Abstract


  INVESTIGATION OF SOLAR CYCLE DISTRIBUTION OF GEOMAGNETIC STORMS

  A. Gwal, Barkatullah University, ashok.gwal@gmail.com

Abstract: To accomplish this study we have considered the previous four solar cycles namely cycle 21 to cycle 24. They are classified into three categories on the basis of Dst value, as intense (Dst≤-100nT),
moderate (-100≤Dst≤-50) and weak (-50≤Dst≤-30). The total number of storms observed during 1976-2015 were 1717, out of which 265 (15.43%) were intense, 749 (43.62%) were moderate and 703 (40.94%) were weak. The maximum number of storms was observed during the descending phase of each solar cycle. The number of storms( two years before and three years after the peak of each solar cycle) have been calculated. From the analysis we found that 73.20% of intense storms while 58.07% and 47.93% of moderate and weak storms were observed during two year before and three years after the peak of all solar cycles. The storm events with Dst≤-200nT were classified as Outstanding Sun Earth connections (OSEC). We calculated the total number of OSEC events as well as OSEC events two years before and three years after the peak of each solar cycle and found that the ratio NOSE23/NOSEt was 88.37%. It is also noticed a double peak behaviour in the occurrence of intense and OSEC events. The correlation between the size of solar cycle and the percentage of intense, moderate, weak as well as OSEC events are also investigated.