Infrasonic Waves of the Auroral Zone

Abstract

INFRASONIC waves of the auroral zone have been observed^1,2 using a suitable microphone system. These waves are thought to originate in the joule heating by the electrojet currents¹ or in the corpuscular heating during ionization and excitation processes² in the auroral ionosphere—at about the 100-km level. Periodic influx of electrons at this level due to processes, which may be solar, magnetospheric or extra-magnetospheric, could cause periodic fluctuations in the current systems and the heating processes; hence the observed periods (in the range 20–80 sec and, at times, upwards of 100 sec). Time-scales of this order are known in auroral pulsations. It is suggested here that it is also possible to account for the energy fluctuations from the atmospheric dynamics, specifically turbulence near 100 km, which can generate these waves via the pressure fluctuations.