HR: 0800h
AN: SA21B-0346    [Abstracts]
TI: Mid-latitude Ionospheric Irregularity Diagnostic Results From Dynasonde Observations at Bear Lake, Utah
AU: * Zabotin, N A
EM: nikolay.zabotin@colorado.edu
AF: CIRES, University of Colorado, 216 UCB, Boulder, CO 80309-0216
AU: Wright, B
EM: bill.wright@noaa.gov
AF: CIRES, University of Colorado, 216 UCB, Boulder, CO 80309-0216
AB: We use the available time series (11 Feb. 2003 to present) of dynasonde recordings from a mid-latitude (Bear Lake, Utah) location, for a climatological study of small-scale irregularity parameters using our "Phase Structure Function" and "Anomalous Attenuation" methods. Real-time data transfer to NGDC, automatic processing, and display of the data is a result of a shared effort with observatory managers and is supported under NSF project ATM 0125297 and a USAF SBIR project F19628-03-C-0019. The Phase Structure Function method is based on precision measurements of short-period phase variations in totally-reflected radio echoes, as statistically summarized in the temporal structure function, SF. We relate parameters of the SF to the irregularity spectrum parameters by means of diffraction theory. Another diagnostic approach, based on the theory of multiple scattering, predicts a significant level of anomalous attenuation (tens of dBs) of totally-reflected echoes arising from their specific mode of interaction with ionospheric irregularities. Our study of about one year's data yields the following results: a) Characteristic (and different) average diurnal variations are found for E and F regions, and for the seasons. We find evident cause-effect relations between, for example, the sunrise/sunset processes in the ionosphere and irregularity amplitude. b) We have found evidence that the electron density irregularity absolute-amplitude, $\Delta$N, is of more fundamental significance than the relative amplitude $\Delta$N/N for small scales. Clearly, $\Delta$N is less dependent on diurnal variations of average electron density and we find that it has a distinct tendency to preserve its value (on the average) along a magnetic tube, even between E and F regions. c) There is an evident correlation between irregularity amplitude and plasma gradient, in both E and F regions. d) Irregularity amplitude is well correlated with the local magnetic K index at higher latitudes, but not at Bear Lake. e) On the other hand, we observed indications of a significant increase of the anomalous attenuation during some stages of the record Halloween 2003 magnetic storm.
DE: 2439 Ionospheric irregularities
DE: 2443 Midlatitude ionosphere
DE: 2788 Storms and substorms
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting