A Fresh Look at the Sun: New Opportunities with the launch of Solar-B

Lead Research Organisation: Armagh Observatory
Department Name: Astronomy


In 2006 a new solar satellite called Solar-B will be launched. It is the first of a number of new solar missions that are due to be launched in the coming years. To maintain the momentum of solar physics in the UK, it is necessary to not only continue to support those missions that are still ongoing, e.g. CDS on SoHO, but to also work out ways to combine and complement the upcoming missions, particularly Solar-B. Here, we wish to address several topics where we have already made progress via SoHO observations but also to include new avenues of research. These include bright points, their relation to coronal heating, the contribution from waves, the contribution of plumes and streamers to the solar wind. Solar-B will enable substantial progress on understanding the origin and evolution of plumes, relatively dense structures that have been identified in the EUV in both polar and non-polar coronal holes. It is important to recognize that plumes can serve as probes of the coronal hole environment, which is otherwise largely unobservable without integrating over long intervals and/or lines of sight. Line width studies are an important probe for coronal heating. The reported decrease in line width above the limb coincides with the location where the observed line ratio of two coronal lines indicates a change from a collisionally to a radiatively dominant excitation regime. This has implications for far off-limb electron density measurements, as all density diagnostics calculations uses theoretical line ratios which only take collisional excitation into consideration. Further investigation into this is required. Interpretation of the observational data is highly dependent on many atomic physics parameters, one of these being the ionization fractions of the ion under consideration. A significant increase in intensity in lines from Li-like ions can occur at high electron densities if one considers electron density dependent dielectronic recombination. However, a decrease in the intensity of lines from Be-like ions can also occur at higher density. This may have major implications when comparing spectral lines formed at similar temperatures in high-density transient events.


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