The solar coronal green line as an index of cosmic ray modulation

In recent years several papers have indicated that the solar coronal green line emission (λ=5303Å) is the ‘best’ indicator of cosmic ray modulation. This paper questions this result for the following reasons: (a) the problems of green line measurement obscure the true meaning of the resulting observations; (b) there is a lack of any direct physical mechanism relating green line intensity and modulation; (c) a negative result came from a careful attempt to relate the cosmic ray diurnal variation and green line emission.