Cosmic ray modulation and global heliospheric parameters: Non-linear relations
Abstract
Despite the great success of sophisticated cosmic ray modulation models, the heliospheric modulation strength is still a useful parameter for formal description of the long-term modulation of cosmic rays, which alone defines shape of the cosmic ray energy spectrum in the neutron monitor energy range. Annual averaged values of the modulation strength have recently been computed for the neutron monitor era since 1951-2002 (Usoskin et al., Sol. Phys., 207, 389, 2002). Here we study a physics-based semi-empirical, non-linear relation between the modulation strength and the following global heliospheric parameters: the heliospheric current sheet tilt angle, the open solar magnetic flux and the global magnetic field polarity. The suggested relation, which includes four fitting parameters, reproduces the measured annual NM count rates within the accuracy of 0.8%. Using the measured interplanetary magnetic field parameters and the modulation strength values computed since 1951, this relation allows us to reconstruct the annual tilt angle for about 20 years before the time of direct measurements of the tilt angle.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.1685U