Explanation:
It was a quiet day on the
Sun.
The above image shows, however, that even during off days the
Sun's surface is a busy place.
Shown in ultraviolet light, the relatively
cool dark regions have temperatures of thousands of degrees
Celsius.
Large sunspot group AR 9169 from the last
solar cycle is
visible as the bright area near the horizon.
The bright glowing gas flowing around the
sunspots
has a temperature of over one million degrees
Celsius.
The reason for the high temperatures is
unknown
but thought to be related to the rapidly changing
magnetic field loops that channel solar plasma.
Large
sunspot group AR 9169 moved across the
Sun during 2000 September and decayed in a few weeks.
