scholarly journals An Interpretation of Solar Flare Microwave Spikes as Gyrosynchrotron Masering

1980 ◽  
Vol 86 ◽  
pp. 457-459 ◽  
Author(s):  
G. D. Holman ◽  
D. Eichler ◽  
M. R. Kundu
Keyword(s):  
Solar Flare ◽  
Solar Flares ◽  
Plasma Frequency ◽  
Microwave Emission ◽  
Plasma Radiation ◽  
Alternative Possibility ◽  
High Brightness ◽  
Brightness Temperatures

Repeated bursts of microwave emission were observed by Slottje (1978) during the solar flares of April 11 and April 28, 1978. The high brightness temperatures which are inferred for these bursts indicate that a coherent mechanism must be responsible for the observed radiation. Slottje suggests that the emission is plasma radiation at the fundamental plasma frequency. We consider here the alternative possibility that the emission is coherent gyrosynchrotron radiation.

scholarly journals High-Resolution Dynamic Spectrum of a Spectacular Radio Burst from AD Leonis

1995 ◽  
Vol 151 ◽  
pp. 32-35
Author(s):  
Meil Abada-Simon ◽  
Alain Lecacheux ◽  
Monique Aubier ◽  
Jay A. Bookbinder
Keyword(s):  
High Resolution ◽  
Dynamic Spectrum ◽  
Plasma Radiation ◽  
The Sun ◽  
Radio Bursts ◽  
Radio Radiation ◽  
High Brightness ◽  
Brightness Temperatures ◽  
Cyclotron Maser ◽  
Intense Burst

AD Leonis is a very active, single dMe flare star. The similarities between this type of star and the Sun has led to study their radio radiation, which originates from their corona. The high brightness temperatures and other characteristics of most dMe radio bursts can be attributed to a non-thermal, coherent mechanism: plasma radiation or a cyclotron maser instability (CMI) are both plausible explanations. Even for the strongest burst of AD Leo which reached 940 mJy at 21 cm, it was not possible to discriminate between these two mechanisms (Bastian et al. 1990).Here we present an intense burst from AD Leo, exhibiting strong spikes for which the CMI seems to be the only reasonable explanation. In Sect. 2 we describe the observations, and in Sect. 3 we give an interpretation for this event.

Peculiarities of the microwave emission from active regions generating intense solar flares

2003 ◽  
Vol 29 (4) ◽  
pp. 263-273 ◽  
Author(s):  
V. M. Bogod ◽  
S. Kh. Tokhchukova
Keyword(s):  
Solar Flares ◽  
Active Regions ◽  
Microwave Emission

On the Possible Connection between Photospheric 5-Min Oscillation and Solar Flare Microwave Emission

Solar Physics ◽  
2006 ◽  
Vol 233 (1) ◽  
pp. 89-106 ◽  
Author(s):  
A. G. Kislyakov ◽  
V. V. Zaitsev ◽  
A. V. Stepanov ◽  
S. Urpo
Keyword(s):  
Solar Flare ◽  
Microwave Emission

scholarly journals Comparison of measured brightness temperatures from SMOS with modelled ones from ORCHIDEE and H-TESSEL over the Iberian Peninsula

2015 ◽  
Vol 12 (12) ◽  
pp. 13019-13067
Author(s):  
A. Barella-Ortiz ◽  
J. Polcher ◽  
P. de Rosnay ◽  
M. Piles ◽  
E. Gelati
Keyword(s):  
Soil Moisture ◽  
Radiative Transfer ◽  
Iberian Peninsula ◽  
Land Surface ◽  
Function Analysis ◽  
Microwave Emission ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Brightness Temperatures

Abstract. L-Band radiometry is considered to be one of the most suitable techniques to estimate surface soil moisture by means of remote sensing. Brightness temperatures are key in this process, as they are the main input in the retrieval algorithm. The work exposed compares brightness temperatures measured by the Soil Moisture and Ocean Salinity (SMOS) mission to two different sets of modelled ones, over the Iberian Peninsula from 2010 to 2012. The latter were estimated using a radiative transfer model and state variables from two land surface models: (i) ORganising Carbon and Hydrology In Dynamic EcosystEms (ORCHIDEE) and (ii) Hydrology – Tiled ECMWF Scheme for Surface Exchanges over Land (H-TESSEL). The radiative transfer model used is the Community Microwave Emission Model (CMEM). A good agreement in the temporal evolution of measured and modelled brightness temperatures is observed. However, their spatial structures are not consistent between them. An Empirical Orthogonal Function analysis of the brightness temperature's error identifies a dominant structure over the South-West of the Iberian Peninsula which evolves during the year and is maximum in Fall and Winter. Hypotheses concerning forcing induced biases and assumptions made in the radiative transfer model are analysed to explain this inconsistency, but no candidate is found to be responsible for it at the moment. Further hypotheses are proposed at the end of the paper.

scholarly journals On the Possibility of Local Magnetic Field Intensification in Evaporating Chromospheric Solar Flare Plasma

1989 ◽  
Vol 104 (2) ◽  
pp. 341-344
Author(s):  
V. N. Dermendjiev ◽  
G. T. Buyukliev ◽  
I. Ph. Panayotova
Keyword(s):  
Magnetic Field ◽  
Solar Flare ◽  
Solar Flares ◽  
Local Magnetic Field ◽  
Plume Structure ◽  
The Subject ◽  
Convective Plume ◽  
Flare Plasma ◽  
Initial Magnetic Field ◽  
Moving Vortex

The investigations of plasma motions at the initial phases of solar flares (Antonucci and Dennis, 1983; Doschek, 1983; Watanabe, 1987) suggest evaporation from the chromospheric flaring area. According to de Jager (1983) when seen at the limb the evaporated plasma will look like a “convective plume” and it can be seen separated from heated footpoint areas.The subject of this work is the study of the possibility of forming hydrodynamic structures o-f thermal and starting plume's kind at the time of evaporation of the upper chromosphere in a flaring area. Also the possibility of increasing an initial magnetic field by a periodically moving vortex in a plume structure is investigated.

scholarly journals Preface

1991 ◽  
Vol 336 (1643) ◽  
pp. 323-323
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Gamma Rays ◽  
Solar Flares ◽  
Solar Maximum ◽  
Interplanetary Space ◽  
Release Site ◽  
Solar Maximum Mission ◽  
New Information ◽  
Three Space

During the period of the 1980 solar maximum three space missions (P78-1, Solar Maximum Mission and Hinotori ) carried out extensive studies of solar flares. In their different ways all of these missions contributed significant new information to our understanding of the solar flare phenomenon. In this volume the contribution made by these three spacecraft to the study of the energy release and the related creation of high-tem perature plasma, the transport of energy from the primary release site, the production of gamma-rays at energies up to 10 MeV and the ejection of solar matter into interplanetary space are reviewed.

Comparing ERA-40-Based L-Band Brightness Temperatures with Skylab Observations: A Calibration/Validation Study Using the Community Microwave Emission Model

2009 ◽  
Vol 10 (1) ◽  
pp. 213-226 ◽  
Author(s):  
Matthias Drusch ◽  
Thomas Holmes ◽  
Patricia de Rosnay ◽  
Gianpaolo Balsamo
Keyword(s):  
Soil Moisture ◽  
Dynamic Range ◽  
Microwave Radiometer ◽  
Space Station ◽  
Microwave Emission ◽  
Emission Model ◽  
Soil Database ◽  
Brightness Temperatures ◽  
L Band ◽  
Rms Errors

Abstract The Community Microwave Emission Model (CMEM) has been used to compute global L-band brightness temperatures at the top of the atmosphere. The input data comprise surface fields from the 40-yr ECMWF Re-Analysis (ERA-40), vegetation data from the ECOCLIMAP dataset, and the Food and Agriculture Organization’s (FAO) soil database. Modeled brightness temperatures have been compared against (historic) observations from the S-194 passive microwave radiometer onboard the Skylab space station. Different parameterizations for surface roughness and the vegetation optical depth have been used to calibrate the model. The best results have been obtained for rather simple approaches proposed by Wigneron et al. and Kirdyashev et al. The rms errors after calibration are 10.7 and 9.8 K for North and South America, respectively. Comparing the ERA-40 soil moisture product against the corresponding in situ observations suggests that the uncertainty in the modeled soil moisture is the predominant contributor to these rms errors. Although the bias between model and observed brightness temperatures are reduced after the calibration, systematic differences in the dynamic range remain. For NWP analysis applications, bias correction schemes should be applied prior to data assimilation. The calibrated model has been used to compute a 10-yr brightness temperature climatology based on ERA-40 data.

Atomic physics calculations relevant to solar flare spectra

1991 ◽  
Vol 336 (1643) ◽  
pp. 471-484 ◽  
Keyword(s):  
Solar Flare ◽  
Atomic Physics ◽  
Solar Flares ◽  
Solar Maximum ◽  
Emission Lines ◽  
Atomic Data ◽  
Solar Maximum Mission ◽  
X Ray ◽  
Physical Conditions ◽  
Recombination Processes

Solar flare spectra in the ultraviolet and X-ray wavelength regions are rich in emission lines from highly ionized ions, formed at temperatures around 10 7 K. These lines can be used as valuable diagnostics for probing the physical conditions in solar flares. Such analyses require accurate atomic data for excitation, ionization and recombination processes. In this paper, we present a review of work which has already been carried out, in particular for the Solar Maximum Mission observations, and we look to future requirements for Solar-A .

scholarly journals “Tau-Omega”- and Two-Stream Emission Models Used for Passive L-Band Retrievals: Application to Close-Range Measurements over a Forest

2018 ◽  
Vol 10 (12) ◽  
pp. 1868 ◽  
Author(s):  
Mike Schwank ◽  
Reza Naderpour ◽  
Christian Mätzler
Keyword(s):  
Water Content ◽  
Deciduous Forest ◽  
Microwave Emission ◽  
Retrieval Algorithm ◽  
Brightness Temperatures ◽  
Retrieval Algorithms ◽  
Close Range ◽  
Emission Models ◽  
L Band ◽  
Two Parameter

Microwave Emission Models (EM) are used in retrieval algorithms to estimate geophysical state parameters such as soil Water Content ( W C ) and vegetation optical depth ( τ ), from brightness temperatures T B p , θ measured at nadir angles θ at Horizontal and Vertical polarizations p = { H , V } . An EM adequate for implementation in a retrieval algorithm must capture the responses of T B p , θ to the retrieval parameters, and the EM parameters must be experimentally accessible and representative of the measurement footprint. The objective of this study is to explore the benefits of the multiple-scattering Two-Stream (2S) EM over the “Tau-Omega” (TO) EM considered as the “reference” to retrieve W C and τ from L-band T B p , θ . For sparse and low-scattering vegetation T B , E M p , θ simulated with E M = { TO , 2 S } converge. This is not the case for dense and strongly scattering vegetation. Two-Parameter (2P) retrievals 2 P R C = ( W C R C , τ R C ) are computed from elevation scans T B p , θ j = T B , TO p , θ j synthesized with TO EM and from T B p , θ j measured from a tower within a deciduous forest. Retrieval Configurations ( R C ) employ either E M = TO or E M = 2 S and assume fixed scattering albedos. W C R C achieved with the 2S RC is marginally lower ( ~ 1 m 3 m − 3 ) than if achieved with the “reference” TO RC, while τ R C is reduced considerably when using 2S EM instead of TO EM. Our study outlines a number of advantages of the 2S EM over the TO EM currently implemented in the operational SMOS and SMAP retrieval algorithms.

scholarly journals Electrons and X-Ray Emission of Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 409-413
Author(s):  
V. G. Kurt
Keyword(s):  
Solar Activity ◽  
Statistical Analysis ◽  
Solar Flare ◽  
Frequency Dependence ◽  
Power Law ◽  
Solar Flares ◽  
X Rays ◽  
Fast Electrons ◽  
X Ray ◽  
Flare Frequency

A statistical analysis of solar flare X-rays and interplanetary particle fluxes, measured onboard VENERA-13, 14 Spacecraft, was performed. The correlation of fluences for different manifestations of solar flares is strong, especially for fast electrons and hard and soft X-ray emissions. Frequency dependence on fluence value ϵi for practically all Kinds of solar flare emission can be described by power law ν (ϵ > ϵO) ∼ ϵ−0.45±0.15 which does not change significantly with solar activity. For different Hα flare importances the values of ϵi were obtained. It is proposed that appearance of certain energy flare frequency is strongly dependent on some scale factor.

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