Spectrum of solar flare protons

Most of big solar flares are accompanied by relativistic protons. The prompt component of relativistic protons moves along the interplanetary magnetic field lines and arrives at the Earth's orbit when the flare favorably located in the western solar hemisphere. The neutron monitor measurements reveal an exponential law energy spectrum. Calculations of relativistic proton acceleration in the flare current sheet with magnetic and electric fields found from 3D MHD simulations also demonstrate an exponential law spectrum. A comparison of the measured and calculated spectra permits to estimate the rate of reconnection in the Bastille flare (14 July 2000) as ∼107cm/s. The delay component of relativistic protons exhibits a power law energy spectrum.