Cosmic rays in solar system By: Tiva Sharifi
Cosmic ray The earth atmosphere is bombarded with the energetic particles originating from the outer space called cosmic rays 1) Galactic cosmic rays (GCR) 2) Solar cosmic rays (SCR)
cosmic rays sources solar event lasts at least for a couple of days…….. time averaged flux of SCR is higher than the GCR flux. Large flares produce most of the SCR particles emitted during 11-year solar cycle
Nature of cosmic rays • Proton (89%) • Alpha particles (10%) • Heavy (z=3 to 90) nuclei (1%) GCR particles; high energies and low flux SCR particles; low energies (<300MeV) and high flux
Cosmic ray interactions with magnetic field Deflection! GCR encounter with galactic, interstellar, solar and the earth magnetic field Impossible to realize the source of GCR via their incoming direction
Sun and Earth magnetic field • Solar magnetic field variations Long term (solar cycle) Short term (magnetic clouds originating from solar flares) • The earth magnetic field variations Solar wind
Cosmic ray interactions with matter • Based on the energy, charge and mass of the energetic particle the nature of interaction process and its products can be estimated • It is on the surface in which the cosmic ray records can be readily determined
Nuclide production Atmospheric cascade: A “primary” cosmic ray particle strike an atom in Earth's atmosphere, this collision results in the production of one or more "secondary" cosmic ray particle are
The EarthNuclide production • The nuclear by products of the cascade can reach Earth's surface if the primary cosmic ray has energy greater than 500 million electron volts (neutrons and pions) • The low energy solar protons and alpha particles stop very close to the surface of the atmosphere by ionization energy loss
The EarthFlux of the cosmic ray • The earth magnetic field • The solar wind either decelerate or exclude the particles with energies below 1GeV
Earth weather In the lower atmosphere, • Muons ionize the gas molecules. • A positive ion is created • The released electron is captured (creation negative ion or recombination) • The ionization and recombination effect is balanced • the negative ions are more mobile which results in an electric field (100 V/m).
Earth weather Thunderstorm • Separation of positive and negative ions forms an electric field. Discharge (lightening) happens if the electric field is high enough. • Cosmic rays have a direct influence on earth weather
C , the most famous cosmogenic radionuclide • A correlation between solar activity, climate variables (especially temperature) and C activity. • low number of sunspots, higher activity of C and colder climate. • The weak solar field allows more GCR protons to reach the earth results in the higher content of C .