Australian Cosmic Ray Modulation Research

Duldig, M. L.

doi:10.1071/as01003

Cited by 26 publications

(11 citation statements)

References 97 publications

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“…The first three columns of Table 2 show the name of the NM station, the all-period mean phase by the pileup method, and the all-period mean GCR intensity of the diurnal variation. The remaining three columns show the all-period mean phase, the amplitude of the diurnal variation, and the ratio of perpendicular to parallel diffusion coefficients by the method of Duldig (2001). As the latitude of the NM station gets higher, that is, the cut-off rigidity gets lower, the phase gets later, as shown in Figure 2 and Table 2.…”

Section: Methods and Datamentioning

confidence: 97%

Modulation Cycles of Galactic Cosmic Ray Diurnal Anisotropy Variation

Bieber

2010

Sol Phys

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The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the 'pile-up' method and the F -test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle.

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Section: Methods and Datamentioning

confidence: 97%

Modulation Cycles of Galactic Cosmic Ray Diurnal Anisotropy Variation

Bieber

2010

Sol Phys

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“…Registration of GLE events by ground‐based neutron monitors began in the early 1940s. More details can be studied in a number of papers and books [e.g., Meyer et al , 1956; Park , 1957; Dorman and Venkatesan , 1993; Kudela et al , 1993; Reames , 1995; Shea et al , 1999; Miroshnichenko , 2001; Duldig , 2001; Smart and Shea , 2002; Cliver et al , 2004; Gopalswamy et al , 2005].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of ground‐level enhancement–associated solar flares, coronal mass ejections, and solar energetic particles

et al. 2010

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[1] Ground-level enhancements (GLEs) are sudden, sharp, and short-lived increases in cosmic ray intensities registered by neutron monitors. These enhancements are known to take place during powerful solar eruptions. In the present investigation, the cosmic ray intensities registered by the Oulu neutron monitor have been studied for the period between January 1979 and July 2009. Over this span of time, increase rates of 32 GLEs have been deduced. In addition, we have studied characteristics of the 32 event-associated solar flares, coronal mass ejections (CMEs), and solar energetic particle (SEP) fluxes. We found that all of the 32 GLEs were associated with solar flares, CMEs, and SEP fluxes. Approximately 82% of the events were associated with X-class flares. Most of the flares that were associated with GLEs of increase rates >10% originated from the active regions located on the southwest hemisphere of the Sun. The average speed (1726.17 km/s) of GLE-associated CMEs was much faster than the average speed (423.39 km/s) of non-GLE-associated CMEs. It also became evident that ∼67% GLEs were associated with very fast (>1500 km/s) CMEs. Although a GLE event is often associated with a fast CME, this alone does not necessarily cause the enhancement. Solar flares with strong optical signatures may sometimes cause GLE. High SEP fluxes often seem to be responsible for causing GLEs as the correlation with SEP fluxes implies.

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“…The 11-year solar cycle is clearly visible in TSI and in both proxies: SSN and NM. The latter showing features which cannot be found in TSI data such as Forbush decreases (Lockwood, 1971) and ground-level enhancements (Duldig, 2001). Both are characterised by distinct count rate changes.…”

Section: The Datamentioning

confidence: 94%