Coronal and interplanetary transport of solar energetic protons and electrons

A new method is presented for separating interplanetary and coronal propagation, starting from intensity variations observed by spaceprobes at different heliolongitudes. In general, a decrease in absolute intensities is observed simultaneously with an increase in temporal delays. The coupling of these two effects can be described by Reid's model of coronal diffusion and can in principle be used to determine the two coronal time constants, diffusion time t sub(c) and escape time A. In addition, a least-squares fit method is used to determine the parameters of interplanetary transport, assuming a radial dependence as lambda (r)= lambda sub(0) (r/1 AU) super(b) . The method is applied to the two solar events of December 27, 1977 and January 1, 1978 which were observed by the spaceprobes Helios-1, Helios-2, and Prognoz-6. Energetic particle data are analysed for 13-27 MeV protons and [perspective to] 0.5 MeV electrons. For the regions in space encountered during these events the mean free path of electrons is smaller than that of protons. Straight interpolation between the two rigidities leads to a rather flat rigidity dependence lambda (P) similar to P super(n) with n=0.17-0.25. This contradicts the prediction of a constant mean free path or of the transition to scatter-free propagation below about 100 MV rigidity. In three of the four cases the mean free path of 13-27 MeV protons is of the order 0.17 AU, the mean free path of electrons of the order of 0.06 AU. For protons we find b[perspective to] 0.7 for the exponent of the radial variation. The concept of two different coronal propagation regimes is confirmed. It is remarkable that in both regimes electrons are transported more efficiently than protons. This holds for the temporal delay as well as for the amplitude decrease. This is in contrast with the long existing concept of `rigidity independent transport' and puts severe limits to any model of coronal transport. For the December event all three spaceprobes are in the fast propagation regime up to an angular distance of 62 degrees . For protons we find a finite delay even in the fast propagation region, corresponding to a coronal delay rate of about 0.8 hr rad super(-) super(1) up to 60 degrees angular distance. In contrast, relativistic electrons may reach this distance within a few minutes. The fast transport of electrons and the different behaviour of electrons and protons is in contradiction to the expanding bottle concept. An explanation of corona