PC index as a proxy of the solar wind energy that entered into the magnetosphere: 3. Development of magnetic storms

• Published in: Journal of atmospheric and solar-terrestrial physics 2018-11, Vol.180, p.60-77
• Main Authors: Troshichev, O.A., Sormakov, D.A.
• Format: Article
• Language: English
• Subjects: CME and SIR solar drivers; Delay time; Magnetic storms; PC evolution and storm progression; PC index; Polar cap magnetic activity; SymH index
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2017.10.012

Relationships between the 30-min smoothed PC and SymH indices in course of 430 magnetic storms observed in period of 1998–2015 have been examined. The storms were classified, by features of the PC evolution, as classic, pulsed and composite magnetic storms. It is shown these storm types are related, correspondingly, to such solar drivers as Interplanetary Coronal Mass Ejections (ICME), Stream Interaction Regions (SIR), and their joint action. Results of the statistical analysis demonstrate that depression of geomagnetic field (“Dst variation”) starts to develop as soon as PC index steadily excess the threshold level ∼1.5 mV/m, like to case of magnetic substorms. SymH index in course of magnetic storms (during 48 h preceding and succeeding the maximal depression of geomagnetic field) generally follows the time evolution of the PC index with typical delay time of ΔT ∼ 1 ± 0.5 h. The storm intensity (SymHMIN) is linearly related to maximal value of the foregoing PC index (PCMAX) observed ∼0.5÷2 h before the moment of maximal depression. The conclusion is made that the PC index can be successfully used for nowcasting the magnetic storm development. •Development of magnetic storms is predetermined by the PC index evolution.•Magnetic storms start to develop as soon as PC index steadily excess the level 1.5 mV/m.•The storms is developed as long as PC increases and starts to decay when PC value displays decline.•The maximal depression of magnetic field follows, with ∼1 h delay time, the maximum of PC index.•The PC index provides the unique on-line information on solar wind energy that entered into magnetosphere.