On the formation of extreme-ultraviolet helium lines in the Sun: Analysis of SOHO data
The resonance lines of helium in the Sun are several times stronger than expected, relative to lines of other ions. To explore the origins of this "helium enhancement,'' we have studied data from the SUMER, CDS, MDI, and EIT instruments on the Solar and Heliospheric Observatory (SOHO). Time series data obtained in a quiet region and a coronal hole indicate that the spatio-temporal properties of th
