As forecast, the cloud of particles from Friday’s solar flare (the “coronal mass emission”, or “CME”) arrived at our planet a few hours after my last post, early in the morning New York time. If you’d like to know how I knew that it had reached Earth, and how I know what’s going on now, scroll down to the end of this post and I’ll show you the data I was following, which is publicly available at all times.

So far the resulting auroras have stayed fairly far north, and so I haven’t seen any — though they were apparently seen last night in Washington and Wyoming, and presumably easily seen in Canada and Alaska. [Caution: sometimes when people say they’ve been “seen”, they don’t quite mean that; I often see lovely photos of aurora that were only visible to a medium-exposure camera shot, not to the naked eye.]  Or rather, I should say that the auroras have stayed fairly close to the Earth’s poles; they were also seen in New Zealand.

Russia and Europe have a good opportunity this evening. As for the U.S.? The storm in the Earth’s magnetic field is still going on, so tonight is still a definite possibility for northern states. Keep an eye out! Look for what is usually a white or green-hued glow, often in swathes or in stripes pointing up from the northern horizon, or even overhead if you’re lucky.  The stripes can move around quite rapidly.

Now, here’s how I knew all this.  I’m no expert on auroras; that’s not my scientific field at all.   But the U.S. Space Weather Prediction Center at the National Oceanic and Atmospheric Administration, which needs to monitor conditions in space in case they should threaten civilian and military satellites or even installations on the ground, provides a wonderful website with lots of relevant data.

The first image on the site provides the space weather overview; a screenshot from the present is shown below, with my annotations.  The upper graph indicates a blast of x-rays (a form of light not visible to the human eye) which is generated when the solar flare, the magnetically-driven explosion on the sun, first occurs.  Then the slower cloud of particles (protons, electrons, and other atomic nuclei, all of which have mass and therefore can’t travel at light’s speed) takes a couple of days to reach Earth.  It’s arrival is shown by the sudden jump in the middle graph.  Finally, the lower graph measures how active the Earth’s magnetic field is.  The only problem with that plot is it tends to be three hours out of date, so beware of that! A “Kp index” of 5 shows significant activity; 6 means that auroras are likely to be moving away from the poles, and 7 or 8 mean that the chances in a place like the north half of the United States are pretty good.  So far, 6 has been the maximum generated by the current flare, but things can fluctuate a little, so 6 or 7 might occur tonight.  Keep an eye on that lower plot; if it drops back down to 4, forget it, but it it’s up at 7, take a look for sure!

Also on the site is data from the ACE satellite.  This satellite sits 950 thousand miles [1.5 million kilometers] from Earth, between Earth and the Sun, which is 93 million miles [150 million kilometers] away.  At that vantage point, it gives us (and our other satellites) a little early warning, of up to an hour, before the cloud of slow particles from a solar flare arrives.  That provides enough lead-time to turn off critical equipment that might otherwise be damaged.  And you can see, in the plot below, how at a certain time in the last twenty-four hours the readings from the satellite, which had been tepid before, suddenly started fluctuating wildly.  That was the signal that the flare had struck the satellite, and would arrive shortly at our location.

It’s a wonderful feature of the information revolution that you can get all this scientific data yourself, and not wait around hoping for a reporter or blogger to process it for you.  None of this was available when I was a child, and I missed many a sky show.  A big thank you to NOAA, and to the U.S. taxpayers who make their work possible.