MAGNETIC SCALING LAWS FOR THE ATMOSPHERES OF HOT GIANT EXOPLANETS
MAGNETIC SCALING LAWS FOR THE ATMOSPHERES OF HOT GIANT EXOPLANETS
复制标题
热巨系外行星大气层的磁缩放定律
DOI：
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发表时间：
2011
期刊：
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通讯作者：
K. Menou
中科院分区：
文献类型：
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作者：
K. Menou
我们提出了热巨系外行星大气中平流、辐射、磁阻力和欧姆耗散的标度律。在弱热电离的极限下，欧姆耗散随行星平衡温度（Teq = 1000 K）的增加比日射功率的增加更快，最终达到日射功率的10.1%，这可能足以膨胀热彗星的半径。在较高的Teq值仍然磁阻力迅速制动大气风，这降低了相关的欧姆耗散功率。例如，对于行星磁场强度B = 10 G，基准标度律表明，在平衡温度范围Teq = 1300-2000 K内，欧姆耗散超过日射功率的1%，在Teq = 1600 K时贡献最大。在行星热光球层的磁拖曳风的证据可能会出现在减少纵向偏移的昼侧红外热点的形式。这表明热点偏移量和半径膨胀程度之间可能存在一种因果关系，以一种可观测的方式将热巨型系外行星的大气和内部性质联系起来。虽然提供了一个有用的框架来探索磁场的情况下，标度律也揭示了强烈的参数依赖性，特别是对于未知的行星磁场强度。
We present scaling laws for advection, radiation, magnetic drag, and ohmic dissipation in the atmospheres of hot giant exoplanets. In the limit of weak thermal ionization, ohmic dissipation increases with the planetary equilibrium temperature (Teq ≳ 1000 K) faster than the insolation power does, eventually reaching values ≳ 1% of the insolation power, which may be sufficient to inflate the radii of hot Jupiters. At higher Teq values still magnetic drag rapidly brakes the atmospheric winds, which reduces the associated ohmic dissipation power. For example, for a planetary field strength B = 10 G, the fiducial scaling laws indicate that ohmic dissipation exceeds 1% of the insolation power over the equilibrium temperature range Teq ∼ 1300–2000 K, with a peak contribution at Teq ∼ 1600 K. Evidence for magnetically dragged winds at the planetary thermal photosphere could emerge in the form of reduced longitudinal offsets for the dayside infrared hotspot. This suggests the possibility of an anticorrelation between the amount of hotspot offset and the degree of radius inflation, linking the atmospheric and interior properties of hot giant exoplanets in an observationally testable way. While providing a useful framework to explore the magnetic scenario, the scaling laws also reveal strong parameter dependencies, in particular with respect to the unknown planetary magnetic field strength.