M-I Coupling from the Ionosphere-Thermosphere
Perspective: Melting the Frozen-In Flux
Jeff Thayer
Center for GeoSpace Studies
SRI International
Photo by Craig Heinselman
GEM Tutorial 2003 – J. Thayer
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What is the Role of the IT system in M-I Coupling?
• A Depository for distant sources of energy flux
– Absorbing VUV solar radiation,
magnetospheric Poynting flux and Kinetic
energy flux
• An Intermediary for charged and neutral gases
– Enforcing the physical laws of a
multiconstituent, collision dominated, weakly
ionized gas
• A Regulator of the magnetosphere
– Regulating M-I energy exchange through
coupled electrodynamic processes
GEM Tutorial 2003 – J. Thayer
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A Depository
GEM Tutorial 2003 – J. Thayer
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VUV Solar Radiation
TIMED SEE Measurements
July 4, 2002
Solar zenith angle 46 degrees
0-30 nm
30-105 nm
121-122 nm
105-175 nm
Courtesy of Stan Solomon, NCAR
8
Magnetospheric Energy Transfer
to the Polar IT System
Kinetic
Energy Flux
Poynting Flux
Ionization
ε∼ 20%
Neutral
Momentum
ε∼ 80%
Chemical
Reactions
Cascading
e–
ε∼ 5%
Neutral
Heating
ε∼ 50%
hν
Excitation
Ti
Te
9
Power Input to the Polar IT System
Solar VUV; Poynting Flux; Kinetic Energy Flux
Knipp et al. [2003]
10
Local Energy Deposition Rates
Solar VUV ; Poynting Flux; Kinetic Energy Flux
Measured at 67N, solar maximum, summer solstice conditions
Height-Integrated Energy Flux
8.3 mW/m2
2.5 mW/m2
35.3 mW/m2
1.7 mW/m2
5.1 mW/m2
46.3 mW/m2
Thayer and Semeter, 2003 JASTP
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IT System as a Depository
These fluxes drive the physics and chemistry
of the polar IT system
These fluxes are each processed differently
by the polar IT system
These fluxes can have competing contributions
in localized regions
GEM Tutorial 2003 – J. Thayer
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An Intermediary
GEM Tutorial 2003 – J. Thayer
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Ion and Electron Mobility Properties
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Ion & Electron Momentum Equations
!
!!
! ! !
! !
dVi
!
ni mi
= −∇Pi + ni mi g + eni ( E + Vi × B ) − ni miυin (Vi − U n )
dt
!!
!
! !
∇Pi
k ! ! !
g
Vi = U n +
−
+ i ( E + Vi × B )
υin ni miυin B
ki =
Ωi
υin
Ion momentum equation in static E- and B-fields
with ion-neutral collisions only,
! k ! k ! !
Vi = i E + i Vi × B
B
B
!
Vi =
2
3
 k !
 ki  ! !  ki  ! ! ! 
i
E +
E × B +   ( E • B) B
2 B ⊥  B 
1 + ki 
 
B

1
Electron momentum equation in static E- and B-fields
with electron-neutral collisions only,
!
Ve =
2
3
 −k !
 ke  ! !  ke  ! ! ! 
e
E⊥ +   E × B −   ( E • B ) B 

1 + ke2  B
B
B

1
15
Ion & Electron Behavior in the E-region
Ion direction perpendicular to B
 Ωi 

 υin 
θ = arctan 
Ion magnitude perpendicular to B
Vi ⊥ ( z ) =
ki
1 + ki2
Vi ⊥ ( z ) = sin (θ i )
E⊥
B
E⊥
B
Electron magnitude and direction perpendicular to B
ke " 1
θ e = 90#
Ve⊥ =
E⊥
B
16
Ion & Electron Motion through the E-region
17
F-region Plasma Motion & Frozen-in Flux
! !
!
E×B
Ve,i = 2
B
!
! !
E = −V × B
N
E
18
E-Region Ion Motion – Where the Frozen-In Flux
gets Slushy
N
E
19
E-region Current Behavior
! !
!
j = ene (Vi − Ve )
ke " 1
Assuming
!
!
!
 ki E⊥
!
1 E⊥ × B 
j⊥ = ene 
−
 1 + k 2 B 1 + k 2 B 2 
i
i


Current direction perpendicular to B
 −υin 

 Ωi 
φ = arctan 
Current magnitude perpendicular to B
j⊥ =
ene
1
E⊥
B 1+ k2
i
j⊥ =
ene
sin φ E⊥
B
20
Currents in the E-region
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E-Region Currents
! !
!
j ( z ) = ene ( z ) (Vi − Ve )
N
E
22
E-region Electrodynamics with Neutral Winds
Ion momentum equation
! ! !
Vi′ = Vi − U n =
2
3
 k !
 ki  ! ′ !  ki  ! ′ ! ! 
i ′
E +
E × B +   ( E • B) B
2 B ⊥  B 
 
B
1 + ki 

1
Electron momentum equation
2
3
!
! !
ke  ! !  ke  ! ! ! 
1  −ke !

Ve′ = Ve − U n =
E⊥′ +   E ′ × B −   ( E ′ • B ) B 

B
B
1 + ke2  B

Current density
! !
! !
! !
! !
!
!
j = ene (Vi − Ve ) = ene Vi − U n − (Ve − U n ) = ene (Vi′ − Ve′ ) = j′
(
)
! ! !
!
!
2
2  !
3
3  E′ • B B 
 k



!
(
) 
k
k
k
k
k
E′
E′ × B
j = ene  e 2 + i 2  ⊥ −  e 2 − i 2  2 +  e 2 + i 2 

3
1+ k
 B 1+ k
 B
1+ k

k
k
k
B
1
+
1
+
1
+


e
i 
e
i 
e
i 


! !
!
!
!
E′ × B
j = σ P E⊥′ − σ H
E
σ
+
$ $′
2
B
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Currents including neutral winds
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Poynting Flux to Energy Deposition
Poynting’s Theorem
! !
∂W ! !
+∇•S = − j •E
∂t
Energy Equation
(
d ρ u + ρU n2 2
dt
) = −∇ • ( P% • U!
! !
! !
!
+
q
+
ρ
U
•
g
+
ρ
Q
+
j•E
) n
n
Kinetic Energy Equation
(
d ρU n2 2
dt
) = −U!
! %
! ! ! ! !
•
∇
•
+
P
ρ
U
n
n • g + Un • j × B
Internal Energy Equation
% ! !
! !
d ( ρu )
!
= −∇ • q + ρ Q − P : ∇U n + j • E ′
dt
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IT System as an Intermediary
Determining the relative roles of the neutral
and charged particles of the IT system
Understanding the processes that govern
the response of the IT system
GEM Tutorial 2003 – J. Thayer
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A Regulator
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Kinetic Energy Flux
Newell et al., Reviews of Geophysics, May 2001
Suppression of intense aurora in sunlight
SZA < 85°
SZA > 110°
12
12
18
06 18
00
0
3
PROBABILITY (%)
06
6
Total electron flux threshold: 5 ergs cm–2 s–1
00
28
Neutral Wind Observations
!
∂j
% !
% !
∇ • (σ • E ) + ∇ • (σ • U n × B ) = − $
∂z
130 km
12
12
06
18
00
180 km
18
500 ms–1
06
00
WINDII O(1S) derived winds
Zhang and Shepherd, 2000, JGR
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Neutral Wind Influence on EM Energy Deposition
Thayer and Semeter, 2003 JASTP
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Electric Field Variability
<V2> = <V> 2 + σ 2
Qj α
12
σ (m s–1)
<V2>
500.0
416.6
333.3
18
06
250.0
166.6
83.3
0
ION DRIFT
1000 m s–1
00
Codrescu et al. 2000, JGR
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Poynting Flux and Kinetic Energy Flux Exchange
Ionospheric Response
Thayer and Semeter, 2003 JASTP
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IT Mass Loading of Magnetosphere
Courtesy of R. Chappell
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IT System as a Regulator
Determining how the preconditioned state
of the IT system impacts future coupling
Determining how the the energy flux of one source
impacts the flux of another
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Upcoming Observing Programs
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Observing Programs
NASA Missions
•
LWS geospace probes (IT Mappers ; Radiation Belt
Mappers) 2008-2010
•
MIDEX THEMIS mission – 2007 (PI Vassilis
Angelopoulos)
•
Solar-Terrestrial Probes (TIMED, MMS, GEC,
MAGCON)
Ground-based Initiatives
•
Advanced Modular Incoherent Scatter Radar (AMISR)
NSF program approved
•
Improved SuperDarn coverage of the southern polar
region
•
Enhanced auroral imaging network to support THEMIS
36
Geospace Electrodynamic Connection Mission
•
Solar Terrestrial Probe mission within NASA SEC program
(planned launch date 2010)
•
Three or four deep dipping spacecraft (perigee ~130 km)
37
Advanced Modular Incoherent
Scatter Radar (AMISR)
A Transportable Ionospheric Radar
– Poker Flat, Alaska 2004
– Resolute Bay, Nunavut 2006
38
Issues in I-T Coupling to the Magnetosphere
• Mass Loading
• Current Closure
• Regulation
• Source spectrum and interplay
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Summary of Polar IT System
Contributions
+
+
+
M-I Coupling from the I-T perspective?
YES! I-M Coupling
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When Nature Calls…
Opportunity Knocks
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