Southern aurora (aurora australis) composited with NASA imagery

As we're in the midst of experiencing some particularly stormy solar weather it seems appropriate to make a quick post with some nifty auroral images and time-lapse movies (see below). It's also fun to point out that the phenomenon of aurorae (or auroras) is truly universal. Caused when high-velocity particles like electrons and protons expelled by (for example) stellar activity crash into the upper reaches of planetary atmospheres, aurorae are one of the most beautiful manifestations of fundamental physics. These speedy particles can dump energy into the electrons bound into atoms of atmosphere - oxygen and nitrogen on Earth for example. As the electrons rid themselves of this energy in order to snuggle back up to their atomic nuclei they bleed photons - the photons that light up the skies.

The complexity of the illuminated structures is testament to the complexity of the flows of atmospheric electrical currents and particles within a planetary magnetic field, together with the tendrils of incoming particle streams from a star.

Hubble Space Telescope of UV light emitted by aurorae in upper atmosphere of Jupiter (J. Clarke, ESA/NASA)

Earth does it, Jupiter and Saturn do it, Neptune and Uranus have been caught at it, and even Mars does it. We also presume that many exoplanets must also do it - in fact auroral emission mechanisms (which can also produce radio frequencies) could offer a truly unique way to detect and study planets around other stars.

For now though we can simply marvel at a light show that has played out across billions of years in the skies of planet Earth.


..and from space (the International Space Station/