scholarly journals Brightness temperature of decameter solar bursts with high-frequency cut-off

2018 ◽  
Keyword(s):  
Brightness Temperature ◽  
High Frequency ◽  
Solar Bursts

scholarly journals Complementary Bursts, Coronal Inhomogeneities and New Microscopic Spectral Features of Solar Bursts in Type IV Bursts

1980 ◽  
Vol 86 ◽  
pp. 269-271
Author(s):  
H. S. Sawant ◽  
R. V. Bhonsle ◽  
S. S. Degaonkar ◽  
T. Takakura
Keyword(s):  
High Frequency ◽  
High Sensitivity ◽  
Line Of Sight ◽  
Spectral Features ◽  
Frequency Range ◽  
Type Iv ◽  
Linear Extent ◽  
Solar Bursts ◽  
Almost All ◽  
Density Irregularity

Complementary bursts (C.B's) have been observed in the decametric range during noise storms and/or type IV activity. These bursts essentially consist of two components, each component having a duration ~ 1 second. The first component shows weak emission or emission gap over a certain frequency range. The second component is observed after a certain delay. If the bursts are assumed to be generated at the fundamental, and if the radiation corresponding to the gap propagates through an electron density irregularity located close to the source along the line of sight, whose cross-section is less than the linear extent of the source, then almost all properties of the C.B.'s can be explained. High sensitivity, and high frequency and time resolution spectra of type IV bursts at 137 MHz revealed new microscopic spectral features displaying “wave-like” and “fork-like” shapes.

scholarly journals Microwave signatures of ice hydrometeors from ground-based observations above Summit, Greenland

2015 ◽  
Vol 15 (23) ◽  
pp. 34497-34532
Author(s):  
C. Pettersen ◽  
R. Bennartz ◽  
M. S. Kulie ◽  
A. J. Merrelli ◽  
M. D. Shupe ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Liquid Water ◽  
High Frequency ◽  
Passive Microwave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cloud Radar ◽  
Brightness Temperatures ◽  
High Frequency Microwave

Abstract. Multi-instrument, ground-based measurements provide unique and comprehensive datasets of the atmosphere for a specific location over long periods of time and resulting data compliments past and existing global satellite observations. This paper explores the effect of ice hydrometeors on ground-based, high frequency passive microwave measurements and attempts to isolate an ice signature for summer seasons at Summit, Greenland from 2010–2013. Data from a combination of passive microwave, cloud radar, radiosonde, and ceilometer were examined to isolate the ice signature at microwave wavelengths. By limiting the study to a cloud liquid water path of 40 g m−2 or less, the cloud radar can identify cases where the precipitation was dominated by ice. These cases were examined using liquid water and gas microwave absorption models, and brightness temperatures were calculated for the high frequency microwave channels: 90, 150, and 225 GHz. By comparing the measured brightness temperatures from the microwave radiometers and the calculated brightness temperature using only gas and liquid contributions, any residual brightness temperature difference is due to emission and scattering of microwave radiation from the ice hydrometeors in the column. The ice signature in the 90, 150, and 225 GHz channels for the Summit Station summer months was isolated. This measured ice signature was then compared to an equivalent brightness temperature difference calculated with a radiative transfer model including microwave single scattering properties for several ice habits. Initial model results compare well against the four years of summer season isolated ice signature in the high-frequency microwave channels.

scholarly journals Combined Radiometer–Radar Microphysical Profile Estimations with Emphasis on High-Frequency Brightness Temperature Observations

2003 ◽  
Vol 42 (4) ◽  
pp. 476-487 ◽  
Author(s):  
Gail M. Skofronick-Jackson ◽  
James R. Wang ◽  
Gerald M. Heymsfield ◽  
Robbie Hood ◽  
Will Manning ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
High Frequency ◽  
Temperature Observations

scholarly journals The Linear Polarization of Radiation from Jupiter at 6 cm Wavelength

1968 ◽  
Vol 21 (3) ◽  
pp. 337 ◽  
Author(s):  
D Morris ◽  
JB Whiteoak ◽  
F Tonking
Keyword(s):  
Synchrotron Radiation ◽  
Brightness Temperature ◽  
Linear Polarization ◽  
High Frequency ◽  
Central Meridian ◽  
Thermal Component ◽  
Nonthermal Radiation ◽  
Polarization Of Radiation ◽  
The Mean ◽  
Direction Of Polarization

At a wavelength of 6 cm the degree of linear polarization of the radiation from Jupiter is 0�076�0�002. The variation of the direction of polarization with longitude of the central meridian is consistent with the increased period of rotation determined by Komesaroff and McCulloch (1967). There is evidence of an asymmetricl beaming of the nonthermal radiation with longitude in addition to the latitude asymmetry that was detected previously by Roberts and Komesaroff (1965). The mean flux density normalized to a distance of 4�04 a.u. is 1O�7�0�2 f.u. The small nonthermal contribution (3'7 f.u.) is further evidence for a high frequency cutoff in the synchrotron radiation; the thermal component corresponds to a brightness temperature of about 250oK.

scholarly journals Dual-high-frequency VLBI study of blazar-jet brightness-temperature gradients and collimation profiles

2021 ◽  
Author(s):  
P. R. Burd ◽  
M. Kadler ◽  
K. Mannheim ◽  
A.-K. Back ◽  
J. Ringholz ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
High Frequency ◽  
Temperature Gradients

Spatial and temporal analysis of high-frequency internal gravity wave signatures in brightness temperature satellite images

2021 ◽  
Author(s):  
Robert Vicari
Keyword(s):  
Water Vapor ◽  
Brightness Temperature ◽  
Gravity Wave ◽  
Gravity Waves ◽  
High Frequency ◽  
Satellite Images ◽  
Internal Gravity Wave ◽  
Internal Gravity Waves ◽  
Small Scale ◽  
Wave Patterns

<p>Highly idealized model studies suggest that convectively generated internal gravity waves in the troposphere with horizontal wavelengths on the order of a few kilometers may affect the lifetime, spacing, and depth of clouds and convection. To answer whether such a convection-wave coupling occurs in the real atmosphere, one needs to find corresponding events in observations. In general, the study of high-frequency internal gravity wave-related phenomena in the troposphere is a challenging task because they are usually small-scale and intermittent. To overcome case-by-case studies, it is desirable to have an automatic method to analyze as much data as possible and provide enough independent and diverse evidence.<br>Here, we focus on brightness temperature satellite images, in particular so-called satellite water vapor channels. These channels measure the radiation at wavelengths corresponding to the energy emitted by water vapor and provide cloud-independent observations of internal gravity waves, in contrast to visible and other infrared satellite channels where one relies on the wave impacts on clouds. In addition, since these water vapor channels are sensitive to certain vertical layers in the troposphere, combining the images also reveals some vertical structure of the observed waves.<br>We propose an algorithm based on local Fourier analyses to extract information about high-frequency wave patterns in given brightness temperature images. This method allows automatic detection and analysis of many wave patterns in a given domain at once, resulting in a climatology that provides an initial observational basis for further research. Using data from the instrument ABI on board the satellite GOES-16 during the field campaign EUREC<sup>4</sup>A, we demonstrate the capabilities and limitations of the method. Furthermore, we present the respective climatology of the detected waves and discuss approaches based on this to address the initial question.</p>

Solar Simple Bursts Observed with High Spectral Resolution in the 18-23 GHz Range

1994 ◽  
Vol 142 ◽  
pp. 693-695
Author(s):  
H. S. Sawant ◽  
R. R. Rosa ◽  
J. R. Cecatto ◽  
N. Gopalswamy
Keyword(s):  
Solar Flares ◽  
High Frequency ◽  
Impulsive Phase ◽  
Frequency Resolution ◽  
High Spectral Resolution ◽  
Spectral Evolution ◽  
Radiation Mechanisms ◽  
Estimated Parameters ◽  
Solar Bursts ◽  
First Time

AbstractFor the first time, solar bursts in the frequency range of (18-23) GHz have been observed with high-time (0.6-1.2 s) and high-frequency resolution (1 GHz), by using the Itapetinga 13.7m diameter antenna. Here, we investigate the microwave type “simple low level (< 10 SFU) bursts” associated with the impulsive phase of solar flares. Observed properties of these simple bursts are: rise time tr ~3 s, decay time td ~ 5 s and spectral index ranging between −1 and −4. These bursts were found to be associated with SF or SN flares as seen in Hα. The above properties suggest that they are likely to be a microwave counterpart of elementary flare bursts. In the majority of the cases the spectral evolution is soft-hard-soft. This suggests a nonthermal gyrosynchrotron mechanism for generating these elementary flare bursts. Estimated parameters of these simple burst sources are height (h ~ 2400 km), electron density (Nє < 8.8 × 109 cm−3 ), and magnetic field (B ~ 300 G).Subject headings: radiation mechanisms: nonthermal — Sun: radio radiation

scholarly journals Microwave signatures of ice hydrometeors from ground-based observations above Summit, Greenland

2016 ◽  
Vol 16 (7) ◽  
pp. 4743-4756 ◽  
Author(s):  
Claire Pettersen ◽  
Ralf Bennartz ◽  
Mark S. Kulie ◽  
Aronne J. Merrelli ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Temperature Difference ◽  
Liquid Water ◽  
High Frequency ◽  
Passive Microwave ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Cloud Radar ◽  
Brightness Temperatures ◽  
High Frequency Microwave

Abstract. Multi-instrument, ground-based measurements provide unique and comprehensive data sets of the atmosphere for a specific location over long periods of time and resulting data compliment past and existing global satellite observations. This paper explores the effect of ice hydrometeors on ground-based, high-frequency passive microwave measurements and attempts to isolate an ice signature for summer seasons at Summit, Greenland, from 2010 to 2013. Data from a combination of passive microwave, cloud radar, radiosonde, and ceilometer were examined to isolate the ice signature at microwave wavelengths. By limiting the study to a cloud liquid water path of 40 g m−2 or less, the cloud radar can identify cases where the precipitation was dominated by ice. These cases were examined using liquid water and gas microwave absorption models, and brightness temperatures were calculated for the high-frequency microwave channels: 90, 150, and 225 GHz. By comparing the measured brightness temperatures from the microwave radiometers and the calculated brightness temperature using only gas and liquid contributions, any residual brightness temperature difference is due to emission and scattering of microwave radiation from the ice hydrometeors in the column. The ice signature in the 90, 150, and 225 GHz channels for the Summit Station summer months was isolated. This measured ice signature was then compared to an equivalent brightness temperature difference calculated with a radiative transfer model including microwave single-scattering properties for several ice habits. Initial model results compare well against the 4 years of summer season isolated ice signature in the high-frequency microwave channels.

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