Today begins a brand new month and maybe a break from February’s long cold spell. It might also be the start of a new round of auroral activity. Last night a nice G1 geomagnetic storm brought us active streamers and rays across the northern sky. This despite moonlight and, at least for northern Minnesota, pesky clouds, too.
NOAA space weather forecasters are calling for a second round of G1 or minor auroral storms this evening between about 6 p.m. and midnight (CST). Solar disturbances at Earth are rated on a 1 to 5 scale. G1 events usually bring auroras down to the northern tier of U.S. states from Maine to Washington. Other effects include minor fluctuations in power grids and possible impacts on computer hardware in orbiting satellites.
With a G5 or extreme storm, even Floridians should expect auroras. Satellite electronics and poorly protected power grids can suffer damage, shortwave radio propagation cuts out and induced electric charges in oil pipelines by rapidly changing electrical currents in Earth’s ionosphere can lead to corrosion.
Let’s hope tonight’s predicted aurora brings a similar parade of active rays in the northern sky. Naturally, the moon will be a problem, but if your sky is otherwise dark, you might see a fair show.
Like last night, tonight’s source of auroral inspiration is that large, dark “hole” seen in images taken in ultraviolet light by NASA’s orbiting Solar Dynamics Observatory (SDO). Coronal holes are regions small and large on the Sun, where the solar wind of electrons and protons flows freely away from our star at high speeds. All the fluffy yellow plumage in the photo above are magnetic fields that form a sort of canopy over much of the Sun, constraining the flow of particles into space. Holes are free-for-all zones.
Video showing the Sun rotating with a coronal hole
Last night, the magnetic field embedded within the stream pointed south upon its arrival, canceling Earth’s northward-pointing magnetic field and opening a channel into our protective magnetic domain called the magnetosphere. Once “in the building”, the particles shot down into the upper atmosphere and struck atoms and molecules there to create the aurora we saw.
Besides the K-index described above, another excellent tool to check on aurora is the Aurora 30-minute forecast site. Here you’ll see a near-live view of the auroral oval, the halo of permanent auroras found centered on Earth’s geomagnetic poles. When a storm ensues, the oval (or ovals – there’s a southern one, too) expands southward from its polar lair into southern Canada and the U.S.
The forecast here is for clear tonight, so I’ll be out watching. Check back for an update then. Good luck!