Galactic Cosmic Rays - high energetic, charged particles accelerated at shockwaves in supernova remnants - are modulated by the sun in the inner heliosphere. A high solar activity results in a lower cosmic ray flux, a lower activity to a higher flux. This is shown in the right figure using measurements from the Kiel neutronmonitor (indirect measurement of the cosmic ray flux, black line) and the sunspot number (an index for the solar activity, red line).
Due to the Lorentz force, charged particels need a minimum momentum per charge not to be reflected by the Earth`s magnetic field. The geomagnetic cutoff rigidity is a quantity to express the particles capability to reach a defined interplanetary space. Due to the low geomagnetic cutoff rigidity in Kiruna, there will be higher flux of GCR.
The primary and secondary particles of the GCR interact with the moleculs and atoms in the atmosphere. The radiation environment in the atmosphere is therefore determined by the generation of secondary charged and neutral particles i. e. electrons, muons and protons as well as neutrons and gamma rays. These particles undergo the same interactions as the primary cosmic rays leading to a particle flux maximum at a height of about 20 km (Pfotzer-Maximum).In order to measure the radiation dose it is necessary to measure the altitude dependent flux of the neutral particles i.e. neutrons, gamma rays and charged particles simultaneously.