The Principal Investigator (PI) and her collaborators will take multi-spectral observations during several upcoming solar eclipses in order to map the ion abundance, electron temperature, and direction of the coronal magnetic field in the inner corona. The team plans to study the distribution of neutral hydrogen and helium in the solar corona, as well as to investigate the properties of dust grains in the near-Sun environment. Data will be obtained in the spectral lines of ionized iron, sulfur, and silicon, as well as in neutral helium and hydrogen. Coupled with laboratory experiments, these observations will enable detection of fluorescence signatures of interplanetary dust grains present in the solar corona.
This project will exploit the complementary diagnostic techniques of resonant scattering and polarization to follow the evolution of ions and neutrals in the solar corona. Heavy ions and traces of lighter neutral atoms (such as hydrogen and helium) in the inner corona serve as local probes of the physical processes that heat the solar atmosphere to over one million degrees and accelerate the solar wind. While ions are tied to coronal magnetic fields, neutrals reflect the fate of cooler material from solar as well as interstellar origin. As ions and neutrals expand away from the Sun, they interact and evolve under the influence of the local magnetic field, the local electron temperature, and through collisions. This research will enhance our understanding of these phenomena.
In previous eclipse expeditions, members of the research team have been successful in raising public awareness of scientific research in general and of solar physics in particular. Their prior efforts have proved to be engaging for the imagination and intellect of younger students specifically. The research team represents a fruitful collaboration involving small and large universities led by a senior female scientist. The eclipse expeditions will involve graduate students, postdoctoral fellows, and a K-12 teacher, with an emphasis on education.
In this project, a partnership between University of Hawaii, University of Illinois, and Bridgwater College conducted studies to better understand the corona and solar wind as well as contribute to the effort to unlock the 35 year old mystery of the extended red/blue emission from the Milky Way and other galaxies, which cannot be satisfactorily explained by any atomic, ionic or other material known in the galaxies. According to the International Astronomy Union (IAU), this phenomenon is one of a number of remaining unexplained spectral phenomena in the interstellar medium. This mystery red glow, called the Extended Red Emission (ERE), is present throughout the Milky Way and other galaxies, but never on Earth. More recently extended blue emission (EBE) has also been observed. The red and blue may exhibit different spatial distribution or they may originate from different objects. The red rectangle in which the red extended emission was first discovered has now been additionally identified with blue extended emission, which makes it more like pink. Hydrocarbon-based as well as semiconductor silicon-based nano grains have been proposed as possible carriers for the extended emissions. The University of Illinois part of the project focused on studies related to elucidation of the semiconductor-based carrier model and employed observation, laboratory measurements as well as simulations. The eventual goal is to identify a nano silicon-based carrier with a plausible mechanism for formation that exhibits the optical characteristics of the extended background whilst maintaining brightness and withstanding harsh radiation without being destroyed. The project has made significant advances on the experimental front as well as on advanced computations. We have shown that (i) Molecular-like ultra-small silicon grains are a carrier that can account for the spectral content of the extended red and blue emission. The carrier is a hydrogenated silicon nano cluster or super molecule. It is a discreet set of clusters ranging from 1-3 nm in size. The 1 nm cluster with a molecular configuration of Si29H24 accounts for the extended blue emission. The 3 nm particles account for the extended red emission. (ii) We developed patented processes for the preparation of high quality commercial quantities of the nanoparticles with repeatable structure and characteristics. (iii) The grains are rugged and do not dim, and are not disintegrated by the harsh radiation or ionization environment of the galaxies. They grow brighter with extreme pressure and do not fragment. (iv) Their ionized version stays luminescent, and may be tied to and locked into paths controlled by the coronal magnetic field. (v) Advanced quantum molecular dynamics calculations of the electronic, optical, mechanical, and ionic interaction properties of the grains confirm the experimental results. Our continuing laboratory work focuses on examining the flight of these Si nanoparticle grains and their ionized form in external electric and magnetic field to examine if they can be locked into paths controlled by the fields. The success of the project was due in large part to the careful selection of those involved to provide a cross-disciplinary environment integrating expertise in observational astronomy and eclipses, solar science, nanoscience, and computation and simulations. There was also a strong educational element to the project as the team sought to foster inspiration among the younger generation. We encouraged students to be involved in research as well as present results at in-house seminars or at scientific meetings. Several graduate students as well as two undergraduate students were co-authors on refereed Journal publications resulting from the project.
