Untitled

McDonald, F. B.

doi:10.1023/a:1005052908493

Cited by 110 publications

(28 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They give the same values of the modulation parameter as obtained from C nuclei using the same source spectrum $P À2:30 = and propagation dependence $P 0.50 for the interstellar He spectra. Since these measured He spectra are essentially identical to the He intensities measured in the McDonald et al (1992), McDonald (1998), andReinecke et al (2000) studies for these four time intervals, this allows one to intercalibrate the solar modulation levels for the entire set of He measurements, using IMP 8 near the Earth, V1, V2, and P10, extending from 1972 to the present time, as derived by McDonald and coworkers.…”

Section: The Solar Modulation Effectsmentioning

confidence: 74%

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹

Webber

McDonald

Lukasiak

2003

ApJ

View full text Add to dashboard Cite

We have made a new analysis of cosmic-ray data from the CRS experiment on the Voyager 2 (V2) spacecraft. This analysis, which includes both penetrating and stopping particles in the HET telescope, extends the energy range from an upper energy limit of 100-300 MeV nucleon À1 for stopping particles to over 1 GeV nucleon À1 . This analysis provides almost continuous spectra over this broad energy range, including the peak in the differential spectra of the various nuclei. This enables us to obtain the relationship between the shape of the low-energy interstellar differential spectrum and the amount of solar modulation. Measurements at V2 at the modulation minimum in 1987 and again in 1997-1998 give nearly the same intensities and therefore the same solar modulation parameter, ¼ 260 MV, which is much lower than the value of 400 MV at the Earth. most of the modulation was occurring beyond 54 AU and also that the interplanetary part of the solar modulation out to $54 AU in the two time periods of opposite solar magnetic polarity was greatly different. The measured secondary/ primary ratios B/C and N/O can be fitted equally well using a simple leaky-box Galactic propagation model with an escape length $ P À0:5 either with a break in the escape dependence at 1 GeV nucleon À1 or with no break in the escape-length dependence to the accuracy of the experimental data itself, AE3%, over the entire energy range from less than 100 MeV nucleon À1 to over 10 GeV nucleon À1 using a combination of both V2 data at the lower energies and HEAO data at the higher energies. This same escape-length dependence also predicts the measured higher Z secondary/primary ratio Z ¼ 21-23/Fe well at all energies.

show abstract

Section: The Solar Modulation Effectsmentioning

confidence: 74%

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹

Webber

McDonald

Lukasiak

2003

ApJ

View full text Add to dashboard Cite

show abstract

“…The latter two approaches have already contributed much in limiting the values of the various diffusion coefficients. This is certainly a result of the rather comprehensive numerical models that have been developed and applied over the past 20 years as discussed above, and also the excellent cosmic ray observations from a unique combination of spacecraft in the heliosphere, see Heber et al (1997), McKibben et al (1998), andMcDonald (1998). The first approach is more difficult, but progress is been made to come to an 'ab initio' formulation of cosmic ray modulation in the heliosphere, that is one in which the diffusion coefficients are determined on the basis of scattering theory and the underlaying fluctuation parameters are computed from plasma theory and known features of the heliospheric magnetic field.…”

Section: The Diffusion Tensor From Fundamental Principlesmentioning

confidence: 99%

Cosmic Rays at High Heliolatitudes

2007

View full text Add to dashboard Cite

The Ulysses spacecraft has been the first to orbit the Sun over its poles and to explore the heliosphere at these high heliolatitudes. It has now completed two fast latitude scans, one at solar minimum and one at solar maximum. Since its launch in October 1990, this mission has led to several surprising discoveries concerning energetic particles, cosmic rays, Jovian electrons, the solar wind, the heliospheric magnetic field and the global features of the heliosphere. This review addresses mainly the propagation and modulation of cosmic rays and other charged particles, from both an observational and theoretical point of view, with emphasis on what has been learned from exploring the inner heliosphere to high heliolatitudes. This is done for solar minimum and maximum conditions. The review is concluded with a summary of the main scientific discoveries and insights gained so far from the Ulysses mission.

show abstract

“…Returning to Figure 6, some (but not all) of the peaks in the SEP rate and variations in other parameters are closely related with the step decreases in the GCR intensity (eleventh panel) that are typical of the ascending phase of a solar cycle (e.g., McDonald, 1998). The GCR steps may be related to diffusive barriers propagating away from the Sun that are driven by changes in the solar magnetic field (e.g., Cane et al, 1999;Cane, Richardson, and Wibberenz, 2001;Wibberenz, Richardson, and Cane, 2002;and references therein).…”

Section: Relationship Of the Sep Rate With Solar And Interplanetary Pmentioning

confidence: 85%

North/South Hemispheric Periodicities in the ${>}\,25\mbox{ MeV}$ Solar Proton Event Rate During the Rising and Peak Phases of Solar Cycle 24

2016

View full text Add to dashboard Cite

We present evidence that > 25 MeV solar proton events show a clustering in time at intervals of ≈ six months that persisted during the rising and peak phases of Solar Cycle 24. This phenomenon is most clearly demonstrated by considering events originating in the northern or southern solar hemispheres separately. We examine how these variations in the solar energetic particle (SEP) event rate are related to other phenomena, such as hemispheric sunspot numbers and areas, rates of coronal mass ejections, and the mean solar magnetic field. Most obviously, the SEP event rate closely follows the sunspot number and area in the same hemisphere. The ≈ six-month variations are associated with features in many of the other parameters we examine, indicating that they are just one signature of the episodic development of Cycle 24. They may be related to the "≈150 day" periodicities reported in various solar and interplanetary phenomena during previous solar cycles. The clear presence of ≈six-month periodicities in Cycle 24 that evolve independently in each hemisphere conflicts with a scenario suggested by McIntosh et al. (2015, Nature Com. 6, 6491) for the variational time scales of solar magnetism.

show abstract

Untitled

Cited by 110 publications

References 39 publications

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹

Cosmic Rays at High Heliolatitudes

North/South Hemispheric Periodicities in the ${>}\,25\mbox{ MeV}$ Solar Proton Event Rate During the Rising and Peak Phases of Solar Cycle 24

Contact Info

Product

Resources

About

Untitled

Cited by 110 publications

References 39 publications

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon−1to More than 1.0 GeV Nucleon−1

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon−1to More than 1.0 GeV Nucleon−1

Cosmic Rays at High Heliolatitudes

North/South Hemispheric Periodicities in the ${>}\,25\mbox{ MeV}$ Solar Proton Event Rate During the Rising and Peak Phases of Solar Cycle 24

Contact Info

Product

Resources

About

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹

Voyager 2Measurements in the Outer Heliosphere of the Energy Spectra of Cosmic‐Ray Nuclei from Less than 100 MeV Nucleon⁻¹to More than 1.0 GeV Nucleon⁻¹