Found this description, on ESA website, for an old SOHO picture taken around 304 Å : "304 Å : spectral line emitted by ionised helium (He II). Corresponding to a temperature of about 60,000 Kelvin, emission in this line shows the upper chromosphere of the Sun."

That gives another meaning to the expression "hot like HeII" ... sorry ;)

(but apparently it's less hot that the pictures in 94 Å linked to emission of Fe XVIII with temperature of about 7,000,000K)

Aren't sunspots darker than the rest of the sun in visible light? Must be because the output has all shifted to UV.