Monday, August 27, 2018

Freak magnetic storm causes wretched band conditions

Your radio isn't busted.  A variety of events affecting the Earth's magnetic field have caused one of the longest geomagnetic storms in recent memory.  The K index has reached 7 on a number of occasions in the last three days, and this is expected to continue on and off.  K is back to 7 as of this writing. 

Surface events such as ground currents in Norway have taken place. We also saw some extreme southward Bz, including a sustained period of -17 nT yesterday.  Strong aurora has occurred in high geomagnetic latitudes. Geomagnetic storming has reached the G3 level at times.

A large coronal hole is the current cause of all this, but when it started it was due to some less common phenomena.  For various reasons, the resulting band conditions have been some of the year's worst, with extended periods of weak or missing signals.  We have not seen the sudden dropouts related to solar flares, since there haven't been any flares.  It's been just days of truly dreadful propagation.

The flow from the coronal hole is expected to persist for several more days.

While it has no relation to the geomagnetic activity, the appearance of a large sunspot pair with an opposite magnetic field is also getting attention.  If this group (AR 2720) was at a higher solar latitude, we would definitely have the first spots of Cycle 25. However, it is near the solar equator.

Even in quiet-sun conditions, our neighborhood star is good for surprises.