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

Abstract

For a number of impulsive solar particle events we examine variations ofmaximum intensities and times to maximum intensity as a function oflongitude, using observations from the two Helios spacecraft and nearthe Earth. We find that electrons in the MeV range can be detected morethan 80° from the flare longitude, corresponding to a considerablywider ``well connected'' region than that (~20° half-width) reportedfor 3He-rich impulsive solar events. This wide range and thedecrease of peak intensities with increasing connection angle revive theconcept of some diffusive propagation process in the low corona. Delaysto intensity maxima are not systematically correlated with connectionangles. We argue that interplanetary scattering parallel to the averageinterplanetary magnetic field, which varies with position in space,plays an important role in flare particle events. In a specific casevariations of the time profiles with radial distance and with particlerigidity are used to quantitatively confirm spatial diffusion. For a fewcases near the edges of the well-connected region, the very long timesto maximum intensity might result from interplanetary lateral transport.