scholarly journals Two‐dimensional Magnetohydrodynamic Models of the Solar Corona: Mass Loss from the Streamer Belt

2003 ◽  
Vol 589 (2) ◽  
pp. 1040-1053 ◽  
Author(s):  
Eirik Endeve ◽  
Egil Leer ◽  
Thomas E. Holzer
Keyword(s):  
Solar Corona ◽  
Mass Loss ◽  
Two Dimensional ◽  
Streamer Belt ◽  
Magnetohydrodynamic Models

scholarly journals Two-dimensional modeling of density and thermal structure of dense circumstellar outflowing disks

2018 ◽  
Vol 613 ◽  
pp. A75 ◽  
Author(s):  
P. Kurfürst ◽  
A. Feldmeier ◽  
J. Krtička
Keyword(s):  
Mass Loss ◽  
Optical Depth ◽  
Massive Stars ◽  
Thermal Structure ◽  
Time Dependent ◽  
Navier Stokes ◽  
Viscous Heating ◽  
Two Dimensional ◽  
Dense Region ◽  
Loss Rates

Context. Evolution of massive stars is affected by a significant loss of mass either via (nearly) spherically symmetric stellar winds or by aspherical mass-loss mechanisms, namely the outflowing equatorial disks. However, the scenario that leads to the formation of a disk or rings of gas and dust around massive stars is still under debate. It is also unclear how various forming physical mechanisms of the circumstellar environment affect its shape and density, as well as its kinematic and thermal structure. Aims. We study the hydrodynamic and thermal structure of optically thick, dense parts of outflowing circumstellar disks that may be formed around various types of critically rotating massive stars, for example, Be stars, B[e] supergiant (sgB[e]) stars or Pop III stars. We calculate self-consistent time-dependent models of temperature and density structure in the disk’s inner dense region that is strongly affected by irradiation from a rotationally oblate central star and by viscous heating. Methods. Using the method of short characteristics, we specify the optical depth of the disk along the line-of-sight from stellar poles. Within the optically thick dense region with an optical depth of τ > 2∕3 we calculate the vertical disk thermal structure using the diffusion approximation while for the optically thin outer layers we assume a local thermodynamic equilibrium with the impinging stellar irradiation. For time-dependent hydrodynamic modeling, we use two of our own types of hydrodynamic codes: two-dimensional operator-split numerical code based on an explicit Eulerian finite volume scheme on a staggered grid, and unsplit code based on the Roe’s method, both including full second-order Navier-Stokes shear viscosity. Results. Our models show the geometric distribution and contribution of viscous heating that begins to dominate in the central part of the disk for mass-loss rates higher than Ṁ ≳ 10−10 M⊙ yr−1. In the models of dense viscous disks with Ṁ > 10−8 M⊙ yr−1, the viscosity increases the central temperature up to several tens of thousands of Kelvins, however the temperature rapidly drops with radius and with distance from the disk midplane. The high mass-loss rates and high viscosity lead to instabilities with significant waves or bumps in density and temperature in the very inner disk region. Conclusions. The two-dimensional radial-vertical models of dense outflowing disks including the full Navier-Stokes viscosity terms show very high temperatures that are however limited to only the central disk cores inside the optically thick area, while near the edge of the optically thick region the temperature may be low enough for the existence of neutral hydrogen, for example.

Some features of the streamer belt in the solar corona and at the Earth’s orbit

2006 ◽  
Vol 50 (9) ◽  
pp. 748-761 ◽  
Author(s):  
M. V. Eselevich ◽  
V. G. Eselevich
Keyword(s):  
Solar Corona ◽  
Streamer Belt

Helmet Streamers Gone Unstable: Two‐Fluid Magnetohydrodynamic Models of the Solar Corona

2004 ◽  
Vol 603 (1) ◽  
pp. 307-321 ◽  
Author(s):  
Eirik Endeve ◽  
Thomas E. Holzer ◽  
Egil Leer
Keyword(s):  
Solar Corona ◽  
Magnetohydrodynamic Models ◽  
Two Fluid

Coronal Broadening of the Crab Nebula 1969-71: Observations

1972 ◽  
Vol 2 (2) ◽  
pp. 84-86 ◽  
Author(s):  
R. G. Blesing ◽  
P. A. Dennison
Keyword(s):  
Solar Cycle ◽  
Solar Corona ◽  
Crab Nebula ◽  
Two Dimensional ◽  
Dimensional Image ◽  
Two Dimensional Image ◽  
The Crab Nebula

A description was given in a previous paper of the first observations of the two-dimensional image of the Crab Nebula as it became broadened by the solar corona in June 1969. In this paper we describe further observations at 80 MHz during 1970 and 1971, again using the CSIRO Radioheliograph at Culgoora, N.S.W., and we discuss the derived values for radial and tangential broadening in relation to previous work at various phases of the solar cycle. Other methods of observing angular broadening have generally employed two or three interferometers at different position angles, and only the simplest model for the image could be assumed in interpreting the results. The radioheliograph, however, has the advantage of recording the complete two-dimensional image and also, simultaneously, the surrounding background.

scholarly journals Off-limb EUV observations of the solar corona and transients with the CORONAS-F/SPIRIT telescope-coronagraph

2008 ◽  
Vol 26 (10) ◽  
pp. 3007-3016 ◽  
Author(s):  
V. Slemzin ◽  
O. Bougaenko ◽  
A. Ignatiev ◽  
S. Kuzin ◽  
A. Mitrofanov ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Corona ◽  
White Light ◽  
Extreme Ultraviolet ◽  
Temporal Correlation ◽  
Intermediate Region ◽  
Fast Solar Wind ◽  
Radial Line ◽  
Streamer Belt ◽  
The West

Abstract. The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 Rsun from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 Rsun. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments.

Streamer belt in the solar corona and the Earth’s orbit

2007 ◽  
Vol 47 (3) ◽  
pp. 291-298 ◽  
Author(s):  
M. V. Eselevich ◽  
V. G. Eselevich
Keyword(s):  
Solar Corona ◽  
Streamer Belt

Radio Observations of the Structure of the Solar Corona

1970 ◽  
Vol 1 (7) ◽  
pp. 304-305 ◽  
Author(s):  
K. V. Sheridan
Keyword(s):  
Solar Corona ◽  
Stable Structure ◽  
Two Dimensional ◽  
Radio Observations ◽  
Quiet Sun ◽  
Preliminary Study

In this preliminary study the first two-dimensional pictures showing detailed features of the quiet Sun and weak but moderately stable structure at metre wavelengths are presented. The observations were made at 80 MHz with the Culgoora radioheliograph.

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