scholarly journals Stellar Winds and Spindown in Solar Type Stars

1983 ◽  
Vol 102 ◽  
pp. 449-460 ◽  
Author(s):  
I.W. Roxburgh
Keyword(s):  
Angular Momentum ◽  
Loss Rate ◽  
Neutrino Flux ◽  
Flow Speed ◽  
Stellar Winds ◽  
Sudden Increase ◽  
Momentum Loss ◽  
Rotational Discontinuity ◽  
Angular Momentum Loss ◽  
Solar Type

The angular momentum loss produced by stellar winds is reviewed and a simple model of angular momentum loss with multipole fields is presented in which the field is potential when the flow speed is less than the Alfvén speed, and radial when greater than the Alfvén speed. The simpler the magnetic geometry, the larger is the angular momentum loss rate. This result is used to explain the rotational discontinuity across the Vaughan-Preston gap as being due to a sudden increase in angular momentum loss when the dynamo field switches from a quadropole to a dipole geometry.The evolution of the internal rotation of stars as a result of surface angular momentum loss is considered. In the absence of a magnetic field, differential rotation can drive instabilities which then transport angular momentum out from the interior down the angular velocity gradient. Other instabilities such as that caused by the build up of 3He can also transport angular momentum outwards. If angular momentum is transported by such weak turbulence, it also makes the star more homogeneous than standard evolutionary models and lowers the predicted value of the solar neutrino flux.The recent results on rotational splitting of solar oscillations are considered: these suggest that the inside of the sun is spinning faster than the surface and are compatible with models in which angular momentum is transported by mild turbulence. But data is scarce — and in such circumstances the speculations of the theorist must be viewed with caution!

scholarly journals The rotation of very low-mass stars and brown dwarfs

2007 ◽  
Vol 3 (S243) ◽  
pp. 241-248
Author(s):  
Jochen Eislöffel ◽  
Alexander Scholz
Keyword(s):  
Angular Momentum ◽  
Brown Dwarfs ◽  
Magnetic Interaction ◽  
Stellar Winds ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Angular Momentum Loss ◽  
Rotational Evolution ◽  
Solar Type ◽  
Low Mass

AbstractThe evolution of angular momentum is a key to our understanding of star formation and stellar evolution. The rotational evolution of solar-mass stars is mostly controlled by magnetic interaction with the circumstellar disc and angular momentum loss through stellar winds. Major differences in the internal structure of very low-mass stars and brown dwarfs – they are believed to be fully convective throughout their lives, and thus should not operate a solar-type dynamo – may lead to major differences in the rotation and activity of these objects. Here, we report on observational studies to understand the rotational evolution of the very low-mass stars and brown dwarfs.

scholarly journals Formation and Evolution of Low-Mass Algols

1989 ◽  
Vol 107 ◽  
pp. 141-153
Author(s):  
L.R. Yungelson ◽  
A.V. Tutukov ◽  
A.V. Fedorova
Keyword(s):  
Angular Momentum ◽  
Gravitational Waves ◽  
Stellar Winds ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Low Mass ◽  
Formation And Evolution

AbstractWe discuss the origin, evolution and fate of low-mass Algols (LMA) that have components with initial masses less than 2.5 M0. The semi-major axes of orbits of pre-LMA do not exceed 20-25 R0. The rate of formation of Algol-type stars is ~ 0.01/year. Magnetic stellar winds may be the factor that determines the evolution of LMA. Most LMA end their lives as double helium degenerate dwarfs with M1/M2 ~ 0.88 (like L870-2). Some of them even merge through angular momentum loss caused by gravitational waves.

scholarly journals Loss of magnetic flux and angular momentum from molecular clouds

1991 ◽  
Vol 147 ◽  
pp. 67-74
Author(s):  
Takenori Nakano
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Magnetic Flux ◽  
Molecular Clouds ◽  
Loss Rate ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
The Magnetic Field ◽  
Flux Loss

The magnetic field and the angular momentum are major obstacles against cloud contraction. I will review recent results on magnetic flux loss rate and angular momentum loss rate and will investigate a gross feature of cloud contraction.

scholarly journals Coronal Mass Ejections and Angular Momentum Loss in Young Stars

2013 ◽  
Vol 8 (S300) ◽  
pp. 318-321
Author(s):  
Alicia N. Aarnio ◽  
Keivan G. Stassun ◽  
Sean P. Matt
Keyword(s):  
Angular Momentum ◽  
Coronal Mass Ejections ◽  
Necessary Conditions ◽  
Central Star ◽  
Young Stars ◽  
Activity Levels ◽  
Stellar Rotation ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Solar Type

AbstractIn our own solar system, the necessity of understanding space weather is readily evident. Fortunately for Earth, our nearest stellar neighbor is relatively quiet, exhibiting activity levels several orders of magnitude lower than young, solar-type stars. In protoplanetary systems, stellar magnetic phenomena observed are analogous to the solar case, but dramatically enhanced on all physical scales: bigger, more energetic, more frequent. While coronal mass ejections (CMEs) could play a significant role in the evolution of protoplanets, they could also affect the evolution of the central star itself. To assess the consequences of prominence eruption/CMEs, we have invoked the solar-stellar connection to estimate, for young, solar-type stars, how frequently stellar CMEs may occur and their attendant mass and angular momentum loss rates. We will demonstrate the necessary conditions under which CMEs could slow stellar rotation.

scholarly journals Mass-Loss From Spinning Stars

1980 ◽  
Vol 5 ◽  
pp. 601-613
Author(s):  
S. R. Sreenivasan
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Massive Stars ◽  
Stellar Winds ◽  
Late Type ◽  
Momentum Loss ◽  
Adequate Understanding ◽  
Angular Momentum Loss ◽  
Evolutionary Consequences ◽  
Acceptable Theory

AbstractThe effects of mass-loss and angular momentum loss on the evolution of massive stars are discussed bringing out the main results as well as the limitations of recent studies. It is pointed out that an acceptable theory of stellar winds in early as well as late type stars is needed as well as a satisfactory assessment of a number of instabilities in these contexts for an adequate understanding of the evolutionary consequences for a wide variety of population I and polulation II stars, which are affected by mass-loss.

scholarly journals Loss of magnetic flux and angular momentum from molecular clouds

1991 ◽  
Vol 147 ◽  
pp. 67-74
Author(s):  
Takenori Nakano
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Magnetic Flux ◽  
Molecular Clouds ◽  
Loss Rate ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
The Magnetic Field ◽  
Flux Loss

The magnetic field and the angular momentum are major obstacles against cloud contraction. I will review recent results on magnetic flux loss rate and angular momentum loss rate and will investigate a gross feature of cloud contraction.

scholarly journals A nonextensive approach for the angular momentum loss rate in low-mass stars

2012 ◽  
Vol 8 (S294) ◽  
pp. 197-198
Author(s):  
Daniel B. de Freitas ◽  
J. R. De Medeiros
Keyword(s):  
Angular Momentum ◽  
Loss Rate ◽  
Rotational Velocity ◽  
Low Mass Stars ◽  
New Approach ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Low Mass

AbstractThe present study demonstrates that behavior of rotational velocity as a function of stellar age is consistent using Tsallis' nonextensive formalism, resulting in a new approach to understanding the stellar rotational scenario.

scholarly journals THE EFFECT OF MAGNETIC SPOTS ON STELLAR WINDS AND ANGULAR MOMENTUM LOSS

2009 ◽  
Vol 699 (2) ◽  
pp. 1501-1510 ◽  
Author(s):  
O. Cohen ◽  
J. J. Drake ◽  
V. L. Kashyap ◽  
T. I. Gombosi
Keyword(s):  
Angular Momentum ◽  
Stellar Winds ◽  
Momentum Loss ◽  
Angular Momentum Loss

scholarly journals Contact Binary Evolution and Angular Momentum Loss

1981 ◽  
Vol 93 ◽  
pp. 181-182 ◽  
Author(s):  
Osmi Vilhu ◽  
Timo Rahunen
Keyword(s):  
Angular Momentum ◽  
Time Scale ◽  
Contact Discontinuity ◽  
Magnetic Activity ◽  
Thermal Time ◽  
Momentum Loss ◽  
Short Period ◽  
Angular Momentum Loss ◽  
Mass Ratios ◽  
Solar Type

Some fundamental problems connected with the evolution of W UMa stars are considered. While no generally accepted theory for the evolution of these systems exists, different scenarios lead to single stars on a nuclear or thermal time scale, or even to dwarf novae. The cycling and contact discontinuity models for zero age systems have gained much attention during the last few years. The contact discontinuity hypothesis has been heavily criticized on physical grounds, and the cycling at small mass ratios will probably be too violent leading to overcontact. On the other hand, there is increasing evidence of strong magnetic activity in short period solar type binaries, including W UMa stars (spots, flares, strong chromospheres and coronae etc.). This points to enhanced dynamo action inside rapidly rotating components of solar type close binaries. Extrapolating from single stars one finds that this may efficiently brake the orbital rotation. With an angular momentum loss rate of about 1043 g cm2 s−1 per year corresponding to the thermal time scale of the secondary the scenario, where the angular momentum loss controls the zero age contact evolution, seems at least possible. This scenario needs an (hypothetical) equilibrium process between the degree of contact and magnetic activity, damping the angular momentum loss if the contact becomes too thick, so that marginal contact will be preserved. If the angular momentum loss time scale is longer (comparable to the nuclear time scale of the primary), the system is likely to evolve towards more extreme mass ratios and with less violent cycling. (The complete paper will be published elsewhere.)

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