Origin of density enhancements in the winter polar-cap ionosphere

Technical Report · Thu May 07 04:00:00 EDT 1987

OSTI ID:5812614

Anderson, D N; Buchau, J; Heelis, R A

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 that 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 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/degree/ polar cap radius is abruptly changed to a 100-kV crosstail potential and a 15/degree/ polar-cap radius. The horizontal extent of the patch is related to the length of time the new convection pattern remains turned-on.

• Research Organization: Air Force Geophysics Lab., Hanscom AFB, MA (USA)
• OSTI ID: 5812614
• Report Number(s): AD-A-205704/0/XAB; AFGL-TR-88-0251
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGE EXCHANGE
CONVECTION
DIFFUSION
EARTH ATMOSPHERE
ELECTROMAGNETIC RADIATION
ENERGY TRANSFER
GREENLAND
HEAT TRANSFER
INCOHERENT SCATTERING
IONIZATION
IONOSPHERE
MASS TRANSFER
OPTIMIZATION
PARTICLES
PLANETARY IONOSPHERES
PLASMA DENSITY
PLASMA DRIFT
POLAR REGIONS
RADIATIONS
SCATTERING
SCINTILLATIONS
SEASONAL VARIATIONS
SIMULATION
ULTRAVIOLET RADIATION
VARIATIONS