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– 48 satellites reported anomalies– 1 total loss

• Satellite ~ US$ 250 M• Launch ~ US$ 100 M• Insure ~ 3% /year

• 300 satellites in Geo orbit alone

• ~ 1000 satellites in orbit

• Effects of an extreme event? Baker et al. Nature [2004]

2003 Hallowe’en magnetic storm

Satellites – Total Loss• 2010

• Eutelsat W3B 28 Oct Fuel leak, total loss a few hours after launch

• IS-4 (PAS-4) 1 Feb Out of service after anomaly, moved to junk orbit

• Eutelsat W2 27 Jan Out of service after anomaly, moved to junk orbit

• Sterkh 1 and 2 Jan Both satellites failed shortly after launch

• 2009

• Koronas-Foton 2 Dec Contact lost after power supply problem; total loss

• Orbcomm 22 Feb Total loss of one satellite expected after power system failure

• Iridium 33 10 Feb Destroyed in accidental collision with defunct Russian milsat

• Astra 5A 16 Jan Total loss after malfunction announced

• 2008

• NiqComSat 1 9 Nov Second solar array fails; total loss

• DSP 23 Mid-Sept Total loss

• EchoStar 2 14 July Power system failure, total loss

• NRO-L21 Feb Failed satellite deliberately destroyed by missile

• What is the cause – Space Weather ? Other ?

• Can we help protect satelites?

Satellites – Serious Interruption to Service• 2010

• IGS 4B 23 Aug Power failure, status unknown• GOCE July Glitch prevents science data transmission (recovered Sept 2010)• INSAT 4B 7 July Solar array anomaly; 50% power loss• Galaxy 15 5 Apr Contact lost, transponders still working • Aura 12 Mar Attitude disturbance, slight power loss • AMC-16 Mar Further degradation of solar arrays, some transponders switched off • Satmex V 27 Jan Loss of XIPS propulsion system, operational life shortened

• 2009• GeoEye 1 11 Dec Problem with transmit antenna pointing mechanism • Landsat 5 Dec Lost transponder replaced by one thought to have failed earlier • MTSAT-1R 11 Nov 15.5-hour outage • Eurobird 1 12 Sep 90-minute outage starting at 2124 UTC attitude problems • Chandrayaan 1 28 Aug Contact lost; mission abandoned • Orbcomm 24 Aug Coast Guard demo satellite fails • Landsat 5 13 Aug 1-day outage • Herschel 3 Aug SEU causes anomaly in HIFI instrument • Sinosat 3 13 Jul 12-hour outage, starting at 1350 UTC• Yamal 202 3 June 8½-hour outage • Eutelsat W2A May IOT: S-band payload anomaly announced • GeoEye 1 May Problems with colour imagery announced • Chinasat 6B 9 Feb 47-minute outage starting 0259; recovered• Eutelsat W2M 28 Jan IOT: Major anomaly of power subsystem, likely total loss

• How important is Space Weather ?• Can we help protect satellites?

Importance of Energetic Particles – Space Weather

• NOAA anomaly database

• High flux of MeV electrons cause satellite anomalies (malfunctions)

• Cumulative radiation dose limits spacecraft lifetime

• Iucci et al. SW [2005]

Solar wind – Radiation Belts

• Increased MeV electron flux in the radiation belts

• Driven by high speed solar wind and Bz fluctuations

• Galileo - Giove – A

• Science and applications

• 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

• As electrons drift around the Earth they encounter many types of waves:

• 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

• Radial diffusion

• Wave-particle interactions

• Whistler mode hiss waves

• Loss to the atmosphere

• Underestimates flux

• Needs electron acceleration

• Lam et al. GRL [2007]

Cyclotron Resonant Electron Acceleration: Chorus

• Whistler mode chorus waves excited by ~1-50 keV electrons

• Waves accelerate electrons up to MeV energies

• Horne et al., Nature [2005]

Cluster data

3d Dynamic Global Modelling• 3d = Include wave-particle interactions

• 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

Diffusion Coefficients

• Radial diffusion coefficients

• Due to ULF waves

• 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

• [Varotsou et al. 2005, 2008; Horne et al., 2006]

• Radial diffusion + wpi due to chorus – steady state

• No cross terms

• Significant increase in electron flux due to chorus acceleration

Radiation Belt Environment Model

SAMPEX Data

2-6 MeV electrons• 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

• Electrons flux - CRRES satellite during a magnetic storm

• Model without wave-particle interactions - inadequate

• Model with wave-particle interactions

• Wave-particle interactions are essential for radiation belt variations and loss to atmosphere

USAF Model

• Albert et al. [2009]

• Includes cross terms

• 2 grids – coordinates of the second grid are chosen so the cross terms vanish

• Radial diffusion + chorus give best agreement with data

• Cross terms reduce chorus acceleration

Data

Radial diffusion alone

Chorus and RD

Coupling High and Low Energy Electrons

Coupling low and High Energy Electrons

• No coupling • 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

• Benck et al. [2010]

• Electron lifetimes (0.23 – 0.34 MeV) are longer when measured at low altitude compared to equator

• Why?

Loss timescales

• SAC – C measures pa ~ 20O

• CRRES measures 0-90

• Suggest here

– Active conditions

– Energy diffusion at large p.a.

– Energy diffusion at small p.a

• Important to resolve for global dynamic models

Conclusions

• Satellite losses and service interruptions are still significant

• Radiation belts are variable and pose a hazard

• Global dynamic radiation belt models are being developed to forecast risk

• 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

• Galileo provides new opportunities for science as well as applications

• New SPACECAST project will develop European models and forecasting

• Wave-particle interactions – radial diffusion

Reserve Slides

Needs to improve models

• Need more wave data for different wave modes – diffusion rates

• Need better ULF waves data for radial diffusion

• Couple high and low energy electrons

• Need better E field model for convection - transport

• Better coupling from solar wind to magnetosphere – effects of boundaries

• Develop global models into forecasting models

• New FP7 SPACECAST project will do some, not all

Resonance Cone

• Waves do not propagate at all directions

• Need to restrict wave power in angle

• What is the angular spread??

• Need observations

– CLUSTER

Resonance cone

Vg

k

Electrostatic

Electromagnetic

Wave Power Near the Resonance Cone

• Pitch angle diffusion rate

• Including wave power near the resonance cone reduces the diffusion rate !!

• Paradox

• Reason

• waves become electrostatic – not electromagnetic

• Need to revise model

• Need to identify EM and ES waves in wave data

Dynamic Modelling Approach

• Diffusion - complexity in transformations

• Gyro-kinetic - complexity in wave diffusion

• Both need very good magnetic field models

Observations Transform to a dipole field (L*)

Diffusion Calculations

Observations Use a realistic magnetic field model

Gyro-kinetic Calculations

or