Jl. Bertaux et al., Monitoring solar activity on the far side of the Sun from sky reflected Lyman alpha radiation, GEOPHYS R L, 27(9), 2000, pp. 1331-1334
Solar active regions are known to be brighter in Lyman alpha radiation than
the quiet sun. Accordingly, they illuminate more H atoms in interplanetary
space through resonance scattering. As we show here, this excess of illumi
nation related to active regions is clearly seen in full-sky Lyman alpha ma
ps recorded by the SWAN instrument on board SOHO, including those excesses
resulting from active regions which are on the far side of the Sun. Since s
olar activity is most often connected to solar active regions, this techniq
ue could be used in the future to improve the quality of Space Weather fore
cast, by earlier detection of the birth of a new active region on the far s
ide of the sun, before it comes into Earth's view at the East limb.