The enigma surrounding the solar corona continues to be the focus of observations from space and the ground. Recent space-based imaging experiments have added significantly to the complexity and dynamics of coronal structures. However, these are limited by the coverage of the inner corona over a distance range limited to half a solar radius at best. They thus fall short in placing the observed structures within the context of the expanding corona from the solar surface out into interplanetary space.
The unique scientific wealth of eclipse observations is the motivation behind our team’s many expeditions. Solar eclipses allow us to view part of the solar atmosphere (the corona) that is not observed by satellites or would otherwise be blocked by the brightness of the solar surface. The following image shows the importance of the field of view of eclipse observations. The area between the black and yellow circles represent the section of the atmosphere that is “filled in” by eclipse observations.
Eclipse images allow us to complete a map of the coronal structure. Coronal dynamics (events) are observed starting from the solar surface and include jets, coronal mass ejections (CMEs) and plasma instabilities.
The goal of this year’s total solar eclipse observations is to capitalize on the diagnostic properties of coronal forbidden emission lines, to infer electron temperatures, ion densities, abundances and charge states, and the properties of the coronal magnetic field. The scientific advantage of observing these lines stems from the strength of their radiatively excited component, which enables the emission to extend out to large heliocentric distances, matching that of white light.
The observational plans of the eclipse of 9 March 2016 in Indonesia will be carried out the same as on 20 March 2015 in Svalbard, namely imaging and imaging spectroscopy. The solar corona will be imaged in white light, Fe XI and Fe XIV. The latter lines detect plasma at 1 million and 2 million degrees respectively. Application of state-of-the-art image processing techniques will maximize the scientific return for exploring the details of coronal structures and their thermodynamic and dynamic properties. Furthermore, this eclipse corresponds to the declining phase of the solar activity in cycle 24, hence will extend our eclipse data base to span almost a full solar activity cycle.