Author/Authors :
Muraki، نويسنده , , Y. and Matsubara، نويسنده , , Y. and Masuda، نويسنده , , S. and Sakakibara، نويسنده , , S. and Sako، نويسنده , , T. and Watanabe، نويسنده , , K. and Bütikofer، نويسنده , , R. and Flückiger، نويسنده , , E.O. and Chilingarian، نويسنده , , A. and Hovsepyan، نويسنده , , G. and Kakimoto، نويسنده , , F. and Terasawa، نويسنده , , T. and Tsunesada، نويسنده , , Y. and Tokuno، نويسنده , , H. and Velarde، نويسنده , , A. and Evenson، نويسنده , , P. and Poirier، نويسنده , , J. and Sakai، نويسنده , , T.، نويسنده ,
Abstract :
In association with the large solar flare of April 15, 2001, the Chacaltaya neutron monitor observed a 3.6σ enhancement of the counting rate between 13:51 and 14:15 UT. Since the enhancement was observed beginning 11 min before the GLE, solar neutrons must be involved in this enhancement. The integral energy spectrum of solar neutrons can be expressed by a simple power law in energy with the index γ = - 3.0 ± 1.0 . On the other hand, an integral energy spectrum of solar protons has been obtained in the energy range between 650 MeV and 12 GeV. The spectrum can also be expressed by a power law with the power index γ = - 2.75 ± 0.15 . The flux of solar protons observed at Chacaltaya (at ⩾12 GeV) was already one order less than the flux of the galactic cosmic rays. It may be the first simultaneous observation of the energy spectra of both high-energy protons and neutrons. Comparing the Yohkoh soft X-ray telescope images with the observed particle time profiles, an interesting picture of the particle acceleration mechanism has been deduced.
Keywords :
Solar neutron and proton , Neutron telescope , Solar cosmic rays , Neutron monitor , Easter event
