Some museums have 'whispering galleries' where sound waves are
reflected and focused in specific ways so the listener hears clear
echoes. The IMAGE RPI instrument has found a way to use radio echoes
traveling along magnetic field 'ducts' to probe the properties of the
plasma flowing along these magnetic pipes. This new technique lets
scientists use remote sensing to study distant space plasmas.
(2003: Fung, S.F., R.F. Benson, D.L. Carpenter, J.L. Green, V. Jayanti, I.A. Galkan,
and B.W. Reinisch)