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.
This project has focussed on observations of the solar corona, the outermost layer the Sun's atmosphere, during total solar eclipses in an effort to better understand the corona's structure and temperature distribution. Gas in the corona is much less dense than gas at the Sun's "surface", the photosphere, and therefore light from the photosphere overwhelms the corona, preventing it from being seen in much the same way the daytime Sun overwhelms the much fainter stars. It is only if the photosphere is blocked that the corona can be seen and studied. This can be done artificially, but only by blocking the inner part of the corona as well. But since the Moon perfectly blocks just the photosphere during a total solar eclipse, this crucial region of the corona, between 1 and 2 solar radii, can be observed. Because the gas in the corona is very hot it is completely ionized, composed of charged particles. (Collisions cause electrons to escape from atoms). Therefore it is highly influenced by the complex magnetic fields, loops, and other structures that rise from the photosphere. As the gas escapes it spreads out into interplanetary space to form the solar wind. Occasionally large amounts of gas will escape and, if they impact the Earth, will cause a dramatic increase in the radiation environment near Earth orbit, where vital communications and monitoring satellites are located. Understanding the corona and how it is influenced by variations in the Sun's magnetic field will lead to better predictions of this "space weather". This project has helped to clarify the link between gas in the corona and in interplanetary space. Complicated magnetic structures have been observed with unprecedented clarity, including the passage of gas ejections through the corona. Temperature ranges and gas densities throughout the inner corona have been established as well. This information will greatly aid efforts to better model the magnetic field variations, from the photosphere to interplanetary space, that influence the solar wind, as well as lead to a better understanding of the physics of the solar corona.
