engleski

COSMIC RAY MODULATION AND GEOEFFECTIVENESS OF COROTATING INTERACTION REGIONS DERIVED FROM CORONAL HOLE AREA MEASUREMENTS

When the occurrence of interplanetary coronal ejections (ICME) becomes very low in the declining phase and during the minimum of the solar cycle, the major driver of solar-wind disturbances and geomagnetic storms are corotating interaction regions (CIR). They are produced when fast solar wind streams, originating from coronal holes (CH), interact with the preceding slow solar wind. To improve space weather predictions, we investigated the relationship between the area of CHs, satellite cosmic ray (CR) measurements and the Dst index during the minimum phase of the solar cycle 23-24 (2007- 2010). Cosmic ray mea- surements were taken from EPHIN (Electron Proton Helium Instrument) detectors onboard SOHO spacecraft. CHs were extracted with an intensity-based thresholding technique from the SOHO EIT 195 Å images. They are visible as dark regions in the solar corona due to their low temperature and electron density. The SOHO/LASCO CME catalogue and ICME lists were used to remove time periods in which ICMEs were observed. We acknowledge the support of the Croatian Science Foundation under the project 6212 "Solar and Stellar Variability" and of the European social fond under the project "PoKRet".

corotating interacting regions ; coronal holes

nije evidentirano