Application of Spectrum of Energetic Protons Accelerated by CME to Geomagnetic Storm Forecast

Abstract

AbstractThe character of CME is crucial in forecasting geomagnetic storms. In this work, the flux and spectrum of interplanetary energetic protons, together with the particularity of their evolution, were investigated to get the judgment of the acceleration process occurring in CME and evaluate the effect of the CME on the geomagnetic field. The proton flux data from ACE/EPAM during 1998 to 2010 was employed and a so‐called spectrum index was derived by modeling the data. Through the statistic work on the proton flux, spectrum and relative CME and geomagnetic disturbance, following conclusions were drawn: (1) The background of spectrum index was –2.6 while its fluctuation reached ±0.4 in the high period of solar activity and it was stable in the low period of solar activity with a value of –3.0; (2) The elevating of the spectrum usually corresponded to the acceleration process in CME, and the scale of 20% or more increasing in spectrum index means a big probability of geomagnetic storms; (3) The energetic proton flux would grow when the shock by high speed stream from coronal hole reached the earth but the spectrum declined slightly; (4) The efficiency of the application of spectrum to geomagnetic storm forecast was evaluated with the relevant data in 2004 and the result shows that the CME originated geomagnetic storm always followed the significant increasing spectrum index, and the proton spectrum index can be used as an indicator of geomagnetic storms.