Solar Modulation of the Local Interstellar Spectrum With Voyager 1, Ams-02, Pamela, and Bess

Abstract

In recent years, the increasing precision of direct cosmic rays measurements opened the door to high-sensitivity indirect searches of dark matter and to more accurate predictions for radiation doses received by astronauts and electronics in space. The key ingredients in the study of these phenomena are the knowledge of the local interstellar spectrum (LIS) of galactic cosmic rays and the understanding of how the solar modulation affects the LIS inside the heliosphere. Voyager 1, AMS-02, PAMELA, and BESS measurements of proton and helium fluxes provide valuable information, allowing us to shed light on the shape of the LIS and the details of the solar modulation during solar cycles 22-24. A new parametrization of the LIS is presented, based on the latest data from Voyager 1 and AMS-02. Using the framework of the force-field approximation, the solar modulation parameter is extracted from the time-dependent fluxes measured by PAMELA and BESS. A modified version of the force-field approximation with a rigidity-dependent modulation parameter is introduced, yielding better fits than the forcefield approximation. The results are compared with the modulation parameter inferred by neutron monitors.

A predictive analytic model for the solar modulation of cosmic rays

“…Note added: After the completion of this work, we became aware of a related parallel study by Corti, Bindi, Consolandi and Whitman [66]. Using similar data sets they have independently reached the conclusion for a needed deviation from the force field approximation to account for the rigidity dependence of the solar modulation of CRs.…”

Solution of Heliospheric Propagation: Unveiling the Local Interstellar Spectra of Cosmic-ray Species

“…The Voyager 1 data combined with recent AMS-02, PAMELA, and earlier BESS-Polar measurements, triggered a series of papers (Cholis et al 2016;Corti et al 2016;Ghelfi et al 2016) aiming at the derivation of the LIS for protons and He, and producing a generalization of the modulation potential that depends on time, charge sign, and rigidity, using the force-field approximation (Gleeson & Axford 1968) as a baseline. The parameterizations proposed in these papers and the correlations with the neutron monitor rate, the tilt angle of the heliospheric current sheet, and the polarity and strength of the heliospheric magnetic field they found is certainly a large step forward over the use of the simple force-field approximation in a not-so-distant past.…”

The new local interstellar spectra and their influence on the production rates of the cosmogenic radionuclides 10Be and 14C

“…[] as red solid line, Herbst et al [this study] as red dashed line, Corti et al . [] in black, and Bisschoff and Potgieter [] in magenta with Voyager1 (downward triangles), PAMELA (gray filled circles), and AMS02 (upward triangles) measurements. The energy range most important for the production of the cosmogenic radionuclides 10 Be and 14 C is shown in gray.…”

“…[], Bisschoff and Potgieter [], and Corti et al . [] published new LIS models aiming to smoothly bridge the gap between the measured lower‐ and higher‐energy GCR spectra.…”

“…The parameters for the LIS by Corti et al . [] are given for both the “normal” force‐field approximation and the modified force‐field approximation. In order to study solar activity on longer time scales the use of the modified force‐field approximation is, however, too complex.…”