Low-energy particle events associated with sector boundaries

Onsets of some 40 to 45 low-energy proton events during the years 1957–1969 coincided in time with transits of well-defined sector boundaries across the Earth. These events can be interpreted as long-lived proton streams filling up some of the magnetic sectors, indicating an acceleration of protons which is not associated with typical proton-producing flares. The sharp onsets of these particle streams, as well as a deficiency of flare-associated particle events shortly before the boundary transit, indicate that in some cases magnetic sector boundaries can inhibit transverse propagation of low-energy particles in the solar corona or in interplanetary space.