Geomagnetically induced
currents – p
physics
y
and
applications
Antti Pulkkinen
UMBC/GEST @ NASA/GSFC
June 25, 2010, GEM Workshop,
Snowmass, CO.
1
Contents
• Motivation/background
i i /b k
d – why
h should
h ld we care?
• Some observational facts of interest about
geomagnetically induced currents (GIC).
(GIC)
• Theory and modeling.
• Forecasting – the Solar Shield project.
project
• Future challenges.
• Summary
Summary.
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Geomagnetically induced current (GIC)
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Why do we care? (applications)
(
)
• GIC causes saturation of power
transformers:
• Transformer damage
• Electric
El i bl
blackout
k
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Why do we care? (physics)
(
)
June 25, 2010, GEM Workshop,
Snowmass, CO.
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What
does
GIC
look
like?
Typical amplitudes
Bursts
Sudden start
Complex waveform
June 25, 2010, GEM Workshop,
Snowmass, CO.
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57°
geomag. lat.
What drives (large)
(
) GIC?
June 25, 2010, GEM Workshop,
Snowmass, CO.
Huttunen et al. (Space Weather, 2008)
7
35°
geomag. lat.
What drives (large)
(
) GIC?
(CME-driven)
Pulkkinen et al. (JASR, 2010)
Coronal mass ejections the most significant driver of
large GIC at midmid and high-latitudes.
high latitudes
June 25, 2010, GEM Workshop,
Snowmass, CO.
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57°
geomag. lat.
What drives (large)
(
) GIC?
storm-time
storm
time
substorms
storm-time
storm
time
pulsations
Viljanen et al. (Space Weather, 2006)
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Theory and modeling
• Modeling
d li off G
GIC
C iis d
done iin two steps:
– Geophysical step – compute the geoelectric field using
ggeomagnetic
g
induction theory.
y
– Engineering step – compute the GIC using the known system
parameters.
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Geomagnetic (quasi-static) induction
i lilinear, iisotropic
in
t i and
d nondispersive
di
i
medium
Theory and modeling
∇⋅ E =
ρ
ε0
∇×E =−
j = σE
June 25, 2010, GEM Workshop,
Snowmass, CO.
∂
B
∂t
(1)
∇⋅ B =0
(3)
∇ × B = μ0 j + μ0ε0
(2)
∂
E
∂t
(4)
(5)
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Theory and modeling
Time derivative of the horizontal
magnetic field
Ey = −
Conductivity
June 25, 2010, GEM Workshop,
Snowmass, CO.
1
πμ0σ
t
∫
−∞
∞
Source field needs to be
known (proportional to
source currents)
gx
dt'
t − tt'
History needs to be
known
Conductivity structure needs
to be known
12
Complex Image Method
Pirjola and Viljanen (Annales Geophysicae, 1998)
Pulkkinen et al. (PIER, 2009)
Theory and modeling
j (r ')
j (r ')
Ai , Ar
σ (z)
ez
C ⋅ j (C ⋅ r ')
μ0
Ai =
4π
∫
V
j (r )
j(r')
dV '
r − r'
(1)
μ0
C ⋅j
⋅j(C
(C ⋅r
⋅r'))
Ar =
dV ' (2)
∫
4 π V Workshop,
r − r '−2 p(ω,σ (z))ez
June 25, 2010, GEM
Snowmass, CO.
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Theory and modeling - GIC
• General solutions for discretely and
g
systems
y
byy Lehtinen
continuouslyy grounded
and Pirjola, Ann. Geophys. (1985) and
pp Geophys.
p y (2001).
Pulkkinen et al.,, JJ. Appl.
• In practice, GIC can be computed from:
GICi = ai E x (ri ) + bi E y (ri )
System parameters can be solved
empirically or theoretically
Output of the geomagnetic
June 25, 2010, GEM Workshop,
Snowmass, CO.
induction computations
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Forecasting – Solar Shield
• In Solar Shield, we developed a two-level
experimental system to forecast space weather effects
on the
h North
N hA
American
i
power grid;
id project
j funded
f d d by
b
NASA’s Applied Sciences Program.
• NASA/GSFC/CCMC and Electric Power Research
Institute (EPRI) the key players.
• Pulkkinen et al. ((Natural Hazards,, 2009).
)
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Level 1 forecasts
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Solar observations of eruptive events
are used to compute “cone model”
parameters. NASA/ESA
SOHO/LASCO
used.
MHD outputdata
at the
Earth used in a statistical model
Level 1 forecasts
providing probabilistic estimate for GIC at individual
nodes of the power grid. GIC forecast file is generated.
Plasma “cone” introduced to the inner boundary of a
heliospheric MHD model. Model propagates the
disturbance to the Earth.
Earth Computations carried out at the
Community Coordinated Modeling Center.
April 3, 2008
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Level 2 forecasts
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Lagrange 1 observations used as
boundary conditions for
magnetospheric MHD. NASA’s ACE
Magnetospheric
MHD output used to drive geomagnetic
data used.
induction and GIC code providing GIC at individual
nodes of the power grid. GIC forecast file is generated.
Magnetospheric MHD model used to model the
magnetospheric-ionospheric dynamics. Computations
carried out at the Community Coordinated Modeling
Center.
April 3, 2008
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Level 2 forecast example
June 25, 2010, GEM Workshop,
Snowmass, CO.
Oct 24, 2003
20
Future challenges
• Need
d to account for
f the
h 3D
3 structure off the
h Earth?
h
• Do we capture the substorm-related ionospheric
current fluctuations in the global MHD-based
MHD based
modeling approach? Substorms important driver of
large GIC.
• Need to expand the global MHD-based modeling
approach to cover lower latitudes. This is of significant
US and
d possibly
ibl European
E
interest.
i
June 25, 2010, GEM Workshop,
Snowmass, CO.
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Summary
•G
GIC
C global
l b l phenomenon
h
that
h a)) iimpacts llong
conductor systems and b) is at the end of chain of
complex physical processes.
• CMEs the most significant driver of large GIC.
• Modeling of GIC carried out in two steps - geophysical
and engineering steps.
• Emerging capability to forecast GIC based on the firstprinciples.
• Many interesting challenges ahead.
June 25, 2010, GEM Workshop,
Snowmass, CO.
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