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Low energy cosmic ray spectrum and its components

The launch of PAMELA occurred during the minimum of solar cycle 23 and it has been continuously taking data up to now, going from the deep minimum in 2006 - 2009, toward solar maximum of the ongoing  cycle 24. The observation of low energy particles, of galactic and solar origin, using a magnetic spectrometer allows several aspects of solar and heliospheric cosmic ray physics to be addressed. 


Modulation of galactic cosmic rays in the heliosphere

The outflowing solar wind acts as a diffusive barrier for low energy galactic cosmic rays (R <~10 GV), affecting their propagation. The resulting so called solar modulation effect modifies  the charged particle energy spectra in shape and intensity, respect to the interstellar ones, depending on time (solar activity) and particle mass, energy and sign of charge. This effect has to be correctly taken into account when calculating the expected secondary antiparticle flux, as a background for a non-standard production mechanism. PAMELA is providing crucial data for a firm understanding of the propagation of cosmic rays in the heliosphere.


Solar Energetic Particle Spectra
PAMELA has measured the high energy component of solar proton event between 80 MeV and some GeV.
Moreover, PAMELA is able to separately analyze the high energy tail of the positron and electron spectra obtaining information both on particle production and charge dependent propagation in the heliosphere.




Edited by Laura Marcelli