Revised neutron monitor scaling factor and modulation potential determination for 1964-2021
Pauli Väisänen, UniOulu, Ilya Usoskin, University of Oulu/SGO, Riikka Kähkönen, University of Oulu, Sergey Koldobskiy, University of Oulu/SGO, Kalevi Mursula, University of Oulu
The flux of galactic cosmic rays (GCR) is considered to be constant in the local interstellar medium, but upon arriving in the heliosphere, they experience modulation due to the magnetic activity of the Sun. This variation can be observed, e.g., when measuring GCR fluxes with neutron monitors (NMs). In order to parameterize the level of modulation, the heliospheric modulation potential, phi, is often used. This parameter is usually evaluated from the measurements by multiple NM stations by employing models of the cosmic ray yield functions, after correcting for the geomagnetic rigidity cutoff and atmospheric effects. In this work, we employ the recently updated yield function as presented in Mishev2020 and a new method of minimized root-mean-square errors in order to compute the modulation potential and the station-specific scaling factors.