ISSN:0048-6604    

DOI:10.1029/RS009i002p00075

年代:1974

数据来源: WILEY

摘要:

The original Nançay‐St. Santin incoherent scatter facility based on the radio astronomy antenna at Nançay and a CW transmitter located at St. Santin (300 km south) was improved in many ways between 1965 and 1970: doubling of the transmitted power to 140 kw, lowering of the receiver noise level down to 100 K, monitoring of the antenna and data acquisition through the use of a computer, rejection of the parasitic tropospheric echoes.However, the most important improvement brought to the system is the addition of two new receiving stations 100 km east and west of the transmitter. Each of the new stations is equipped with a three‐beam Cassegrain antenna (25‐m parabola) aimed to simultaneously intersect the vertical transmitted beam at three different heights. Both new receivers have wide band (38 MHz at 3 db) gaseous helium cooled parametric amplifiers and on‐line computers. While one of the two new stations is equipped with filter banks for the purpose of spectral analysis, a different choice has been made for the other station. For the latter the data acquisition will imply multibit correlators, for both the ionic spectrum and plasma line measurements.Most of the improved electronic equipment designed for the new stations has also been implemented in the Nançay receiver. The frequency and time synchronization between the four sites is now accomplished by employing a single 5‐MHz frequency standard in each station monitored by standard time and frequency signals from MSF and/or HBG stations.The observation procedure consists of tilting the different receiving antennas so as to gather the signal scattered from the ionospheric vertical column illuminated by the transmitter. For calibration purposes a standard ionosonde is operating at St. Santin.The main objective of the quadristatic system is to determine completely the ion drift vector in order to study the electric fields and the neutral tidal winds. Other capabilities offered by the new system are a determination of the plasma line and a higher data acquisition rate.The first observations with one of the new stations were performed in D

ISSN:0048-6604    

DOI:10.1029/RS009i002p00077

年代:1974

数据来源: WILEY

摘要:

The UK incoherent scatter system operates in two modes. The monostatic pulsed system has been in operation since 1968, and a summary of the results obtained in this mode is given. The full multistatic CW system has been operating since September 1972 and among the preliminary results are measurements of the total vector of velocity drift.

ISSN:0048-6604    

DOI:10.1029/RS009i002p00085

年代:1974

数据来源: WILEY

摘要:

An observation scheme is described in which it is possible to measure the three velocity components of plasma drift in the ionosphere by using a single monostatic incoherent scatter facility with a steerable antenna. The scheme involves a least‐mean‐squares fitting of the line‐of‐sight velocity observed in several different directions to what one would compute from a given set of three orthogonal velocity components. The method is applied to data gathered at the Arecibo Observatory and is shown to be capable of providing velocity information with rms errors of better than 10 m sec−1for all three components with a time resolution

ISSN:0048-6604    

DOI:10.1029/RS009i002p00089

年代:1974

数据来源: WILEY

摘要:

A new large incoherent scatter radar system has been proposed as the principal element in a binational center for studies of the upper atmosphere. The radar has been designed to yield a sensitivity comparable to the best now available and yet provide a latitude coverage of theFregion of ±13°.The radar shall comprise a 100‐m diameter parabolic reflector antenna that can be tilted in the magnetic meridian plane by ±85° from the zenith. This antenna will be coupled to a UHF pulse transmitter with a peak power of 10 Mw, and will serve for both transmitting and receiving. Two auxiliary fully steerable antennas will be located northeast and northwest of the main antenna and will also receive the signals. This will enable the velocity of the ion drift to be studied, permitting measurements of neutral winds, electric fields, and fluxes of ions into or from the magnetosphere. The auxiliary antennas will form 10 coplanar pencil beams, so that these drift measurements may be made at 10 heights simultaneously.The paper describes how the above concept was developed and the work of selecting a site for the radar. By locating the main station nearL= 4, and the auxiliary stations about 550 km distant, it will be possible to measure the electric fields in theFregion over the range 3 ≤L≤ 8 to an accuracy of ±2 mv m−1. Thus, the radar should be able to map the electric fields produced by substorms at auroral and subauroral latitudes. In addition, the properties of the ionosphere and many parameters of the atmosphere will be determined over the altitude range 10

ISSN:0048-6604    

DOI:10.1029/RS009i002p00095

年代:1974

数据来源: WILEY

摘要:

EISCAT is a project presented by scientists from Finland, France, Germany, Norway, Sweden, and the United Kingdom for establishing a new incoherent scatter facility in the northern part of Scandinavia. The initial constraints and choices introduced by the scientific purpose of high latitude ionospheric studies are recalled and the general characteristics of the facility are described. The facility involves a multistatic system in the UHF range and a monostatic system in the VHF range. Tromsø, Norway, at a geomagnetic latitude corresponding toL= 6.3 at the ground, is the main axis of the measurements. Remote stations are located at Kiruna, Sweden, and Sodankyla, Finland. Some design concepts related to the capabilities of pulse‐coded modulation of a powerful UHF transmitter and others related to new types of receiving antennas are described. The expected performance of the facility is evaluated and compared with desirable performance criteria and with those of other existing or proposed faciliti

ISSN:0048-6604    

DOI:10.1029/RS009i002p00113

年代:1974

数据来源: WILEY

摘要:

The present understanding of the ionization processes, and of the positive and negative ion chemistry of theDregion, is reviewed with particular attention being given to outstanding problems.Rocket‐borne mass spectrometer observations carried out in the past decade have shown that the change in positive ion composition with height (from NO+, O2+and metallic ions above to water cluster ions H+· (H2O)nbelow) is a general feature of theDregion at all latitudes and under all geophysical conditions. Furthermore, these observations indicate that this change occurs over a very small range of heights, between 82 and 86 km under normal conditions and at lower heights during auroral or Polar Cap Absorption conditions. These results are discussed in terms of current ideas concerning the formation of water cluster ions from O2+and NO+ions.Mass spectrometer observations by two experimental groups have provided conflicting results concerning the negative ion composition in theDregion and cannot be used to test theoretical models. Such models have been derived from laboratory measurements, and involve reaction schemes leading from O2−ions, formed by electron attachment, to ions O3−, O4−, CO3−, CO4−, NO2−and NO3−. The effect on these models of including recent laboratory measurements of negative ion hydration is considered, and the importance of photodetachment i

ISSN:0048-6604    

DOI:10.1029/RS009i002p00121

年代:1974

数据来源: WILEY

摘要:

This paper reviews the ground‐based and rocket techniques that are presently being used to determine electron density profiles in the ionosphericDregion. Ground‐based techniques include VLF, LF, and MF sounding, differential absorption and differential phase using partial reflections, wave interaction, and incoherent scatter. Rocket techniques include differential absorption and Faraday rotation in association with high‐resolution dc probes calibrated by means of the radio measurements. The characteristics of the aforementioned techniques are presented, including time and height resolution, accuracy estimates, preferred height ranges, and problems encountered. Electron density profiles obtained with these techniques are presented for comparable solar zenith angles and undisturbed solar and geophysical conditions, and variances are desc

ISSN:0048-6604    

DOI:10.1029/RS009i002p00137

年代:1974

数据来源: WILEY

摘要:

D‐region electron densities have been measured with a height resolution of less than 1 km using the incoherent scatter technique with coded pulses. Using a theoretical production model and the measured densities, recombination coefficients were computed for the altitude range from 80 to 95 km. The effective recombination coefficient decreases across theD‐region ledge from a value of about 2 × 10−5cm3sec−1below the ledge to a value of the order of 1 to 5 × 10−7above. The change is presumably due to a transition from water cluster ions to the molecular ions

ISSN:0048-6604    

DOI:10.1029/RS009i002p00151

年代:1974

数据来源: WILEY

摘要:

A review of physical and chemical processes in theEregion is given with emphasis on the absolute ionization balance and relative ion composition. The importance of transport processes in the nighttimeEregion is emphasized. It is concluded that the electron, ion, and neutral gases are in thermal equilibrium.

ISSN:0048-6604    

DOI:10.1029/RS009i002p00159

年代:1974

数据来源: WILEY