High-latitude observations of ULF waves with large azimuthal wavenumbers

The Doppler Pulsation Experiment (DOPE) is;In HF Doppler sounder deployed a t Tromso, northern Norway, for the investigation of the ionospheric signatu res of ULF wave phenomena of magnetospheric origin. This high-latitude Dopp ler sounder has been demonstrated to be a highly sensitive instrument for t he investigation of ULF waves of large azimuthal wavenumber m. Such waves a re assumed to be driven by magnetospheric wave-particle interactions and ar e difficult to study by other ground-based techniques owing to their strong spatial integration between the ionosphere and the ground. A new populatio n of high-m waves has been identified in the ground-based data from DOPE, w hich could represent a significant new sink for ring current energy. These waves have m numbers of order 100 and are observed primarily in the morning sector. Their characteristics are described and compared to previous stati stical observations from spacecraft. The DOPE sounder now offers routine me asurements of he occurrence and characteristics of such high-m wave populat ions.