| 释义 |
riometer Geophysics.|riːˈɒmɪtə(r), ˈraɪəʊmiːtə(r)|
[f. the initial letters of relative ionospheric opacity + -meter.]
An instrument which permits continuous measurement of the absorption of cosmic radio waves by the ionosphere.
1959Little & Leinbach in Proc. IRE XLVII. 315/2 Thirteen of the commercially built units, now called ‘riometers’ (Relative Ionospheric Opacity Meters) are currently in use... The riometer is a self-balancing receiving system in which a local noise source is continuously made equal to the noise power from the antenna. 1968G. M. B. Dobson Explor. Atmos. (ed. 2) viii. 151 An entirely different method which is now being much used is to measure the intensity of cosmic radio waves which are constantly reaching the earth from the galaxy. These radio waves will be absorbed as they come down through the D region, so that low intensity of cosmic radio waves received at the ground means strong absorption by the D region. These instruments are generally known as riometers. 1972Nature 28 Jan. 215/1 Ground based observations using a 27 MHz riometer and an H magnetometer indicated almost quiet ionospheric conditions. 1980Ibid. 17 Jan. 278/2 The Siple riometer operates at 30 MHz and has a response time of 0.25 s to increases or decreases in signal intensity. |