Nonlinear physics of the ionosphere and LOIS/LOFAR

Abstract

The ionosphere is the only large-scale plasma laboratory without walls that we have direct access to. Here we can study, both in situ and from the ground, basic small- and large-scale processes and fundamental physical principles that control planet Earth's interaction with its space environment. From results obtained in systematic, repeatable experiments, where we can vary the stimulus and observe its response in a controlled, laboratory-like manner, we can draw conclusions on similar physical processes occurring naturally in the Earth's plasma environment as well as in parts of the plasma universe that are not easily accessible to direct probing.Of particular interest is electromagnetic turbulence excited in the ionosphere by beams of particles (photons, electrons) and its manifestation in terms of secondary radiation (electrostatic and electromagnetic waves), structure formation (solitons, cavitons, alfveons, hybrons, striations) and the associated exchange of energy, linear momentum and angular momentum.The primarily astrophysics-oriented, distributed radio telescope Low Frequency Array (LOFAR) currently under construction in the Netherlands, Germany and France, will operate in a frequency range (10–240 MHz), close to fundamental ionospheric plasma resonance/cut-off frequencies, with a sensitivity that is orders of magnitude higher than any radio (or radar) facility used so far. The LOFAR Outrigger in Scandinavia (LOIS) radio and radar facility, with one station in Växjö in southern Sweden and three more planned in the same area (Ronneby, Kalmar, Lund) plus one near Poznan in Poland, supplements LOFAR with optimized Earth and space observing extensions. For this purpose LOIS will operate in the same frequency range as LOFAR (but extended on the low-frequency side) and will augment the observation capability to enable direct radio imaging of plasma vorticity.