A new modeling technique to derive spectra of relativistic solar particle fluxes from neutron monitor parameter data

  1. Polar geophysical institute of Kola science center of RAS

Some solar flare events are accompanied by flux of solar energetic particles (SCR) in wide energetic range up
to 20 GeV. The particles spreads to the Earth and cosmic ray flux increase too. Ground based detectors (muon
telescopes and neutron monitors) register significant increases. They are called Ground Level Enhancement
(GLE). The amplitude of these increases amount to 5000 percent for the strongest flares in relation to the
cosmic ray flow before a flare. The flux of SCR usually has considerable anisotropy whereas galactic cosmic ray
flow is almost isotropic. A new modeling technique was created to derive energetic spectra of solar relativistic
proton fluxes on the data of ground based measurements of neutron monitor network. Parameters of primary
flux are calculated by inverse problem. The technique was proved on more than 30 events of GLEs occurred in
the past. In all the cases the average discrepancy was not more than 5 percent. The derived spectra have good
agreement with direct measurements of primary flux in the stratosphere (balloons) and in space (spacecrafts) in
adjacent energetic range 50-700 MeV. The advantage of these spectra is that they determine the flux in the range
from 400 MeV to 10 GeV with good accuracy whereas spacecraft measurements are limited to the range of up to
700 MeV only. The spectra of SCR primary flux can be used to calculate the increase of cosmic radiation flux
at any point on the Earth both at the ground level and at different altitudes to estimate atmosphere ionization,
absorbed doze and other applications.