Unusual solar activity might lead to an increase in incident radiation.

How good are our records of solar activity during the periods described?

He expected changes in solar activity would affect climate patterns on Earth.

Thus solar activity in the 21th century is expected to be lower than it was for most of the 20th century.

The disturbance is caused by temporary changes in solar activity.

Been hearing about a new ice age due to low solar activity?

After a period of low solar activity, the Sun's radiation is scheduled to rise again in the coming months.

When solar activity is at a minimum, more appearances occur north of the line.

With solar activity at a maximum, more occur south of that line.

Some military detection or early warning systems are also affected by solar activity.