First European Space Weather Week 2004 1
Magnetic environment:
science of GIC
Ari Viljanen and Risto Pirjola
Finnish Meteorological Institute
Antti Pulkkinen
NASA/GSFC
This presentation is a contribution to
First European Space Weather Week 2004 2
Contents
1) General scientific background
2) Operative calculation & some science
3) On-going and future science
First European Space Weather Week 2004 3
Before the modern ”space weather”, there was GIC
B(r,t)
)j (r,tn (r,t)
E(r,t)
air dragS/C anomalies
signal degradation
cosmic rays
GIC
particle radiation
auroras
First European Space Weather Week 2004 4
GIC deals with the inductive coupling
between the ionosphere and the earth
Activity of the Sun
Propagation of the solar wind
Magnetospheric processes
Ionospheric processes
Geoelectric fieldat the Earth's surface
Earth's structure(induction)
GIC in ground–basedtechnological systems
GIC problems
Possible countermeasures,alarm systems, etc.
Network configuration
Figure 1: Schematic GIC chain. ”Science blocks” marked by blue.
First European Space Weather Week 2004 5
1. Modelling of the geoelectric field
• Ionospheric currents or ground magnetic data
• Earth’s conductivity
These results also applicable in magnetotelluric studies.
2. Modelling of GIC
• Discretely grounded systems
• Continuously grounded systems
3. Analysis of GIC effects
First European Space Weather Week 2004 6
GIC and dB/dt are closely related
06:30 06:40 06:50 07:00 07:10 07:20 07:30
-50
0
50
GIC
[A]
Mäntsälä 29.10. 2003 (10 s values)
natural gas pipeline
06:30 06:40 06:50 07:00 07:10 07:20 07:30
-20
-10
0
10
20
-dX
/dt [
nT/s
]
Nurmijärvi observatory
Figure 2: Largest GIC measured in the Finnish natural gas pipeline.
First European Space Weather Week 2004 7
GIC is a manifestation of Faraday’s law
hor. ground electric field E dH/dt
geomagnetically induced current (GIC)
Roughly speaking:
~ 90 deg
any angle
hor. magnetic field H
spat
ial i
nteg
ratio
n
Figure 3: Measured: ground magnetic field variation.
To be determined: E and GIC.
First European Space Weather Week 2004 8
Space currents cause the varying magnetic field
equivalent current J
horizontal field H
Figure 4: Potential theory states that the ground magnetic variation
field can be explained by an equivalent current distribution at the iono-
spheric plane. Approximately, rotate H 90 degrees clockwise.
First European Space Weather Week 2004 9
Ionospheric currents flow all the time
max(|H|) = 3843 nT
20031030 20:07:00
0 o
20oE
40o E
60 oN
65 oN
70 oN
Figure 5: Interpolated and rotated ground H at 20:07:00 UT on October
30, 2003, at the time of the GIC blackout in southern Sweden.
First European Space Weather Week 2004 10
Diversity of dB/dt is eye-catching
Two nearby timesteps, nearly identical patterns of ground H,
but very different dH/dt:
max(|dH/dt|) = 28.4 nT/s
20031030 20:06:30
0 o
20oE
40o E
60 oN
65 oN
70 oN
max(|dH/dt|) = 34.1 nT/s
20031030 20:08:40
0 o
20oE
40o E
60 oN
65 oN
70 oN
First European Space Weather Week 2004 11
Small scales are important
t1
t1t -2
First European Space Weather Week 2004 12
Arising questions:
• Which ionospheric events cause large GIC?
How do these events couple to magnetospheric and solar
wind dynamics?
• What are the characteristic spatial and temporal scales related to
these events?
Are there any characteristic scales?
• Can we forecast such events?
What features of these events can we forecast?
First European Space Weather Week 2004 13
Earth has a remarkable effect on the geoelectric field
Ionospheric currents → primary field Ep
Telluric currents → secondary field Ehor,s ≈ −Ehor,p
Earth conductivity models are obtained from magnetotelluric studies.
10˚
10˚
15˚
15˚
20˚
20˚
25˚
25˚
30˚
30˚
35˚
35˚
40˚
40˚
55˚ 55˚
60˚ 60˚
65˚ 65˚
70˚ 70˚
75˚ 75˚
80˚ 80˚
0 500km
B50LOV
B16JOK
B23ULL
B34MIS
B42SAL
B47LEH
B48TOP
B49UPO
B26NUR
B31PEL
B32HAN
B33OUL
B35SOD
B30YLIB22
BODB15ARV
B11HEM
B14LYC
B10NOR
B05ARE
B09BRA
B08SOD
B13HAR
B21SKE
B37VIR
B38PUU
B45NII
B46ILO
B39JUU
B40LOT
B41KUO
B29VIH
B20VOL B28
KIV
B27KOR
B19HON
B18AUR
B17HII
B25RAK
B24SIN
B36PEI
B44PERB02
LUD
B01ASK
B12MAR
B07UPS
A01KIRi
A02MUOi
A03ABKi
A04KILi
A05ANDi
A06MASi
A07TROi
A08KEVi
A09SORi
A10BJNi
A11HOPi
A12HORi
A13LYRi
A14NALi
A15IVA
A16LOVi
A18KVIs
A19NORs A20
OULs
A23LAU
B E A RBaltic Electromagnetic Array Research
Norwegian Sea
BothnianBay
Gulf ofBothnia
LakeLadoga
Gulf of Finland
Baltic Sea
Barents Sea
WhiteSea
Vanern
LakeOnega
MTS: Bx,By,Bz,Ex,EyOulu
& NurmijarviUppsala
& EdinburghGoettingen
& Potsdam
St. Petersburg
Lviv, Ukraina
Observatories
GDS: Bx,By,BzIMAGE/SAMNET
TK ’99
First European Space Weather Week 2004 14
Operative method - ground B
max = 382 nT
20010411 21:30:00
Figure 6: Measured ground horizontal field rotated 90 deg clockwise to
mimic ionospheric equivalent currents.
First European Space Weather Week 2004 15
Operative method - interpolated B
20010411 21:30:00
0 o 20oE
40o E
60 oN
65 oN
70 oN
75 oN max(H)
414 nT
Figure 7: Use of equivalent currents is a robust interpolation method.
First European Space Weather Week 2004 16
Operative method - earth’s conductivity
3 km
6 km
5 km
7 km
23 km
106 km
5000 ohmm5000 ohmm
500 ohmm
100 ohmm
10 ohmm
20 ohmm
1000 ohmm
1 ohmm
Figure 8: Rough model of southern Finland. The local magnetotelluric
relationship E(ω) ∼ Z(ω) · B(ω) is the first approximation.
First European Space Weather Week 2004 17
Operative method - geoelectric field
max = 63 mV/km
21:29:00
max = 57 mV/km
21:30:00
max = 158 mV/km
21:31:00
max = 432 mV/km
21:32:00
max = 470 mV/km
21:33:00
max = 334 mV/km
21:34:00
max = 226 mV/km
21:35:00
max = 152 mV/km
21:36:00
Figure 9: Snapshots of the calculated electric field.
GIC is basically a measure for the electric field integrated along the
conductors. The conductor system defines the relevant scales.
First European Space Weather Week 2004 18
Operative method - power grid
220 kV
400 kV
Rauma
First European Space Weather Week 2004 19
Operative method - GIC
15 16 17 18 19 20 21 22 23 24-12
-10
-8
-6
-4
-2
0
2
4
6
UT [h]
GIC
[A]
Rauma, 20010411
modelledmeasured
Figure 10: Measured and modelled transformer neutral GIC.
First European Space Weather Week 2004 20
Operative method - ESA SDA Gasum Now!
First European Space Weather Week 2004 21
Science is progressing
Classify quantitatively ionospheric currents causing large GIC. Apply
pattern recognition methods originally used for auroral all-sky images.
20031030 20:07:00
0 o
20oE
40o E
60 oN
65 oN
70 oN
Figure 11: Scalar representation of equivalent currents.
First European Space Weather Week 2004 22
Forecasting GIC is demanding
-1500
-1000
-500
0
X [n
T]
NUR, 29.10. 2003
black: measured, blue: "forecasted"
6 6.5 7 7.5 8-20
0
20
UT [h]
dX/d
t [nT
/s]
Figure 12: Artificial example: not enough to forecast B fairly accurately.
First European Space Weather Week 2004 23
Summarising
• Recordings of the geomagnetic field reveal ionospheric (equivalent)
currents
• Solid earth studies reveal the Earth’s conductivity structure
• Ionospheric phenomena affecting GIC have highly varying spatial
scales, which are determined by dB/dt
• Operative nowcasting of GIC is well established
• Quantitative classification of GIC events is advancing
• Producing reliable GIC forecasts may require completely new ideas
• Producing GIC forecasts as accurately as forecasts for terrestrial
weather may be impossible forever
First European Space Weather Week 2004 24
There are many scientific challenges of a general interest
• Investigate the basic nature of spatio-temporal variability of our
geomagnetic environment
• Understand how our geomagnetic environment couples to the large
scale dynamics of the magnetosphere
• Understand implications of the coupling and apply new knowledge
to science of GIC
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