L. J. Baddeley

Ionospheric Signatures of ULF Waves: Active Radar Techniques

High-frequency radar backscatter which has been artificially induced by a high-power radiofrequency facility such as the EISCAT heater at Tromso has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Waves with a large-scale nature, driven externally to the magnetosphere, and also those waves with small azimuthal scale lengths, driven by wave-particle interactions are investigated. Large-scale events are revealed to be able to achieve latitudinal scale lengths which lead them to be completely screened from ground magnetometer data under some circumstances. Small-scale waves are strongly attenuated in ground magnetometer data, with this screening being well explained by existing theory. Such high azimuthal wavenumber events in the dawn sector appear to be predominantly driven by particles of energies of ∼10 keV via the drift-bounce resonance interaction. In the dusk sector, both drift-bounce and drift-resonance interactions with particles of energies in the range 30-50 keV have been detected. Such energetic particle populations can also drive waves at higher Pc1 frequencies, and these waves play a role in determining the spectral width of artificial high-frequency radar backscatter.