Multi-Spacecraft Observations of Solar Flare Particles in the Inner Heliosphere

For a number of impulsive solar particle events we examine variations of maximum intensities and times to maximum intensity as a function of longitude, using observations from the two Helios spacecraft and near the Earth. We find that electrons in the MeV range can be detected more than 80° from the flare longitude, corresponding to a considerably wider "well connected" region than that (~20° half-width) reported for ³He-rich impulsive solar events. This wide range and the decrease of peak intensities with increasing connection angle revive the concept of some diffusive propagation process in the low corona. Delays to intensity maxima are not systematically correlated with connection angles. We argue that interplanetary scattering parallel to the average interplanetary magnetic field, which varies with position in space, plays an important role in flare particle events. In a specific case variations of the time profiles with radial distance and with particle rigidity are used to quantitatively confirm spatial diffusion. For a few cases near the edges of the well-connected region, the very long times to maximum intensity might result from interplanetary lateral transport.