Observation of the Radio Radiation Flux of the Sun and Flares at a Wavelength of 5 cm

2020 ◽  
Vol 60 (8) ◽  
pp. 1087-1092
Author(s):  
A. G. Tlatov ◽  
V. M. Bogod ◽  
O. Pons ◽  
M. Rodriges ◽  
R. Estrada ◽  
...  
Keyword(s):  
Radiation Flux ◽  
The Sun ◽  
Radio 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.

scholarly journals Solar flares as proxy for the young Sun: satellite observed thermosphere response to an X17.2 flare of Earth's upper atmosphere

2012 ◽  
Vol 30 (8) ◽  
pp. 1129-1141 ◽  
Author(s):  
S. Krauss ◽  
B. Fichtinger ◽  
H. Lammer ◽  
W. Hausleitner ◽  
Yu. N. Kulikov ◽  
...  
Keyword(s):  
Solar Flares ◽  
Radiation Flux ◽  
Extreme Ultraviolet ◽  
Upper Atmosphere ◽  
Radiation Environment ◽  
The Sun ◽  
Satellite Drag ◽  
Grace Satellites ◽  
Early Phases ◽  
Activity Indices

Abstract. We analyzed the measured thermospheric response of an extreme solar X17.2 flare that irradiated the Earth's upper atmosphere during the so-called Halloween events in late October/early November 2003. We suggest that such events can serve as proxies for the intense electromagnetic and corpuscular radiation environment of the Sun or other stars during their early phases of evolution. We applied and compared empirical thermosphere models with satellite drag measurements from the GRACE satellites and found that the Jacchia-Bowman 2008 model can reproduce the drag measurements very well during undisturbed solar conditions but gets worse during extreme solar events. By analyzing the peak of the X17.2 flare spectra and comparing it with spectra of young solar proxies, our results indicate that the peak flare radiation flux corresponds to a hypothetical Sun-like star or the Sun at the age of approximately 2.3 Gyr. This implies that the peak extreme ultraviolet (EUV) radiation is enhanced by a factor of about 2.5 times compared to today's Sun. On the assumption that the Sun emitted an EUV flux of that magnitude and by modifying the activity indices in the Jacchia-Bowman 2008 model, we obtain an average exobase temperature of 1950 K, which corresponds with previous theoretical studies related to thermospheric heating and expansion caused by the solar EUV flux.

Flux Density Distribution in the Focal Region of a Solar Concentrator System

1991 ◽  
Vol 113 (2) ◽  
pp. 112-116 ◽  
Author(s):  
M. Schubnell ◽  
J. Keller ◽  
A. Imhof
Keyword(s):  
Density Distribution ◽  
Flux Density ◽  
Ray Tracing ◽  
Radiation Flux ◽  
Focal Length ◽  
Solar Furnace ◽  
Focal Region ◽  
The Sun ◽  
Parabolic Dish ◽  
Flux Density Distribution

In high temperature solar energy applications highly concentrating optical systems, such as, e.g., parabolic dishes, achieve typical radiation flux densities >2 MW/m2. In order to investigate thermo and photochemical reactions at temperatures >1500 K and radiation flux densities >2 MW/m2 a solar furnace was built at Paul Scherrer Institute (PSI). This furnace is a two-stage concentrator. The first stage is a prefocusing glass heliostat with a focal length of 100 m. The second stage is a highly concentrating parabolic dish with a focal length of 1.93 m. To design experiments to be carried out in the focal region of the parabolic dish, the radiation flux as well as its density distribution have to be known. This distribution is usually measured by radiometric methods. However, these methods are generally rather troublesome because of the high temperatures involved. In this paper we present a simple method to estimate the characteristic features of the radiation flux density distribution in the focal region of a concentrator system. It is well known from solar eclipses that the mean angular diameter of the moon is almost equal to that of the sun (9.1 mrad versus 9.3 mrad). Hence, the lunar disk is well suited to be used as a light source to investigate the flux distribution in a solar furnace. Compared to the sun the flux density is reduced by 4·105 and the flux density distribution can be inspected on a sheet of paper located in the plane of interest, e.g., the focal plane. This distribution was photographed and analyzed by means of an image processing system. The density distribution was also simulated using a Monte Carlo ray tracing program. Based on this comparison, and on further ray tracing computations, we show that the peak flux density decreases from 8.9 MW/m2 in December to values below 4 MW/m2 in June and the net radiation flux from 25 kW to 15 kW, respectively.

Radio Waves Tell About the Universe

2005 ◽  
Author(s):  
S.Ya. Braude ◽  
V.M. Kontorovich
Keyword(s):  
Neutron Stars ◽  
Radio Astronomy ◽  
Radio Galaxies ◽  
The Sun ◽  
Radio Radiation ◽  
Radio Telescopes ◽  
Radio Waves ◽  
Evolution Of The Universe ◽  
Space Objects ◽  
The Universe

The book tells about the achievements of modern radio astronomy. Data on radio galaxies, quasars, pulsars, space masers, and other space objects emitting radio waves are presented in a popular form. The ways of evolution of stars, supernovae and radio eruptions of their remains, the formation of white dwarfs and neutron stars, the phenomena in the centers of galaxies and the fusion of galaxies responsible for the formation of radio galaxies and quasars are considered. The radio radiation of the Sun and planets is discussed. A modern view of the evolution of the universe, the origin of the relic radiation left over from the Great Eruption, and its anisotropy is presented. A separate chapter is devoted to the description of radio telescopes.

scholarly journals 71. A peculiar type of scintillation of solar radio radiation

1957 ◽  
Vol 4 ◽  
pp. 371-372
Author(s):  
A. D. Fokker
Keyword(s):  
The Netherlands ◽  
Radio Emission ◽  
Radio Astronomy ◽  
Solar Radio ◽  
Solar Radio Emission ◽  
The Sun ◽  
Radio Radiation ◽  
Selective Fading ◽  
Continuous Survey ◽  
Solar Radio Radiation

Some authors (Payne-Scott and Little (1952) [1]; Owren (1952) [2]) have mentioned a phenomenon in the enhanced solar radio emission which they call ‘non-selective fading’. The present paper is meant to call attention to another, rather peculiar, type of scintillation in the radio emission of the sun, which differs from the non-selective fading in some important respects. This scintillation has been observed since 1952 by the division ‘Ionosphere and Radio Astronomy’ of the Netherlands Telecommunications Service in the course of a continuous survey of solar radio radiation. It has been found at the radio frequencies 140, 200 and 545 Mc./s.

scholarly journals Hard Solar X-Ray Bursts

1968 ◽  
Vol 1 ◽  
pp. 541-543
Author(s):  
C. de Jager
Keyword(s):  
Solar Radiation ◽  
Solar Flares ◽  
Spectral Region ◽  
Radiation Flux ◽  
Point Of View ◽  
The Sun ◽  
X Ray ◽  
Quiet Sun ◽  
Observational Techniques

A tentative spectrum of the Sun in the X-ray region is shown in Figure 1 (De Jager, 1967). The quiet Sun emits a measurable spectrum at photon energies below about 3 keV. During the occurrence of solar flares an enhancement of the emitted energy, and a hardening of the spectrum is clearly visible. The soft X-ray bursts apparently show a maximum radiation flux at wavelengths of about 10 Å.In the spectral region above about 10 keV hardly any quiet solar radiation is observable. During the occurrence of solar flares hard X-ray bursts are occasionally observed. From the point of view of observational techniques these bursts may be divided in the so-called deka-keV bursts, covering the range 10-200 keV, and the deci-MeV bursts in the range between 0·2 and 1 MeV. Many deka-keV bursts have been observed during the years 1966-67 by Winckler et al., by means of the OGO-I and OGO-III satellites (see Arnoldy et al., 1967). The existence of deci-MeV bursts has been doubted various times (see e.g. Chubb et al., 1966). Its reality seems now to be proved (see also De Jager, 1967). However, they may be much rarer than the deka-keV bursts, although it is not yet completely sure that the selection is not observational.

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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