New clue to solving the mystery of the sun’s hot atmosphere

The elemental composition of the Sun's hot atmosphere known as the 'corona' is strongly linked to the 11-year solar magnetic activity cycle, a team of scientists from UCL, George Mason University and Naval Research Laboratory has revealed for the first time. The study, published and funded by the NASA Hinode program, shows that an increase in magnetic activity goes hand in hand with an increase of certain elements, such as Iron, in the solar corona. It is thought that the results could have significant implications for under-standing the process leading to the heating of the Sun's corona. "Elemental composition is an important component of the flow of mass and energy into the atmos-pheres of the Sun and other stars. How that composition changes, if it does indeed change, as mate-rial flows from the surface of the Sun to its corona influences ideas we have about the heating and activity in atmospheres of other stars," said Dr Deborah Baker (UCL Space & Climate Physics). Through its 11-year cycle, the Sun moves from relatively quiet periods at solar minimum, to intense magnetic activity at solar maximum, when large numbers of sunspots appear and there is an in-crease in radiation.  "Previously, many astronomers thought that elemental composition in a star's atmosphere depended on the properties of the star that don't change, such as the rotation rate or surface gravity. Our re-sults suggest that it may also be linked with the magnetic activity and heating processes in the at-mosphere itself, and they change with time, at least in the Sun," said the study's lead author, Dr David H. Brooks (George Mason University).