1. Plasmasphere Refilling Rates Inferred from Polar and IMAGE Satellite Spectrogram Data T. Huegerich(1), J. Goldstein(1), P.H. Reiff(1), B.W. Reinisch(2) (1) Department of Physics and Astronomy, Rice University, Houston, TX (2) Center for Atmospheric Research, University of Massachusetts Lowell, Lowell, MA

2. Abstract. In situ measurements of electron number density, as inferred from dynamic spectrogram data recorded by the Polar Plasma Wave Instrument (PWI) (1996-97) and IMAGE Radio Plasma Imager (RPI) (2000-01), are used to calculate plasmasphere refilling rates for several refilling events. In order to compare subsequent measurements of electron density at the same local latitude of the corotating plasmasphere, the measurement at a given Magnetic Local Time (MLT) must be compared with the corresponding measurement taken either approximately 12n, for n = 1, 3, 5,..., hours later at the opposite MLT or 24n, for n = 1, 2, 3,..., hours later at the same MLT. The orbit of the Polar satellite provides subsequent measurements of this sort separated by time intervals of approximately 24 and 36 hours, while the IMAGE satellite provides appropriate measurements separated by approximately 12 hours. Temporal refilling effects are thereby isolated as much as possible from spatial effects due to irregularities in the plasmasphere. This method of observing refilling allows the calculation of refilling rates for a range of L-shells (3 Re < L < 7 Re) and MLT positions. Calculated refilling rates are consistent with previous measurements. ________ 1 Department of Physics and Astronomy, Rice University, 6100 Main Street, MS 108, Houston, TX 77005, USA 2 Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk Street, Lowell, MA 01854, USA Plasmasphere Refilling Rates Inferred from Polar and IMAGE Satellite Spectrogram Data Timothy Huegerich 1, Jerry Goldstein 1, Patricia H. Reiff 1, and Bodo W. Reinisch 2

3. Observing Refilling from Polar Orbit Subsequent Plasmasphere Profiles Exhibit Refilling (Carpenter- Anderson model for the saturated values shown in orange.)

4. Orbital Path Through the Plasmasphere The Polar satellite passes through the plasmasphere on each 17-18 hour orbit. Each pass consists of an inbound pass through one latitudinal slice of the plasmasphere and an outbound pass through the opposite side of the plasmasphere.

5. Matching Subsequent Passes of Polar through the Co-Rotating Plasmasphere View of co-rotating plasmasphere from above (EUV perspective), with satellite passes marked. View of satellite passes through the co-rotating plasmasphere

6. Matching Subsequent Passes of IMAGE through the Co-Rotating Plasmasphere View of satellite passes through the co-rotating plasmasphere View of co-rotating plasmasphere from above (EUV perspective), with satellite passes marked.

7. Measuring Flux Tube Refilling Picture of plasmasphere profiles from slide 3 with bins drawn. Aligned below: calculations of (change in density)/time Explain that we know refilling may not be occuring the whole time.

8. Applying Rasmussen Refilling Model Rasmussen has developed a simple model for the rate of plasmasphere refilling: Where is a constant with the units of time that we wish to calculate for different events, seeking to find its dependence on L, Kp, or other factors. From two subsequent measures of electron density in a given flux tube, and a value for the electron density of a saturated flux tube, we may calculate as:

9. Case Studies: January 15, 1997

10. Case Studies: October 5, 1996

11. Case Studies: November 27, 2001

12. Case Studies: June 5, 2001