Cohen Ofer, Glocer Alex, Garraffo Cecilia, Drake Jeremy J, Bell Jared M
Lowell Center for Space Science and Technology, University of Massachusetts Lowell 600 Suffolk St., Lowell, MA 01854, USA.
Harvard-Smithsonian Center for Astrophysics,60 Garden St., Cambridge, MA 02138, USA.
Astrophys J Lett. 2018 Mar 20;856(1). doi: 10.3847/2041-8213/aab5b5. Epub 2018 Mar 23.
We present a method to quantify the upper-limit of the energy transmitted from the intense stellar wind to the upper atmospheres of three of the Trappist-1 planets (e, f, and g). We use a formalism that treats the system as two electromagnetic regions, where the efficiency of the energy transmission between one region (the stellar wind at the planetary orbits) to the other (the planetary ionospheres) depends on the relation between the conductances and impedances of the two regions. Since the energy flux of the stellar wind is very high at these planetary orbits, we find that for the case of high transmission efficiency (when the conductances and impedances are close in magnitude), the energy dissipation in the upper planetary atmospheres is also very large. On average, the Ohmic energy can reach 0.5 - 1 , about 1% of the stellar irradiance and 5-15 times the EUV irradiance. Here, using constant values for the ionospheric conductance, we demonstrate that the stellar wind energy could potentially drive large atmospheric heating in terrestrial planets, as well as in hot jupiters. More detailed calculations are needed to assess the ionospheric conductance and to determine more accurately the amount of heating the stellar wind can drive in close-orbit planets.
我们提出了一种方法，用于量化从强烈的恒星风传输到Trappist-1星系中三颗行星（e、f和g）高层大气的能量上限。我们采用一种形式主义，将该系统视为两个电磁区域，其中一个区域（行星轨道处的恒星风）到另一个区域（行星电离层）的能量传输效率取决于这两个区域的电导率和阻抗之间的关系。由于在这些行星轨道处恒星风的能量通量非常高，我们发现，在高传输效率的情况下（当电导率和阻抗在量级上接近时），行星高层大气中的能量耗散也非常大。平均而言，欧姆能量可达0.5 - 1，约为恒星辐照度的1%，是极紫外辐照度的5 - 15倍。在这里，我们使用电离层电导率的恒定值，证明恒星风能量有可能在类地行星以及热木星中驱动大量的大气加热。需要进行更详细的计算来评估电离层电导率，并更准确地确定恒星风在近轨道行星中能够驱动的加热量。
