Multiple frequency radar observations of high-latitude E region irregularities in the HF modified ionosphere

Journal Article · Tue Dec 01 04:00:00 EST 1987 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA092iA12p13613· OSTI ID:5715685

Noble, S T; Djuth, F T; Jost, R J; Gordon, W E; Hedberg, A; Thide, B; Derblom, H; Bostroem, R; Nielsen, E; Stubbe, P; others, and

In September 1983, experiments were conducted in Scandinavia using the high-power heating facility near Tromso-dash-bar, Norway. The purpose of the HF ionospheric modification experiments was to investigate the behavior of artificially produced E region irregularities at auroral latitudes. The majority of observations were made with backscatter radars operating at 46.9 and 143.8 MHz, but limited observations were also made at 21.4 and 140.0 MHz. These radars are sensitive to irregularities having scale lengths of between 1 and 7 m across the geomagnetic field lines. The growth and decay of the irregularities are scale length dependent with the shorter lengths growing and dissipating more rapidly than the longer lengths (e-folding growth times = 10/sup 1/--10/sup 2/ ms; decay times = 10/sup 2/--10/sup 3/ ms). During periods of full power ordinary mode heating, irregularities having peak cross sections of 10/sup 4/ m/sup 2/ at 46.9 MHz and 10/sup 5/ m/sup 2/ at 143.8 MHz are observed. However, the cross sections normally measured are 1 to 2 orders of magnitude smaller than the peak values. The cross sections are nonlinearly dependent on the HF power and begin to saturate at levels greater than 50--75 percent of full power. Past E and F region data from Arecibo are used in conjunction with the Tromso-dash-bar measurements to ascertain the relative roles played by various mechanisms in exciting irregularities. In the E region, the results tend to favor those instability processes which operate at the upper hybrid resonance level (e.g., thermal parametric and resonance instabilities) over those that operate at the reflection level (e.g., parametric decay instability). However, it is likely that anyh of the mechanisms studied could at times contribute to irregularity production in the E regions.

• Research Organization: Department of Space Physics and Astronomy, Rice University, Houston, Texas
• OSTI ID: 5715685
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 92:A12; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
DATA
E REGION
EARTH ATMOSPHERE
ELECTROMAGNETIC FIELDS
ELECTROMAGNETIC RADIATION
ENERGY TRANSFER
EUROPE
EXPERIMENT PLANNING
EXPERIMENTAL DATA
F REGION
GEOGRAPHICAL VARIATIONS
HEAT TRANSFER
HYBRID RESONANCE
INFORMATION
INSTABILITY
IONOSPHERE
LATITUDE EFFECT
MEASURING INSTRUMENTS
NORWAY
NUMERICAL DATA
PARAMETRIC INSTABILITIES
PLANETARY IONOSPHERES
PLANNING
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA SIMULATION
RADAR
RADIANT HEAT TRANSFER
RADIATIONS
RADIOWAVE RADIATION
RANGE FINDERS
RESONANCE
SCANDINAVIA
SIMULATION
VARIATIONS
WAVE PROPAGATION
WESTERN EUROPE