Features of the Sun in Hydrogen Alpha:
By observin g the sun
with a
narro
w
bandpass filter tun ed
to 6562.8Å, we ca n
observe the behavior
of the Sun'
s
Chromosphere
. The
chromosphere is like a shell of g as aro und the Sun' s p hotosphere,
always movi ng a nd changing. Th e chromosphere's stru cture behaves
differently in active regions than quiet areas, where magnetic field
lines are stronger. T hought to be tied to the photo
sphere, the
chromosphere is governed by magnetic forces and, yet it still has its own
IntraNetwork (IN) of material oscillating every 5 minutes.
On the limb, even a
rather wide filter of 1Å
or more will show
prominences
, a
detail of
the
chromosphere
projected ag ainst th e
dark black contrast of
space. To observe the details of chromosphere on the face of the sun,
we ne ed a narrower fil ter to elimin ate more off-band li ght of the
photosphere and continuum. We need a filter l ess tha n 1.0Å. Th e
narrower the filter's bandpass, the mo re contrast we w ill see - down to
0.4Å, where promi nence stru cture is reduced due t o high vel ocity and
subsequent wing shift.
Filaments
appear a s
large, dark eyebrows
across the surface of
the Sun.
With a b rightness of
about 10% of the disk
due to scatterin
g,
they appear
dark on the surfa ce, but on the limb, sho w as a prominence. Active
Region Filaments (ARF) di ffer from Qui escent Region Filaments (QRF ).
ARF are da rker, smaller and have m ore cohe rent f ibril structu re along
their axis. A sheared magnetic field runs parallel to this axis, permitting a
sizeable flare. QRF may produce a big Coronal Mass Ejection (CME). An
ARF may erupt and reform several times.
