Accession Number : ADA309841

Title :   Study of Equatorial Clutter Using Observed and Simulated Long Range Backscatter Ionograms.

Descriptive Note : Interim rept.,

Corporate Author : PHILLIPS LAB HANSCOM AFB MA

Personal Author(s) : Dandekar, B. S.

PDF Url : ADA309841

Report Date : 29 AUG 1995

Pagination or Media Count : 72

Abstract : This synoptic study of equatorial clutter used over 6200 long range (8000 nmi) backscatter ionograms from the East Coast Radar System at Bangor, ME, obtained from 1100 to 0600 Local Time during the 22 month period from October 1991 to July 1993 Data were collected in five 7.5 deg width azimuthal sectors (radar beams 1-6, 1-8, 2-4, 2-8 and 3-5) from 58 to 170 deg. T. The backscatter clutter signatures can be identified with an equatorial clutter region covering a dip latitude range of +/- 40 deg. Equatorial clutter typically begins after sunset and continues through midnight, with a minimum of activity between 1700 and 2200 LT. The clutter range shows some dependence on solar activity with a reduction in range from the radar during low solar activity periods. These data did not show any dependence of clutter on operating frequency or on magnetic activity. Synthetic backscatter ionograms were generated using the Parameterized Ionospheric Model developed by Anderson at Phillips Laboratory, with the raytrace technique of Jones and Stephenson. The analysis shows that the equatorial dome of the ionosphere favors the chordal mode of reflection from the south side of the dome, which produces horizontal traces as clutter signatures on the backscatter ionograms. The reduction in range at low solar activity is associated with the lowering of the mean height of the ionospheric dome. In beams 2-8 and 3-5 the ionospheric dome structure is associated with the equatorial (Appleton) anomaly. This dome structure geometry favors the chordal mode of reflection.

Descriptors :   *IONOSPHERIC MODELS, *OVER THE HORIZON RADAR, EQUATORIAL REGIONS, MAGNETIC FIELDS, COASTAL REGIONS, BACKSCATTERING, RADAR CLUTTER, SOLAR ACTIVITY, RAY TRACING, RADAR SIGNATURES, DIURNAL VARIATIONS, IONOGRAMS.

Subject Categories : Active & Passive Radar Detection & Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE