Solar cycle modulation of galactic protons and electrons

Perko, J. S.

doi:10.1029/ja092ia08p08502

Cited by 41 publications

(37 citation statements)

References 41 publications

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“…However, this is not the antiproton flux measured by antiproton experiments, which is affected at low energies by solar modulation. Under the force field approximation [41], the antiproton flux at the top of the Earth's atmosphere is related to the interstellar antiproton flux [42] by the simple relation…”

Section: Constraints From the Antiproton Fluxmentioning

confidence: 99%

Probing gravitino dark matter with PAMELA and Fermi

Buchmüller

Ibarra

Shindou

et al. 2009

J. Cosmol. Astropart. Phys.

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Abstract. We analyse the cosmic-ray signatures of decaying gravitino dark matter in a model-independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying gravitinos to the gamma-ray spectrum, in particular a line at an energy below 300 GeV. Future measurements of the gamma-ray flux will provide important constraints on possible signatures of decaying gravitino dark matter at the LHC.

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Section: Constraints From the Antiproton Fluxmentioning

confidence: 99%

Probing gravitino dark matter with PAMELA and Fermi

Buchmüller

Ibarra

Shindou

et al. 2009

J. Cosmol. Astropart. Phys.

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“…1 GV [e.g., Perko, 1987]. B 0 = 5 nT is the mean magnetic field strength at the Earth's orbit, and B results from equation (3) with jAj = 3.4 nT Á AU 2 .…”

Section: Basic 2-d Stochastic Simulation Modelmentioning

confidence: 99%

Stochastic simulation of cosmic ray modulation including a wavy heliospheric current sheet

et al. 2007

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[1] We present a quasi-steady two-dimensional (axisymmetric) model of the heliospheric transport of galactic cosmic rays. The model is based on stochastic simulation techniques and includes all the modulation mechanisms that cosmic rays experience in the heliosphere: convection, adiabatic cooling, diffusion, and drifts. A special emphasis is given to the cosmic ray transport in the vicinity of the heliospheric current sheet (HCS), and a new method to calculate the wavy current sheet drift is presented. We study cosmic ray modulation in different solar modulation conditions and levels of waviness of the current sheet. We discuss changes in the cosmic ray spectrum and the dominant streaming patterns of cosmic rays in the heliosphere for different solar polarities and HCS tilt angles.Citation: Alanko-Huotari, K., I. G. Usoskin, K. Mursula, and G. A. Kovaltsov (2007), Stochastic simulation of cosmic ray modulation including a wavy heliospheric current sheet,

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“…Varying the frequency with which these drops were ejected from the origin caused the model intensity to cycle from maximum to minimum and back. Perko [1987] compared details of this model's results to data. Left unspecified was the physical nature of these regions of strong diffusion.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, it shows the traveling solar minimum and changes in radial gradient with time [Van Allen, 1988]. gher, 1975;Perko and Fisk, 1983;Perko, 1987;Chih and Lee, 1986], so this result could not have been seen in the force-field models.…”

Section: Introductionmentioning

confidence: 99%

Time‐dependent modulation of galactic cosmic rays by merged interaction regions

Perko¹

1993

J. Geophys. Res.

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Models that solve the one‐dimensional, solar modulation equation have reproduced the 11‐year galactic cosmic ray cycle using functional representations of global merged interaction regions (MIRs). This study extends those results to the solution of the modulation equation with explicit time dependence. The magnetometers on Voyagers 1 and 2 provide local magnetic field intensities at regular intervals, from which one calculates the ratio of the field intensity to the average local field. These ratios in turn are inverted to form diffusion coefficients. Strung together in radius and time, these coefficients then fall and rise with the strength of the interplanetary magnetic field, becoming representations of MIRs. These diffusion coefficients, calculated locally, propagate unchanged from ∼10 AU to the outer boundary (120 AU). Inside 10 AU, all parameters, including the diffusion coefficient are assumed constant in time and space. The model reproduces the time‐intensity profiles of Voyager 2 and Pioneer 10. Radial gradient data from 1982‐1990 between Pioneer 10 and Voyager 2 are about the same magnitude as those calculated in the model. It also shows agreement in rough magnitude with the radial gradient between Pioneer 10 and 1 AU. When coupled with enhanced, time‐dependent solar wind speed at the probe's high latitude, as measured by independent observers, the model also follows Voyager 1's time‐intensity profile reasonably well, providing a natural source for the observed negative latitudinal gradients. The model exhibits the 11‐year cyclical cosmic ray intensity behavior at all radii, including 1 AU, not just at the location of the spacecraft where the magnetic fields are measured. In addition, the model's point of cosmic ray maximum correctly travels at the solar wind speed, illustrating the well‐known propagation of modulation. Finally, at least in the inner heliosphere this model accounts for the delay experienced by lower‐rigidity protons in reaching their time‐intensity peak. The actual delays in this model, however, are somewhat smaller than the data. In the outer heliosphere the model sees no delays, and the data are ambiguous as to their existence. It appears that strong magnetic field compression regions (merged interaction regions) that are 3‐4 times the average field strength can, at least in a helioequatorial band, disrupt effects, such as drifts, that could dominate in quieter magnetic fields. The question remains: Is the heliosphere ever quiet enough to allow such effects to be unambiguously measured, at least in the midlatitudes?

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Solar cycle modulation of galactic protons and electrons

Cited by 41 publications

References 41 publications

Probing gravitino dark matter with PAMELA and Fermi

Probing gravitino dark matter with PAMELA and Fermi

Stochastic simulation of cosmic ray modulation including a wavy heliospheric current sheet

Time‐dependent modulation of galactic cosmic rays by merged interaction regions

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