Earth–ionosphere waveguide Earth and the ionosphere. The round-the-world nature of the waveguide produces resonances, like a cavity, which are at ~7 Hz. Radio propagation within the ionosphere depends on frequency, angle of incidence, time of day, season, Earth's magnetic field, and solar activity. At vertical incidence, waves with frequencies larger than the electron plasma frequency (f) of the F-layer maximum (1) f = 9 (N) kHz (N in cm is the electron density) can propagate through the ionosphere nearly undisturbed. Waves with frequencies smaller than f are reflected within the ionospheric D-, E-, and F-layers. f is of the order of 8–15
Night Waves Night Waves Night Waves was a radio programme broadcast on BBC Radio 3. The BBC described it as "Radio 3's flagship arts and ideas programme". "The Guardian" said in May 2010 "...the king of radio arts programmes is undoubtedly "Night Waves", a programme so clever that it regularly makes me stand still and listen, usually halfway to the dishwasher with a plate in my hand...It's the desire to untangle arguments, to lift up their corners and see what lurks there. There's a gleeful range of references too...and a relish for intelligent debate." It was broadcast every Monday to Thursday evening,