Reconstruction of the D-Region from HF Measurements Using GPSII Assimilative Model

Le résumé fourni par la source

We extend altitude coverage of the NWRA assimilative model of the ionosphere called GPSII [1] down into the D-region, to the lower boundary of about 40 km. The model is coupled with the model of neutral atmosphere (NRL MSIS) which makes the combined model suitable for simulating HF propagation and absorption as well as for VLF field analysis. Currently GPSII is able to assimilate two types of D-region sensitive HF data. First is the ratio of amplitudes of ordinary and extraordinary polarization components of HF signals observed over a known communication links. The second is the relative temporal change of the amplitude of the signal received from an HF transmitter whose radiated power is constant. Both data types rely on signal power measurements. Such measurements are generally very difficult to calibrate. But this uncertain power calibration factor is virtually eliminated after formulating the input data for GPSII. We demonstrate the operation of the new inversion algorithm using observations from ionosondes. GPSII solutions display the correct D-region behavior throughout strong solar flare events. Finally, we validate GPSII performance during a strong solar flare event against HF absorption data from riometers; Validation of GPSII vertical profiles is aided by a physics-based model [4].

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.