| Summary: | Includes bibliographical references (page 3694). Horizontal magnetic field variations in the frequency range of the Earth-ionosphere cavity resonances are observed at Silberborn, Germany, simultaneous with 19 sprite-associated lightning flashes in the midwestern United States, on July 15, 1995. The measured horizontal magnetic intensities are linearly related to the horizontal magnetic intensities of slow tails of radio atmospherics which were simultaneously recorded at Palmer Station, Antarctica. Enhancement of the Earth-ionosphere cavity resonances is verified by spectral analysis, and the measured arrival azimuths are in agreement with the expected orientation of the Poynting vector along the great-circle path. The estimated accuracy of the arrival azimuth determination is on the order of ±5°.
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