Final answer:
An active region is an area on the Sun where magnetic fields are concentrated. It is associated with several phenomena such as sunspots, flares, prominences, and CMEs. Active regions vary with the sunspot cycle and are indicative of increased solar activity.
Step-by-step explanation:
An active region is an area on the Sun where strong magnetic fields are concentrated. It is a region in the photosphere surrounding a sunspot group that can erupt violently and unpredictably. During sunspot maximum, the number of active regions is also at maximum.
Active regions are associated with several phenomena such as sunspots, prominences, flares, and coronal mass ejections (CMEs). These phenomena tend to occur together in active regions, which vary with the sunspot cycle. They have similar longitudes and latitudes but are located at different heights in the atmosphere. The presence of active regions is usually indicated by an increase in solar activity and energy emission from the Sun.