Electron beams in large coronal loops

The type U(N) radio burst observed at February 23, 1993 is presented. Using a 1-D test particle model, this radio burst is modeled as an electron beam propagating in a large coronal loop. For modeling of transport processes Coulomb collisions, mirroring of electrons in the loop magnetic field, and scattering in zones of enhanced whistler wave turbulence are taken into account. In the model electrons are injected upwards along the loop axis in one leg. In the zone of whistler turbulence near the loop top the original beam is splitted up into two beams propagating from the top back and forward into both loop legs. It explains two widely separated radio sources observed during the descending branch of U burst spectra.