Radio Meteor Research Articles

Deceleration of Radio Meteors.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Deceleration of Radio Meteors. Southworth, Richard B. Abstract Meteors observed with the six-station system of the Harvard Radio Meteor Project show rates of deceleration from 5 to 30 or more km/sec2. Among shower meteors, the first velocity observed for any one meteor is some one to three km/sec below the no-atmosphere velocity. Decelerations of this size are predicted by the classical single-body theory, but are also consistent with fragmentation of the meteoroid. Somewhat less than half of the meteors show evidence of fragmentation; either the Fresnel oscillations damp out faster than they would under diffusion alone, or the ionization curve is irregular. Plasma resonance in the ion column seriously disturbs velocity measures from the Fresnel patterns of meteors of about magnitude 6 or brighter. The average effect, predicted and observed, is a spurious acceleration. Possibly this effect has prevented earlier deceleration measures. Publication: The Astronomical Journal Pub Date: 1962 DOI: 10.1086/108655 Bibcode: 1962AJ.....67S.283S full text sources ADS |

Comments on tidal winds in the high atmosphere

Radio meteor observations have shown the existence of strong semidiurnal tidal winds in the high atmosphere. The accuracy of published tidal-wind determinations is discussed on the basis of computations of the radius of the probable-error circle. It is shown that the strong variations of the tidal winds with the seasons and with elevation may be regarded as real, although their actual magnitude cannot yet be regarded as known reliably. The implications of these variations for the solar air tide are discussed.

Atmospheric tides and ionospheric electrodynamics

A brief review is given of the resonance theory of atmospheric tidal oscillations including both thermal and gravitational excitation. Semiempirical wind patterns for various latitudes are given in Figure 1, and the semiempirical variation of solar semidiurnal wind velocities with height are given in Figure 2, based on (1) solar barometric variations at ground level [Chapman, 1951], (2) wind measurements at balloon heights [Johnson, 1955], (3) radio meteor echo experiments [Greenhow and Neufeld, 1955], (4) E-region winds from radio pulse techniques [Briggs and Spencer, 1954], and (5) airglow cell movements [Roach and others, 1958]. Finally, current work on the extension of modern tidal theory (valid for a neutral envelope) into the dynamo region is discussed [White, in press].

The Harvard radio-meteor program.

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Harvard radio-meteor program. Hawkins, Gerald S. ; Hemenway, Curtis L. ; Whipple, Fred L. Abstract Harvard College Observatory, in conjunction with the Lincoln Laboratory of M.I.T., is embarking on an extensive program for the study of meteors by radar methods. A megawatt transmitter and six receiving stations are being set up in southern Massachusetts to be operated during the International Geophysical Year. The antennae will be broadside arrays each containing approximately 100 dipoles tuned to 32 megacycles and phased to radiate or receive at an elevation of 450 in an easterly direction. The experiment will give information on the radiant, velocity, and deceleration, of individual meteors down to 12th magnitude. In this way accurate orbits will be obtained for both sporadic and stream meteors. With the help of an electronic computer it is hoped to obtain 10,000 accurate orbits, from which we can determine the gross distribution of sporadic orbits and the structure of meteor streams. The orbital distribution will give the rate of meteor influx to the earth's surface as a function of time and location. Echo characteristics will give information on the diffusion of the trail and winds in the upper atmosphere. In addition the echo amplitude will be measured at six points along a meteor trail giving a direct measure of the ionization curve of individual meteors. It is anticipated that these curves will permit the fragmentation process to be studied for radio meteors, which, together with orbital data, should extend our knowledge of the origin of these particles. Harvard College Observatory, Cambridge, Mass. Publication: The Astronomical Journal Pub Date: 1956 DOI: 10.1086/107389 Bibcode: 1956AJ.....61Q.179H full text sources ADS |

Meteor Velocities Determined by Radio Observations.

view Abstract Citations (35) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Meteor Velocities Determined by Radio Observations. McKinley, D. W. R. Abstract The phenomenological theory of radio echoes from meteors is reviewed and extended to show how meteor velocities may be computed from amplitude-time records of meteor echoes. Observational data are presented for 10,933 meteors, based on 847 hours of operation from December,1948, to March, 1950. The average error of a velocity determination was about 5 per cent, and there was no instrumental limitation on the measurement of velocities up to 150 km/sec. A statistical analysis of the observations during the Geminid shower yielded a corrected geocentric Geminid velocity of 34.2 km/sec. An empirical probability function, expressing the rates of radio meteors in terms of the zenith angle of the radiant, is deduced from the Geminid shower data. Using this function, it is shown that reasonable agreement is obtained between the observed distributions of velocities and the distributions predicted by assuming all or nearly all the meteors to be moving in elliptical orbits, more being direct than retrograde, with heliocentric velocities up to 42 km/sec. All the observed geocentric velocities were in the range 1079 km/sec, and only 32 lay in the interval 7579 km/sec. The existence of any appreciable number of interstellar meteors down to the eighth visual magnitude is doubtful. Publication: The Astrophysical Journal Pub Date: March 1951 DOI: 10.1086/145396 Bibcode: 1951ApJ...113..225M full text sources ADS |