challenges.
Active Regions are a
concentration
of
magnetic acitivity with
several
types
of
features contained in
a close area.
Field
Transition
Arches
(FTA's)
connect P and F
spots – elements of
opposite
polarity.
Inside
an
active
region,
where
sunspots
are
originally linked by a
FTA, a shear boundary forms. Field Transition Arches are different from
filaments in that they are thin and not very dark. The
FTA usually has plage or granular structure underneath.
Plages: Most of the
active region area is
occupied by plage.
Considerable
atmospheric heating
takes place in the
plage. It is bright in
everything from Halpha to the Calcium H and K lines. This heating is
thought to account for an absence of spicule. While absent over plage,
spicule are prominent around its edges.
