Satonori Nozawa

Mean neutral wind velocity vectors observed at auroral E region altitudes by European incoherent scatter radar (EISCAT) for disturbed days are found to be rather similar to the mean wind velocity vectors observed on quiet days. It is demonstrated that the main difference in the E field between quiet and disturbed days is an enhancement in the diurnal component by a factor of 3. The semidiurnal, 6‐, and 8‐hour components display only minor differences. The amplitudes of the tidal components of th

Results are presented of a survey of (C-13)O cloud cores in the Ophiuchus region in the north of the Rho Oph molecular cloud core by using results of a (C-12)O unbiased survey as a guide. Twenty-three (C-13)O clouds and 51 (C-13)O cores are identified. The total mass of the (C-13)O clouds is estimated to be 2000-6000 solar masses, and the typical densities of the (C-13)O cores are around 3000/cu cm. Lists of the physical parameters such as size, mass, average density, etc. are presented for all

Abstract. Ground-based remote sensing of atmospheric parameters is often limited to single station observations by vertical profiles at a certain geographic location. This is a limiting factor for investigating gravity wave dynamics as the spatial information is often missing, e.g., horizontal wavelength, propagation direction or intrinsic frequency. In this study, we present a new retrieval algorithm for multistatic meteor radar networks to obtain tomographic 3-D wind fields within a pre-define

Using MF radar data obtained at Tromsø (69.6°N, 19.2°E) for ∼37 months between 1 November 1998 and 8 December 2001, we have examined characteristics of the quasi 2‐day wave (Q2DW) in the polar mesosphere in the height range from 70 to 91 km. The activity of the Q2DW is higher in winter months (November–February) than in summer months (May–August) over this height region. The maximum values of the amplitude are ∼25 m s −1 in winter and ∼15 m s −1 in summer. Between 70 and 82 km, the amplitude app

On the basis of the data obtained by the European Incoherent Scatter radar located in northern Scandinavia, we have studied E region neutral wind characteristics between 95 and 119 km under geomagnetic quiet conditions ( Ap < 16) over a solar cycle between November 1986 and October 1996. Data of 56 days were analyzed and grouped in order to investigate variations of the wind in different seasons and solar cycle conditions. Seasonal and solar cycle dependences of mean winds as well as diurnal

Abstract. Meteor radars have become widely used instruments to study atmospheric dynamics, particularly in the 70 to 110 km altitude region. These systems have been proven to provide reliable and continuous measurements of horizontal winds in the mesosphere and lower thermosphere. Recently, there have been many attempts to utilize specular and/or transverse scatter meteor measurements to estimate vertical winds and vertical wind variability. In this study we investigate potential biases in verti

A new solid‐state sodium lidar installed at Ramfjordmoen, Tromsø (69.6°N, 19.2°E), started observations of neutral temperature together with sodium density in the mesosphere‐lower thermosphere (MLT) region on 1 October 2010. The new lidar provided temperature data with a time resolution of 10 min and with good quality between ∼80 and ∼105 km from October 2010 to March 2011. This paper aims at introducing the new lidar with its observational results obtained over the first 6 months of observation

Simultaneous European Incoherent Scatter (EISCAT) radar observations using two EISCAT radars, the Tromsø (69.6°N, 19.2°E) UHF radar and the EISCAT Svalbard radar (Longyearbyen, 78.2°N, 16.0°E), were conducted for 8 consecutive days, from 11 to 19 November 2003, to study the lower thermospheric wind dynamics in the polar region. Altitude profiles of the amplitudes of the diurnal and semidiurnal components at Tromsø and Longyearbyen are similar. The semidiurnal amplitudes in the meridional and zon

A comparison of the quasi 2‐day wave (Q2DW) observed at Tromsø (69.6°N, 19.2°E) and Poker Flat (65.2°, 147.6°W) is presented at four heights of 70, 76, 82, and 88 km using wind data taken for ∼4 years, from 1 November 1998 to 7 November 2002. The characteristics of the Q2DW such as seasonal variation, occurrence of period of maximum amplitude, ratio of meridional to zonal amplitudes, shape of altitude profile of phase, and modulation of amplitude at a 4–10 days rate found at Poker Flat are very

A comparative study of the neutral wind in the polar upper mesosphere/lower thermosphere is conducted using two radars, the European Incoherent Scatter (EISCAT) UHF radar (ν = 931 MHz) and the Tromsø MF radar (ν = 2.8 MHz) colocated in northern Scandinavia. Comparisons of winds are made in case studies as well as on a statistical basis. On the basis of simultaneous observations obtained by the two radars, comparisons over a height range from ∼90 to ∼100 km are made for about 20 days between Febr

Characteristics are presented of the lower thermospheric wind from a long run data set obtained by the EISCAT UHF radar at Tromsø (69.6°N, 19.2°E) over ∼23 days, from September 6 to 29, 2005. The derived semidiurnal amplitude exhibited day‐to‐day variations (∼5–30 ms −1 ) at and above 109 km, while the phase varied little with the day. We have found a mode change of the semidiurnal tide occurring during September 17–22, 2005. Between September 6 and 16, the vertical wavelengths were estimated to