Modulation of low-energy galactic cosmic rays over solar maximum (Cycle 20)

Hollebeke, M. A. I. Van; Wang, J. R.; McDonald, F. B.

doi:10.1029/ja077i034p06881

Cited by 20 publications

(14 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…He suggested that variations in the intensity of low energy electrons,which also contributed to the rates measured by the satellite detectors,might account for some of the deviation. Recent observations of the electron spectrum (Schmidt 1972;Burger and Swanenburg 1973) and of low energy protons and helium nuclei (Van Hollebeke, Wang and McDonald, 1972) have made it evident that the regression relationship for the current declining phase of solar activity, which is indicated schematically in Figure 1 by the curve DEA, is different from that traced out along ABC during the increasing phase. This deviation from a single-valued relationship is conventionally described as a "hysteresis effect" but the significance of this behavior is simply that the phenomenon of cosmic-ray modulation depends upon more than one variable.…”

Section: Introductionmentioning

confidence: 99%

Modulation of cosmic ray protons and helium nuclei near solar maximum

Rygg

O’Gallagher²,

Earl³

1974

J. Geophys. Res

View full text Add to dashboard Cite

Balloon observations of proton and helium spectra in 1970, 1971 and 1972, which (1970)(1971)(1972).Computer generated spectra based on simple two parameter modulation models describe the basic features of the observations if one of the variable parameters is used to characterize the rigidity dependence of the diffusion coefficient. On the other hand, models which do not allow such a variation are not consistent with the observations.

show abstract

Section: Introductionmentioning

confidence: 99%

Modulation of cosmic ray protons and helium nuclei near solar maximum

Rygg

O’Gallagher²,

Earl³

1974

J. Geophys. Res

View full text Add to dashboard Cite

show abstract

“…In Figure 8b we show the data of Van Hollebeke,et al (1972) and the calculated regression produced by varying K with R constant (dashed curve).…”

Section: Atmentioning

confidence: 99%

“…However, despite the phenomenalogical description of hysteresis in terms of time-lags by some, virtually all of the attempts to explain the phenomena have been based solely on the first interpretation. For example, O'Gallagher (1969), Schmidt (1972), Van Hollebeke, et al (1972), Le.zniak and Webber (1971), Burger and Swanenburg (1973), Bedijn, Burger, and Swaneaiburg (1973), Van Hollebeke, et al (1973), and Rygg, et al (1974), all discuss in one way or another the description of the observations in terms of a change in the rigidity dependence of some "modulating function" in a timeindependent model. On the other hand, the model developed in Paper I and discussed in the Introduction, provides for the first time a framework for the second interpretation by incorporating time-dependent diffusion and convection.…”

Section: Time-lags and The "Hysteresis Effect"mentioning

confidence: 99%

“…The electron and integral proton measurements clearly show a gradually shortening of the delay with increasing rigidity. The low rigidity proton and helium points are from the data of Van Hollebeke, et al (1972). Data for protons observed near solar maximum and solar minimum are shown together with computed spectra based on the modulation parameters indicated.…”

Section: Observed Regressions For Cosmic Ray Protons Versus Neutronmentioning

confidence: 99%

“…In the first interpretation above, the relevant observational parameter to characterize the hysteresis effect is the "hysteresis ratio", the ratio of the relative levels at low energy which are observed on the two branches of the regression curve at the same value of the reference intensity (Van Hollebeke, Wang and McDonald, 1972;Rygg, O'Gallagher and Earl, 1974). For example, in Figure 1 the regressions for the intensity at two different proton energies, -500 MeV and 1~00 MeV with respect to the Deep River neutron intensity show that this hysteresis ratio is energy dependent, varying from %1.9 at 100 MeV to 'nl.6 for n500 MeV protons.…”

Section: Time-lags and The "Hysteresis Effect"mentioning

confidence: 99%

See 2 more Smart Citations

A dynamic model for the time evolution of the modulated cosmic ray spectrum

O’Gallagher

Maslyar

1976

J. Geophys. Res.

View full text Add to dashboard Cite

Solar‐Driven Variation in the Atmosphere of Uranus

Aplin

Harrison

2017

Geophysical Research Letters

View full text Add to dashboard Cite

Long-term measurements (1972-2015) of the reflectivity of Uranus at 472 and 551 nm display variability that is incompletely explained by seasonal effects. Spectral analysis shows that this nonseasonal variability tracks the 11 year solar cycle. Two mechanisms could cause solar modulation: (a) nucleation onto ions or electrons created by galactic cosmic rays (GCR) or (b) UV-induced aerosol color changes. Ion-aerosol theory is used to identify expected relationships between reflectivity fluctuations and GCR flux, tested with multiple regression and compared to the linear response predicted between reflectivity and solar UV flux. The statistics show that 24% of the variance in reflectivity fluctuations at 472 nm is explained by GCR ion-induced nucleation, compared to 22% for a UV-only mechanism. Similar GCR-related variability exists in Neptune's atmosphere; hence, the effects found at Uranus provide the first example of common variability in two planetary atmospheres driven through energetic particle modulation by their host star. Plain Language Summary Measurements of the planets Uranus and Neptune have been made using a telescope, for every year from 1972 to 2015. How bright a planet appears to us is an indicator of the cloud cover in its atmosphere. An 11 year brightness variation was spotted in the Neptune observations many years ago, indicating that a process linked to the the Sun's 11 year activity cycle affects the planet's clouds. This inspired us to look at the data for Uranus more closely, and we found the same signal as for Neptune. There are two possible explanations. One possibility is chemical, when light from the Sun affects the color of particles in the planet's atmosphere. Our other possibility is that energetic particles from outside the solar system, cosmic rays, influence particle, or cloud formation. (Cosmic rays are "bent" away from the solar system by the Sun acting as a magnet, so are also affected by its 11 year activity cycle). In our results, we actually find that both of them have a small effect on the clouds on Uranus. This is the first evidence of two planetary atmospheres-Neptune originally and now Uranus-showing similar variations, in both cases originating from their host star.

show abstract

Modulation of low-energy galactic cosmic rays over solar maximum (Cycle 20)

Cited by 20 publications

References 14 publications

Modulation of cosmic ray protons and helium nuclei near solar maximum

Modulation of cosmic ray protons and helium nuclei near solar maximum

A dynamic model for the time evolution of the modulated cosmic ray spectrum

Solar‐Driven Variation in the Atmosphere of Uranus

Contact Info

Product

Resources

About