Cosmic ray modulation: Effects of high speed solar wind streams

Badruddin,

doi:10.1007/bf00645638

Cited by 35 publications

(12 citation statements)

References 32 publications

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“…The highest correlation coefficient for shock-associated events is for the magnetic field fluctuations both in measurement-I and measurement-II. This is similar to the results obtained for SWDs in general (Paper I) and agrees with studies that emphasize post-shock turbulence as the main cause of the CR depression (e.g., Badruddin et al 1986;Badruddin 1996), where increased fluctuations lead to CR reduction because of shortened diffusion length (see e.g. Wibberenz et al 1998).…”

Section: Shock-associated and No-shock Eventssupporting

confidence: 92%

“…Note that all Forbush decrease curves were cut at the end of FD, i.e., at the point where CR count comes to the pre-event level. Figure 4 clearly depicts differences between CIRs, ICMEs and mixed events in both |FD| and B, in agreement with results presented by Badruddin et al (1986); Badruddin (1996); Singh & Badruddin (2007). In ICMEs the magnetic field strength increases sharply and returns to the pre-increase level fairly gradually.…”

Section: Solar Wind Disturbances Divided By Typesupporting

confidence: 87%

“…Therefore, we conclude that ICMEs and mixed events generally cause deeper depressions than CIRs, even if the IMF increase is the same for the two. This agrees with the results of the superposed epoch analysis in Badruddin et al (1986) and Badruddin (1996). The same statistical procedure (a two-sample t-test) was applied for the magnetic field fluctuations where similar results were obtained.…”

Section: Solar Wind Disturbances Divided By Typesupporting

confidence: 86%

“…Burlaga et al 1984;Cane 2000). Differences between the shock-associated and no-shock events were studied by Badruddin et al (1986) and Badruddin (1996). However, they applied only the superposed epoch analysis, lacking quantitative statistical results.…”

Section: Methodsmentioning

confidence: 99%

“…Iucci et al 1979;Badruddin et al 1986;Badruddin 1996;Singh & Badruddin 2007), statistical analysis (e.g. Cane et al 1996;Richardson et al 1996;Belov et al 2001;Čalogović et al 2009;Chilingarian & Bostanjyan 2010) and case-studies (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Cosmic ray modulation by different types of solar wind disturbances

Dumbović

Vršnak

Čalogović

et al. 2012

A&A

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Context. Solar wind disturbances such as interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) cause short-term cosmic ray depressions, generally denoted as Forbush decreases. Aims. We conduct a systematic statistical study of various aspects of Forbush decreases. The analysis provides empirical background for physical interpretations of short-term cosmic ray modulations. Methods. Firstly, we analyzed the effects of different types of solar wind disturbances, and secondly, we focused on the phenomenon of over-recovery (the return of the cosmic ray count to a value higher than the pre-decrease level). The analysis is based on groundbased neutron monitor data and the solar wind data recorded by the Advanced Composition Explorer. The correlations between various cosmic ray depressions and solar wind parameters as well as their statistical significance are analyzed in detail. In addition, we performed a normalized superposed epoch analysis for depressions and magnetic field enhancements. Results. The analysis revealed differences in the relationship between different solar wind disturbances and cosmic ray depression parameters. The amplitude of the depression for ICMEs was found to correlate well with the amplitudes of magnetic field strength and fluctuations, whereas for CIRs we found only the correlation between the amplitude of the depression and the solar wind disturbance dimension proxy vt B . Similar behavior was found for shock and no-shock events, respectively. The CIR/ICME composites show a specific behavior that is a mixture of both ICMEs and CIRs. For all analyzed categories we found that the duration of the depression correlates with the duration of the solar wind disturbance. The analysis of the over-recovery showed that there is no straightforward relationship to either "branching-effect" or geomagnetic effects, therefore we propose a scenario where the "branching-effect" is caused by several factors and is only indirectly related to the over-recovery.

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Section: Shock-associated and No-shock Eventssupporting

confidence: 92%

Section: Solar Wind Disturbances Divided By Typesupporting

confidence: 87%

Section: Solar Wind Disturbances Divided By Typesupporting

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cosmic ray modulation by different types of solar wind disturbances

Dumbović

Vršnak

Čalogović

et al. 2012

A&A

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Solar magnetic cycle dependence in corotating modulation of galactic cosmic rays

Gupta

Badruddin

2009

Astrophys Space Sci

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We study the temporal evolution of cosmic ray intensity during ∼27-day Carrington rotation periods applying the method of superposed epoch analysis. We discuss about the average oscillations in the galactic cosmic ray intensity, as observed by ground based neutron monitors, during the course of Carrington rotation in low solar activity conditions and in different polarity states of the heliosphere (A < 0 and A > 0). During minimum and decreasing phases in low solar activity conditions, we compare the oscillation in one polarity state with that observed in other polarity state in similar phases of solar activity. We find difference in the evolution and amplitude of ∼27-day variation during A < 0 and A > 0 epoch. We also compare the average variations in cosmic ray intensity with the simultaneous variations of solar wind parameters such as solar wind speed and interplanetary magnetic field strength. From the correlation analysis between the cosmic ray intensity and the solar wind speed during the course of Carrington rotation, we find that the correlation is stronger for A > 0 than A < 0.

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