Long-Term Cosmic Ray Intensities: Physical Reconstruction

Details Long-Term Cosmic Ray Intensities: Physical Reconstruction Long-Term Cosmic Ray Intensities: Physical Reconstruction

Jul 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003icrc....7.4041u&link_type=abstract

Proceedings of the 28th International Cosmic Ray Conference. July 31-August 7, 2003. Trukuba, Japan. Under the auspices of the I

Physics

Scientific paper

Solanki et al. (2000) have recently calculated the open solar magnetic flux for the last 400 years from sunspot data. Using this reconstructed magnetic flux as an input to a simple spherically symmetric quasi-steady state model of the heliosphere, we calculate the expected differential spectra and integral intensity of galactic cosmic rays at the Earth's orbit since 1610. The calculated cosmic ray integral intensity is in good agreement with the neutron monitor measurements during the last 50 years. Moreover, using the specific yield function of cosmogenic 10 Be radionuclide production in the atmosphere, we also calculate the expected 10 Be production rate which exhibits an excellent agreement with the actual 10 Be abundance in polar ice over the last 400 years. Here we present a physical model for the long-term reconstruction of cosmic ray intensity at 1 AU. The reconstruction is based on a combination of the solar magnetic flux model and a heliospheric model. This model allows us to calculate the expected intensity of galactic cosmic rays (GCR) at the Earth's orbit for the last 400 years. Details can be found in [25]. Using the numerical recip e of Solanki et al. [21] and the group sunspot number series (Fig. 1.a) [11] we have calculated the open solar magnetic flux Fo since 1610 as shown in Fig. 1.b. In order to calculate galactic cosmic ray (GCR) spectra we use a spherically symmetric quasi-steady sto chastic simulation model described in detail elsewhere [24], which reliably describes the long-term GCR modulation during the last 50 years. In this model, the most important parameter of the heliospheric modulation of GCR is the modulation strength [10]: Φ = (D - rE )V /(3κo), where D = 100 AU is the heliospheric boundary and rE = 1 AU, V = 400 km/s is the constant solar wind velocity and κo is the rigidity indep endent part of the diffusion coefficient. Thus, all changes in the modulation strength Φ in our model are related to the changing diffusion

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