Turbulence parameters in the tropo-stratosphere are analyzed using high-resolution balloon temperature measurements collected during the MUTSI (MU radar, Temperature sheets and Interferometry) campaign which took place near the Middle and Upper atmosphere (MU) radar (Japan, 35° N, 136° E) in May 2000. Vertical profiles of the specific dissipation rate of turbulent kinetic energy, ε, and turbulent diffusivity, K, are estimated from the Thorpe lengthscale, L_T. The last is obtained by using two methods. The first one consists of measuring directly L_T by reordering the potential temperature profiles. The second method is based on estimates of the temperature structure constant, C_T². A relationship between L_T and C_T² can be found by assuming either adiabatic vertical displacements or a model based on turbulent energy balance consideration. Analysis shows that the adiabatic assumption gives indirect estimates of L_T more consistent with direct measurements. We also found that vertical profiles of analyzed turbulence characteristics show substantial intermittency, leading to substantial scatter of the local, median and average values. General trends correspond to a decrease in ε and K from the boundary layer up to altitudes 20–25 km. Layers of increased turbulence are systematically observed in the tropo-stratosphere, which may be produced by instabilities of temperature and wind profiles. These maxima may substantially increase local values of turbulence diffusivity. Keywords. Meteorology and atmospheric dynamics (Turbulence)

A source delivering a broad, high current ion beam compatible with both chemically active and inert gases has been developed which gives reliable, long term, maintenance-free operation. It uses a glow discharge with a cold cathode in a magnetic field where a dense uniform plasma is generated in large volumes at low gas pressures. Optimal selection of the electrode configuration and magnetic field ensures operation at pressures lower than 0.1 Pa in pulse–periodic mode (1–10 A discharge current, 1 ms pulse length, 25–50 Hz frequency), and continuous mode (discharge current up to 2 A). The current density of a 15-cm-diam beam can reach 10 mA cm−2 in the former, and 1 mAcm−2 in the latter. Tests with a 50-cm-diam discharge chamber show the uniformity of the ion emission current to be better than ±10%, confirming that the technology is scaleable, and that beams of up to 2000 cm2 cross-sectional area can be obtained without loss of beam uniformity through appropriate design of the extraction system. The source is completely reactive gas-compatible, generating ion beams from oxygen, nitrogen, argon or ionized CH radicals (e.g., using C3H8). Mass-charge beam analysis shows the beams generated to be of high purity (≳99%). Applications include low energy (1–3 keV) ion beam cleaning of glass, ceramic and metal surfaces prior to the deposition of protective and decorative coatings such as TiN and diamondlike carbon, ion beam assisted deposition, and high energy gas ion implantation using, e.g., pulse–periodic beams of ions with energies up to 50 keV.

A statistical procedure is developed to obtain the parameters of spectral harmonics of internal gravity waves (IGW) with horizontal wavelengths larger than ∼ 60 km using measurements of wind velocity in the middle atmosphere from the middle and upper atmosphere (MU) radar. The method is applied to find sets of IGW parameters for the winter and summer seasons of 1987–1988 for 6‐km‐thick layers centered at 70, 75, and 80 km at Shigaraki, Japan (34.9°N, 139.4°E). The numbers of selected IGW harmonics having periods from 5 min up to 6 hours vary between 360 and 2000 depending on the season and altitude. Mean vertical wave numbers are 0.6–0.9 km⁻¹ in winter and 0.5–1 km⁻¹ in summer, and horizontal wave numbers are (3–4)×10⁻² km⁻¹ and (2–4)×10⁻² km⁻¹, respectively. Predominant azimuths of wave vectors and momentum fluxes concentrate near 64° in winter and 90° in summer at all altitudes. In general, the difference between the azimuths of the wave vector and momentum flux is close to zero or 180°. Turbulent and instrumental noise can contribute 20–30% of the observed intensity of the wind variations at altitudes of 70–85 km. The IGW momentum fluxes are 0.2–2.7 m²s⁻² in winter and 0.2–1.9 m²s⁻² in summer. The wave drag of the mean flow is 0.5–45 m²s⁻¹ in winter and 2–25 m²s⁻¹ in summer. In most cases the momentum flux and wave drag are directed oppositely to the mean wind.