Transcript Acceleration of Coronal Mass Ejection In Long Rising Solar

Introduction to Space Weather
Ionosphere
Nov. 12, 2009
Jie Zhang
Copyright ©
CSI 662 / PHYS 660
Fall, 2009
Roadmap
•Part 1: The Sun
•Part 2: The Heliosphere
•Part 3: The Magnetosphere
•Part 4: The Ionsophere
•Part 5: Space Weather
Effects
•Part 4: The Ionosphere
CSI 662 / PHYS 660
Nov. 12
The Ionosphere
Height profile and layers
Ionization production
Ionization loss
Radio wave
Ionosphere Currents
References:
•Kallenrode: Chap. 8.3
•Prolss: Chap. 2, Chap. 4, Chap. 7
2009
Plasma Physics
Reference: Kallenrode, Chap. 8.3.2
•Anisotropic Conductivity: field-aligned, Pederson, and
Hall
Brief History
• Fluctuation of geomagnetic field by atmospheric current
(Kelvin, 1860)
• First transmitting radio waves across Atlantic (Marconi, 1901)
• Solar UV radiation responsible for the charge carriers
(Kennelly, Heaviside and Lodge 1902)
• Radio wave experiment on ionosphere (Appleton 1924)
• Appleton was awarded the Nobel prize for the work of
ionospheric physics.
Atmospheric Layers
Horizontal Structure of the Terrestrial Atmosphere
Atmospheric Layers
Classified by temperature
• Troposphere
• 0  10 km
• ~300 K  200 K
• Stratosphere
• 10 50 km
• ~200 K 250 K
• Mesosphere
• 50 km  80 km
• ~250 K  160 K
• Thermosphere
• > 80 km (~10000)
• 160 K  ~1000 K
Atmos. Layers
Classified by Gravitational binding
• Barosphere
• 0 km 600 km
• binding
• Exosphere
• > 600 km
• Escaping or evaporation
Classified by Composition
• Homosphere
• 0 km 100 km
• Homogeneous
• Heterosphere
• 100 km  ~2000 km
• Inhomogeneous
• Hydrogensphere (Geocorona)
• > ~2000 km
• Dominated by hydrogen
Basic Parameters
Chemical composition (ni/n):
• Height = 0 km, 78% N2, 21% O2, 1% others (trace gases)
• Height = 300 km, 78% O, 21% N2, 1% O2
Pressure:
• Height = 0 km, P = 105 pa
• Height = 300 km, P=10-5 pa
Atomic Number
Mass Number
H
He
N
O
N2
O2
1
1
2
4
7
14
8
16
28
32
f (Degree of freedom) 3
3
3
3 translation
3
5
5
+ 2 rotation
Barospheric Density Distribution
Hydrostatic equilibrium or aerostatic equations
dP
  g
dz
P
  mn  m
kT
dP
P

dz
H
kT (h)
H ( h) 
Pressure Scale Height
m ( h) g ( h)
h
P (h)  p (h0 ) exp{  Hdz( z ) } Barometric Law
h0
h
n(h)  n(h0 ) TT((hh0)) exp{  Hdz( z ) }
h0
n(h)  n(h0 ) exp( 
isothermal
h  h0
H
)
Barospheric Density Distribution
• Isothermal Scale
Heights
– Hi = kT/(mig)
N2
for g(200 km)
HN2 = 0.032* T
HO2 = 0.028* T
HO = 0.0567* T
O
O2
Altitude interval where density
decreases by 10:
SOLAR - TERRESTRIAL
ENERGY SOURCES
Source
Energy
(Wm-2)
Solar Cycle
Change (Wm-2)
Deposition
Altitude
Solar Radiation
• total
• UV 200-300 nm
• VUV 0-200 nm
1366
15.4
0.15
1.2
0.17
0.15
Particles
• electron aurora III
• solar protons
• galactic cosmic rays
0.06
0.002
0.0000007
Peak Joule Heating (strong storm)
• E=180 mVm-1
Solar Wind
0.4
0.0006
surface
10-80 km
50-500 km
90-120 km
30-90 km
0-90 km
90-200 km
above 500 km
SPECTRUM
VARIABILITY
TOTAL
IRRADIANCE
VARIABILITY
Solar Energy
Deposition
Atmospheric
Structure
SPACE
WEATHER
EUV
FUV
MUV
RADIATION
GLOBAL
CHANGE
Atmospheric Absorption Processes
• Ionization
– O2 + h  O2+ + e*, …
• Dissociation
– N2 + h  N + N, …
• Excitation
– O + h  O*
• O* O + h ’
• O* + X  O + X
radiation
quenching or deactivation
• Dissociative ionization – excitation
– N2 + h  N+* + N + e, …
Ionosphere
Structure
Classified by Composition
• D region
• h < 90 km
• Negative ions, e.g., NO3• E region
• 90 km < h < 170 km
• O2+, NO+
• F region
• 170 km < h < 1000 km
• O+
• F1 region, F2 region
•
Plasmasphere
• h > 1000 km
• H+
Ionosphere Structure
Height of maximum
density:
200 – 400 km
F2
Maximum Ionization
Density:
1 – 30 X 1011 m-3
Column Density:
1 – 10 X 1017 m-3
F1
E
Total ne
Chapman Layer
• The Chapman profile of an ionospheric layer results from the
superposition of the height dependence of the particle density
and the flux of the ionizing electromagnetic radiation
q ( z )  n i I ( z )
q : ionizat ionrat e
n : neut ralpart icledensit y
 i : ionizat ioncross sect ion
I : radiat ionint ensit y
Chapman Profile
Chapman Layer
• Neutral particle density: barometric height formula
z
n( z )  n0 exp{  }
H
• Radiation Intensity: Bougert-Lambert-Beer’s Law
dI
  I  a n
dz

1

I ( z )  I  exp{
 a n( z )dz}  I  exp{
}

cos z
cos
 : theSun' s alt itude. T heopticaldepth

    a n( z )dz
z
Optical Depth

• Definition
(z)   n(z')dz'
z
• For several species
– i = N 2 , O2 , O

(z)    ini (z')dz'
i
z
• Altitude of unit optical depth: F(z)= F() e-1
– Solve (z) = 1 for z
– Where solar radiation is effectively extinct
Continued on
November 19, 2009
Ionosphere Structure
Ionosphere:
• Weak ionization
• Electrons and ions
represent trace
gases
• Ion/neutral ratio
(n/nn)
• 10-8 at 100 km
• 10-3 at 300 km
• 10-2 at 1000 km
Ionization Production
• Photoionization
• Primary
• Secondary
• Charge Exchange
• Particle Precipitation
Photoionization
Processes
– O + h ( 91.0 nm)  O+ + e
– O2 + h ( 102.8 nm)  O2+ + e
– N2 + h ( 79.6 nm)  N2+ + e
Ionization Energies
Species Dissociation Dissociation
(Å)
(eV)
O
O2
N2
2423.7
1270.4
5.11
9.76
Ionization
(Å)
Ionization
(eV)
910.44
1027.8
796
13.62
12.06
15.57
Charge Exchange

CE

X Y  X Y
qX   k x,Y  nX nY 
CE
CE
Charge Exchange Process
Charge Exchange Rate
• Does not change the total ionization density
• Important source for NO+ and O2+ in the lower
ionosphere
• Important source for H+ for the plasmasphere
Particle Precipitation

X  e primary ( E  12ev)  X  esec onday  e primary
• Play an important role in high latitude
Ionization Loss
• Dissociative Recombination of Molecular Ions

DR
XY  e  X  Y
l XY 
DR
 k x,Y  nX Y  ne
DR
k x,Y   1013 m3s 1
DR
Ion loss Rate
Dissociation Recombination
Reaction constants for O2+,N2+,
and NO+
Largest reaction constant
Ionization Loss
• Radiative Recombination of Atomic Ions
RR

X  e  X  photon
kO
RR
18
3 1
 10 m s
• Charge Exchange
kO  , N
k O  ,O
19
3 1
CE
 5 10
CE
 125 10 19 m3 s 1
ms
2
2
Ionization Loss
• E region (O2+)
• Dissociative recombination is the quickest way of
removing ions and elections
l E  region
DR
 kO 
DR
2
nO  ne
2
nO   ne  n
2
l E  region (h)  n (h)
2
Ionization Loss
• F region (O+)
• Charge exchange is the quickest way of removing O+ ions
lF region
DR
 k O  ,O
2
CE
nO nO 
2
nO   ne  n
lF region (h)   (h)n(h)
where... (h)  kO  ,O
2
CE
nO2 (h)
Density Balance Equation
ns
t
 qs  ls  ds
• Density is determined by the ion production term, ion
loss term and ion diffusion term, for species s

d s    (nsus )
• Day time: production-loss equilibrium
qs  ls
• Night time: production is negligible
ns
t
 ls
Variation of Ion Density
• The ionization production depends on the solar
radiation intensity and the zenith angle
• The ion density shows daily, seasonal variation as well
solar rotation and solar cycle effects
After sunrise
n
t
3 1
 10 m s
8
TEC (Total Electron
Content) diurnal
variation
Variation of Ion Density
D and F1layers may
disappear at
night
Radio Waves in the Ionosphere
• Radio wave is altered during its passage through the
ionosphere
– Propagation direction changes: refracted, reflected
– Intensity changes: attenuated, absorbed
Natural Oscillation in a Plasma:
Plasma Frequency
nme
d 2 ( x )
dt
2

e2n2
0
x
x  (x) 0 sin( p t )
p 
e2n
 0 me
 p [ s ]  56.4 n[m ]
1
3
3
fp[ Hz]  9 n[m ]
Forced Oscillation in a Plasma:
d 2 ( x )
nme
dt
2
 nme
d ( x )
dt

e2n2
0
x  en 0 sin(t )
x  (x) 0 sin(t   )
  (x) 0 sin(t   )   (x) 0 cos(t   ) 
2
 p (x) 0 sin(t   )  (e / me ) 0 sin(t )
2
Ionosphere as a Dielectric
• Interaction depends on frequency
   p
  
phase  0
conductivity  0
p 2

nref  1  ( )
• Nref < 1, radio wave will be refracted according to
the familiar Snell’s law. Θ2 > Θ1
sin  2 
sin 1
nref
Ionosphere as a Dielectric
Wave damping due to electron interaction with neutral
particles
 Pfr 
e 0
2 me
2
2
n e , n
2
Radio wave (e.g., 5 Mhz) refraction and damping
usually occur in the upper D region and lower E
region
Ionosphere as a Conducting
Reflection
   p (h)
• Wave interacts strongly with plasma, inducing a
large current. Ionosphere acts like a conductor
• Radio wave is reflected
• This often occurs in the F-region
Radio Wave
Ionosonde
A special radar to examine
ionosphere from ionogram:
Elapsed time  height
Frequency  electron density
ionosonde
Ionosphere Currents
Polar Upper Atmosphere
• Polar Cap: ~ 30°
• Polar oval: a few degree
• Subpolar latitude
Polar Upper Atmosphere
Magnetic field connection
• Polar Cap: magnetotail lobe region, open field
• Polar oval:
• (1) night side: connect to plasma sheet
• (2) day side: connect to cusp region
• Subpolar latitude: conjugate dipole field, closed
Convection and Electric Field
Convection and Electric Field
• Polar cap electric field Epc (from measurement)
• Dawn to dusk direction
• Epc = 10 mV/m
• Polar cap potential: ~ 30 kV from 6 LT to 18 LT, over 3000
km
• Polar oval electric field
• Dawn sector: equatorward
• Dusk sector: poleward
• Epc=30 mV/m
• Potential drop: ~ 30 kV, counterbalance of the polar cap E
• Subpolar region electric field
• < 5 mV/m
Convection and Electric Field
• Polar cap convection
• Caused by E X B drift
• anti-sunward
• Drift time scale cross the polar cap ~ 2 hours
• Polar oval convection
• Sunward convection
• Form a close loop with the polar cap convection
• Two convection cells
Drift velocity = 500 m/s,
when
E=10 mV/m, and
B=20000 nT
UD  E / B
Solar Wind Dynamo
• Polar cap electric field originates from solar wind dynamo
electric field
• Same direction
• Same overall electric potential drop
• Electric field is ~ 40 times as strong as in solar wind



Esw  U sw  BE
Ionosphere Current
• Pederson current: perpendicular B, parallel E ; horizontal
• Hall current:
perpendicular B, perpendicular E ; horizontal
• Burkeland current: parallel to B ; vertical
Ionosphere Current
• Birkeland current: Field-aligned current
• Region 1 current: on the poleward side of the polar oval
• Region 2 current: on the equatorward side of the polar oval
Ionosphere-Magnetosphere Coupling
• Region 1 current
• Magnetotail current is
re-directed to the
ionosphere
• Current flows into the
ionosphere in the dawn
sector
• Current flows out the
ionosphere in the dusk
section
Ionosphere-Magnetosphere Coupling
• Region 2 current
• Associated magnetic
field lines end in the
equatorial plane of the
dawn and dusk
magnetosphere at a
geocentric distance of
L ≈ 7-10
• Driven by excess
charge in the dawn and
dusk sectors of the
dipole field, caused by
different particle paths
of electrons and ions
Ionosphere-Magnetosphere Coupling
• Drift of particles from the
plasma sheet
uD   L
E
3
E
B
uD  L
2
gr
u D gr
uD E
 L1
• Ions and electrons drifts in different
• At small L, curvaturedirection along the dipole
gradient drift dominates
• Particles can only drift to • There is a forbidden zone for ions
within a certain distance of (electrons)
• Excess charges accumulate
the dipole
Ionosphere Conductivity
j  E
j  en(u  u )
i
e
  en(u  u ) / E
i
e
Deriving conductivity σ is to find the drift velocity under the
E in the three components:
• Birkeland σ: parallel to B
• Pederson σ: parallel to E, E per B
• Hall σ: per E and B
Ionosphere Conductivity
Parallel conductivity


qs E  ms s ,nu s  0
 // 
e2n
me e ,i
 
E // B
Force equilibrium:
Electric force = frictional force
No Lorentz force
For plasmas (without neutral), Coulomb collision
 //  8103 (Te[k ])3/ 2 / ln 
Ionosphere Conductivity
Transverse conductivity
 
EB
  

qs ( E  us  B)  ms s,nus  0
Force equilibrium:
Electric force + magnetic force=
frictional force
Ionosphere Conductivity
 
EB
Transverse conductivity
P  {
 e ,n B e
H  {
( B e ) 2
en
B ( ) 2  ( e ) 2
e ,n
B
en
B ( ) 2  ( e ) 2
e ,n
B
 (
 i , n B i
i ,n )
 (
2
 ( B )
i 2
}
( B i ) 2
i ,n )
2
 ( B )
i 2
}
Maximum conductivity:    i
i ,n
B
Transverse conductivity, especially Hall, confines to a
rather narrow range of height (~ 125 km), the so called
dynamo layer
The End