PARTICLE PROPAGATION CHANNEL DETECTED AT 4.7 AU INSIDE A COROTATING INTERACTION REGION

This study presents an interplanetary particle (electrons and ions) ev ent which was detected at 4.7 AU by the instruments on the Ulysses spa cecraft inside a corotating interaction region between a fast and slow solar wind stream. A particle propagation channel is identified where the particles can propagate from the Sun nearly scatter free within a region bounded by tangential discontinuities. This channel is found t o be rooted in the vicinity of a solar active region where the flare a ssociated with the interplanetary event was produced. The ions (energy over 600 keV) detected inside this channel are shown to be of solar o rigin: dispersion occurs in the proton arrival time versus proton ener gy, there is a strong anisotropy in the proton pitch angle distributio n, and a hard energy-spectrum for the protons. The electrons were alre ady present when the spacecraft crossed the structure. The chemical co mposition is also indicative of a solar origin, with a decrease in the He-4/H (He-4 in the energy range 389-1278 keV and H in the range 480- 1204 keV) abundance ratio by a factor of 2 inside the channel. Mapped back to the solar surface, the size of the propagation channel is esti mated to be of the order of 30,000 km. The channel is found to be magn etically quiet, without a preferred direction for the minimum of varia nce.