Diagnostics of the solar corona using EUV radiation backscattered by pick-up ions close to the Sun Original Research Article

Recent investigations of pick-up ion data obtained with the AMPTE and Ulysses spacecraft led to the discovery that, in contrast to previous expectations, pick-up ion velocity distributions can be anisotropic. Such anisotropy implies a pitch-angle scattering being less efficient than is usually assumed and translates into scattering mean free paths longer than those previously attributed to these particles. Dedicated observations could give valuable insights into the details of the scattering process. Here we demonstrate that existing and forthcoming in-situ observations can be supplemented with Earth-bound observations of the extreme-ultraviolet resonance glow of pick-up ions in the vicinity of the Sun. The proposed observations, combined with a theory of ions being picked-up by the heliospheric magnetic field close to the Sun, will not only allow us to obtain information about the anisotropy of the pick-up ion velocity distributions, but also about the coronal magnetic field topology as well as the accelerating solar wind. Therefore, such observations will contributed to an improvement of our understanding of the physics of the solar corona in general.