a-index amateur radio angle of attack angle of incidence arecibo observatory atmospheric electricity atom broadcast band canada canadian geospace monitoring colorado critical frequency cutoff frequency d region diurnal eiscat earth electric field electrodynamic tether electron equator equatorial electrojet exosphere f region fading galactic cosmic ray geomagnetic storm geophysics guglielmo marconi high frequency active auroral research program horizon horizontal plane incoherent scatter international geophysical year international standard serial number ion ionosonde ionospheric absorption jicamarca radio observatory k-index lightning line-of-sight propagation list of electronics topics lloyd berkner lyman series magnetic field magnetosphere mesopause mesosphere molecule morse code nasa nanometre new horizons nikola tesla nitric oxide nobel prize nozomi oliver heaviside open system oscillation ottawa oxygen ozone layer paris photon pioneer venus project poldhu puerto rico radio radio propagation radio telescope recombination robert watson-watt shortwave skywave soft gamma repeater solar flare solar proton event solar variation solar wind sporadic e propagation stratopause stratosphere sun table mountain tether propulsion thermopause thermosphere tropopause troposphere turbopause ultraviolet van allen radiation belt vitaly ginzburg wavelength wiktionary x-ray