Two types of electron events in solar flares

The fluxes and spectra of the flare electrons measured on board Venera-I3 and I4 space probes are compared with the parameters of the hard (E sub x approximately 55 keV) and thermal X-ray bursts. The electron flux amplitude has been found to correlate with flare importance in the thermal X-ray range (r approximately 0.8). The following two types of flare events have been found in the electron component of SCR. The electron flux increase is accompanied by a hard X-ray burst and the electron spectrum index in the approximately 25 to 200 keV energy range is gamma approximately 2 to 3. The electron flux increase is not accompanied by a hard X-ray burst and the electron spectrum is softer (Delta gamma approximately 0.7 to 1.0)

Observations of Electrons from the Decay of Solar Flare Neutrons

We have found evidence for fluxes of energetic electrons in interplanetary space on board the ISEE-3 spacecraft which we interpret as the decay products of neutrons generated in a solar flare on 1980 June 21. The decay electrons arrived at the s/c shortly before the electrons from the flare and can be distinguished from the latter by their distinctive energy spectrum. The time profile of the decay electrons is in good agreement with the results from a simulation based on a scattering mean free path derived from a fit to the flare electron data. The comparison with simultaneously observed decay protons and a published direct measurement of high-energy neutrons places important constraints on the parent neutron spectrum.Comment: 4 pages (postscript), accepted by Astrophysical Journal Letter

Solar and heliospheric sources of suprathermal and energetic particle populations

Objectives and some preliminary findings of an ongoing international team project carried out at ISSI, Bern will be presented. Suprathermal and energetic particle s in interplanetary space have a multitude of origins, i.e. acceleration and propagation hi stories. Solar flares, coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), the heliospheric termination shock, planetary bow shocks and magnetospheres have all been recognized as energetic particle sources. Less energetic (suprathermal) particles of solar origin and pick-up ions have also a vital role both in their own right and as seeds of energetic particles accelerated in interplanetary disturbances. The relative contributions of various particle populations vary with energy and with the phase of the solar cycle. Particular attention will be given in our project to quiet periods and to large events. While quiet-time fluxes are expected to shed light on some base-line features of coronal and interplanetary acceleration processes, relatively large events dominate bot h the long-term fluence levels and the statistical properties of cumulative fluence plots. The importance of energetic and suprathermal particles that mostly cannot escape into interplanetary space, but contribute to co ronal heating and possibly also to solar wind composition, will also be discussed. B. Sripathi Acharya, Sunil Gupta, P. Jagadeesan, Atul Jain, S. Karthikeyan, Samuel Morris, and Suresh Tonwa