Overview of Infrared Solar Physics

Jefferies, J. T.

doi:10.1007/978-94-011-1926-9_1

Cited by 4 publications

(1 citation statement)

References 16 publications

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“…From the one-year cumulative opacity results we may predict the approximate atmospheric transmission at the upper frequency atmospheric "window" bands at 670 GHz and 850 GHz assuming a proportional attenuation with respect to the 400 GHz band (as shown in [23] for example). We find that for nearly 30% of the total time (i.e., 100 days/year) the opacity will be less than 2.0 Nepers (or % transmission).…”

Section: Discussionmentioning

confidence: 99%

Submillimeter-wave atmospheric transmission at El Leoncito, Argentina Andes

Melo

Kaufmann

Castro

et al. 2005

IEEE Trans. Antennas Propagat.

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We present the results of one year of daytime atmosphere transmission measurements obtained at 212 and 405 GHz by a 1.5 m solar radio telescope located at El Leoncito site, 2550 m altitude in Argentina Andes. We used three different methods: 1) absolute derivation from strong solar signal at different elevation angles; 2) direct derivation from observed known solar brightness times the antenna coupling factor; and 3) fitting the observed sky emission plots as a function of elevation angle, also known as "tipping." Some differences were found for the transmission determined by the three methods, the most important is that methods 1) and 2) are restricted to smaller values of opacity. Method 1) is restricted to measurements at low elevation angles. Method 2) has the advantage to extend measurements to considerably higher values of attenuation. For the El Leoncito site the correlation of optical depth at 405 and 212 GHz was found ( 405 212 ) = 4 43, smaller than model predictions ( 5 0). Measurements at both frequencies obtained for 319 days in one year indicate that 50% of time 212 0 3 (or 74% zenithal transmission) and 405 1 5 (or 22% transmission), with small seasonal dependence compared to other sites. The opacity related precipitable water vapor is smaller compared to model estimates, suggesting an upper atmosphere water vapor depression, characteristic to the region.Index Terms-Atmosphere opacity at submillimeter-wavelengths, methods for atmosphere opacity, passive radiometer sensing of the atmosphere, submillimeter attenuation, submillimeter wavelengths sites.

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Section: Discussionmentioning

confidence: 99%

Submillimeter-wave atmospheric transmission at El Leoncito, Argentina Andes

Melo

Kaufmann

Castro

et al. 2005

IEEE Trans. Antennas Propagat.

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Some Aspects of Polarimetry with LEST

Keller

1994

Solar Surface Magnetism

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Limb observations of He I 1083 nm

Penn¹,

Jones

1996

Sol Phys

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Imaging spectroscopic data of the He i 1083 nm limb emission were taken on several dates in October and November 1995 with the NASA/NSO spectromagnetograph at the NSO/Kitt Peak vacuum telescope and on 9 December, 1993 with the Michigan infrared camera at the NSO/Sacramento Peak vacuum tower telescope. Emission line profiles were observed in quiet-Sun and coronal hole locations on the northern and southern solar poles and on the east solar limb. The height of the He I 1083 nm shell above the continuum limb at 1083 nm was measured to be 2.11 -4-0.12 Mm with the Kitt Peak data, and 1.74 -4-0.05 Mm with the Sacramento Peak data. The Kitt Peak data show (1) within the measurement error there is no significant difference in the height or thickness of the emission shell in coronal holes compared with the quiet Sun, (2) the 1083 nm emission intensity drops by 50% in coronal holes, (3) the line width decreases by about 2 km s -~ in coronal holes (suggesting less inclined spicules), (4) the line width of the He l 1083 nm line jumps significantly as the line of sight crosses the solar limb (consistent with a higher temperature upper shell), (5) a quiescent prominence shows a smaller spectral line width (consistent with a cooler temperature or less velocity broadening), and (6) the entire emission shell and the prominence show a He I spectral component ratio of about 8 (suggesting optically thin emission).

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Overview of Infrared Solar Physics

Cited by 4 publications

References 16 publications

Submillimeter-wave atmospheric transmission at El Leoncito, Argentina Andes

Submillimeter-wave atmospheric transmission at El Leoncito, Argentina Andes

Some Aspects of Polarimetry with LEST

Limb observations of He I 1083 nm

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