The atmosphere between 85 and 105 km studied by means of radio-echoes from meteor trails
✍ Scribed by I. C. Browne
- Publisher
- John Wiley and Sons
- Year
- 1955
- Tongue
- English
- Weight
- 175 KB
- Volume
- 81
- Category
- Article
- ISSN
- 0035-9009
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✦ Synopsis
Abstract
Meteors falling into the earth's atmosphere produce, by a process which was described briefly, a trail of ionised air. By studying the reflection of radio waves from these trails (‘meteor echoes’) the atmosphere at heights near 95 km can be sampled several hundred times per hour throughout the day, simply and at low cost. The paper summarized results obtained by many workers at Jodrell Bank since 1946 (see references).
The intensities and heights of appearance of meteor echoes lead directly to estimates of air density (about 3 × 10^−9^ g/cm^3^ at 95 km) and of scale height (about 6·5 km at 95 km), while the durations of meteor echoes afford a means of measuring the atmospheric diffusion coefficient. The measurements were compared briefly with independent estimates.
By a special technique, movements of meteor trails of the order of 1 m are detected, and hence winds measured at heights of the order of 95 km. Although ‘winds’ obtained by ionospheric methods may represent travelling disturbances, the ‘meteor’ winds are true mass movements of the air. It is found that there is usually a prevailing wind of the order of 10 m/sec, upon which is superimposed a semi‐diurnal variation which may have an amplitude of 30 m/sec. The phase and amplitude of the semi‐diurnal component show seasonal changes. The winds increase with height, the shear having a value of about 2 × 10^−3^ sec^−1^, a value comparable with that found in the troposphere, although there is no change in wind direction with increasing height. There is no detectable vertical component of wind.