Halo Electrons Research Articles

Whistler heat flux instability in the solar wind with bi-Lorentzian velocity distribution functions

The dependence of the growth rate and the threshold level of the whistler heat flux instability in the solar wind at 1 AU on the shape of the velocity distribution function and on the electron halo temperature anisotropy is examined by using a drifted bi-Lorentzian distribution function. We find that for a given set of plasma parameters the maximum growth rate increases sharply with increasing slope of the halo electron velocity distribution and that the whistler instability threshold level increases sharply with increasing halo temperature anisotropy. In view of the sensitivity of the whistler instability threshold level to details of the shape of halo electron distribution functions it is not now possible to decide unambiguously if the whistler mode regulates the interplanetary heat flux some of the time at 1 AU, but it remains a strong candidate.

Electron Diffraction at Low Temperature IV. Amorphous Films of Iron and Chromium Prepared by Low Temperature Condensation

Films of iron and chromium were prepared at 4.2°K which show diffuse halo electron diffraction patterns characteristic of an amorphous state. In order to decide whether these films are in an amorphous state or consist of very fine crystallites, the radial distribution analysis was carried out for them. The results of analysis lead to the conclusion that the state of atomic aggregate of these films is certainly amorphous.