Brightness temperatures and intensity measurements in flash discharges

1961 ◽  
Vol 262 (1310) ◽  
pp. 409-419 ◽  
Keyword(s):  
Brightness Temperature ◽  
Wavelength Range ◽  
Intensity Distribution ◽  
Wave Number ◽  
Brightness Temperatures ◽  
Intensity Measurements ◽  
Capillary Type ◽  
Standard Lamp ◽  
The Continuum

The brightness temperature and the intensity distribution of the Lyman, coaxial and capillary-type flash tubes have been measured and compared over the wavelength range from 2580 to 4520 Å. The brightness temperature, obtained by comparison with a standard lamp, for these flash tubes ranged from 13 000 to 30 000 °K. The intensity per unit wave number was found to be independent of wave number over the above range for the Lyman and coaxial tubes. For the capillary flash the region independent of wave number extended up to 31 000 cm -1 beyond which the continuum decreased exponentially, in agreement with the predictions of the Unsöld-Kramers theory.

INFLUENCE OF REGULARITY OF SATELLITE MICROWAVE RADIOMETER MEASUREMENTS ON THE ACCURACY OF BRIGHTNESS TEMPERATURE REPRODUCTION IN AREAS OF THE TROPICAL CYCLONES

2021 ◽  
pp. 78-85
Author(s):  
А. G. Grankov ◽  
◽  
А. А. Milshin ◽  
Keyword(s):  
Brightness Temperature ◽  
Tropical Cyclones ◽  
Microwave Radiometer ◽  
Measurement Data ◽  
Hurricane Wilma ◽  
Brightness Temperatures ◽  
Atmosphere System ◽  
Ocean Atmosphere ◽  
The Caribbean ◽  
Satellite Microwave

An accuracy of reproduction of daily variations in the ocean–atmosphere system brightness temperature in the areas of development and movement of tropical hurricanes in the Caribbean Sea and Gulf of Mexico is analyzed. The analysis is based on the data of single and group satellite microwave radiometer measurements. The results are obtained using archival measurement data of SSM/I radiometers from the F11, F13, F14, and F15 DMSP satellites during the period of existence of tropical hurricanes Bret and Wilma. An example is given to demonstrate the use of daily brightness temperatures obtained from DMSP satellites for monitoring the development and propagation of hurricane Wilma.

scholarly journals Comparison of SMMR and SSM/I passive microwave data collected over Antarctica

1993 ◽  
Vol 17 ◽  
pp. 131-136 ◽  
Author(s):  
Kenneth C. Jezek ◽  
Carolyn J. Merry ◽  
Don J. Cavalieri
Keyword(s):  
Brightness Temperature ◽  
Microwave Radiometer ◽  
Correlated Data ◽  
Data Sets ◽  
Microwave Brightness Temperature ◽  
Brightness Temperatures ◽  
Scatter Plots ◽  
Microwave Imager ◽  
Highly Correlated ◽  
The Antarctic

Spaceborne data are becoming sufficiently extensive spatially and sufficiently lengthy over time to provide important gauges of global change. There is a potentially long record of microwave brightness temperature from NASA's Scanning Multichannel Microwave Radiometer (SMMR), followed by the Navy's Special Sensor Microwave Imager (SSM/I). Thus it is natural to combine data from successive satellite programs into a single, long record. To do this, we compare brightness temperature data collected during the brief overlap period (7 July-20 August 1987) of SMMR and SSM/I. Only data collected over the Antarctic ice sheet are used to limit spatial and temporal complications associated with the open ocean and sea ice. Linear regressions are computed from scatter plots of complementary pairs of channels from each sensor revealing highly correlated data sets, supporting the argument that there are important relative calibration differences between the two instruments. The calibration scheme was applied to a set of average monthly brightness temperatures for a sector of East Antarctica.

scholarly journals Combined SMAP–SMOS thin sea ice thickness retrieval

2019 ◽  
Vol 13 (2) ◽  
pp. 675-691 ◽  
Author(s):  
Cătălin Paţilea ◽  
Georg Heygster ◽  
Marcus Huntemann ◽  
Gunnar Spreen
Keyword(s):  
Soil Moisture ◽  
Sea Ice ◽  
Brightness Temperature ◽  
Incidence Angle ◽  
Data Availability ◽  
Ice Thickness ◽  
Polar Regions ◽  
Sea Ice Thickness ◽  
Brightness Temperatures ◽  
Spatial Coverage

Abstract. The spaceborne passive microwave sensors Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) provide brightness temperature data in the L band (1.4 GHz). At this low frequency the atmosphere is close to transparent and in polar regions the thickness of thin sea ice can be derived. SMOS measurements cover a large incidence angle range, whereas SMAP observes at a fixed 40∘ incidence angle. By using brightness temperatures at a fixed incidence angle obtained directly (SMAP), or through interpolation (SMOS), thin sea ice thickness retrieval is more consistent as the incidence angle effects do not have to be taken into account. Here we transfer a retrieval algorithm for the thickness of thin sea ice (up to 50 cm) from SMOS data at 40 to 50∘ incidence angle to the fixed incidence angle of SMAP. The SMOS brightness temperatures (TBs) at a given incidence angle are estimated using empirical fit functions. SMAP TBs are calibrated to SMOS to provide a merged SMOS–SMAP sea ice thickness product. The new merged SMOS–SMAP thin ice thickness product was improved upon in several ways compared to previous thin ice thickness retrievals. (i) The combined product provides a better temporal and spatial coverage of the polar regions due to the usage of two sensors. (ii) The radio frequency interference (RFI) filtering method was improved, which results in higher data availability over both ocean and sea ice areas. (iii) For the intercalibration between SMOS and SMAP brightness temperatures the root mean square difference (RMSD) was reduced by 30 % relative to a prior attempt. (iv) The algorithm presented here allows also for separate retrieval from any of the two sensors, which makes the ice thickness dataset more resistant against failure of one of the sensors. A new way to estimate the uncertainty of ice thickness retrieval was implemented, which is based on the brightness temperature sensitivities.

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.

A Gyro-Synchrotron Maser in the Solar Corona?

1978 ◽  
Vol 3 (3) ◽  
pp. 231-233 ◽  
Author(s):  
D. B. Melrose ◽  
S. M. White
Keyword(s):  
Synchrotron Radiation ◽  
Solar Corona ◽  
Brightness Temperature ◽  
Early Phase ◽  
Relativistic Electrons ◽  
High Brightness ◽  
Brightness Temperatures ◽  
Type Iv ◽  
Alternative Suggestion ◽  
Lower Frequencies

Stewart (1978) has reported four moving type IV bursts observed with the Culgoora radio heliograph at 43, 80 and 160 MHz. After an early phase, the brightness temperatures of the observed bursts decreased with increasing frequency and with time. The highest brightness temperature observed at 43 MHz was 1010K, and it seems that the brightness temperature would have been still higher at even lower frequencies. Existing theoretical ideas on moving type IV bursts are based on data (at 80 MHz primarily) which included no brightness temperatures in excess of 109K. the accepted interpretation involved gyro-synchrotron radiation from mildly relativistic electrons (energies ≈ 100 keV); reabsorption by the electrons themselves restricts the brightness temperature to less than about 100 keV ≈ 109K (Wild and Smerd 1972, Dulk 1973). Stewart’s (1978) new data at 43 MHz require that this accepted interpretation be modified; he has suggested that higher energy electrons are involved. An alternative suggestion is explored here, namely that the absorption might be negative. In other words, the high brightness temperatures observed could be due to a gyro-synchrotron maser involving electrons with energies of about 100 keV.

scholarly journals The stellar temperature scale from O5 to A0

1970 ◽  
Vol 36 ◽  
pp. 83-89 ◽  
Author(s):  
D.S. Hayes
Keyword(s):  
Wavelength Range ◽  
Temperature Scale ◽  
B Stars ◽  
Stellar Temperature ◽  
The Continuum

An absolute spectrophotometric calibration of Vega and eleven other standard stars was completed by the author in 1967. This calibration extends from 3200 to 10870 Å, and therefore gives a useful calibration of the Paschen discontinuity as well as the Balmer discontinuity, for which calibrations have been available for some time.The measured values of the ratio of the size of the Paschen discontinuity to the size of the Balmer discontinuity have been compared with corresponding values predicted by model atmospheres. The comparison shows that LTE models satisfactorily predict the continuum in the wavelength range given above.A stellar temperature scale has been determined by fitting the measured sizes of the Balmer discontinuity of 43 stars to blanketed model atmospheres. This temperature scale agrees very well with Morton's modified form of the Morton-Adams temperature scale for all except the latest B-stars, for which higher temperatures are predicted.

scholarly journals Spectroscopic Observations of Be Stars Especially in the Infrared

1982 ◽  
Vol 98 ◽  
pp. 211-228
Author(s):  
L. Houziaux ◽  
Y. Andrillat
Keyword(s):  
Wavelength Range ◽  
Be Stars ◽  
Frequency Range ◽  
Infrared Wavelength ◽  
Spectroscopic Observations ◽  
The Continuum

Since the time of I.A.U. Colloquium n° 70, new data have been obtained in the infrared, far less however than in the ultraviolet or in the visible. Few line spectra have been recorded but numerous results have been published in the field of spectrometry of the continuum. It is however neither easy nor very useful to report on the infrared wavelength range alone, and therefore we shall consider when appropriate other spectral regions in this review. After all, the astrophysicist nowadays has the advantage to seek for information in a spectrum which encompasses a fantastic frequency range of about 10 dex, from ν = 108s−1 up to ν = 1018s−1. This means that a contemporary astronomer will have to become familiar with a somewhat larger span of phenomena than with the rather narrow one he has been accustomed to for the last 40 or 50 years.

scholarly journals Climatology of Passive Microwave Brightness Temperatures in Tropical Cyclones and their Relations to Storm Intensities as Seen by FY-3B/MWRI

2020 ◽  
Vol 12 (1) ◽  
pp. 147
Author(s):  
Bo Qian ◽  
Haiyan Jiang ◽  
Fuzhong Weng ◽  
Ying Wu
Keyword(s):  
Brightness Temperature ◽  
Tropical Cyclones ◽  
Inner Core ◽  
Surface Wind ◽  
Radial Distance ◽  
Estimation Algorithm ◽  
Passive Microwave ◽  
Intensity Estimation ◽  
Brightness Temperatures ◽  
Dependent Samples

A new database, the tropical cyclones passive microwave brightness temperature (TCsBT) database including 6273 overpasses of 503 tropical cyclones (TC) was established from 6-year (2011–2016) Fengyun-3B (FY-3B) Microwave Radiation Imager (MWRI) Level-1 brightness temperature (TB) data and TC best-track data. An algorithm to estimate the TC intensity is developed using MWRI TB’s from the database. The relationship between microwave TB and the maximum sustained surface wind (Vmax) of TCs is derived from the TCsBT database. A high correlation coefficient between MWRI channel TB and Vmax is found at the radial distance 50–100 km near the TC inner core. Brightness temperatures at 10.65, 18.70, 23.8, and 36.5 GHz increase but 89 GHz TB’s and polarization corrected TB at 36.5 GHz (PCT36.50) and PCT89 decrease with increasing TC intensity. The TCsBT database is further separated into the 5063 dependent samples (2010–2015) for the development of the TC intensity estimation algorithm and 1210 independent samples (2016) for algorithm verification. The stepwise regression method is used to select the optimal combination of storm intensity estimation variables from 12 candidate variables and four parameters (10.65h, 23.80v, 89.00v and PCT36.50) were selected for multiple regression models development. Among the four predictors, PCT36.50 contributes the most in estimating TC intensity. In addition, the errors are lower for estimating 6-h and 12-h future Vmax than estimating the current Vmax.

A Theory of Type I Solar Radio Bursts

1973 ◽  
Vol 2 (4) ◽  
pp. 215-217 ◽  
Author(s):  
W. N. -C. Sy
Keyword(s):  
Narrow Band ◽  
Plasma Frequency ◽  
Type I ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Circularly Polarized ◽  
Average Decrease ◽  
Brightness Temperatures ◽  
Solar Storm ◽  
The Continuum

Type I radio bursts, as distinct from the continuum component frequently associated with them in a solar storm, are short-lived (0.1-2 s), narrow-band (2-10 MHz) bursts with frequency drift rates from 0 to 20 MHz s−1. They come from coronal regions close to the corresponding plasma levels, i.e. the frequency of radiation ω is close to the local plasma frequency ωp. They occur more frequently at frequencies above ~100 MHz but at times extend to frequencies as low as 20 MHz. Their observed equivalent brightness temperatures are usually about 109 K but they can reach 1011 K or higher. Except for an average decrease in polarization towards the limb and except for initial stages of a storm, type I bursts are strongly circularly polarized (approaching 100 per cent) in the sense of the O-mode.

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