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首页> 外文期刊>The Astrophysical journal >A GRID OF MHD MODELS FOR STELLAR MASS LOSS AND SPIN-DOWN RATES OF SOLAR ANALOGS
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A GRID OF MHD MODELS FOR STELLAR MASS LOSS AND SPIN-DOWN RATES OF SOLAR ANALOGS

机译:恒星质量损失和太阳能模拟速度下降的MHD模型的网格

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Stellar winds are believed to be the dominant factor in the spin-down of stars over time. However, stellar winds of solar analogs are poorly constrained due to observational challenges. In this paper, we present a grid of magnetohydrodynamic models to study and quantify the values of stellar mass loss and angular momentum loss rates as a function of the stellar rotation period, magnetic dipole component, and coronal base density. We derive simple scaling laws for the loss rates as a function of these parameters, and constrain the possible mass loss rate of stars with thermally driven winds. Despite the success of our scaling law in matching the results of the model, we find a deviation between the "solar dipole" case and a real case based on solar observations that overestimates the actual solar mass loss rate by a factor of three. This implies that the model for stellar fields might require a further investigation with additional complexity. Mass loss rates in general are largely controlled by the magnetic field strength, with the wind density varying in proportion to the confining magnetic pressure B 2. We also find that the mass loss rates obtained using our grid models drop much faster with the increase in rotation period than scaling laws derived using observed stellar activity. For main-sequence solar-like stars, our scaling law for angular momentum loss versus poloidal magnetic field strength retrieves the well-known Skumanich decline of angular velocity with time, Ω∝t –1/2, if the large-scale poloidal magnetic field scales with rotation rate as .
机译:恒星风被认为是恒星随时间推移而旋转的主要因素。然而,由于观测方面的挑战,太阳类似物的恒星风受到的约束较弱。在本文中,我们提出了一个磁流体动力学模型网格,以研究和量化恒星质量损失和角动量损失率与恒星旋转周期,磁偶极子分量和日冕碱密度的函数关系。我们根据这些参数得出损耗率的简单缩放定律,并用热驱动风约束恒星的可能质量损耗率。尽管我们的缩放定律在匹配模型结果方面取得了成功,但基于太阳观测结果,我们发现“太阳偶极子”情况与实际情况之间存在偏差,该偏差将实际太阳质量损失率高估了三倍。这意味着恒星场的模型可能需要进一步研究,并且具有额外的复杂性。一般而言,质量损失率主要受磁场强度控制,风密度与围压B 2成正比。我们还发现,使用网格模型获得的质量损失率随着旋转的增加而下降得更快。比使用观测到的恒星活动推导的定标定律。对于像太阳这样的主序恒星,我们的角动量损耗与极向磁场强度的比例定律可以检索到众所周知的斯库曼尼希角速度随时间的下降,Ω∝t –1/2(如果是大规模极向磁场)以旋转速率缩放。

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