A Discussion on solar studies with special reference to space observations - A measurement of the brightness temperature of the Sun in the range 65 to 180 cm-1

1971 ◽  
Vol 270 (1202) ◽  
pp. 55-58 ◽  
Keyword(s):  
Brightness Temperature ◽  
Beam Splitter ◽  
Michelson Interferometer ◽  
The Sun ◽  
Temperature Minimum ◽  
Balloon Flight ◽  
Infrared Spectral ◽  
Infrared Wavelengths ◽  
Golay Cell ◽  
Absolute Measurements

The Bilderberg continuum atmosphere (B.c.a.) model of the Sun (Gingerich & de Jager 1968) has a temperature minimum of 4600 K between the photosphere and low chromosphere, which is based mainly on observations in the ultraviolet. This layer of the solar atmosphere is observable in both the ultraviolet and infrared spectral regions. However, at the time that the B.c.a. model was developed, there were no absolute measurements of the brightness temperature between 12 um and 1 mm although there was some evidence to indicate the shape of the expected minimum in this spectral region. Since then several experiments have been performed from aircraft and high altitude balloons with the object of measuring the brightness temperature of the sun at long infrared wavelengths. The measurement described in this paper made use of a Michelson interferometer employing Fourier transform multiplex techniques and was flown from a balloon to a height of 32.6 km from the N.C.A.R. Balloon Flight Station, Texas, U.S.A., in September 1969. The beam splitter consisted of a stretched film of Melinex 8 um thick and the detector used was a Golay cell. Radiation of wavelengths shorter than about 45 um was completely attenuated by optical filtering with black Melinex, polyethylene loaded with a uranium salt and by the quartz window of the detector. The Michelson interferometer was used with a continuous movement of one of its mirrors at 4 pm s-1 and further shortwave attenuation was achieved by suitable electrical filtering of the signal frequencies in the resulting interferogram.

scholarly journals Intensity Simulation of a Fourier Transform Infrared Spectrometer

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1833 ◽  
Author(s):  
Zhuoya Ni ◽  
Qifeng Lu ◽  
Yishu Xu ◽  
Hongyuan Huo
Keyword(s):  
Fourier Transform ◽  
Brightness Temperature ◽  
Michelson Interferometer ◽  
Fourier Transform Infrared ◽  
Core Element ◽  
Simulation Process ◽  
Fourier Transform Infrared Spectrometer ◽  
Infrared Spectrometer ◽  
Input Spectrum ◽  
The Fourier Transform

This paper introduces an intensity simulation for the Fourier transform infrared spectrometer whose core element is the Michelson interferometer to provide support for the on-orbit monitoring of the instrument and to improve the data processing and application of the Fourier transform spectrometer. The Geostationary Interferometric Infrared Imager (GIIRS) aboard on Fengyun-4B (FY-4B) satellite, which will be launched in 2020, aims to provide hyperspectral infrared observations. An intensity simulation of the Michelson interferometer based on the GIIRS’s instrument parameters is systematically analyzed in this paper. Off-axis effects and non-linearity response are two important factors to be considered in this simulation. Off-axis effects mainly cause the wavenumber shift to induce a large brightness temperature error compared with the input spectrum, and the non-linearity response reduces the energy received by the detector. Then, off-axis effects and a non-linearity response are added to the input spectrum successively to obtain the final spectrum. Off-axis correction and non-linearity correction are also developed to give a full simulation process. Comparing the corrected spectrum with the input spectrum, we can see that the brightness temperature errors have a magnitude of 10−3 K, and this fully proves the reliability and rationality of the whole simulation process.

scholarly journals HCl and ClO in activated Arctic air; first retrieved vertical profiles from TELIS submillimetre limb spectra

2012 ◽  
Vol 5 (2) ◽  
pp. 487-500 ◽  
Author(s):  
A. de Lange ◽  
M. Birk ◽  
G. de Lange ◽  
F. Friedl-Vallon ◽  
O. Kiselev ◽  
...  
Keyword(s):  
Michelson Interferometer ◽  
The Arctic ◽  
Optical Absorption Spectroscopy ◽  
Altitude Range ◽  
Balloon Flight ◽  
Total Uncertainty ◽  
Atmospheric Sounding ◽  
Systematic Effects ◽  
Equilibrium Profile ◽  
Peak Value

Abstract. The first profile retrieval results of the Terahertz and submillimeter Limb Sounder (TELIS) balloon instrument are presented. The spectra are recorded during a 13-h balloon flight on 24 January 2010 from Kiruna, Sweden. The TELIS instrument was mounted on the MIPAS-B2 gondola and shared this platform with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the mini-Differential Optical Absorption Spectroscopy (mini-DOAS) instruments. The flight took place within the Arctic vortex at an altitude of ≈34 km in chlorine activated air, and both active (ClO) and inactive chlorine (HCl) were measured over an altitude range of respectively ≈16–32 km and ≈10–32 km. In this altitude range, the increase of ClO concentration levels during sunrise has been recorded with a temporal resolution of one minute. During the daytime equilibrium, a maximum ClO level of 2.1 ± 0.3 ppbv has been observed at an altitude of 23.5 km. This equilibrium profile is validated against the ClO profile by the satellite instrument Microwave Limb Sounder (MLS) aboard EOS Aura. HCl profiles have been determined from two different isotopes – H35Cl and H37Cl – and are also validated against MLS. The precision of all profiles is well below 0.01 ppbv and the overall accuracy is therefore governed by systematic effects. The total uncertainty of these effects is estimated to be maximal 0.3 ppbv for ClO around its peak value at 23.5 km during the daytime equilibrium, and for HCl it ranges from 0.05 to 0.4 ppbv, depending on altitude. In both cases the main uncertainty stems from a largely unknown non-linear response in the detector.

scholarly journals Emission of solar chromospheric and transition region features related to the underlying magnetic field

2018 ◽  
Vol 619 ◽  
pp. A5 ◽  
Author(s):  
K. Barczynski ◽  
H. Peter ◽  
L. P. Chitta ◽  
S. K. Solanki
Keyword(s):  
Magnetic Field ◽  
Transition Region ◽  
Power Law ◽  
Plasma Heating ◽  
Coronal Holes ◽  
Magnetic Flux Density ◽  
The Sun ◽  
Temperature Minimum ◽  
Flux Tubes ◽  
Power Law Index

Context. The emission of the upper atmosphere of the Sun is closely related to magnetic field concentrations at the solar surface. Aims. It is well established that this relation between chromospheric emission and magnetic field is nonlinear. Here we investigate systematically how this relation, characterised by the exponent of a power-law fit, changes through the atmosphere, from the upper photosphere through the temperature minimum region and chromosphere to the transition region. Methods. We used spectral maps from the Interface Region Imaging Spectrograph (IRIS) covering Mg II and its wings, C II, and Si IV together with magnetograms and UV continuum images from the Solar Dynamics Observatory. After a careful alignment of the data we performed a power-law fit for the relation between each pair of observables and determine the power-law index (or exponent) for these. This was done for different spatial resolutions and different features on the Sun. Results. While the correlation between emission and magnetic field drops monotonically with temperature, the power-law index shows a hockey-stick-type variation: from the upper photosphere to the temperature-minimum it drops sharply and then increases through the chromosphere into the transition region. This is even seen through the features of the Mg II line, this is, from k1 to k2 and k3. It is irrespective of spatial resolution or whether we investigate active regions, plage areas, quiet Sun, or coronal holes. Conclusions. In accordance with the general picture of flux–flux relations from the chromosphere to the corona, above the temperature minimum the sensitivity of the emission to the plasma heating increases with temperature. Below the temperature minimum a different mechanism has to govern the opposite trend of the power-law index with temperature. We suggest four possibilities, in other words, a geometric effect of expanding flux tubes filling the available chromospheric volume, the height of formation of the emitted radiation, the dependence on wavelength of the intensity-temperature relationship, and the dependence of the heating of flux tubes on the magnetic flux density.

scholarly journals Observations of Solar Continuum Emission at Decameter Wavelengths

1990 ◽  
Vol 142 ◽  
pp. 513-514
Author(s):  
Ch. V. Sastry
Keyword(s):  
Electron Temperature ◽  
Brightness Temperature ◽  
Large Scale ◽  
Continuum Emission ◽  
The Sun ◽  
Temperature Variations ◽  
One Dimensional ◽  
Wave Radio ◽  
Grating Interferometer ◽  
The Continuum

We observed the continuum emission from the radio sun when there is no burst activity at λ = 8.7 m with the large decameter wave radio telescope at Gauribidanur (Latitude 13° 36‘ 12“ N and 77° 27‘ 07“ E) with a resolution of 26'/40'. A compound grating interferometer with one dimensional resolution of 3' is also used. These observations are made during August 1983 and June 1986. The brightness temperature at the center of the sun varied from 0.2 106 K to 0.8 106 K during these periods on time scales of several hours to a day. Since the sun is absolutely quiet during these periods we believe that the radiation is purely thermal in nature. In this case the observed brightness temperature variations imply large scale density variations by more than a factor of three if the corona is optically thin at these wavelengths. Alternatively if the corona is optically thick the observations imply real electron temperature variations with or without accompanying density variations.

Polarization Beam Splitter Based on a Self-Collimation Michelson Interferometer in a Silicon Photonic Crystal

2012 ◽  
Vol 29 (1) ◽  
pp. 014210 ◽  
Author(s):  
Xi-Yao Chen ◽  
Gui-Min Lin ◽  
Jun-Jun Li ◽  
Xiao-Fu Xu ◽  
Jun-Zhen Jiang ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Beam Splitter ◽  
Michelson Interferometer ◽  
Polarization Beam Splitter ◽  
Silicon Photonic

scholarly journals Study of XUV beam splitter flatness for use on a Michelson interferometer

2004 ◽  
Vol 22 (3) ◽  
pp. 279-284 ◽  
Author(s):  
ANNE-SOPHIE MORLENS ◽  
PHILIPPE ZEITOUN ◽  
LAURENT VANBOSTAL ◽  
PASCAL MERCERE ◽  
GRÉGORY FAIVRE ◽  
...  
Keyword(s):  
Beam Splitter ◽  
Ion Beam ◽  
Michelson Interferometer ◽  
Fourier Transform Spectrometer ◽  
Ion Beam Sputtering ◽  
X Ray ◽  
Interference Fringes ◽  
Beam Sputtering ◽  
20 Nm ◽  
Better Than

A XUV Michelson interferometer has been developed by LIXAM/CEA/LCFIO and has been tested as a Fourier-transform spectrometer for measurement of X-ray laser line shape. The observed strong deformation of the interference fringes limited the interest of such an interferometer for plasma probing. Because the fringe deformation was coming from a distortion of the beam splitter (5 × 5 mm2open aperture, about 150 nm thick), several parameters of the multilayer deposition used for the beam splitter fabrication have been recently optimized. The flatness has been improved from 80 nm rms obtained by using the ion beam sputtering technique, to 20 nm rms by using the magnetron sputtering technique. Over 3 × 3 mm2, the beam splitter has a flatness better than 4 nm rms.

scholarly journals TRIS. I. Absolute Measurements of the Sky Brightness Temperature at 0.6, 0.82, and 2.5 GHz

2008 ◽  
Vol 688 (1) ◽  
pp. 12-23 ◽  
Author(s):  
M. Zannoni ◽  
A. Tartari ◽  
M. Gervasi ◽  
G. Boella ◽  
G. Sironi ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Sky Brightness ◽  
Absolute Measurements

scholarly journals An investigation of radio-frequency radiation from the sun

1948 ◽  
Vol 193 (1032) ◽  
pp. 98-120 ◽  
Keyword(s):  
Solar Radiation ◽  
Radio Frequency ◽  
Random Noise ◽  
Internal Noise ◽  
Black Body ◽  
Local Source ◽  
The Sun ◽  
Radio Frequency Radiation ◽  
Absolute Measurements ◽  
Frequency Radiation

It has been known for some time that the sun emits radio-frequency radiation whose intensity greatly exceeds the value expected from a black-body at 6000°K. In the present paper, experiments are described in which measurements have been made of the solar radiation at frequencies of 175 and 80 Mcyc. /sec. Measurement of the small powers which can be abstracted from practical aerial systems requires special types of receiving equipment if absolute measurements are to be recorded automatically over long periods of time. An apparatus has been developed in which the output power of a local source of random ‘noise’ is automatically and continuously adjusted so as to be equal to the aerial power; in this way the receiver is used only as an indicator of balance, and errors due to variation of its gain or internal noise are eliminated. A special type of aerial has been devised which enables the solar radiation to be recorded separately from the galactic radiation, and so enables continuous observation of the sun to be made with aerials of comparatively low directivity. The results obtained on these two frequencies show that the sun normally emits radiation whose intensity corresponds to a surface temperature of the order of 10 6 °K. Large fluctuations in the intensity occur, however, and during the passage of large sunspots, equivalent temperatures as high as 10 8 to 10 9 °K have been observed. In addition to these day-to-day variations the radiation is subject to sudden brief increases of intensity lasting only for a few seconds. Measurements of the diameter of the source, by a method analogous to Michelson’s stellar interferometer, have shown that during periods of very great intensity the radiation originates in an area of the sun of the same order of size as a sunspot. This result means that equivalent temperatures of 10 9 to 10 10 °K must exist. Measurements of the polarization of the radiation have shown that during periods of increased activity the radiation is mainly circularly polarized. The present account covers the experimental methods and the results obtained up to the present time. It is hoped to consider these results theoretically in a future paper.

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