Radio Sounding in the Magnetosphere Prof. Bodo W. Reinisch Environmental, Earth, and Atmospheric Sciences Department Center for Atmospheric Research, University of Massachusetts Lowell Monday, February 11, 2002 Atmospheric and Environmental Research Refreshments at 5:30 pm, Presentation at 6 pm On March 25, 2000, NASA launched the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite into an elliptical polar orbit with an altitude of seven Earth radii at apogee. The satellite carries the Radio Plasma Imager (RPI), a 3 kHz to 3 MHz radio sounder using modern digital processing techniques and long electronically-tuned antennas. Although the radiated power is only between 1 mW and 10 W depending on frequency, clear echoes, similar to those observed by ionospheric topside sounders, are routinely observed that propagated over distances of several Earth radii. Using a novel inversion technique, the observed echo traces have been inverted into electron-density profiles from the location of the IMAGE satellite to the distant reflection point. For the first time it has become possible to instantaneously construct the electron density distributions of the entire plasmasphere using this remote sensing technique. A large variety of echo signals has so far been observed including direct echoes and field-aligned echoes. Typical echoes from the plasmapause boundary, observed from outside the plasmasphere, are often of a diffuse nature indicating a persistently irregular structure of the plasmasphere. Echoes attributed to the cusp and the magnetopause have also been identified. An example of the capability of the RPI was demonstrated during the magnetic storm of 31 March 2001 which depleted the entire plasmasphere. RPI measurements showed that the refilling of electrons occurred within a period of less than 30 hours. This presentation will provide an overview of the RPI (which was developed at the University of Massachusetts Lowell) and show examples of the data and resulting analyses. Dr. Bodo Reinisch is a Professor of Environmental Earth and Atmospheric Sciences at the University of Massachusetts Lowell. He received his Diploma in physics and mathematics from the University of Freiburg, Germany in 1963 and his Ph.D. in physics from the University of Lowell in 1970. Dr. Reinisch has been responsible the development of advanced digital ionospheric remote sensing techniques for more than 20 years. Today, Digisonde HF Sounders, developed and built at the University of Massachusetts Lowell, are deployed on all continents and supply new insights into the dynamics and structures of the ionosphere. Currently he is one of the principal investigators on NASAÕs IMAGE mission, which was launched in March 2000 and was responsible for design and deployment of the Radio Plasma Imager (RPI) system onboard the satellite. Dr. Reinisch served as chairman of the Ionospheric Informatics Group of the International Union of Radio Science (URSI) until he became international vice-chairman of Commission G of URSI in 1993, and chairman in 1996. He has authored or co-authored more than ninety refereed articles in journals and books. This meeting of the Geoscience and Remote Sensing Society chapter will be held at Atmospheric and Environmental Research (AER), 131 Hartwell Ave., Lexington, Massachusetts. Refreshments will be served at 5:30 PM with the technical meeting starting at 6:00 PM. Directions to AER are as follows. From I-95/128 take exit 31B - labeled Rt. 4/225 Bedford. Merge onto 4/225, stay in the right lane (All turns must be made from the right lane). Just before the light, you will bear right into the reverse direction turn. Go through the light and you are now on Hartwell Avenue. You will go to the end of Hartwell Avenue (about 1 1/2 miles). Just before the gate to the Air Force Base, turn right into the parking lot at 131 Hartwell Avenue (you will see a pillar that says 131 Kiln Brook on one side of the entrance). Use the rear entrance to enter AER's Corporate Offices. For more information, contact John Kerekes at 781-981-0805 or kerekes@ll.mit.edu.