Heliospheric modulation of cosmic rays: Monthly reconstruction for 1951–2004

Abstract

[1] The differential energy spectrum of galactic cosmic rays in the vicinity of the Earth can be parameterized by the so-called force field model which has only one parameter, the modulation potential f, for a given local interstellar spectrum. Here we present the series of monthly values of the modulation potential f since February 1951, reconstructed using the data from the worldwide neutron monitor network and calibrated with precise balloon and space-borne direct measurements of cosmic ray energy spectrum. This work provides a long series of a parameter allowing for a quantitative estimate of the average monthly differential energy spectrum of cosmic rays near the Earth. A comparison with other occasional direct measurements of cosmic ray spectra confirms the reliability of the present reconstruction. The results can be applied in studies of long-term solarterrestrial relations and the global evolution of the heliosphere.

First observation of time variation in the solar-disk gamma-ray flux with Fermi

“…The cosmic-ray flux modulation at Earth is frequently described by the force field model with a single empirical parameter, the force field potential Φ [36][37][38]. The value of Φ can be extracted from precision ground-based neutron observations [39][40][41]. We obtain the corresponding values for our observation period by averaging over the monthly values.…”

Assessment of different sunspot number series using the cosmogenic isotope 44 Ti in meteorites

“…The exact value of the modulation potential is not important since it can be defined only relatively, depending on the primary assumption on the local interstellar spectrum (LIS) so that the same GCR spectrum near Earth can be parametrized by different values of φ for different LIS assumptions (Usoskin et al 2005;Herbst et al 2010). However, once the LIS is fixed, the value of φ unambiguously determines the GCR energy spectrum.…”

“…The spectrum of Galactic cosmic rays (GCR) near Earth can be described by the force-field parametrization using a single parameter, called the modulation potential (Gleeson & Axford 1968;Castagnoli & Lal 1980;Usoskin et al 2005), which depends on the level of solar magnetic activity. One of the main heliospheric parameters, affecting the modulation potential, φ, is the OSF.…”

Identification and measurement of neutron-absorbing elements on Mercury’s surface

“…The largest source of uncertainty in the modeled count rate is likely the chosen modulation parameter, which can be uncertain by up to ±100 MV (Usoskin et al, 2005;Wiedenbeck et al, 2009) depending on how it is determined. This uncertainty can easily account for differences of up to 25%.…”