Generation of arti®cial magnetic pulsations in the Pc1 frequency range by periodic heating of the Earth's ionosphere: indications of ionospheric AlfveÂn resonator eects T. BoÈsinger a, *, T. Pashin b , A. Kero a , P. Pollari a , P. Belyaev c , M. Rietveld d , T. Turunen e , J. Kangas e a University of Oulu, Department of Physical Sciences, Oulu, Finland b Polar Geophysical Institute, Apatity, Russia c Radiophysical Research Institute, Nizhny Novgorod, Russia d EISCAT Scienti®c Association, Tromsdalen, Norway e Geophysical Observatory, Sodankyla, Finland Received 12 November 1998; received in revised form 11 October 1999; accepted 20 October 1999 Abstract A series of six experiments with the EISCAT HF heater device assisted by the EISCAT (European-Incoherent- Scatter) radar were carried out with the purpose of producing arti®cial magnetic pulsations in the 0.1±3 Hz frequency range. In only 3 of the 30 h of experiment time under a variety of ionospheric conditions was an arti®cial magnetic signal detected by ground-based magnetometers. A numerical model was used to explain the sporadic nature of the arti®cial signal in terms of ionospheric parameters. For several experiments the EISCAT radar provided an in situ electric ®eld and/or electron density values; otherwise standard neutral atmosphere and ionosphere models were used. The PGI model was only partially successful. It could produce the right order of magnitude for the arti®cial signal when it was observed and it could demonstrate the dierent eciencies when using either the O- or the X-mode of the HF wave, but it could not explain why the arti®cial signal was observed at a particular time and not at others. This is only partially due to the uncertainty in one or more input parameters. When the arti®cial signal was observed its spectrum usually exhibited spectral resonance structures of the Ionospheric AlfveÂn Resonator (IAR), indicating that a ``DC approach'' is insucient and that the generation of oscillating ®eld-aligned currents, and thereby shear AlfveÂn waves, has to be taken into account. We believe, however, that even with the introduction of the IAR into the model it will not be possible to resolve the sporadic character of the heating-induced arti®cial magnetic signal entirely. A more realistic way of D-region modeling will without doubt also be an important factor in resolving the puzzle. 7 2000 Elsevier Science Ltd. All rights reserved. Journal of Atmospheric and Solar-Terrestrial Physics 62 (2000) 277±297 1364-6826/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S1364-6826(99)00125-X * Corresponding author. E-mail address: tilmann.bosinger@oulu.® (T. BoÈsinger).