Ashen light is a hypothesised subtle glow that has been claimed to be seen on the night side of the planet Venus.
[4] A more recent hypothesis is that it is a form of transient aurorae or airglow caused by unusually high solar activity interacting with the upper Venusian atmosphere.
[16] A particularly favourable viewing opportunity occurred on 8 October 2015, with a 40% illuminated Venus reappearing from behind the unlit limb of a 15% sunlit Moon.
The event was visible in dark skies throughout Central Australia and was recorded by David and Joan Dunham (of the International Occultation Timing Association) using a 10" f/4 Newton telescope with a Watec 120N+ video camera from a location just north of Alice Springs.
This magnetic field is induced by an interaction between the ionosphere and the solar wind,[19][20] rather than by an internal dynamo in the core like the one inside Earth.
[22] In 1969, it was hypothesized that the Ashen light is an auroral phenomena due to solar particle bombardment on the dark side of Venus.
[2] In 1990, Christopher T. Russell and J. L. Phillips gave further support to the lightning hypothesis, stating that if there are several strikes on the night side of the planet, in a sufficiently short period of time, the sequence may give off an overall glow in the skies of Venus.
[13] A more recent hypothesis is that unusually high solar activity could induce auroral or airglow-like effects on the dark side of Venus.
It has been observed that after major solar storms, an emission of light with a wavelength of 557.7 nm (the oxygen green line) occurs across the entire upper atmosphere of Venus.