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Additional information about cosmic rays

Neutron monitors  |   Muon telescopes  |   Ground Level Enhancements
Cosmic rays are elementary particles and nuclei of atoms moving with high energies in outer space at a speed of more than 100 000 km / s.

There are distinguish between primary cosmic rays - cosmic rays before entering the atmosphere - and secondary cosmic ray, formed as a result of processes of interaction of primary cosmic rays with the Earth's atmosphere. Falling into the earth's atmosphere, particles of cosmic rays collide with the nuclei of nitrogen and oxygen atoms and destroy them. As a result, flows of new elementary particles arise.

In the initial act of interaction, the main role is played by elementary particles - pi-mesons (pions) are born, among which are neutral and charged. Interacting with air nuclei, charged pions generate new showers until their energy drops to ~ 109 eV. In the first act of interaction, more than 50 new particles are usually born. As a result of the decay of pi-mesons, mu-mesons (muons) and neutrinos are formed. The composition of the secondary radiation contains neutrons. This part of the cascade is called hadron shower.

Neutral mesons — about one third of them — decay into gamma rays, which generate electrons and positrons in the Coulomb field of nuclei. The bremsstrahlung of an electron-positron pair leads to the appearance of low-energy gamma rays - photons. This shower is called electromagnetic. At sea level, no more than 1% of their initial flow of primary particles remains.

Secondary charged particles - electrons and positrons born in a cascade process - can create Cherenkov light and fluorescence of the atmosphere.

To the Cosmic Ray page

Neutron monitors

Since January 2008, the High Resolution Neutron Monitor Database "Real-time database for high resolution Neutron Monitor - NMDB » has been operating measurements , as part of the e-Infrastructures project, supported by the European Commission as part of the Seventh Framework Program.
This initiative aims to develop a real-time database for measuring high-resolution neutron monitors, including data from the largest number of neutron monitors. The main goal is the development of a digital repository with cosmic ray data, which will be available via the Internet for a large number of organizations, using direct access to databases through standardized web interfaces.

Barometric Correction

The primary processing of neutron monitor data includes various actions and procedures that each cosmic ray station performs to provide a worldwide network of neutron monitors with good data quality.
One of the most important corrections to primary data is pressure correction due to the barometric effect . This correction requires the determination of a barometric coefficient, which is calculated experimentally.
There is the online tool , that can efficiently calculate the barometric coefficient of a cosmic ray station using NMDB database data.

To the Neutron Monitor Data page

Muon telescopes

Muon observations complement observations of neutron monitors, but there are some important differences in the two methods. Unlike neutron monitors, muon telescope systems use coincidence methods to obtain information about the direction of the incoming particle. Observations on a neutron monitor require simple corrections for pressure changes, to compensate for the variable mass of the atmospheric absorber at the site. On the contrary, muon observations require additional corrections for positive and negative temperature effects. Using radiosonde balloon measurements of the atmospheric profile, multiple regression can be performed to determine the appropriate correction coefficients used for a particular muon telescope.

To the Muon Telescope Data page

Ground Level Enhancements

Solar cosmic rays (SCR) are called accelerated during flares on the Sun and then charged particles flying into the interplanetary: protons and nuclei of heavier elements, whose energy is in the range from several tens of keV to tens and hundreds of MeV, and sometimes reaches 10-20 GeV, as well as electrons whose energy exceeds 20-40 keV and in rare cases can reach hundreds of MeV.

The Earth’s magnetic field and atmospheric matter impede the penetration of charged particles deep into the atmosphere, therefore, the surface increases in SCR fluxes can be recorded only in the event in which the proton energy exceeds 500 MeV. The intensity increases recorded on Earth are called Ground Level Enhancements (GLE). The relationship between SCR fluxes and solar flares is quite obvious for GLE in SCR, which are usually observed simultaneously or immediately after very large flashes. In cases where there is no clear evidence of a powerful flare in the visible part of the Sun, there is convincing indirect evidence that such a flare occurred behind the solar limb.

The efficiency of detecting an increase in SCR by ground-based neutron monitors depends on the minimum rigidity of the particles penetrating the magnetic field barrier to the station where the neutron monitor is located, so-called cut-off rigidity. Measurements in the stratosphere and on spacecraft, an increase in the sensitivity of particle registration techniques, led to a significant increase in the number of SCR events. Now satellite equipment registers almost all increases in SCR fluxes occurring in near-Earth space.

To the Ground Level Enhancement Data page

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