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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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Contact Information

• Office: 212 Cummings Hall
• Telephone: (603) 646-0096
• E-mail: simon at thayer.dartmouth.edu