The centre of our solar system was the object in focus at the June meeting of Keighley Astronomical Society. The guest speaker was Mr Kevin Kilburn from Manchester Astronomical Society. His presentation was ‘The bipolar magnetic regions on the Sun’. A relatively unknown aspect of solar study, which has been identified in the past but forgotten until, Mr Kilburn noticed these solar bruises through his own solar scopes.
Bipolar magnetic regions were eloquently described by Horace W. Babcock and his son Harold over half a century ago, based on observations madewith a solar magnetograph of their own design for measuring weak magnetic fields on the surface of the Sun. They showed that a poloidal, north-south trending, shallow, sub-surface magnetic field during the course of a 22-year magnetic or an approximately 11-year visible sunspot cycle.
They become wound-up by differential rotation at different solar latitudes into toroidal, predominantly east-west trending magnetic field lines. In turn these would cause increasingly buoyant magnetic loops to break through the solar surface as the wind-up tightened, after roughly three years from the start of the previously relaxed magnetic cycle. Sunspots would then begin to form in active regions caused by the breakthrough of magnetic loops or ‘stitches’.
Mr Kilburn has used since 2012 a Coronado PST for solar imaging. A year later it became apparent to him that monochrome (grey-scaled) images of the sun show these ‘bruises’ as dusky areas. They are the underlying cause of all photospheric and chromospheric solar activity including active sunspot regions, white light faculae and disturbances in the solar granulation. They are especially associated with features best seen in the wavelength of Calcium K or Hydrogen-alpha; plage, filaments and prominences and solar flares.
The work undertaken by Mr Kilburn shows that there is still room for the dedicated amateur to contribute to extending the frontiers of science and knowledge.