As many regular readers know, I’ve pointed out several times the incident of the abrupt and sustained lowering of the Ap Index which occurred in October 2005. The abrupt step change seemed (to me) to be out of place with the data, and the fact that the sun seems so have reestablished at a lower plateau of the Ap index after that event and has not recovered is an anomaly worth investigating.
From the data provided by NOAA’s Space Weather Prediction Center (SWPC) you can see just how little Ap magnetic activity there has been since. Here’s a graph from October 2008 showing the step in october 2005:
click for a larger image
However, some have suggested that this event doesn’t merit attention, and that it is not particularly unusual. I beg to differ. Here’s why.
In mid December I started working with Paul Stanko, who has an active interest in the solar data and saw what I saw in the Ap Index. He did some research and found Ap data that goes back further, all the way to 1932. His source for the data is the SPIDR (Space Physics Interactive Data Resource) which is a division of NOAA’s National Geophysical Data Center (NGDC). He did some data import and put it all into a mult-page Excel spreadsheet which you can access here.
I had planned to do more study of it, but you know how holidays are, lot’s of things to do with that free time. I didn’t get back to looking at it until today, especially after SWPC updated their solar datasets on January 3rd, including the Ap Index. Looking at the data to 1932, it was clear to me that what we are seeing today for levels doesn’t exist in the record.
About the same time, I got an email from David Archibald, showing his graph of the Ap Index, graphed back to 1932. Having two independent sources of confirmation, I’ve decided to post this then. The solar average geomagnetic planetary index, Ap is at its lowest level in 75 years, for the entirety of the record: Read the rest of this entry »
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