Tag: tau

[Update July 30 8:00 am NYC time: there was a weak impact of a coronal mass ejection about 12 hours ago, but nothing big yet.]

After a few significant solar flares over the past few days, the chances of auroras (i.e. northern and southern lights) is high enough that it’s probably worth keeping an eye on polar skies for the next couple of nights. At the moment the forecast is for the best chances to be in Asia, but forecasting auroras is far from an exact science, and there could be surprises.

To know when to start looking, I keep an eye on data from the ACE satellite.  When a cloud of slow particles from a solar flare’s coronal mass ejection arrives, ACE’s data goes all haywire; you’ll see it as a sudden change in the plots’ appearance, as in the example shown below. ACE satellite sits 950 thousand miles [1.5 million kilometers] from Earth, and is located between Earth and the Sun.  At that vantage point, it gives us (and our other satellites) a little early warning, of up to an hour.

Another good place to look is NOAA’s space weather dashboard. Its first panel, an example of which is shown below, displays three plots; the bottom plot is called “Geomagnetic Activity”. When that plot goes deep orange or red, then there’s probably some serious auroras going on in areas where they aren’t so often seen.

But be warned — the plot shows not what is happening now but what happened in a three-hour interval that is already past. If a geomagnetic storm is long enough, that’s still useful, but be aware that the data is out of date by the time we get to see it. That’s why the ACE satellite may well give you the best heads-up.