MIT Haystack 

Statistical Analysis of Solar Geomagnetic Storm Occurrences

Seth Sivak
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     On the results page I have four questions at the top.  They were the backbone for our research and they are:
  • Are there maxima found near the Equinoxes?
  • Do geomagnetic storms occur the most during March and April?
  • Do very large storms happen at random or do they follow a pattern?
  • When is the best time to plan radar operations to collect data on these storms?
  •      The answers to these questions summarize our results very well.  The first question is very important to the study.  It is widely known that geomagnetic activity seems to peak at the equinoxes (however that was not confirmed at the start of the research).  Our research confirmed that there are maxima within a few days of equinox.
    Maximums Found (Within 3 days)
    Kp Level Vernal Equinox Autumnal Equinox
    Kp > 6 April 4 , May 2 September 21
    Kp > 7 March 28 , April 2 September 4 , September 22
    Kp > 8 April 2 September 4
    This table gives the derived maxima for 3 levels of Kp found using our data.  The reason that the dates are within 3 days is due to the 3 day grouping used to eliminate scatter.  Actual equinoxes are March 22nd and September 22nd, our data was fairly close on all levels of Kp.  To answer the question; there is clearly maxima around the equinoxes.

         The second question on the list was answered with a simple histogram.  When the histogram was done on geomagnetic storms with Kp > 6, we found that March and April made a very large peak.  However, September had the most elements.  Therefore geomagnetic storms occur most during September, followed closely by March and April.

         Very large storms became the focus of our research.  Large storms (Kp > 8) happen fairly rarely, but when they do happen, they create havoc in the interplanetary solar wind and within the Earth's magnetosphere.  In order to find out if they follow a pattern we ran a series of tests which looked at only geomagnetic storm elements with Kp > 8.  We found that they occur in the same pattern that smaller storms occur, they have maximums at the equinoxes and minimums in December and January.  However in doing this study we came across something very interesting, we found a large maximum in July.  This maximum is only apparent for large storms but in running tests we confirmed that it is significant.  The answer to the third questions is; large geomagnetic storms essentially follow the same pattern that small storms do, except for the maximum in July.

         The final question on the list is probably the most important.  Operating the radar is very expensive, so knowing the best time to do it is vital knowledge.  In running many different tests on many aspects of the data we found the best time to start radar operations.  We feel that the best time is 18-24 months following solar maximum during the month of March, April, July and September.  These times have the greatest probability of producing storms.  Unfortunately it is impossible to completely predict storm activity, but statistical studies like the one we performed help guide scientists. 

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    Web Page Created 06-03-02