Geomagnetically Induced Currents
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Introduction

Large-scale currents flowing overhead in the ionosphere induce electric and magnetic fields on the surface of the Earth. So-called Geomagnetically Induced Currents (GICs) can in turn be induced in technologically networks located underneath these currents, such as railroads, power transmission lines, and pipelines. During electromagnetic storm periods caused by the Sun these GICs can be large, often exceeding several hundred Amperes, and cause catastrophic consequences to the system in which they flow.

Scientists at Dartmouth are attempting to predict the occurence of GICs using physics-based models of the global magnetosphere, ionosphere, and Earth conductivity together with input from a satellite located in the upstream solar wind. The electric (and magentic) field at the surface of the Earth over North America will be determined with 30-90 minutes warning, allowing an advance warning of GICs to be calculated for specific conducting networks.

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Testing

Earth Models | Electroject | Fields | Techniques
Earth Conductivity Models:    No Earth - Uniform - Layered

Model Electrojet
   Ionospheric Grids:   
Coarse - Medium - Fine
   Current Density:        Coarse - Medium - Fine - Animation
Calculated Fields
   No Earth
     Cartesian Coordinates
       Coarse Grid
        
Latitude Cut
         CANOPUS:    BX - BY - BZ - EX - EY - Animation
       Fine Grid
         Latitude Cut
         CANOPUS:    BX - BY - BZ - EX - EY

     Spherical Coordinates
       Coarse Grid
         CANOPUS:    BX - BY - BZ - EX - EY

   Layered Conductivity
         CANOPUS:    BX - BY - BZ - EX - EY

Techniques
  
Complex Image Method (CIM)
   Finite Difference Time Domain (FDTD)

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Studies

LFM Driver | 2D Earth Model | 2D E/M Polarization

LFM MHD Input (March 19-20, 1999)
A study using a two-day run of the LFM magnetospheric MHD model. Ionospheric currents are extracted from the model run and used as inputs to drive the induced field calculations.

   Interpolated Current Density:   
w/ MHD        w/o MHD        Meridian Profile

   Fields
       - Full period (2 days) :   
BX - BY - BZ - EX - EY
       - EX: 0-6, 6-12, 12-18, 18-24, 24-30, 30-36, 36-42, 42-48
       - EY: 0-6, 6-12, 12-18, 18-24, 24-30, 30-36, 36-42, 42-48
       March 19, 1930-2130 UT        March 20, 1730-1930 UT

Horizontal Gradients
A study using an idealized line current and a 'square' model of the ocean. The effect of the large horizontal gradient in the conductivity between the Earth and the ocean are investigated using the method of auxiliary sources (MAS), adapted by Dr. Shubitidze for this study.

  
Geometry

   2D fields


More Horizontal Gradients
A study using an idealized sheet current and a more realistic model of the ocean. The effect of the large horizontal gradient in the conductivity between the Earth and the ocean are again investigated using the method of auxiliary sources (MAS). In this study two polarizations of the inducing field are used, both parallel and perpendicular to the gradient.

   E Polarization
    
1 min      10 min      30 min      60 min

   M Polarization
     1 min      10 min      30 min      60 min


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People

Name Affil. Phone Email
Bill Lotko Thayer School 603.646.3485 William.Lotko@dartmouth.edu
Kevin O'Neill Thayer/CRREL 603.646.4312 koneill@ERDC.usace.army.mil
Simon Shepherd Thayer School 603.646.0096 Simon.Shepherd@dartmouth.edu
Fridon Shubitidze Thayer School 603.646.3671 Fridon.Shubitidze@dartmouth.edu

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Links

Finnish Meteorological Institute
Swedish Institute for Space Physics
Canadian National Geomagnetism Program
Space Environment Center
CISM at Dartmouth College

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Contact Information