| Galactic cosmic rays are probably
accelerated in the blast waves of supernova remnants in the Milky Way. Solar cosmic rays are produced in high energy processes at or near the Sun after a violent eruption at the Sun. Composition of galactic cosmic rays:
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Energy spectrum of primary cosmic ray particles |
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The trajectories undergo increased geomagnetic
bending as the particle energy (rigidity) is decreased. The Earth's magnetic field can be used as a spectrometer to measure the cosmic ray spectrum down to low primary energies. |
The cosmic ray particles that penetrate the Earth's atmosphere collide with atomic nuclei in the atmosphere and cause them to split. This produces a cascade of secondary particles (pions, muons, electrons, protons, neutrons, photons, etc.). |
Altitude variation of the main cosmic ray components. |
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Average yearly dose from all sources for the
population in Switzerland is about 4 mSv. |
| Despite their decades of tradition, neutron
monitors remain the state-of-the-art instrumentation for measuring GeV
cosmic rays that cannot be measured in the same simple, inexpensive, and
statistically accurate way by space experiments. |
|
The incident nucleons of the secondary
cosmic radiation produce nuclear interactions in the lead target material
of the monitor. The evaporation neutrons produced thereby are thermalised
by the paraffin. The thermalised neutrons can interact with the BF3 gas
inside the counter tubes: The alpha-particles then causes ionisation that can be detected as an electronic impulse. |
| Research on cosmic rays with a worldwide
network of neutron monitors provides key information about the interactions
of galactic cosmic radiation with the plasmas and magnetic fields in the
heliosphere, and about the production of energetic cosmic rays at the Sun. |
|
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Smoothed sunspot numbers (orange) and
relative counting rate of the IGY neutron monitor Jungfraujoch (blue). |
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Relative hourly counting rate of the
IGY neutron monitor at Jungfraujoch. |
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The relativistic solar particle event
of April 15, 2001, as recorded by the neutron monitors at Jungfraujoch. |