Centennial changes in solar activity and the response of galactic cosmic rays

Rouillard, A. P.; Lockwood, Mike

doi:10.1016/j.asr.2007.02.096

Cited by 11 publications

(14 citation statements)

References 25 publications

(34 reference statements)

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“…The exponents lie in the range described by Caballero‐Lopez et al [2004] as physically reasonable ( α ∈ [1;3]) and are in good agreement with the value of 1.75 derived by McCracken [2007]. Rouillard and Lockwood [2007] obtained a very similar exponent, which they call n , of α = 1.8.…”

Section: Calibrationsupporting

confidence: 84%

“…Test of our reconstruction method. The cosmic ray intensity data of Rouillard and Lockwood [2007] are used to reconstruct the IMF (using the exponent α = 1.8 ± 0.2 from Rouillard and Lockwood [2007]). This IMF is compared with the IMF reconstruction (using IDV and aa index, Bayesian least squares) of Rouillard et al [2007], which was the input parameter for the cosmic ray intensity calculation.…”

Section: Datamentioning

confidence: 99%

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Interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides

et al. 2010

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We have reconstructed the interplanetary magnetic field (IMF), its radial component, and the open solar magnetic flux using the solar modulation potential derived from cosmogenic 10Be radionuclide data for a period covering the past 9300 years. Reconstructions using the assumption of both constant and variable solar wind speeds yielded closely similar results. During the Maunder Minimum, the strength of the IMF was approximately 2 nT compared to a mean value of 6.6 nT for the past 40 years, corresponding to an increase of the open solar magnetic flux of about 350%. We examine four cycles of the Hallstatt periodicity in the IMF with a mean period of ∼2250 years and an amplitude of ∼0.75 nT. Grand solar minima have largely occurred in clusters during the Hallstatt cycle minima around the years −5300, −3400, −1100, and +1500 A.D. The last cluster includes the Dalton, Maunder, and Spörer minima. We predict that the next such cluster will occur in about 1500 years. The long‐term IMF has varied between ∼2 nT and ∼8 nT and does not confirm a proposed floor (lower limit). There is a slowly changing long‐term trend of amplitude 1.5 nT, with a minimum around the year −4600 and a maximum around 0 A.D. that may be of solar origin but which also may be due to unknown long‐term changes in the atmospheric effects or geomagnetic field intensity.

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Section: Calibrationsupporting

confidence: 84%

Section: Datamentioning

confidence: 99%

Interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides

et al. 2010

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“…The primary question (1) here is the credibility of the substantial increase in the reconstructed HMF around 1950, just before the spacecraft era of diminished LSEP event rates. The apparent good match in Figure 3 between the HMF reconstructions from geomagnetic indices, SSNs, and cosmic ray 10 Be records has not been confirmed by the recent reconstructions from the IDV index [ Svalgaard and Cliver , 2005] and corrected aa numbers [ Rouillard and Lockwood , 2007]. Furthermore, the HMF reconstructions from SSNs were not independent because they used earlier cosmic ray and geomagnetic HMF reconstructions to set their flux decay parameters to give good matches.…”

Section: Discussionmentioning

confidence: 95%

“… Rouillard and Lockwood [2007] found that a simple 1‐D spherically symmetric model, such as that used by McCracken [2007c], to relate cosmic ray intensities to the HMF cannot explain the long‐term drift of the cosmic ray data from 1903 to 1953 and is systematically offset from the Neher ionization data of 1933 to 1963. They suggested changes in latitudinal extents of CIRs and in CME rates in the 1950s to account for the rapid drop of cosmic ray intensities in the period 1944–1954.…”

Section: Critical Steps On the Path To Enhanced Sep Activitymentioning

confidence: 99%

“…They suggested changes in latitudinal extents of CIRs and in CME rates in the 1950s to account for the rapid drop of cosmic ray intensities in the period 1944–1954. The picture for cosmic ray modulation is further complicated by the ∼14% increase in solar wind speeds from 1903 to 1956 [ Rouillard and Lockwood , 2007].…”

Section: Critical Steps On the Path To Enhanced Sep Activitymentioning

confidence: 99%

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Prospects for future enhanced solar energetic particle events and the effects of weaker heliospheric magnetic fields

Kahler

2008

J. Geophys. Res.

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[1] Recent work based on nitrate abundances in ice cores has shown that large solar energetic (E > 30 MeV) particle (LSEP) events during the spacecraft era of observations (1960-present) are diminished in comparison with those of some preceding eras and that LSEP events have occurred during low cycles of solar activity. McCracken et al. (2004) have reported an inverse correlation between those LSEP events and the magnitude of the associated reconstructed heliospheric magnetic field (HMF). A physical explanation by McCracken (2007aMcCracken ( , 2007b is that the lower HMF and coronal magnetic field B imply that fast coronal mass ejections (CMEs) produce shocks with enhanced Alfvenic Mach numbers M A and higher compression ratios r, leading to more numerous and energetic LSEP events. From a possible decline of the HMF over the next several solar cycles, he has warned of a return to the environment of the more intense LSEP events preceding the current spacecraft era. We formulate and discuss seven questions using recent published observational, modeling, and theoretical work to assess the assumptions and the validity of his explanation and watch. We conclude that a return to more intense LSEP events is certainly possible, but (1) the inferred large increase in HMF characterizing the spacecraft era is in doubt; (2) there is no good evidence to connect more intense LSEP events with weaker HMFs; (3) a new Gleissberg minimum, with lower HMF, may not be imminent; (4) a lower active region B should result in slower CME speeds V less likely to produce shocks; (5) the average CME V increases significantly with SSN; (6) a lower coronal B likely results in a lower V A as the explanation requires; and (7) the lower coronal B leads to weaker, not more intense, LSEP events because of decreased spectral cutoff energies.

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Influence of the 11-Year Solar Cycle on Variations of Cosmic Ray Intensity

Han

Yin

2009

Sol Phys

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The monthly cosmic ray intensity (CRI) time series from Climax, Huancayo, Moscow, Kiel, and Calgary are used to investigate the presence of the 11-year periodic component with special attention paid to the solar influence on these variations. The results show obvious 11-year temporal characteristics in CRI variations. We also find a close anticorrelation between the 11-year solar cycle and CRI variations and time delays of the CRI relative to solar activity.

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Centennial changes in solar activity and the response of galactic cosmic rays

Cited by 11 publications

References 25 publications

Interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides

Interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides

Prospects for future enhanced solar energetic particle events and the effects of weaker heliospheric magnetic fields

Influence of the 11-Year Solar Cycle on Variations of Cosmic Ray Intensity

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