Ionospheric HF pump wave triggering of local auroral activation

• Published in: Journal of Geophysical Research: Space Physics
• Main Authors: Blagoveshchenskaya, N. F., Kornienko, V. A., Borisova, T. D., Thidé, B., Kosch, Mike J., Rietveld, M. T., Mishin, E. V., Lukýanova, R. Yu., Troshichev, O. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2001
• Subjects: Tromsø
• Online Access: https://eprints.lancs.ac.uk/id/eprint/6601/; https://eprints.lancs.ac.uk/id/eprint/6601/1/art_231.pdf

Experimental results from ionospheric HF pumping experiments in the nightside auroral E region above Tromsø are reported. We found intriguing evidence that a modification of the ionosphere-magnetosphere coupling, due to the effects of powerful HF waves beamed into an auroral sporadic E layer, can lead to a local intensification of the auroral activity. Summarizing multi-instrument observations during two consecutive nights, one can distinguish the following peculiarities related to this auroral activation: a modification of the auroral arc and its breakup above Tromsø, local changes in the horizontal currents above Tromsø, a burst-like increase of the electron density and temperature, a large increase in the ion temperature in a wide altitude range and in the north-south component of the electric field, distinctive features in dynamic HF radio scatter Doppler spectra, pump-induced electron precipitation, and substorm activation exactly above Tromsø. We discuss the modification of the ionosphere-magnetosphere coupling in terms of the excitation of a turbulent Alfvén boundary layer between the base of the ionosphere (∼100 km) and the level of sharp increase of the Alfvén velocity (at heights up to one Earth radius), and the formation of a local magnetospheric current system. The results suggest that a possible triggering of local auroral activation requires specific geophysical conditions.