The Sun: A Pictorial Introduction
Slide 20, The Corona Through the Solar Cycle:
Not surprisingly, the changes in the surface magnetic
field distribution through the solar cycle,
as evidenced by the evolving numbers and spatial
distributions of sunspots, prominences and filaments
(slide 17 and slide
18), are also reflected in the corona. The top row
of images are X-ray images from the Yohkoh satellite,
spaced approximately 10 months apart during the descending part
of cycle 22. The overall decrease in X-ray luminosity for the
solar disk as a whole is in many ways as spectacular as the decrease in
the number of active regions seen at a given time on the disk.
The bottom row shows a few eclipse
photographs spanning the time period 1966–1988, together with
a coronal image constructed from Solar Maximum Mission data for
1985, essentially at solar minimum. Note how the corona is reduced
to a belt of streamers symmetrically straddling the solar equator.
The 1980 eclipse of slide 9 occurred at
the very peak of
solar cycle 21; contrast the appearance of the white light corona then,
with streamers appearing at all latitudes, with the solar minimum
corona.
Written By P. Charbonneau and O.R. White - April 18, 1995