Tonight into tomorrow, northern hemisphere sky watchers as far south as Iowa or Michigan to Washington State are on aurora alert. Auroras are caused by charged particles hitching a ride on solar wind, dark skies turn undulating curtains of mischievous colour when charged particles interact with molecules in our atmosphere. Usually, our magnetosphere acts as a planetary shield preventing geomagnetic interaction of charged particles. Every so often fast moving particles overwhelm our magnetic field, create an opening and light up night skies.
On May 12, a magnetic filament on the sun, seen here, became unstable and erupted. (NASA/SDO)
Since Monday, 3 additional solar eruptions sent fast moving charged particles our way. As a result the auroral oval (doughnut shaped ring around the pole where charged particles follow magnetic field lines, reason why far northern latitudes regularly witness geomagnetic storms), has shifted far to the south.
The northern lights as seen looking eastward from just east of Penzance, Sask., at 1:21 a.m. local time Tuesday morning. (Submitted by Notanee Bourassa)
The colour of that light depends on the kind of molecule and the altitude of the collision.
Green is the most common colour, produced when the particles collide with oxygen at an altitude of around 100 to 300 km. At about 300 to 400 km, the interaction with oxygen produces red. Pink occurs below 100 km when nitrogen atoms are struck.
This link – https://www.cbc.ca/news2/interactives/solar-flares/index.html is worth a ponder. One of the best I’ve found in terms of understanding what makes space weather tick.
Bottom line – Space Weather Prediction Centre forecasters say there’s a 75% chance of geomagnetic storm activity tonight. If your skies are clear, go outside. If she’s willing, Aurora will find you. Opportunities like this don’t come along every day.