Abstract
This paper studies the probable roles of interplanetary and geomagnetic parameters in the generation of ‘intense’ and ‘very intense’ magnetic storms as well as the correlation between magnetic field B and flow speed V , southward turning of Bz ( Bs ) and Bs duration BT . 18 storm events were observed and for analysis were divided into two sections. This include 8 ‘intense’ magnetic storm (−250 nT ≤ peak Dst < −100 nT) events and 10 ‘Very intense’ storms (peak Dst < −250 nT); both spanning January 1976 until May 2005. From our analysis, it was observed that the interplanetary magnetic field Bz plays a prominent role alongside Dst in the generation of intense storms. So also is the interplanetary electric field associated with high-speed streams and the solar wind density Np in the ring current intensification. The result further shows that over 67% of the storm events under investigation are generated from magnetic clouds which are characterized by a low beta plasma, high IMF magnitude and large scale coherent field rotations often including large and steady north-south components.As regards the geoeffectiveness of the flow speed V , the Bs and Bs interval ( BT ) with the magnetic field B , it was observed that generally for all the selected storm events, the flow speed is the most correlated, showing a correlation coefficient of 50.9% with B, and hence the most geoeffective. However, the statistical significance of its correlation with B is not so directly implying a higher substorm occurrence during the faster solar wind, but that it is one of the causes of substorm occurrence at a value faster than 400 km/s. Furthermore, the result shows that ‘very intense’ storms whose main feature is a plasma flow speed greater than 550 km/s has a negligible or very low correlation between the flow speed and the magnetic field B ; whereas, ‘intense’ storms have a 58.7% correlation between the two parameters. Lastly, it could be argued that all ‘very intense’ storms are likely to have a plasma flow speed greater than 550 km/s within the storm interval, but not all flow speed greater than 550 km/s are ‘very intense’ storms.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have