This solar imagery is acquired and processed by Dr Malcolm
Wilkinson at the Forest Hill Observatory (FHO) in Victoria.
The white-light image below is a full disc image of the solar photosphere showing sunspots,
typical limb darkening and sometimes faculae near the limb of the
Sun. The date-time label refers to Universal Time (UT or Z) and is of the form yyyymmdd hhmmss. The image resolution is 1024 x 1024 pixels. Higher resolution imagery
from which these images are derived may be available on application to
the ASA (<firstname.lastname@example.org>).
The image below is an H-alpha image of the solar chromosphere as a
full-disc. It shows quite different detail than that shown in a photospheric
image. In particular it gives detail about the chromospheric magnetic fields
that align the filaments and fibril structure seen at the H-alpha
The image above is a panchromatic image of the solar photosphere. This is
sometimes referred to as the solar 'surface', but as there is no solid material
on the Sun it is nothing like the surface of a terrestrial planet. Instead it is
simply the lowest layer in the Sun from which light can escape. This 'surface'
has a diameter of just under 1.4 million kilometres. Above this layer lies the
inner atmosphere of the Sun which is termed the chromosphere (or 'colour
sphere') because of its vivid red colour. This layer is visible at the start or
end of a total solar eclipse. It lies just above the photosphere and extends
for a height of many thousands of kilometres. The temperature in this layer decreases
from the photospheric temperature of 6000 K down to around 4000 K and
then up to over one million K as it merges into the corona, the outer
atmosphere of the Sun. The chromosphere can be imaged by using a narrow
band filter centred on the hydrogen-alpha spectral line at a wavelength of 656.3
nanometres. Because the eye is not sensitive to low contrast features at this wavelength,
solar H-alpha images are usually contrast enhanced and displayed as white-light images.
The H-alpha wavelength is also the one that is most typically used to
monitor solar flares. These high intensity transient brightenings are caused
when large quantities of magnetic energy are released around active regions
(typically around sunspot groups). The lower brightness white areas often
seen in H-alpha images are termed plage.
The images below show zoomed highlights taken from full disc images.
Australian Space Academy