Naslov
Cosmic Ray modulation by Solar Wind Disturbances

Autori
Dumbović, Mateja ; Vršnak, Bojan ; Čalogović, Jaša ; Karlica, Mile

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
7th European space Weather Week

Mjesto i datum
Brugge, Belgija, 15.11.2010. - 19.11.2010

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Cosmic rays ; Interplanetary coronal mass ejections ; Solar wind disturbances

Sažetak
Compressions of interplanetary magnetic field (IMF) associated with interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) cause short-term decreases (so-called Forbush decreases, FDs) in galactic cosmic ray (CR) flux. The mechanism of this modulation is still a matter of research. In this report we analyze the influence of different parameters on the amplitude and the duration of Forbush decreases, using ground- based neutron monitor data and in situ solar wind data from the Advanced Composition Explorer (ACE). Solar wind disturbances were identified as increases of solar wind speed, IMF and magnetic field fluctuations and sorted by the type (ICME/CIR) and the association with a shock. Furthermore, FDs were treated separately for cases showing the over-recovery phase in CR flux. We analyzed correlations between CR depression amplitudes and solar wind speed, IMF and IMF fluctuations. Time profiles of the FDs and solar wind disturbances were also examined. An extensive statistical analysis was made regarding the delay of the depression after the onset of the IMF increase and also magnitude and the duration of the depression. The analysis of relative timing of CR depressions revealed that in the majority of cases the decrease follows the onset in IMF increase. Very high correlation between FD magnitude and IMF fluctuations is indicative of important role of reduced parallel diffusion as a modulation mechanism. Furthermore, the modulation effect was found to be more pronounced when proxies of time integrals are used. The differences obtained for the data sorted by type, shock association and presence of over-recovery are discussed regarding both FD magnitude and time profiles. These results can be used to test theoretical models.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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