Aurora Over Antarctica

Aurora Over Antarctica
  • Credit:

    NASA GSFC, NOAA

We're now at about the peak of solar cycle #23, and thus, auroras like the one pictured here should be more frequent during the coming months than they've been in the past few years. This beautiful light show of luminous bands, arcs and curtains was taken approximately 550 miles above Antarctica on July 21, 1993 by the visible sensor on-board the Defense Meteorological Satellite Platform (DMSP). The South Pole is at the upper right center of the image, in the center of the smallest concentric circle. It's still dark all day over the South Pole area now since the the Earth hasn't yet reached the autumnal equinox. The few scientists (less than 250) who winter-over in Antarctica are sometimes treated to magnificent displays of the aurora australis or the southern lights, which are caused by the release of energy from oxygen and nitrogen molecules as they're bombarded by electrons and protrons (solar wind) originating from the Sun. The Sun is constantly shooting out billions of charged particles, but the amount of particles fluctuates over 11 year cycles. Aurora occur when the charged particles are captured by the Earth's magnetic field and accelerated into currents that move along magnetic field lines, converging over the poles. Here, they may crash into oxygen and nitrogen molecules in the upper atmosphere (about 60 miles or so above the surface). The "electrified" molecules shed their newly-gained energy as light that can be seen in the southern sky as aurora australis or in the northern sky as aurora borealis. Since we're at about the 11-year peak of solar activity, here in the Northern Hemisphere, with any luck, you might be able to see an aurora this year, even if you live as far south as Washington or St. Louis or Salt Lake City.

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