Aurora Borealis

Data supplied curtesy of Space Weather Prediction Center, NOAA

The sunlit side of Earth is indicated by the lighter blue of the ocean. The day-night line or terminator is shown as a yellow line. Note that the Aurora will not be visible during daylight hours and it may be an hour or more before sunrise or after sunset that the aurora can be seen from the ground.

The aurora is a dynamic and visually delicate manifestation of solar-induced geomagnetic storms. The solar wind energizes electrons and ions in the magnetosphere. These particles usually enter the Earth's upper atmosphere near the polar regions. When the particles strike the molecules and atoms of the thin, high atmosphere, some of them start to glow in different colors. Aurora begin between 60 and 80 degrees latitude. As a storm intensifies, the aurora spread toward the equator. During an unusually large storm in 1909, an aurora was visible at Singapore, on the geomagnetic equator.

The aurora provide pretty displays, but they are just a visible sign of atmospheric changes that may wreak havoc on technology systems such as satellites, navigation, radio communications and electrical power lines, other effects can be seen in climate and pipelines plus there is growing evidence indicating that changes in the geomagnetic field affect biological systems.

Auroral Activity Extrapolated from NOAA POES

Northern Hemisphere

Southern Hemisphere

Instruments on board the NOAA Polar-orbiting Operational Environmental Satellite (POES) continually monitor the power flux carried by the protons and electrons that produce aurora in the atmosphere. SWPC has developed a technique that uses the 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.