High-resolution observations of changing magnetic features on the sun

1986 ◽  
Vol 306 ◽  
pp. 304 ◽  
Author(s):  
K. P. Topka ◽  
T. D. Tarbell ◽  
A. M. Title
Keyword(s):  
High Resolution ◽  
The Sun ◽  
Magnetic Features

scholarly journals Hydrodynamic Models of Solar and Stellar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 289-298
Author(s):  
Giovanni Peres
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Light Curves ◽  
Physical Parameters ◽  
The Sun ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Stellar Flares

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.

scholarly journals Quasi-Band-Limited Coronagraph for Extended Sources

2021 ◽  
Vol 10 (01) ◽  
pp. 2150002
Author(s):  
Igor Loutsenko ◽  
Oksana Yermolayeva
Keyword(s):  
High Resolution ◽  
High Ratio ◽  
Gravitational Lens ◽  
High Resolution Imaging ◽  
The Sun ◽  
Extended Source ◽  
Amplitude Image ◽  
Extended Sources ◽  
Resolution Imaging ◽  
Band Limited

We propose a class of graded coronagraphic “amplitude” image masks for a high throughput Lyot-type coronagraph that transmits light from an annular region around an extended source and suppresses light, with extremely high ratio, from elsewhere. The interior radius of the region is comparable with its exterior radius. The masks are designed using an idea inspired by approach due M. J. Kuchner and W. A. Traub (“band-limited” masks) and approach to optimal apodization by D. Slepian. One potential application of our masks is direct high-resolution imaging of exo-planets with the help of the Solar Gravitational Lens, where apparent radius of the “Einstein ring” image of a planet is of the order of an arc-second and is comparable with the apparent radius of the sun and solar corona.

scholarly journals The Radio Brightness Distribution on the Sun at 21 cm from Combined Eclipse and Pencil?Beam Observations

1961 ◽  
Vol 14 (3) ◽  
pp. 403 ◽  
Author(s):  
T Krishnan ◽  
NR Labrum
Keyword(s):  
High Resolution ◽  
High Sensitivity ◽  
Brightness Distribution ◽  
Pencil Beam ◽  
The Sun ◽  
Radio Brightness ◽  
Radio Brightness Distribution ◽  
Grating Interferometer

A study of the brightness distribution on the Sun at 21-cm wavelength on April 8, 1959, is described. High resolution observations were made of the partial eclipse on that day with a simple radiometer of high sensitivity. The brightness distribution of the uneclipsed Sun at the same wavelength was obtained using a cross-grating interferometer, which enabled the bright regions to be located accurately.

II. Spots and Intense Flux Tubes

1988 ◽  
Vol 20 (1) ◽  
pp. 58-63
Author(s):  
J.C. Henoux
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
High Resolution ◽  
Solar Magnetic Field ◽  
Solar Physics ◽  
Small Scale ◽  
The Sun ◽  
Flux Tubes ◽  
Flux Concentration ◽  
Scientific Meetings

The development of research on starspots, stellar activity, and the suspected relationship between coronal heating and magnetic field have reenforced the interest of the study of the solar magnetic field and the study of the associated thermodynamic structures. Several proceedings of scientific meetings appeared from 1984 to 1987 (Measurements of Solar Vector Magnetic Fields, 1985 (I); The Hydrodynamics of the Sun, 1984 (II); High Resolution in Solar Physics, 1985 (III); Theoritical Problems in High Resolution Solar Physics, 1985 (IV); Small Scale Magnetic Flux Concentration in the Solar Atmosphere, 1986 (V)). The finding that the solar irradiance in affected by solar activity has renewed interest in photometry of sunspots and faculae. Sunspots have been used for investigating solar differential and meridional motions. Some results are also found in Section III.

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 Some properties of the sources of slowly varying component and of bursts at 612 Mc/s

1968 ◽  
Vol 35 ◽  
pp. 581-584
Author(s):  
G. Swarup ◽  
M. R. Kundu ◽  
V. K. Kapahi ◽  
J. D. Isloor
Keyword(s):  
High Resolution ◽  
The Sun ◽  
Half Power

A high-resolution 24-element, E–W interferometer situated at Kalyan near Bombay has been used to study the sources of slowly varying component and of bursts at a frequency of 612 Mc/s. This interferometer has a half-power beamwidth of 2·8 min of arc, and the fan beams are located about a degree apart in the sky. Thus, a strip scan is obtained roughly every 4 min as the Sun drifts through the beams. About 20 slowly varying sources and 11 bursts were observed during the period June 1965 to February 1967 at 612 Mc/s.

scholarly journals Observations of Local Interstellar Mg I and Mg II

1984 ◽  
Vol 81 ◽  
pp. 64-66 ◽  
Author(s):  
F. Bruhweiler ◽  
W. Oegerle ◽  
E. Weiler ◽  
R. Stencel ◽  
Y. Kondo
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Upper Limits

AbstractWe have combined Copernicus and IUE observations of 5 stars within 50 pc of the Sun to study the ionization of magnesium in the local interstellar medium (LISM). The high resolution Copernicus spectrometer was used to detect interstellar Mg I 2852 in the spectra of α Gru, α Eri, and α Lyr, while placing upper limits on Mg I in the spectra of α CMa and α PsA. Observations of Mg II 2795, 2802 for these stars were also obtained with IUE and Copernicus. The column densities of Mg I and Mg II are used to place constraints on the temperature of the LISM.

High Resolution Solar Observations at Three Frequencies: 1424 MHz, 696 MHz and 408 MHz

1967 ◽  
Vol 1 (2) ◽  
pp. 45-46
Author(s):  
D. G. Cole ◽  
R. F. Mullaly ◽  
A. Watkinson
Keyword(s):  
High Resolution ◽  
Radio Emission ◽  
Solar Radio ◽  
Solar Radio Emission ◽  
The Sun ◽  
Physical Mechanisms ◽  
Solar Observations ◽  
Source Structure ◽  
East West

During the period 1966 July 12 to August 5 observations were made of the Sun at three radio observatories. The instruments used were the east-west arm of the Mills cross at Molonglo (408 MHz) and the Christiansen cross at Fleurs (696 MHz and 1424 MHz). The aim of these observations was to study the discrete sources of the slowly varying component of solar radio emission, while activity was comparatively quiet. The three frequencies enabled the variation of source structure with height of solar atmosphere to be studied. It has been pointed out by Swarup et al., and Christiansen et al. that the determination of the frequency dependence of these discrete sources is important for defining the physical mechanisms causing the radio emission.

scholarly journals Detailed Analyses of Four Solar Analogs Analysed On High S/N CFH and ESO Spectra

1988 ◽  
Vol 132 ◽  
pp. 429-432
Author(s):  
C. Bentolila ◽  
G. Cayrel de Strobel
Keyword(s):  
High Resolution ◽  
Effective Temperature ◽  
The Sun ◽  
Atmospheric Parameters ◽  
Iron Abundance ◽  
Solar Type ◽  
Solar Analogs

Four solar type G stars claimed to be photometrically very similar to the Sun have been analyzed in detail on high resolution, high S/N spectra. Their atmospheric parameters : effective temperature, spectroscopic gravity, microturbulence and iron abundance, [Fe/H], have been determined.

Correlated Bursts at Distant Sources on the Sun

1969 ◽  
Vol 1 (5) ◽  
pp. 186-188 ◽  
Author(s):  
K. Kai
Keyword(s):  
Time Delay ◽  
High Resolution ◽  
Active Regions ◽  
Solar Observatory ◽  
The Sun ◽  
Quiet Period ◽  
Fast Electrons ◽  
Different Sources ◽  
Large Flare

Since the start of high-resolution observations with the radioheliograph at the Culgoora Solar Observatory it has been noted that some bursts which occur from separate active regions could be physically correlated. It was suggested that the time delay between the correlated bursts is of the order of seconds, and that fast electrons provide the trigger. Wild found that shortly before a large flare weak bursts, stronelv polarized in the same sense, appeared simultaneously in different sources after a quiet period and he discussed the phenomenon in the light of flare mechanisms.

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