engleski

Cosmic Ray modulation by Solar Wind Disturbances

Solar wind disturbances (SWDs), namely interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs), cause short-term depressions in galactic cosmic ray (GCR) flux. The mechanism of this modulation is still a matter of research from observational point and theoretical modeling. Since GCR flux reflects solar activity, solving this problem represents an important aspect of space weather. We analyze the influence of different SWD parameters on the amplitude and the duration of the depressions, using ground-based neutron monitor data and in situ solar wind data from the ACE satellite. We test the correlations between GCR depression amplitudes and solar wind speed, IMF and IMF fluctuations. Time profiles are also examined. The analysis is performed for SWDs in general, ICMEs, CIRs, mixed ICME/CIR events, events associated with an interplanetary shock, and events without the shock. A statistical analysis is also performed regarding the delay of the depression after the onset of the IMF increase. We find that in the majority of cases the decrease follows the onset in IMF increase with an average delay on the order of the typical shock-sheath thickness. High correlation between the depression magnitude and the increase in IMF fluctuations and strength was found, favoring reduced diffusion as a modulation mechanism. Furthermore, the proxies of time integrals are found to behave as physical quantities. The differences were observed between the data sorted by type (ICME, CIR, and mixed) and shock association. Obtained results can be used to test theoretical models.

Cosmic rays ; Interplanetary coronal mass ejections ; Solar wind disturbances

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