Speakers
Description
Precursors (pre – decreases/pre – increases of the cosmic ray intensity) are observed preceding Forbush decreases. The Cosmic Ray Groups of NKUA and IZMIRAN have studied large Forbush decreases (magnitude > 5%) accompanied by geomagnetic storms (i.e., Dst < -100 nT and 5 ≤ Kp-index ≤ 9) regarding precursors. The threshold value of the equatorial anisotropy one hour before the onset of the event (Axyb, %) was set at 0.8%. In total, 59 events with Axyb ≥ 0.8% (test group) and 68 events with Axyb < 0.8% (control group), from 1957 to 2023, were examined. The ‘Forbush Effects and Interplanetary Disturbances’ database was used for selecting events and analyzing the solar, interplanetary, and geomagnetic conditions during each event. The method ‘Ring of Stations’ was also used. The chosen threshold is well set at 0.8%, since precursors are clearly present in the test group and principally absent in the control group.
| Session | 3 - Cosmic Rays and Space Weather effects |
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