Accession Number : ADP006495

Title :   VLF, ELF and Wave Research using the Tromso Heating Facility,

Corporate Author : MAX-PLANCK-INST FUER AERONOMIE LINDAU-UEBER-NORTHEIM (GERMANY F R)

Personal Author(s) : Rietveld, M. T. ; Barr, R. ; Stubbe, P. ; Maul, A. ; Kopka, H.

Report Date : OCT 1990

Pagination or Media Count : 10

Abstract : A review is presented of results from the Tromso Heating facility in the areas of wave generation from ULF (mHz) to VLF (kHz) frequencies, as well as VLF wave propagation under heated ionospheres. Results from similar facilities in the USSR and USA will not be included. High power high frequency (HF) radio waves heat the electrons in the lower ionosphere through non-deviative absorption on the time-scale of microseconds resulting in the enhancement of the electron-neutral collision frequency. The heated region, typically 25 km diameter at 80 km altitude, can act as a perturbation on the upper wall of the Earth-ionosphere waveguide, thereby affecting the propagation of VLF waves. On the other hand, by amplitude modulating the heating wave the heated region can act as an oscillating current source, if there is an external driving electric field, which can itself radiate waves at the modulation frequency into the waveguide or into the magnetosphere. The auroral zone is ideally situated for experiments of the second type because of the frequent presence of large (tens of mV/m) electric fields. For experiments of the first type, the auroral zone is not quite so ideal since large natural ionospheric variations can mask the artificially produced ones. We shall review results from both types of experiment performed using the heating facility of the Max-Planck-Institut fur Aeronomie, a description of which can be found in Stubbe and Kopka (1979) and Stubbe et al. (1982a, 1985). This facility will be operated by the EISCAT scientific association from 1993 onwards.

Descriptors :   *RADIO WAVES, *IONOSPHERIC MODIFICATION, ALTITUDE, AMPLITUDE, AUGMENTATION, COLLISIONS, DIAMETERS, ELECTRIC FIELDS, ELECTRONS, EXTERNAL, HEAT, HEATING, HIGH POWER, IONOSPHERE, MAGNETOSPHERE, MODULATION, NEUTRAL, PERTURBATIONS, POWER, REGIONS, SCALE, TIME, VARIATIONS, WAVE PROPAGATION, WAVEGUIDES, NORWAY, RADIOFREQUENCY POWER, IONOSPHERIC PROPAGATION, RADIATION ABSORPTION, EXTREMELY LOW FREQUENCY, ULTRALOW FREQUENCY, VERY LOW FREQUENCY.

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE