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The
Global Atmospheric Electric Circuit
Colin Price
Department of Geophysics and Planetary Sciences
Tel Aviv University
Israel
cprice@flash.tau.ac.il
Historical Background
1752 Lemonnier discovered
that in fair weather regions
there is a persistent E-field
of ~100 V/m pointing
downward
Why do we not get electric shock? (200 V between head and ground)
1920s: There exists a diurnal variation of the atmospheric
electric field, which is independent of location and local
time, but dependent only on universal time:
~100V/m
“Carnegie Curve”
Implication of E-field Earth has a negative charge of ~500,000 C
Charge of the Earth
Q = 4 πR2 εo E = R2 Eo / k
= 4.5 x 105 Coulomb
εo= permittivity of free space (electric const.)
= 8.85x10-12 F/m
- - - - - - - - - - - - - - - - - - -
450,000 Coulombs
The conductivity of the atmosphere is determined by
the concentration of ions in the atmosphere. The
amount of ions increases
with altitude since the
main source of ionization
is cosmic and solar radiation
from outside the Earth's
atmosphere. The mobility
of ions increases with
decreasing density.
1887 Linss discovered ions in the atmosphere, implying that
air had a finite conductivity
Ionosphere
100km
Conduction Current
J(R) = o E(R) = 2 x 10-12 Amp/m2
σ(R) =σo = 3x10-14 Siemen/m [S/m]
{1 S = Ω-1}
The conduction current
varies little with altitude
up to z~50 km
Globally, i = J(R) 4πR2
~ 1000 Amp
1900 CTR Wilson measured the air-Earth current which has
a value ~2x10-12 A/m2
+ + +
+ +
+ +
+ +
+ +
+ + +
Due to the high conductivity of the Earth, the
Earth-ionosphere represent a spherical capacitor
Volt
Meter
+
-
-+ - - + - + - - +
-- + + - + - + -
- + + - + - - +
ions
Earth
- - - -
- -
- - - -
ionosphere
However,
because of the
ions in the
atmosphere,
the capacitor
discharges
slowly (leaky
capacitor)
(i) ~10-5 S/m
(o) ~1 S/m
(air) ~10-14 S/m
Ionospheric Potential
The potential difference between the ionosphere (height h) and
the Earth’s surface, known as the ionospheric potential, is :
V = - E(r)dr = - E(r)dr
since E=0 for r> R+h (or z>h).
Most measurements show values of V~ 3x105 Volt (300kV)
Resistance of Atmosphere (fair weather)
From here we can also see that the total resistance between the
Earth and ionosphere is
RΩ = V/i = 3x105/1000 ~ 300 Ω
R
R+h
R
ground
ionosphere
Vi
Capacitance of the Earth
C = Q/V ~ 4x105C/3x105V ~ 1 Farad
The typical time scale for the discharging of the capacitor is
τ = RΩ C = 300 sec! (5-10 minutes)
Conclusion: Without a source of charging of the Earth-
ionosphere capacitor, the charge on the Earth would decay
nearly immediately (few minutes). What is the source of
this atmospheric charging? What is the battery in circuit?
+ -
1920 Wilson suggested
the generator was global
thunderstorms
1929 Whipple showed that
the diurnal variations of
the fair weather field
matches the diurnal
variations of global
thunderstorms
+ -
Q ~ -500,000 C
300Ω 300 kV
PG ~ -100 V/m
I ~ 2 pA/m2
DC – Direct Current
Global Circuit
The Global Atmospheric Electric Circuit
There is also an AC component to
the Global Electric Circuit
50-100 flashes per second
Generation of EM waves
Trapped in Earth-ionosphere waveguide
ELF- Schumann Resonances
2a …. Hz 20 , 14, 8~ nc ~ nf
(Schumann, 1952) Extremely Low Frequency (ELF) Range
F < 100 Hz
Earth
Ionosphere
ELECTRIC FIELD MAGNETIC FIELD
Lightning Discharge
14 Hz
8 Hz
Ez
Hx,y
Hx,y
Ez
Schumann Resonance Modes 1 and 2 n c F ~
40,000km
02
0)1(1
cos12)1(
4n
ncr
nn
Pni
ha
ME
Theory
1
1
)1(1
cos12
4n
nc
nn
Pn
ha
MH
ω = angular frequency
Θ = great circle angle from lightning to the observer
ε0 = vacuum permittivity;
a = radius of the Earth;
h = the height of the Ionosphere;
Pn(cos θ) and Pn1(cos θ) are Legendre and associated Legendre functions
of degree n and order 0,1 respectively
, the modal eigenvalue related to the propagation constant of the
Earth-Ionosphere spherical-shell cavity
Mc(ω) is the vertical charge moment of the lightning ground flash.
-2
-1
0
1
2
0 1 2 3 4 5 6 7 8
Ma
gn
eti
c F
ield
Am
pli
tud
e(V
olt
s)
Time (seconds)
0
2
4
6
8
10
12
10 20 30 40 50
Pow
er (
Rela
tive U
nit
s)
Frequency (Hz)
8Hz
14Hz
20Hz
27Hz
33Hz39Hz
Negev Desert
Israel
0.2
0.3
0.4
0.5
0.6
0.7
0.35
0.4
0.45
0.5
0.55
0.6
0.65
50 55 60 65 70 75
Isra
el S
R A
mp
litu
de
Ca
liforn
ia S
R A
mp
litud
e
Julian Day 1998
r=0.9
Time Series
Spectrum
0.007
0.008
0.009
0.01
0.011
0.012
300.5
301
301.5
302
302.5
303
303.5
304
02/11/98 16/11/98 30/11/98 14/12/98
1800
UT
Ligh
tnin
g Ac
tivity
ove
r Sou
th A
mer
ica
(SR
rela
tive m
agni
tude
)
1800 UT Surface Temperature over South Am
erica
(K)
Date
SR
Ts
r=0.57
Price and Asfur (2006)
Tem
pera
ture
(K)
Africa
S. America
Mag
neti
c F
ield
In
ten
sit
y
(au
)
0.04
0.045
0.05
0.055
0.06
0.065
0.07
0 10 20 30 40 50 60 70
0.0007
0.00075
0.0008
0.00085
0.0009
Afr
ica
n L
igh
tnin
g A
cti
vit
y
(SR
Ma
gn
eti
c F
ield
)
Day from 20 October 1998
Sp
ec
ific H
um
idity
(kg
/kg
)
r=0.91
Lightning Activity vs. Specific Humidity (300mb) +24hours
26% SR change => 0.1 g/kg change
Price and Asfur (2006)
Harrison (2002)
Harrison and Usoskin (2010)
Solar Influences
on the Global Circuit
Atmosphere
Nuclear Testing
DC Circuit
297.6 297.8 298.0 298.2 298.4
-20
-10
010
20
Year day
dB
z (
nT
)
297.6 297.8 298.0 298.2 298.4
-20
24
68
10
Year day
sd B
z (
nT
)
01
23
45
6
Bz of IMF from ACE
Jz SD of GEC in Israel
Jz SD of GEC in Israel
Bz SD of IMF from ACE
24 October 2011
ACE
Jz
Monthly averaged Frequency for NS and EW components
7.60
7.65
7.70
7.75
7.80
7.85
7.90
96ר-ואנ י
96לי-יו
97ר-ואנ י
97לי-יו
98ר-ואנ י
98לי-יו
99ר-ואנ י
99לי-יו
00ר-ואנ י
00לי-יו
01ר-ואנ י
01לי-יו
02ר-ואנ י
02לי-יו
03ר-ואנ י
03לי-יו
04ר-ואנ י
04לי-יו
05ר-ואנ י
05לי-יו
Hz
NS
EW
NS, EW frequencies (yearly averaged)
7.65
7.70
7.75
7.80
7.85
1996 1997 1998 1999 2000 2001 2002 2003 2004
Hz
-9.0
-8.0
-7.0
-6.0
-5.0
-4.0
-3.0
X r
ay
flu
x (
W/m
^2
), lo
g. s
ca
le
NS
EW
X rays (0.5 - 4 A)
X rays (1 - 8 A)
NS and EW frequencies with
Log. ( X Ray Flux (1-8A)),
R(NS,1-8A)=0.941, R(EW,1-8A)=0.953
y = 0.0488x + 8.0577
y = 0.0495x + 8.1003
7.65
7.70
7.75
7.80
7.85
-8.0 -7.5 -7.0 -6.5 -6.0 -5.5 -5.0
X ray flux (W/m^2), log. scale
Hz
NS
EW
Linear (NS )
Linear (EW )
Frequency of first SR mode (~7.8Hz)
Monthly mean values
Hz
Hns
Hew
Annual Mean Values (SR and X-rays)
r=0.941 r=0.953
1996 2006
Month/Year
27-day solar rotation
effects on SR frequency
NS frequency (SAO) and X Rays (background flux) 01-03,2005
7.7
7.75
7.8
7.85
7.9
7.95
01/0
1/2
005
08/0
1/2
005
15/0
1/2
005
22/0
1/2
005
29/0
1/2
005
05/0
2/2
005
12/0
2/2
005
19/0
2/2
005
26/0
2/2
005
05/0
3/2
005
12/0
3/2
005
19/0
3/2
005
26/0
3/2
005
Day
Hz
0
10
20
30
40
50
60
70
SS
N
NS Freq. av
SSN (Belgium) av.
NS frequency (SAO) and X Rays background, 01-03, 2005
7.6
7.65
7.7
7.75
7.8
7.85
7.9
7.95
01/0
1/2
005
08/0
1/2
005
15/0
1/2
005
22/0
1/2
005
29/0
1/2
005
05/0
2/2
005
12/0
2/2
005
19/0
2/2
005
26/0
2/2
005
05/0
3/2
005
12/0
3/2
005
19/0
3/2
005
26/0
3/2
005
Day
Hz
-9.00
-8.50
-8.00
-7.50
-7.00
-6.50
-6.00
-5.50
-5.00
X r
ay f
lux (
W/m
^2),
lo
g. scale
NS Freq. av
Log Xrays, av
January-March 2005
Hns freq. and SSN Hns freq. and X-rays
[Füllekrug and Fraser-Smith, 1996]
30day
SR Spectral Power Variation
f1=8 Hz
f2=14 Hz
Solar Flares - X rays
15 Oct-15 Nov 2003
Ez, 8 Hz, Goes 10 - 8A, 4A
7.5
7.7
7.9
8.1
8.3
8.5
15/10
/03
20/10
/03
25/10
/03
30/10
/03
4/11/0
3
9/11/0
3
Day, 2003
Freq.
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
X - ra
ys
Freq. 8Hz
Goes 10 X rays 8A
Goes 10 X rays 4A
Ez, 14 Hz, Goes 10 - 8A, 4A
14.0
14.2
14.4
14.6
14.8
15.0
15/10
/03
20/10
/03
25/10
/03
30/10
/03
4/11/0
3
9/11/0
3
Day, 2003
Freq
.
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
X - r
ays
Freq. 14Hz
Goes 10 X rays 8A
Goes 10 X rays 4A
Ez, 20 Hz, Goes 10 - 8A, 4A
20.0
20.2
20.4
20.6
20.8
21.0
15/10
/03
20/10
/03
25/10
/03
30/10
/03
4/11/0
3
9/11/0
3
Day, 2003
Freq
.
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
X - r
ays
Freq. 20 Hz
Goes 10 X rays 8A
Goes 10 X rays 4A
8Hz
14Hz
20Hz
X Rays and NS Ampl, PKD , 04/11/03
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
18:0
0
18:3
0
19:0
0
19:3
0
20:0
0
20:3
0
21:0
0
21:3
0
22:0
0
22:3
0
23:0
0
23:3
0
Time
W/m
^2
2E-10
3E-10
4E-10
5E-10
6E-10
7E-10
8E-10
9E-10
pT
X-rays:
Ampl.
What do all these changes mean?
Changes in thunderstorms?
Changes in waveguide?
Changes in conductivity?
Data from 1866-1932
(Brooks, 1934)
Solar Cycle in Thunderstorm Frequency?
Stringfellow (1974) showed similar relationships for UK from 1930-1973 (4 solar cycles)
Schlegel et al. (2001)
European Thunderstorms
(Austria and Germany)
Data from ground networks
April-September
What have we learned?
The global atmospheric electric circuit is made up of both a
DC component and AC component
The DC circuit depends on global thunderstorm activity (area
coverage, intensity) and atmospheric conductivity (ions,
aerosols)
The AC circuit depends on global lightning activity (intensity
and number of flashes) and ionospheric parameters (D-layer
reflection height, ionospheric conductivity profile)
There is evidence that solar variability (solar cycle, solar rotation,
solar flares) influence both DC and AC circuit parameters
These Solar impacts may result from changes in
the Earth-ionosphere cavity, and/or even changes in cloud and
thunderstorm activity itself.
The GEC may also be a sensitive tool to study climate change.
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