Polar Mesospheric Waves and Structure

• Main Author: Ulwick, James C.
• Other Authors: UTAH STATE UNIV LOGAN SPACE DYNAMICS LABS
• Format: Text
• Language: English
• Published: 1993
• Subjects: Atmospheric Physics; Electricity and Magnetism; *MESOSPHERE; *ELECTRON DENSITY; POLAR REGIONS; MEASUREMENT; OBSERVATION; TURBULENCE; RADAR; ELECTRONS; LENGTH; ROCKET LAUNCHING; GRAVITY WAVES; ROCKETS; HEIGHT; NORWAY; REFLECTIVITY; WIDTH; ANISOTROPY; ECHOES; SENSITIVITY; POWER SPECTRA; COHERENCE; PROBES; AEROSOLS; MODELS; Norway; Langmuir; Northern Norway
• Online Access: http://www.dtic.mil/docs/citations/ADA265360; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA265360

This report discusses a quantitative comparison of rocket observations of electron density fluctuations and simultaneous 53.5 MHz radar measurements that were obtained during the MAC/SINE campaign in Northern Norway. Two of the three rockets launched during the Turbulence/Gravity Wave salvo were flown during conditions that allowed a detailed investigation. A large part of the data from these rocket flights indicate that the radar reflectivity is about 10 dB enhanced over what would be expected from the rocket observations in the case of isotropic electron density fluctuations. The observations can be reconciled under the assumption of an anisotropic turbulence. Assuming a simple model spectrum for the electron density fluctuations, we derive a relation between the rocket and radar observation that covers the whole range from isotropic turbulent scatter to Fresnel-scatter at horizontal density stratifications. For the observed data set, an anisotropy which typically corresponds to a ratio of horizontal to the vertical coherence length of about 10 is consistent with the comparison of rocket and radar observations. A similar anisotropy is found also from the observed aspect sensitivity of the radar echoes. The variation of the anisotropy with height and time shows an anticorrelation with the turbulence level of the mesosphere as deduced from the spectral width of the radar echoes. The anisotropy is found to maximize in heights where density displays deep 'bite-outs'. These depletion in the electron density were independently observed by a Langmuir and an admittance probe on board the rocket.