ICS-13 Abstract View

 

Some characteristics and associated nightside ionospheric joule heating studies of substorms on St. Patrick's Day 2015 geomagnetic storm
Prince, P.R., princerprasad@gmail.com (1)
Suji, K.J., kjsuji85@gmail.com (1)
The first super storm of solar cycle 24 occurred on "St. Patricks's day" (17 March 2015), with a minimum Dst level of -223 nT. Some striking characteristics of substorms and subsequent variations in joule heating, over night side auroral ionosphere, during the super storm are presented in this study. 6 major substorms were selected, with its minimum values of local electrojet index (IL) ranging from -1662 nT to -673 nT. The selected substorms are all in midnight sector showing negative bay in x component of magnetogram, derived from the IMAGE magnetometer longitudinal (fennoscandia) chain. The solar wind energy input is estimated as time integral of Akasofu's epsilon parameter, determined from SuperMAG magnetometer. The northern hemisphere joule heating rates are estimated using Ahn's empirical conversion and its time integral from onset phase to recovery phase gives the Joule heat energy, which ranges from from 1.2 ×1015J to 5.9×1015J, for the selected events. A close correlation is obtained between the solar wind energy input parameter and the Joule heat energy. This high correlation is a characteristic of directly driven (DD) processes and the selected substorms are proved to be falling in the DD category. In addition, the ionospheric joule energy over midnight sector also shows good correlation with the solar wind energy, which again validates the presence of DD scenario.
(1) Department of Physics, University College, Trivandrum, India, 695034