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Conjugate observation of electron microburst groups by Bremsstrahlung X ray and riometer techniques

1980; American Geophysical Union; Volume: 85; Issue: A12 Linguagem: Inglês

10.1029/ja085ia12p06760

2156-2202

J. C. Siren, T. J. Rosenberg, D. L. Detrick, L. J. Lanzerotti,

Seismic Waves and Analysis

The first evidence is reported of simultaneous conjugate electron microburst group precipitation. Groups of bremsstrahlung X ray microbursts ( E >25 keV) were observed during a substorm recovery phase by a balloon‐borne scintillation counter over Roberval, Quebec, Canada. The microburst groups were accompanied one‐to‐one by time‐delayed and broadened pulses of ionospheric absorption measured by a high sensitivity 30‐MHz riometer at Siple Station, Antarctica ( L ≈ 4.1). For the interval of highest correlation, the absolute lag between the two data sets was 4±1 s, to the limit of the relative timing accuracy. Approximately 2 s of the observed lag had been introduced by a low‐pass filter in the riometer data acquisition unit. The remainder (2 s) was due to the ionospheric recombination process, which evidently had a response time (τ∼5 s) during this event much shorter than that ordinarily associated with the D region of the ionosphere. Model calculations of the ionospheric response to time‐varying precipitation, derived from the profile of the measured X ray flux, provide a consistent picture of simultaneous microburst group precipitation at conjugate points, absolute absorption and the electron spectrum derived from X rays, the degree of variation in absorption and X ray fluxes, and the characteristic ionospheric time constant at the altitude of maximum energy deposition.