Lyman α intensities in a polar coronal hole from a 2D model Original Research Article

We simulate the coronal H I Lyman α intensity for heliocentric distances between 1.5 and 2.5 R⊙, and latitudes between 90° (North pole) and 30°, making use of a 2D semiempirical coronal hole model. Observations are made with the UltraViolet Coronagraph Spectrometer (UVCS) on board the ESA-NASA solar satellite SOHO (SOlar and Heliospheric Observatory). Model electron densities are derived from the collisional part of the O VI λ1037.6 Å line and the proton outflow speed is calculated from mass flux conservation along the magnetic field lines. The expansion factor and the direction of the magnetic flux tubes have been derived by adopting a simple analytical magnetic field configuration. The intensities of the Ly α line predicted by the model are compared with the observed intensities.