SGER: Ground-based Optical Detection of the Ring Current

Sri International, Menlo Park CA

Investigators

Abstract

The investigators will conduct a proof-of-concept exploratory study of an optical technique for ground-based monitoring of ring current precipitation that could ultimately lead to a global distributed photometric network. The study will focus on the feasibility of using ground-based optical observations to determine ring current composition, morphology, and evolution. The observations will be made with a novel telescopic array and photometer to be operated in Hawaii for six months in order to gather data from at least one major magnetic storm. Hawaii is at a geomagnetic latitude of enhanced Energetic Neutral Atom (ENA) precipitation and is an optimal optical location for this initial investigation. Important advances have been made in recent years in understanding the physics of geomagnetic storms. Numerous modeling and observational studies have been aimed at explaining the storm-time changes in mass and energy of the near-Earth region of the magnetosphere known as the ring current. While the advent of satellites such as Thermosphere Ionosphere Mesosphere Energetics and Dynamic (TIMED) and Imager for Magnetopause to Aurora Global Exploration (IMAGE) provide an excellent database for global measurements of the ring current, satellites in general are costly, are able to make measurements of only a particular region once per pass, and have a limited lifetime. Ground-based optical instruments pose an attractive and complementary alternative to satellite-based monitoring of space weather. Although ground-based ring-current-related optical emissions have been observed in the past, this study will verify for the first time the feasibility of continuously monitoring the ring current from the ground and test the relationship between emissions observed at various wavelengths and in situ measurements of O+ and H+ number and energy density. The investigators will quantify the relationships between optical observables and in situ particle measurements by combining ground-based measurements with satellite measurements. Such measurements are particularly timely now, while the IMAGE and POLAR satellites are still in orbit to provide space-based ring current verification. An affirmative result would open the applicability of a network of ground-based optical instruments distributed in both latitude and longitude to measure the weather and climate of the ring current, much like meteorological stations measure the climate and weather of the terrestrial atmosphere. The final goal of this project is to determine whether groundbased optical measurements can be used to systematically detect ring current precipitation and to use these measurements to track ring current composition, morphology, and evolution during strong magnetic storms.