The relation between group path and polarization rotation

Epstein, M.

doi:10.1016/0021-9169(68)90104-9

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…Results of the two receiver experiment. rate of polarization rotation with frequency is proportional to the group propagation time difference between the magnetoionic components [Epstein, 1968b]. Thus the experimental results indicate that, as the radio frequency increases, the two magneto-.ionic components become closer together in relative time delay, cross, and then separate again.…”

Section: Experimental Arrangementsmentioning

confidence: 78%

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

Epstein¹

1969

Radio Science

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Sweep-frequency CW radio signals transmitted over 1300-kin north-south and 1900-km east-west temperate-zone paths were received 24 hours per day for 2•-day periods. Measurements of the incoming one-hop F-layer polarization, as a function of time-of-day and radio frequency, indicate that daytime rates of change of polarization rotation with frequency (at an instant of time) average 1 turn/MI-Iz over the north-south path and 0.25 turn/MHz over the east-west path. These values are in good agreement with computer raytracing predictions of the rates of change of polarization rotation with frequency over similarly disposed paths. It was observed that nighttime polarization rotation rates are about 1 to 4 times as high as those measured during the day. It was also experimentally found that the rate of change of the incoming polarization with frequency first decreased and then increased with incoming radio frequency, the minimum rate occurring near 0.8 MOF0. Daytime rates of polarization rotation with time (at a given frequency) average 0.25 turn/min. The polarization rotation rates with time do not appear to vary either with path azimuth or transmitted radio frequency. Near-zero rates of polarization rotation with time occur for much of the nighttime period. Large fluctuations in the polarization variations occur with both time and frequency throughout the day.Polarization measurements made with signals that were reflected from a nonblanketing, nighttime sporadic E layer of about two hours duration indicate that, for this layer, circumstances other than polarization effects, probably multipath, determine much of the observed signal strength variations with frequency and time.The results suggest that for round-the-clock temperate zone propagation, when linearly polarized antennas are employed, a qualitative threshold for envelope distortion of broadband signals (due to variation in the incoming polarization with frequency) occurs when signal bandwidths exceed appro,rAmately 100 kHz for north-south paths and 400 kHz for east-west paths. The effects of such distortion may be reduced either by operating near 0.8 MOF0 or by the use of circularly polarized antennas.

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Section: Experimental Arrangementsmentioning

confidence: 78%

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

Epstein¹

1969

Radio Science

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Commission 3: Progress in Ionospheric Radio

Villard¹,

Aarons²,

Bibl³

et al. 1969

Radio Science

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The major advances in our understanding of the morphology of the D region in the last three years have come about through the application of rocket techniques. A series of rocket measurements carried out at Wallops Island [Mechtly and Smith, 1968a] at different seasons but at roughly the same solar zenith angle have shown the principal features of the seasonal variation in the electron density profile between 50 and 100 km. It appears that electron densities are lower by a factor of about 3 below 82 km on ‘normal’ winter days as compared with summer days for a solar zenith angle of 60°. The anomalous winter days of high absorption have been the subject of a separate rocket investigation [Sechrist et al., 1969], which has shown that the electron density profile is remarkably similar to that of a normal summer day and that in at least one case was associated with a pronounced temperature inversion near 70 km.

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The relation between group path and polarization rotation

Cited by 2 publications

References 6 publications

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

Commission 3: Progress in Ionospheric Radio

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