While the sun puts out a new and significant cycle 24 spot, the real news is just how quiet the suns magnetic field has been in the past couple of years, and remained during September 2008. From the data provided by NOAA’s Space Weather Prediction Center (SWPC) you can see just how little magnetic field activity there has been. I’ve graphed it below with the latest available data from October 6th, 2008:
click for a larger image
What I find most interesting about the Geomagnetic Average Planetary Index graph above is what happened around October 2005. Notice the sharp drop in the magnetic index and the continuance at low levels.
This looks much like a “step function” that I see on GISS surface temperature graphs when a station has been relocated to a cooler measurement environment. In the case of the sun, it appears this indicates that something abruptly “switched off” in the inner workings of the solar dynamo. Note that in the prior months, the magnetic index was ramping up a bit with more activity, then it simply dropped and stayed mostly flat.
Currently the Ap magnetic index continues at a low level, and while the “smoothed” data from SWPC is not made available for 2008, I’ve added it with a dashed blue line, and the trend appears to be going down.
However, it will be interesting to see if an uptick in the Ap index occurs, now that a significant SC24 spot has emerged. Unfortunately, we’ll have to wait until early November for SWPC to update the data set.