A HIGH-RESOLUTION IMAGING SPECTROMETER FOR VISIBLE CORONAL EMISSION LINES

The Earth orbits through a sea of magnetised plasma flowing from the Sun called the solar wind. Travelling at high speed through the solar wind, Coronal Mass Ejections (CME) are enormous clouds of high-density plasma associated with eruptions and flares at the Sun. The Earth's magnetic field acts as a shield to prevent damage from CMEs. Society, however, depends on satellites and large CMEs under certain conditions may cause widespread damage. The ability to predict the occurrence of a CME, and to predict their subsequent evolution, depends critically on understanding the dominant physical processes which occur in the corona, and on understanding the medium through which CMEs propagate - the solar wind.

In understanding the solar wind and CMEs, the extended inner corona is a critical region. This complex region starts at the solar surface and extends to where the coronal plasma starts to expand radially and becomes supersonic. Current observations of this region are very limited. There are a handful of broadband visible light coronagraphs which provide rather noisy measurements of the Thomson-scattered light from coronal electrons such as the COR1/STEREO coronagraphs, or the MLSO MKIV coronameters (to be upgraded to COSMO soon). Current EUV imagers and spectrometers provide very high-quality data, but their field of view is typically limited to a few tenths of solar radii from the photosphere at best. There is no spectrometer currently in use which can observe the corona above a few tenths of a solar radius from the limb, severely restricting efforts to understand the source region of CMEs and the solar wind.

The goal of the proposed spectrometer is to capitalize on the diagnostic properties of coronal forbidden emission lines in the visible and near-IR, to infer electron temperatures, ion densities, elemental abundances and charge states, bulk flow speeds, non-thermal heating (i.e. wave heating) and indirectly the properties of the coronal magnetic field. The scientific advantage of observing these lines stems primarily from the strength of their radiatively excited component, which enables the emission to extend out to large heliocentric distances. It is surprising therefore that observations of forbidden coronal emission lines in the visible have been seriously neglected in current solar missions. The proposed spectrometer directly addresses this shortcoming and will provide unique constraints on the physical processes that heat the solar atmosphere to over one million degrees and accelerate the solar wind.

Economy
The economical impact of our research can be measured in our efforts to limit the potential trillions of dollars of damage to the worldwide economy in the event of a catastrophic solar storm. The type of research conducted is an important part of understanding, and eventually forecasting, the behaviour of the Sun-Earth system.

The economic beneficiaries of our work will be Public bodies and government, and commerical entities. The increased understanding of the source region of the solar wind and CMEs will aid governments and related bodies to spend public money more effectively.

Society
We are lucky as eclipse scientists to have access to the most spectacular images of the solar system. This places an unique responsibility for us to engage with public audiences. The 2017 US eclipse in particular offers a marvellous chance to engage with a potential audience of millions.

The societal beneficiaries of our work will be:
- - A broad swathe of Welsh societyThe Welsh public. The PI Huw Morgan is heavily involved with public outreach to a Welsh audience. Many aspects of the eclipse observations will be publicised to a large (~100,000) non-scientific (and often disengaged) audience via the national Eisteddfod festival. A broad cross-section of Welsh society attends the week-long Eisteddfod every year, and astronomy at Aberystwyth University has a strong presence on the field. This includes stalls and attractive exhibitions in the science pavilion, solar telescopes, and an enthusiastic group of staff and students to engage the public. The audience will benefit through gaining an understanding of the local space enviroment, and by the increased acceptance of science into a society generally dominated by music and arts. This aspect of the work is bolstered by a recent award for the RAS 200 public outreach project.

- School childrens. With the aid of University officers, we will visit schools to talk about our science, and organise activities where school children visit the University. There are obvious benefits for the children here, through enhancing their understanding of solar and planetary science and by influencing their behaviour in terms of choosing a science career in later lifelearning and their possible future reqruitment into a science career..

- The general public. We will improve on recent work to use social networking to advertise our science, and grow on our impressive media contacts to expose astronomy to a wide audience. Traditionally, Welsh culture is dominated by arts and music (and rugby!). Any work we can do to increase the exposure to science will benefit society as a whole, by increasing public understanding of our complex enviroment, and by creating an enviroment where children (and adults) are encouraged to study science, perhaps as a career.


See our Pathways to Impact document for details on how we plan to reach the beneficiaries, and for recent highlights of our public engagement and impact work.