Recent developments in Dynamic Modelling of
the Earth’s Radiation Belts
Richard B. Horne, Sarah A. Glauert and Nigel P. Meredith
British Antarctic Survey
Cambridge, UK
Invited talk, ESWW7 Bruges, 16 November 2010
Importance of Energetic Particles
2003 Hallowe’en magnetic storm
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2003 Hallowe’en magnetic storm
– 48 satellites reported anomalies
– 1 total loss
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Satellite ~ US$ 250 M
Launch ~ US$ 100 M
Insure ~ 3% /year
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300 satellites in Geo orbit alone
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~ 1000 satellites in orbit
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Effects of an extreme event?
Baker et al. Nature [2004]
Satellites – Total Loss
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2010
Eutelsat W3B
IS-4 (PAS-4)
Eutelsat W2
Sterkh 1 and 2
28 Oct
1 Feb
27 Jan
Jan
Fuel leak, total loss a few hours after launch
Out of service after anomaly, moved to junk orbit
Out of service after anomaly, moved to junk orbit
Both satellites failed shortly after launch
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2009
Koronas-Foton
Orbcomm
Iridium 33
Astra 5A
2 Dec
22 Feb
10 Feb
16 Jan
Contact lost after power supply problem; total loss
Total loss of one satellite expected after power system failure
Destroyed in accidental collision with defunct Russian milsat
Total loss after malfunction announced
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2008
NiqComSat 1
DSP 23
EchoStar 2
NRO-L21
9 Nov
Mid-Sept
14 July
Feb
Second solar array fails; total loss
Total loss
Power system failure, total loss
Failed satellite deliberately destroyed by missile
• What is the cause – Space Weather ? Other ?
• Can we help protect satelites?
Satellites – Serious Interruption to Service
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2010
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2009
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IGS 4B
GOCE
INSAT 4B
Galaxy 15
Aura
AMC-16
Satmex V
23 Aug
July
7 July
5 Apr
12 Mar
Mar
27 Jan
Power failure, status unknown
Glitch prevents science data transmission (recovered Sept 2010)
Solar array anomaly; 50% power loss
Contact lost, transponders still working
Attitude disturbance, slight power loss
Further degradation of solar arrays, some transponders switched off
Loss of XIPS propulsion system, operational life shortened
GeoEye 1
Landsat 5
MTSAT-1R
Eurobird 1
Chandrayaan 1
Orbcomm
Landsat 5
Herschel
Sinosat 3
Yamal 202
Eutelsat W2A
GeoEye
Chinasat 6B
Eutelsat W2M
11 Dec
Dec
11 Nov
12 Sep
28 Aug
24 Aug
13 Aug
3 Aug
13 Jul
3 June
May
1 May
9 Feb
28 Jan
Problem with transmit antenna pointing mechanism
Lost transponder replaced by one thought to have failed earlier
15.5-hour outage
90-minute outage starting at 2124 UTC attitude problems
Contact lost; mission abandoned
Coast Guard demo satellite fails
1-day outage
SEU causes anomaly in HIFI instrument
12-hour outage, starting at 1350 UTC
8½-hour outage
IOT: S-band payload anomaly announced
Problems with colour imagery announced
47-minute outage starting 0259; recovered
IOT: Major anomaly of power subsystem, likely total loss
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How important is Space Weather ?
Can we help protect satellites?
Importance of Energetic Particles – Space Weather
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NOAA anomaly database
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High flux of MeV electrons cause
satellite anomalies (malfunctions)
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Cumulative radiation dose limits
spacecraft lifetime
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Iucci et al. SW [2005]
Solar wind –
Radiation Belts
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Increased MeV electron flux
in the radiation belts
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Driven by high speed solar
wind and Bz fluctuations
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Galileo - Giove – A
• Science and applications
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Thanks to the ESA Galileo
team
ULF Enhanced Radial Diffusion
• Fast solar wind drives ULF waves inside magnetosphere
• ULF wave frequency ~ electron drift frequency ~ mHz
• diffuse electrons towards/away from the Earth
• Conservation of 1st invariant results in electron acceleration/deceleration
Wave-Particle Interactions
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As electrons drift around the
Earth they encounter many
types of waves:
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Chorus
Hiss
Lightning generated whistlers
VLF transmitters
EMIC
Magnetosonic
Z mode
LO and RX modes
Wave-particle interactions are mainly responsible for
radiation belt variations
Radial Diffusion and Losses due to Hiss
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Radial diffusion
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Wave-particle interactions
• Whistler mode hiss waves
• Loss to the atmosphere
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Underestimates flux
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Needs electron acceleration
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Lam et al. GRL [2007]
Cyclotron Resonant Electron Acceleration: Chorus
Cluster data
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Whistler mode chorus waves excited by ~1-50 keV electrons
Waves accelerate electrons up to MeV energies
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Horne et al., Nature [2005]
3d Dynamic Global Modelling
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3d = Include wave-particle interactions
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Radial diffusion is for constant J1 and J2, - OK on a (J1,J2,L*) grid
However
• Momentum diffusion is for constant (L*,y)
• Pitch angle diffusion (y) is for constant (L*,p)
• Requires complex differential operators
Solution - use 2 grids – and transform between them
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Diffusion Coefficients
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Radial diffusion coefficients
• Due to ULF waves
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Pitch angle and energy diffusion
• Due to wave-particle interactions
Scale coefficients by the Kp index and drive global dynamic
model by a time series of Kp
Salammbo Model
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[Varotsou et al. 2005, 2008;
Horne et al., 2006]
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Radial diffusion + wpi due to
chorus – steady state
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No cross terms
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Significant increase in electron
flux due to chorus acceleration
Radiation Belt Environment Model
SAMPEX Data
2-6 MeV electrons
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Radial displacement
+ chorus
No cross terms
Fok et al. [2008]
Radial diffusion and wpi due to chorus
Radial diffusion only
Chorus waves are essential for dynamics
BAS Global Radiation Belt Model
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Electrons flux - CRRES satellite
during a magnetic storm
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Model without wave-particle
interactions - inadequate
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Model with wave-particle
interactions
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Wave-particle interactions are
essential for radiation belt variations
and loss to atmosphere
USAF Model
Data
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Albert et al. [2009]
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Includes cross terms
2 grids – coordinates of the
second grid are chosen so the
cross terms vanish
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Radial diffusion + chorus give
best agreement with data
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Cross terms reduce chorus
acceleration
Chorus and RD
Radial diffusion alone
Coupling High and Low Energy Electrons
Coupling low and High Energy Electrons
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No coupling
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Couple RCM to VERB code
Subbotin et al. JGR [2010]
BAS code – Effects of Hiss Wave Normal Angle
Data
BAS Model
Comparison of Electron Lifetimes
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Benck et al. [2010]
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Electron lifetimes (0.23 – 0.34 MeV)
are longer when measured at low
altitude compared to equator
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Why?
Loss timescales
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SAC – C measures pa ~ 20O
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CRRES measures 0-90
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Suggest here
– Active conditions
– Energy diffusion at large
p.a.
– Energy diffusion at small p.a
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Important to resolve for global
dynamic models
Conclusions
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Satellite losses and service interruptions are still significant
Radiation belts are variable and pose a hazard
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Global dynamic radiation belt models are being developed to forecast risk
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Need for better understanding of the physical processes:
• Wave-particle interactions – ULF, ELF and VLF frequencies
• Coupling of radiation belts to the solar wind
• Transport of low energy electrons – E fields
• Coupling to major boundaries – such as the plasmapause
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Galileo provides new opportunities for science as well as applications
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New SPACECAST project will develop European models and forecasting
• Wave-particle interactions – radial diffusion
Reserve Slides
Needs to improve models
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Need more wave data for different wave modes – diffusion rates
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Need better ULF waves data for radial diffusion
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Couple high and low energy electrons
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Need better E field model for convection - transport
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Better coupling from solar wind to magnetosphere – effects of
boundaries
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Develop global models into forecasting models
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New FP7 SPACECAST project will do some, not all
Resonance Cone
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Waves do not propagate at all
directions
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Need to restrict wave power in
angle
Vg
Resonance
cone
k
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What is the angular spread??
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Need observations
– CLUSTER
Electromagnetic
Electrostatic
Wave Power Near the Resonance Cone
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Pitch angle diffusion rate
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Including wave power near the
resonance cone reduces the
diffusion rate !!
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Paradox
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Reason
• waves become electrostatic –
not electromagnetic
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Need to revise model
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Need to identify EM and ES waves
in wave data
Dynamic Modelling Approach
Observations
Transform to a
dipole field (L*)
Diffusion
Calculations
Use a realistic
magnetic field
model
Gyro-kinetic
Calculations
or
Observations
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Diffusion - complexity in transformations
Gyro-kinetic - complexity in wave diffusion
Both need very good magnetic field
models