EXTREME-ULTRAVIOLET DIAGNOSTICS OF PICK-UP IONS IN REGIONS CLOSE TO THE SOLAR CORONA - I - FEASIBILITY OF NEW OBSERVATIONS

Recent investigations of pick-up ion data obtained with the AMPTE and the Ulysses spacecraft resulted in the discovery that, in contrast to previous expectation, pick-up ion velocity distribution can be anisotr opic. Such anisotropy results from a smaller efficiency of pitch-angle scattering than usually assumed and translates into a larger scatteri ng mean free paths than previously attributed to these particles. We d emonstrate that existing and upcoming in-situ observations can be subs tantially supplemented by Earth-bound observations of the extreme-ultr aviolet resonance glow of pick-up ions in the vicinity of the sun. The proposed observations, in combination with a theory of ions being pic ked-up by the heliospheric magnetic field close to the sun will not on ly allow us to obtain information about the anisotropy of the pick-up ion velocity distributions, but also to deepen our understanding of th e physics of the accelerated solar wind and of the pick-up process of ions in this innermost region of the heliosphere not yet well explored .