Simultaneous satellite and ground-based observations of a discretely driven field line resonance

An analysis is presented of a set of toroidal field line resonances observe d on the ground by CANOPUS magnetometers and scanning auroral photometers o n December 13, 1990, following a substorm onset at 0750 UT and intensificat ion at 0850 UT. Magnetic and electric field data from the CRRES satellite p rovide evidence that the resonance was also observed in the magnetosphere. To our knowledge, this is the first report of discretely driven resonances observed by ground-based magnetometers and photometers and confirmed using satellite data. A spectral peak at 2.1 mHz is present in all data sets at a pproximately the same invariant latitude and universal time, indicating tha t CANOPUS and CRRES are observing the same resonance. Peaks are also presen t at 1.4 and 1.7 mHz in the ground-based magnetometer and CRRES data at a s lightly higher latitude with corresponding spectral peaks apparent in the p hotometer data. The ground signature for each resonance indicates an antisu nward phase velocity, suggesting that the excitation source is in the vicin ity of the dayside magnetosphere, consistent with a waveguide model of the magnetosphere but not with a cavity model. This fact, combined with a possi bly enhanced solar wind dynamic pressure, suggests that the substorm was no t directly responsible for exciting the resonances. The interaction of the resonances with the substorm remains unclear except for the luminosity fluc tuations associated with the resonances.