Electron coronal density irregularity$\overline {n^2 } /(\bar n)^2$ from measurements of K-coronal and lyman lines brightnesses

Abstract

We propose a technique to derive the coronal density irregularity factor$\overline {n^2 } /(\bar n)^2$, wheren is the electron density. The absolute photometric comparison between the intensity of UV lines and the white-light K-coronal polarized brightness (pB) provides an unique constraint on the inhomogeneity of the corona. The ratio of the measured H I Lyman β (Ly-β) line intensity to the resonant-scattering dominated H I Lyman α (Ly-α) intensity can be used to extract the collisonal component of the Ly-β. This component yields an estimate of$\overline {n^2 }$. The quantity$(\bar n)^2$ is then obtained from white-light K-coronal measurements. The use of lines of the same atomic species minimizes the effects due to outflow velocities (i.e., Doppler dimming), and reduces the errors introduced by the uncertainties in the ionization balance, the atomic parameters, and the solar abundances. The UVCS/SOHO unique capability of performing cotemporal and cospatial measurements of the Ly-α and Ly-β lines, and ofpB makes this instrument ideal for implementing this technique.