Anomalous and Galactic Cosmic Rays at 1 AU During the Cycle 23/24 Solar Minimum

Leske, R. A.; Cummings, A. C.; Mewaldt, R. A.; Stone, E. C.

doi:10.1007/978-1-4614-9200-9_18

Cited by 5 publications

(6 citation statements)

References 26 publications

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“…At even lower rigidities, e.g., for 1.1 to 1.8 GV (150 to 380 MeV/n) He, as measured on IMP8 and ACE by, e.g., McDonald et al [2009], the qA >0 plateau intensities are higher than the qA <0 peak intensities. The same is true for 8 to 27 Mev/n ACR oxygen (average P = 1.2 GV), as observed by Leske et al [2009]. This rigidity-dependent pattern in the peak/plateau behavior led Moraal et al [1989] and Reinecke et al [1997] to suggest that the modulated spectra in opposite magnetic cycles should contain more than one crossover.…”

Section: Features Of the Long-term Modulationmentioning

confidence: 58%

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Long‐term neutron monitor observations and the 2009 cosmic ray maximum

Moraal

Stoker

2010

J. Geophys. Res.

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[1] The solar minimum of 2009 was characterized by a prolonged increase toward the maximum cosmic ray intensity, which was higher than it was during the maxima of 22 and 44 years ago. In the previous two so-called qA <0 (solar dipole moment facing South) magnetic cycles, these increases were more sharply peaked than in 2009. The observations of the Sanae, Hermanus, Potchefstroom, and Tsumeb neutron monitors are used to investigate this behavior in terms of propagation conditions due to solar activity, the heliospheric magnetic field, and the profile of the wavy current sheet in the field. This 2009 cosmic ray maximum can only be understood after an investigation of the long-term cosmic ray record. This study is augmented by observations of eight other neutron monitors. During 2009, solar activity parameters were significantly different from previous solar minima: The sun was much quieter, and the the heliospheric magnetic field was more than 20% weaker than during other recent minima. Both of these parameters imply a higher cosmic ray diffusion coefficient, which provides a natural explanation for both the higher galactic cosmic ray intensities that were observed and the absence of such an effect for anomalous cosmic rays.

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Section: Features Of the Long-term Modulationmentioning

confidence: 58%

“…[19] On the other hand, Leske et al [2009] reported that the 2009 anomalous cosmic ray (ACR) O intensity (average P = 1.2 GV) was approximately the same as in 1987. This difference with the general trend is likely due to the fact that this species is anomalous.…”

Section: Features Of the 2009 Cosmic Ray Maximummentioning

confidence: 99%

Long‐term neutron monitor observations and the 2009 cosmic ray maximum

Moraal

Stoker

2010

J. Geophys. Res.

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“…No clear long‐term trend is seen in either V SW or EEP flux until a clear decrease in cycle 23. GCR flux shows the well‐known anticorrelation with sunspot cycle and the exceptional increase in the GCR amount during the last sunspot minimum as a response to the weaker heliospheric magnetic field since the declining phase of cycle 23 [ Smith and Balogh , ; Leske et al , ].…”

Section: Evolution Of Solar‐related Parametersmentioning

confidence: 99%

Spatial distribution of Northern Hemisphere winter temperatures during different phases of the solar cycle

2014

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Several recent studies have found variability in the Northern Hemisphere winter climate related to different parameters of solar activity. While these results consistently indicate some kind of solar modulation of tropospheric and stratospheric circulation and surface temperature, opinions on the exact mechanism and the solar driver differ. Proposed drivers include, e.g., total solar irradiance (TSI), solar UV radiation, galactic cosmic rays, and magnetospheric energetic particles. While some of these drivers are difficult to distinguish because of their closely similar variation over the solar cycle, other suggested drivers have clear differences in their solar cycle evolution. For example, geomagnetic activity and magnetospheric particle fluxes peak in the declining phase of the sunspot cycle, in difference to TSI and UV radiation which more closely follow sunspots. Using 13 solar cycles (1869-2009), we study winter surface temperatures and North Atlantic oscillation (NAO) during four different phases of the sunspot cycle: minimum, ascending, maximum, and declining phase. We find significant differences in the temperature patterns between the four cycle phases, which indicates a solar cycle modulation of winter surface temperatures. However, the clearest pattern of the temperature anomalies is not found during sunspot maximum or minimum, but during the declining phase, when the temperature pattern closely resembles the pattern found during positive NAO. Moreover, we find the same pattern during the low sunspot activity cycles of 100 years ago, suggesting that the pattern is largely independent of the overall level of solar activity.

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“…The recent solar minimum provided an unprecedented opportunity to study these phenomena under relatively steady conditions. The recurrent variation of GCR intensities during this period have been extensively measured using ground‐based neutron monitors [ Modzelewska and Alania , ] and space probes [ Leske et al , ].…”

Section: Introductionmentioning

confidence: 99%

Corotating interaction regions and the 27 day variation of galactic cosmic rays intensity at 1 AU during the cycle 23/24 solar minimum

Guo

Florinski

2014

JGR Space Physics

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The results show that the CIR forward/reverse shock pairs or compression/rarefaction regions play important roles in the transport of GCR particles and directly control the observed 27 day periodic intensity variations. We find that stream interfaces (SIs) in CIRs and the heliospheric current sheet (HCS) are both closely associated with the GCR depression onset, in agreement with the observations at 1 AU. The HCS is more important when its tilt angle becomes small during the declining phase of the solar minimum, while the passages of SIs control the onset of GCR depressions for larger HCS tilt angles. The mechanism of GCR intensity variation near 1 AU can be explained through an interplay between the effects of particle drift and diffusion. The simulated plasma background and GCR intensity are compared with the observations from spacecraft and a neutron monitor on the ground, to find good qualitative agreement. Evidently, CIRs had a substantial modulational effect on GCR during the recent solar minimum.

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Anomalous and Galactic Cosmic Rays at 1 AU During the Cycle 23/24 Solar Minimum

Cited by 5 publications

References 26 publications

Long‐term neutron monitor observations and the 2009 cosmic ray maximum

Long‐term neutron monitor observations and the 2009 cosmic ray maximum

Spatial distribution of Northern Hemisphere winter temperatures during different phases of the solar cycle

Corotating interaction regions and the 27 day variation of galactic cosmic rays intensity at 1 AU during the cycle 23/24 solar minimum

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