JpGU-AGU Joint Meeting 2017

講演情報

[JJ] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS15] [JJ] 地球流体力学:地球惑星現象への分野横断的アプローチ

2017年5月24日(水) 15:30 〜 17:00 ポスター会場 (国際展示場 7ホール)

コンビーナ:伊賀 啓太(東京大学大気海洋研究所)、吉田 茂生(九州大学大学院理学研究院地球惑星科学部門)、柳澤 孝寿(海洋研究開発機構 地球深部ダイナミクス研究分野)、相木 秀則(名古屋大学)

[MIS15-P02] Preliminary results of linear stability analysis on the onset of convection in a thick rotating spherical shell with implications for a dynamo in an icy moon

*谷口 陽菜実1高橋 太1 (1.九州大学)

キーワード:熱対流、組成対流、キネマティックダイナモ、線型安定性解析、鉄雪

Convection in the fluid core of a terrestrial planet, which maintains its intrinsic magnetic field by dynamo action, is driven by thermal and/or chemical buoyancy. In case of the Earth, the former is fed by secular cooling of the core, latent heat release upon inner core solidification, and possibly decay of radioactive elements in the core, while the latter arises from light element ejection into the outer core at the front of inner core growth. On the other hand, let us consider a celestial body smaller than the Earth. In that case, compositional convection could occur in various ways due to different pressure-temperature conditions, strongly depending on bulk sulfur content in the core. Among them, we here focus on the iron snow process, which might drive the present Ganymede’s dynamo.

In order to understand a basic flow structure of convection driven by the iron snow process, onset of thermal/compositional convection in rotating spherical shells is studied with linear analysis. First, we consider thermal convection of a Boussinesq fluid contained in a rotating spherical shell. We solve the linearized equations as an eigen-value problem, and then, check validity of our linear code by comparing the results with those in a literature (Ardes et al., 1997). Thus, the Ekman number adopted here is not very low, . Afterwards, linear stability problem of compositional convection driven by iron snow is examined. In this case, relative inner core size smaller than the Earth is given to mimic possible Ganymede’s core geometry. Using the results, we then solve kinematic dynamo problem to gain some insights into dynamos driven by iron snow. We will report our preliminary results about these issues.