Did the 2000 July 14 solar flare accelerate protons to ⩾40 GeV?

It has been reported that a 4.2 σ directional muon excess coincident with the 2000 July 14 solar flare was registered by the L3 precision muon spectrometer [The L3 collaboration, P. Achard et al., A&A, 456 (2006) 351]. Using similar analysis method and optimized criteria for event selection we have obtained a 5.7 σ muon excess in the same sky region and a time duration which well coincides with the peak increase of solar protons observed at lower energies and the hard X-ray and γ -ray. Furthermore, the momenta of those enhanced muons is investigated. From the counts of μ + and μ - a low muon charge ratio of μ + μ - is obtained as about 1.1 during this event. A Monte Carlo simulation was carried out for this primary proton beam to produce those secondary muons in this sky region, including extensive air shower simulation starting at the top of the atmosphere and L3+C muon chamber simulation underground. The simulation result indicates that the enhanced muons are produced by primary protons over 40 GeV with a most probable energy of ∼82 GeV. Based on this simulation, a flux upper limit of such a solar proton beam has been estimated as 2.5 × 10 - 3 ( cm - 2 s - 1 sr - 1 ) . These high energy protons were accelerated in the impulsive phase of the flare, at about 2 min late of start of the hard X-ray and γ -ray.