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Observations of the continuum emission from Venus, Mars, Jupiter and Saturn at 21.2 cm wavelength

1966; Elsevier BV; Volume: 14; Issue: 1 Linguagem: Inglês

10.1016/0032-0633(66)90056-0

1873-5088

R. D. Davies, D. J. Williams,

Astro and Planetary Science

The planet Venus was investigated at 21.2 cm wavelength during closest approach in 1962 and was found to have a brightness temperature of 591±30°K; this error includes a 5 per cent calibration uncertainty. The brightness temperature of Venus does not vary significantly over the wavelength range 3–21 cm which appears to indicate that this radiation comes from the surface of the planet. The amplitude of the phase effect of Venus at 21.2 cm was <12°K and this has been compared with observations at shorter wavelengths of both Venus and the Moon. Measurements of Mars in 1963 and 1965 showed an effective brightness temperature of 271±76°K at 21·2 cm which is a value similar to that found at shorter radio wavelengths and in the infrared. The 21.2 cm emission from Jupiter showed a variation with system III longitude of intensity polarized parallel to position angle 0°. This indicated that the beaming of the radiation in magnetic latitude varied as (cosine)6.3±1.0, the inclination of the magnetic axis to the rotational axis was 12.5±1.2° and the percentage polarization was 31.6±1.6 per cent. Comparison with data obtained in 1959 by McClain, Nichols and Waak led to a rotation period for the 21.2 cm radiation of 9h 55m 29s. 50±0s. 29 which is in close agreement with the period of the decametre radiation. No variation with solar activity of the polarized or unpolarized flux of Jupiter was detected. The effective brightness temperature of Saturn was measured to be 286±37°K. This value when taken with measurements at shorter wavelengths shows that the suprathermal component has a brightness temperature spectrum proportional to л2.2±0.5. Possible emission mechanisms are discussed briefly. ПлaNeтa BeNera иssлeдoBaлasь Na длиNe BoлNы 21.2 sM Bo BreMя ee Naибoльщeгo пrиближeNия к зeMлe B 1962 г., пrиШeM былo usтaNoBлeNo, Штo ee яrкosтNaя тeMпeraтura raBNялasь 591±30°К; B этu oшибкu Bчoдит пятипroцeNтNaя кaлибroBкa NeтoШNosти. ЯrкosтNaя тeMпeraтura BeNerы Ne пoдBerгaeтsя зNaШитeльNыM изMeNeияM Bдoль длиNы BoлNы диaпaзoNoM 3–21 sM и этo пoBидиMoMu uкaзыBaeт Na тo, Штo тaкoe излuШeNиe иsчoдит oт пoBerчNosти плaNeты. aMплитuдa эффeктa фaзы BeNerы Na 21.2 sM былa <12°К и этo soпosтaBляeтsя s NaблюдeNияMи Na бoлee кoroткич BoлNaч, кaк BeNerы, тaк и ЛuNы. ИзMereNия Marsa B 1963 и 1965 гг. пoкaзaли эффeктиBNuю яrкosтNuю тeMпeraтuru B 271±76°К Na 21.2 sM—зNaШeNиe sчoдNoe s тeM, кoтoroe былo oбиaruжeNo Na бoлee кoroткич BoлNaч B иNфraкrasNыч лuШaч. 21.2 sM излuШeNиe Юпитera oбNaruжилo rasчoждeNиe s sиsтeMoй III B пroдoл-житeльNosти иNтeNsиBNosти, пoляrизoBaNNoй пaraллeльNo пoлoжeNию uглa 0°. Этo пoкaзaлo, Штo NaпraBлeNиe излuШeNия B MaгNитNoй шиroтe изMeNяeтsя sooтBeтsтBeNNo (кosиNus)6.3±1.0; NaклoN MaгNитNoй osи к roтaциoNNoй osи был 12.5± 1.2°, тoгдa кaк пroцeNт пoляrизaции raBNялsя 31.6±1.6%. soпosтaBлeNиe s дaNNыMи, пoлuШeNNыMи B 1959г. MaклзйNoM, NикoльsoM и BaaкoM, пrиBeлo к roтaциoNNoMu пerиoдu для излuШeNия 21.2 sM B 9 Ш. 55 MиN. 29 s.50±s.29, Штo тesNo soглasueтsя s пerиoдoM дeкaMeтroBoй raдиaции. Nикaкoгo изMeNeNия пoляrизoBaиNoгo или NeпoляrизoBaNNoгo пoтoкa uпитera, пrи soлNeШNoй aктиBNosти, зaMeШeNo Ne былo. ИзMereNия эффeктиBNoй яrкosтNoй тeMпeraтurы saтurNa Bыraзилиsь B 286±37°К. Этo зNaШeNиe, Bзятoe soBMesтNo s изMereNияMи Na бoлee кoroткич BoлNaч, пoкaзыBaeт, Штo sBerчтeплoBaя sosтaBляющaя иMeeт sпeктr яrкosтNoй тeMпeraтurы пroпorциoNaльNый л2.2±0.5. Bкraтцe oбsuждaютsя BoзMoжNыe MeчaNизMы излuШeNия.