How does hydrogen emission from the Sun change over the solar cycle?

False colour image of the solar disk in EUV (left) and irradiance measured over a range of wavelengths around the Ly-α line (right). We expect the shape of the dominant peak to change with solar cycle.

Hydrogen is the most abundant element in the universe, and it makes the brightest emission line in the solar spectrum.

The shape of the line is determined by conditions in the outer atmosphere of the Sun, which change on both long and short time-scales. The goal of this project is to see how the shape of one particular hydrogen line changes from year to year as the Sun becomes more active, and to correlate these changes to other indicators of solar activity.