Multiple frequency backscatter observations of heater-induced field-aligned striations in the auroral E region

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 1985

OSTI ID:5796807

Noble, S T

In September 1983 a series of HF ionospheric modification experiments were conducted in Scandinavia using the heat facility near Tromosoe Norway. The purpose of these experiments was to examine the mechanisms by which high-power HF radio waves produce geomagnetic field-aligned striations (FAS) in the auroral E region. The vast majority of the backscatter observations were made with radars operating at 47 and 144 MHz (STARE Finland). Additionally, limited observations were conducted at 140 (STARE Norway) and 21 MHz (SAFARI). These radars are sensitive to irregularities having scale lengths between 1 and 7 m across the geomagnetic field lines. During periods of full power O-mode heating, striations having peak cross sections of 40 to 50 dBsm are observed. Striations are not detected during times of X-mode heating. When the heater output is varied, a corresponding change in the cross section is measured. The magnitude of the change is most pronounced for heater level changes in the range 12.5 to 50% of full power. These cross sections are significantly larger than those measured at midlatitudes using the Arecibo heater (approx.10/sup 1/ m/sup 2/). This is consistent with theoretical studies which indicate that it is easier to excite short-scale FAS at places where the geomagnetic dip angle is large. The growth and decay times of the striations are frequency dependent.

• Research Organization: Rice Univ., Houston, TX (USA)
• OSTI ID: 5796807
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
E REGION
HEATING
RADIOWAVE RADIATION
STRIATIONS
FREQUENCY DEPENDENCE
CROSS SECTIONS
GEOMAGNETIC FIELD
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
IONOSPHERE
MAGNETIC FIELDS
PLANETARY IONOSPHERES
RADIATIONS
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena