Double diffusive convection in the Earth's core and the morphology of the geomagnetic field

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9 Citations (Scopus)

Abstract

The convection in the Earth's outer core is driven by thermal and compositional buoyancy. Here we examine the effects of the co-existence of these two buoyancy sources on the core dynamics and morphology of the geomagnetic field using numerical dynamo models with double diffusive convection at the thermal Prandtl number, Pr T=0.1 and compositional Prandtl number, Pr C=1. We find that the morphology of the magnetic field is determined by the dynamic ratio of the two driving mechanisms. A dipolar magnetic field is maintained as long as the power injected by thermal buoyancy comprises less than 60% of the total. Otherwise, non-dipolar fields prevail due to helicity reduction. The dominantly dipolar structure of the present geomagnetic field suggests that the fraction of power injection by thermal convection in the present geodynamo is below the threshold.

Original languageEnglish
Pages (from-to)83-87
Number of pages5
JournalPhysics of the Earth and Planetary Interiors
Volume226
DOIs
Publication statusPublished - Jan 1 2014
Externally publishedYes

Fingerprint

Earth core
geomagnetism
geomagnetic field
buoyancy
convection
Prandtl number
magnetic field
geodynamo
outer core
thermal convection
magnetic fields
free convection
coexistence
injection
thresholds

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Space and Planetary Science
  • Physics and Astronomy (miscellaneous)
  • Astronomy and Astrophysics

Cite this

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title = "Double diffusive convection in the Earth's core and the morphology of the geomagnetic field",
abstract = "The convection in the Earth's outer core is driven by thermal and compositional buoyancy. Here we examine the effects of the co-existence of these two buoyancy sources on the core dynamics and morphology of the geomagnetic field using numerical dynamo models with double diffusive convection at the thermal Prandtl number, Pr T=0.1 and compositional Prandtl number, Pr C=1. We find that the morphology of the magnetic field is determined by the dynamic ratio of the two driving mechanisms. A dipolar magnetic field is maintained as long as the power injected by thermal buoyancy comprises less than 60{\%} of the total. Otherwise, non-dipolar fields prevail due to helicity reduction. The dominantly dipolar structure of the present geomagnetic field suggests that the fraction of power injection by thermal convection in the present geodynamo is below the threshold.",
author = "Futoshi Takahashi",
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volume = "226",
pages = "83--87",
journal = "Physics of the Earth and Planetary Interiors",
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T1 - Double diffusive convection in the Earth's core and the morphology of the geomagnetic field

AU - Takahashi, Futoshi

PY - 2014/1/1

Y1 - 2014/1/1

N2 - The convection in the Earth's outer core is driven by thermal and compositional buoyancy. Here we examine the effects of the co-existence of these two buoyancy sources on the core dynamics and morphology of the geomagnetic field using numerical dynamo models with double diffusive convection at the thermal Prandtl number, Pr T=0.1 and compositional Prandtl number, Pr C=1. We find that the morphology of the magnetic field is determined by the dynamic ratio of the two driving mechanisms. A dipolar magnetic field is maintained as long as the power injected by thermal buoyancy comprises less than 60% of the total. Otherwise, non-dipolar fields prevail due to helicity reduction. The dominantly dipolar structure of the present geomagnetic field suggests that the fraction of power injection by thermal convection in the present geodynamo is below the threshold.

AB - The convection in the Earth's outer core is driven by thermal and compositional buoyancy. Here we examine the effects of the co-existence of these two buoyancy sources on the core dynamics and morphology of the geomagnetic field using numerical dynamo models with double diffusive convection at the thermal Prandtl number, Pr T=0.1 and compositional Prandtl number, Pr C=1. We find that the morphology of the magnetic field is determined by the dynamic ratio of the two driving mechanisms. A dipolar magnetic field is maintained as long as the power injected by thermal buoyancy comprises less than 60% of the total. Otherwise, non-dipolar fields prevail due to helicity reduction. The dominantly dipolar structure of the present geomagnetic field suggests that the fraction of power injection by thermal convection in the present geodynamo is below the threshold.

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U2 - 10.1016/j.pepi.2013.11.006

DO - 10.1016/j.pepi.2013.11.006

M3 - Letter

VL - 226

SP - 83

EP - 87

JO - Physics of the Earth and Planetary Interiors

JF - Physics of the Earth and Planetary Interiors

SN - 0031-9201

ER -