ELECTRON-BEAMS AND RADIO-WAVES OF SOLAR-TYPE-III BURSTS

Using the radio wave and energetic particle experiments on the Wind sp acecraft, we examine how the radio flux density of interplanetary type III bursts depends on the flux and energy of the energetic electrons. We derive the relationship between them; first by giving detailed rad io and electron characteristics of one type III burst, and then using the results of similar analyses of 10 bursts. The times of commencemen t of the radio waves from decametric to kilometric wavelengths, in rel ation to the onset time of Langmuir waves, demonstrate forcibly that t he initial type III radiation is at the fundamental and not the harmon ic. Near and after the time of peak flux density the radiation could b e either at the fundamental or the harmonic. In our theoretical analys is we examine this point, i.e., how the emissivity of the fundamental and harmonic at the time of peak flux density depends on the beam prop erties. The data of the 10 events are in good accord (r(c) approximate to 0.9) with the theoretical relation for fundamental emission, but i n disaccord with the theoretical relation for harmonic radiation. For the 10 bursts we find poor correlation between the radio flux density and the electron flux N(E-parallel to) at the energy E-parallel to est imated to be that of the two-stream instability. However there is exce llent correlation when N(E-parallel to) is weighted by E-parallel to t o a high power. From the best fit, we find r(c) approximate to 0.96 wh en N(E-parallel to) is replaced by E-parallel to(3.98) N (E-parallel t o). Finally, we infer the efficiency of energy conversion from the kin etic energy of the electron beam to fundamental emission, and examine the attenuation of the peak emission within the source.