Satellites continually monitor the power flux carried by the
protons and electrons that produce aurora in the atmosphere. Power flux
observations obtained during a single pass of the satellite over a polar region
(which takes about 25 minutes) to estimate the total power deposited in an
entire polar region by these auroral particles. The power input estimate is
converted to an auroral activity index that ranges from 1 to 10.
Over 100,000 satellite passes comprise the historical database
that was used to construct statistical patterns of auroral power flux for each
of the 10 levels of auroral activity as defined by total power dissipation as
illustrated in the following tables. Current Northern Hemisphere Activity Current Southern Hemisphere Activity Northern Hemisphere Aurora Visibility
