Rocket measurements of positive ions during polar mesosphere winter echo conditions

[摘要] On 18 January 2005, two small, instrumented rockets were launchedfrom Andøya Rocket Range (69.3° N, 16° E) duringconditions with Polar Mesosphere Winter Echoes (PMWE).Each of therockets was equipped with a Positive Ion Probe (PIP) and a Faradayrotation/differential absorption experiment, and was launched aspart of a salvo of meteorological rockets measuring temperature andwind using falling spheres and chaff.Layers of PMWE were detectedbetween 55 and 77 km by the 53.5 MHz ALWIN radar.The rockets werelaunched during a solar proton event, and measured extremely highion densities, of order 10¹⁰ m⁻³, in the region where PMWEwere observed.The density measurements were analyzed with thewavelet transform technique.At large length scales, ~10³ m,the power spectral density can be fitted with a k⁻³ wave numberdependence, consistent with saturated gravity waves.Outside the PMWE layers the k⁻³ spectrum extends down toapproximately 10² m where the fluctuations are quickly damped anddisappear into the instrumental noise.Inside the PMWE layers thespectrum at smaller length scales is well fitted with a k^−5/3dependence over two decades of scales.The PMWE are thereforeclearly indicative of turbulence, and the data are consistent withthe turbulent dissipation of breaking gravity waves.We estimate alower limit for the turbulent energy dissipation rate of about10⁻² W/kg in the upper (72 km) layer.

[学科分类] 大气科学