Numerical simulations of geomagnetic short-timescale variations

• Project/Area Number: 23740334
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: The University of Tokyo
• Principal Investigator: SAKURABA Ataru 東京大学, 理学(系)研究科(研究院), 助教 (50345261)
• Project Period (FY): 2011 – 2012
• Project Status: Completed (Fiscal Year 2013)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2012: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000); Fiscal Year 2011: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
• Keywords: 地磁気永年変化 / 地球ダイナモ / 西方移動 / ジャーク / ねじれ振動 / 数値シミュレーション / 磁気不安定 / 地磁気西方移動 / 磁気流体波動 / 電磁流体力学 / 地磁気ジャーク / 地球電磁気 / 流体力学 / 地球磁場

Research Abstract

I performed numerical simulations of convection and geomagnetic field generation processes in Earth's liquid metallic core to reproduce several characteristic geomagnetic secular variations. The numerical result exhibits torsional oscillations that are composed of traveling waves toward and out of the Earth's rotation axis, suggesting that they are created by turbulence in internal core convection. The result also shows clear westward drift in the core-surface magnetic field particularly in high-wavenumber components and in the low latitudes, and I pointed out existence of dispersion in the westward drift. In order to figure out this dispersion property, I conducted linear stability analysis of axisymmetric magnetic field in an inviscid rotating fluid sphere, and discussed possible relations between westward propagation of slow hydromagnetic wave and the geomagnetic westward drift.

Research Products

• [Presentation] 回転流体球における磁気不安定と地磁気西方移動 (2013)
  • Author(s): 桜庭 中
  • Organizer: 地球電磁気・地球惑星圏学会秋季大会
  • Place of Presentation: 高知大学(高知)
  • Year and Date: 2013-11-05
• [Presentation] 遅い電磁流体波動と地磁気西方移動 (2013)
  • Author(s): 桜庭 中
  • Organizer: 日本地球惑星科学連合2013年大会
  • Place of Presentation: 幕張メッセ(千葉)
  • Year and Date: 2013-05-19
• [Presentation] 回転流体球における磁気不安定と地磁気西方移動 (2013)
  • Author(s): 桜庭 中
  • Organizer: 地球電磁気・地球惑星圏学会秋季大会
  • Place of Presentation: 高知大学・高知
• [Presentation] 遅い電磁流体波動と地磁気西方移動 (2013)
  • Author(s): 桜庭 中
  • Organizer: 日本地球惑星科学連合２０１３年大会
  • Place of Presentation: 幕張メッセ・千葉
• [Presentation] 地磁気西方移動の起源 (2012)
  • Author(s): 桜庭 中
  • Organizer: 地球電磁気・地球惑星圏学会秋季大会
  • Place of Presentation: 札幌コンベンションセンター(北海道)
  • Year and Date: 2012-10-22
• [Presentation] Westward drift, torsional oscillations and jerks in a low viscosity numerical geodynamo model (2012)
  • Author(s): A. Sakuraba
  • Organizer: SEDI (Study of Earth's Deep Interior) Symposium
  • Place of Presentation: リーズ(イギリス)
  • Year and Date: 2012-07-02
• [Presentation] 地球ダイナモモデルにおける西方移動,ねじれ振動およびジャーク (2012)
  • Author(s): 桜庭 中
  • Organizer: 日本地球惑星科学連合2012年大会
  • Place of Presentation: 幕張メッセ(千葉)
  • Year and Date: 2012-05-25
• [Presentation] Westward drift, torsional oscillations and jerks in a low-viscosity numerical geodynamo model (2012)
  • Author(s): 桜庭 中
  • Organizer: The 13th Symposium of SEDI (Study of the Earth's Deep Interior)
  • Place of Presentation: Leeds, UK
• [Presentation] 地球ダイナモモデルにおける西方移動、ねじれ振動およびジャーク (2012)
  • Author(s): 桜庭 中
  • Organizer: 地球惑星連合2012年大会
  • Place of Presentation: 幕張メッセ, 千葉県
• [Presentation] 地磁気西方移動の起源 (2012)
  • Author(s): 桜庭 中
  • Organizer: 地球電磁気・地球惑星圏学会
  • Place of Presentation: 札幌コンベンションセンター, 北海道
• [Presentation] Numerical simulations of geomagnetic field variations : from jerks to superchrons (2011)
  • Author(s): A. Sakuraba
  • Organizer: AGU Fall Meeting 2011
  • Place of Presentation: サンフランシスコ(アメリカ)
  • Year and Date: 2011-12-07
• [Presentation] Simulating geomagnetic field variations : from jerks to superchrons (2011)
  • Author(s): 桜庭 中
  • Organizer: 地球電磁気・地球惑星圏学会秋季大会
  • Place of Presentation: 神戸大学(兵庫)
  • Year and Date: 2011-11-04
• [Presentation] Numerical simulations of short-timescale geomagnetic field variations (2011)
  • Author(s): A. Sakuraba
  • Organizer: IUGG General Assembly
  • Place of Presentation: メルボルン(オーストラリア)
  • Year and Date: 2011-07-02
• [Presentation] Numerical simulations of geomagnetic field variations: from jerks to superchrons (2011)
  • Author(s): Ataru Sakuraba
  • Organizer: American Geophysical Union Fall Meeting(招待講演)
  • Place of Presentation: San Francisco, USA
• [Presentation] Numerical simulations of short-timescale geomagnetic field variations (2011)
  • Author(s): Ataru Sakuraba
  • Organizer: IUGG General Assembly
  • Place of Presentation: Melbourne, Australia
• [Presentation] Numerical simulations of magnetostrophic dynamo (2011)
  • Author(s): Ataru Sakuraba
  • Organizer: IUGG General Assembly
  • Place of Presentation: Melbourne, Australia
• [Presentation] Simulating geomagnetic field variations: From jerks to superchrons (2011)
  • Author(s): 櫻庭 中
  • Organizer: 地球電磁気・地球惑星圏学会
  • Place of Presentation: 神戸
• [Presentation] Nonlinear solutions of inviscid magnetostrophic dynamos (2011)
  • Author(s): 櫻庭 中
  • Organizer: 地球惑星科学連合大会
  • Place of Presentation: 千葉
• [Book] On thermal driving of the geodynamo, in "The Earth's Magnetic Interior" (Eds. E. Petrovsky et al.), IAGA Special Sopron Book Series 1 (2011)
  • Author(s): A. Sakuraba and P. H. Roberts
  • Publisher: Springer
• [Book] On thermal driving of the geodynamo (in "The Earth's magnetic interior", Eds. E. Petrovsky, E. Herrero-Bervera, T. Harinarayama, D. Ivers) (2011)
  • Author(s): Ataru Sakuraba and Paul H. Roberts
  • Publisher: Springer