RECURRENCE OF ENERGETIC PARTICLE-FLUX ANISOTROPY AS OBSERVED BY ERNE ON 9 JULY 1996

A solar energetic particle event was observed on 9 July 1996, by the E RNE sensors LED and HED on board the SOHO spacecraft. The arrival of t he first protons in the energy range > 20 MeV took place at 09:55 UT, 43 min after the maximum in the X-ray and H alpha radiation of a flare located at S10 W30. The rise phase of the particle intensities at all energies was exceptionally rapid. At 12:50 UT, the intensities droppe d in all energy channels. Simultaneously, the magnetic field instrumen t MFI on board WIND, not far from SOHO, detected a sharp and large cha nge in the magnetic field direction. The analysis of the directional m easurements of ERNE in the energy range 14-17 MeV shows the presence o f a strong flux anisotropy during the whole period 10:10-12:50 UT. Fro m 12:50 UT until about 16:00 UT, the directional analysis of the proto n Ru?;es gives only a weak anisotropy at the limit of the sensor resol ution. Later on, the flux anisotropy was found to recur, indicating a continuous injection of particles into the flux tubes connected to the SOHO spacecraft. These experimental results lead to strict limits on particle injection and transport models. The first period of the aniso tropy and its recurrent phase cover 24 hours. This suggests an extende d injection of particles. The strength and stability of the anisotropy indicate that, during these periods, SOHO was in an interplanetary se ctor where the particle transport was almost scatter-free. On the othe r hand, during the intermediate 3-hr period, we observed particles whi ch traveled in a sector of diffusive transport or which were retarded by magnetic field disturbances not far from the observation site.