Hadley circulations and Kelvin wave-driven equatorial jets in the atmospheres of Jupiter and Saturn

We propose a dynamical mechanism that can plausibly explain the origin of the broad prograde equatorial winds observed on Jupiter and Saturn, and examine the feasibility of this mechanism using two- (2D) and three-dimensional (3D) numerical simulation models. The idea is based on combining a narrow Gaussian jet peaking at the equator, which is induced by the momentum transfer from an upward propagating equatorial Kelvin-wave, and a pair of off-equatorial jets due to a meridional-vertical circulation similar to the tropical Hadley circulation on Earth. We employ for this feasibility study a 2D mechanistic mean-flow model which incorporates the influence of prescribed waves, and a 3D general circulation model, based on the generalised primitive equations of atmospheric motion. We then confirm that the dynamical models of both kinds can successfully reproduce theoretically expected flows of a reasonable magnitude, and that when two mechanisms are combined, a broad super-rotating jet is produced with off-equatorial maxima in zonal velocity for both Jupiter and Saturn, approximately in accordance with observations.     

有限导电内核的驱动方式对发电机模型的影响

本文以两种绝缘内核的发电机为基准,设置内核电导率与外核相同,选择了以固定速度超速旋转和在外核驱动下发生旋转的两种内核旋转模式,比较分析不同模型间的能量差异、磁场强度、磁雷诺数、磁极翻转频率和四个类地发电机参数.结果表明:对于弱偶极子发电机模型,有限导电内核的引入会对其偶极子强度的相对变化量造成较大影响,最高达103.00%;由外核驱动旋转的有限导电内核模型对于本文其他目标研究量所带来的影响比较小,均小于5%;而固定旋转速度的有限导电内核的模型对磁极翻转频率、赤道对称性和纬向性均存在较明显影响,最大变化量达124.62%.综合本文所选用的发电机模型的特征和数值分析结果,可以发现虽然由外核驱动旋转的有限导电内核模型其转速不可控且存在较大波动,但各物理量变化量与实际内核与外核的能量比更为接近,因此可以推断其驱动机制较自驱动模式更为合理可靠.