Origin of Density Enhancements in the Winter Polar Cap Ionosphere

• Main Authors: Anderson, D. N., Buchau, J., Heelis, R. A.
• Other Authors: AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
• Format: Text
• Language: English
• Published: 1987
• Subjects: Atmospheric Physics; *RADAR REFLECTIONS; *CONVECTION(ATMOSPHERIC); POLAR REGIONS; TIME INTERVALS; REPRINTS; DENSITY; OPTIMIZATION; PLASMAS(PHYSICS); COHERENCE; TIME; VARIATIONS; DRIFT; PARTICLES; WINTER; DARKNESS; TRANSPORT; PATTERNS; IONIZATION; CHARGE TRANSFER; DIFFUSION; INCOHERENT SCATTERING; ENERGETIC PROPERTIES; HIGH LATITUDES; IONOSPHERIC SCINTILLATION; RADIO WAVES; GREENLAND; SOLAR ULTRAVIOLET RADIATION; SIMULATION; IONOSPHERE; THULE(GREENLAND); SONDRESTROM(GREENLAND); PE61102F; WUAFGL2310G9035; Greenland; Thule
• Online Access: http://www.dtic.mil/docs/citations/ADA205704; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA205704

Coherent and incoherent ground-based radar measurements of the winter polar cap ionosphere at Thule and Sondrestrom, Greenland, have established the existence of patches of enhanced ionization which drift across the polar cap in an antisunward, noon-midnight direction. Associated with these patches is strong radio scintillation activity which severely disrupts ground-to-satellite communication systems and interferes with the operation of space surveillance radar at high latitudes. Several recent studies have shown that the source of enhanced ionization is the sunlit sub-cusp ionosphere rather than production by precipitating energetic particles. This problem is studied by solving the time dependent plasma continuity equation including production by solar ultraviolet radiation, loss through charge exchange and transport by diffusion and convection E X B drifts. Time and spatially varying, horizontal E X B drift patterns are imposed and subsequent ionospheric responses are calculated to determine how enhanced plasma densities. In the dark polar cap could result from extended transit of relevant flux tubes through regions of significant solar production. A density enhancement in NMAX from 70,000 to 500,000 el/cu cm occurs at Thule when a time-varying convection pattern is included in the simulation. The patch of ionization is generated when an initial convection pattern characterized by an 80 KV crosstail potential and a 12 polar cap radius is abruptly changed to a 100 KV crosstail potential and a 15 deg polar cap radius. The horizontal extent of the patch is related to the length of time the new convection pattern remains turned-on. Reprints. Pub. in The Effect of the Ionosphere on Communication, Navigation, and Surveillance Systems Based on Ionospheric Effects Symposium p619-657, 5-7 May 1987.