The Role of Ionosphere in Ring Current Development During the Super Storm in November 2003

Mei-Ching Fok1, Thomas E. Moore1, Dominique C. Delcourt2, Steven P. Slinker3 Joel A. Fedder4, Yusuke Ebihara5, and Samuel T. Jones6

1NASA Goddard Space Flight Center, USA2CETP-CNRS-IPSL, Saint-Maur des Fosse, France

3Naval Research Laboratory, USA4Leading Edge Technology, Inc., USA

5Nagoya University, Japan6University of Texas in Arlington, USA

ST11-A0009August 2, 2007

2007 AOGS Meeting, Bangkok, Thailand

Outline

The super storm in November 2003

Lyon-Fedder-Mobarry (LFM) global magnetospheric simulation of the Nov03 storm

Modeling the polar wind and auroral wind (O+) outflow from the ionosphere during the Nov03 storm

Modeling the ring current development during the Nov03 storm with solar, polar and auroral sources

Effect of ionospheric conductivity on ring current development

November 2003 Storm

Solar wind velocity

Solar wind density

IMF Bz

Dst

• Solar wind velocity increased to ~750km/s.

• Solar wind density was unusually high

• IMF Bz decreased to -50 nT.• Negative IMF Bz lasted for ~ 12 hours.

• Dst reached -472 nT.

LFM Simulation of the November 2003 Storm

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Ionospheric Outflow Driven by MHD Condition

Parameter Scaling Notes

Auroral windO+ flux

NVprecip = 2.8×109×N2.2 [cm -2s-1]NV poynt = 5.6×107×(0.245×S120)1.26 [cm -2s-1]NV = (NV precip × NV poynt)0.5

Subject to local flux limi t = 3×109 [cm -2s-1]MHD density is reduced by a loss cone fillingfactor from Chen and Schulz [2001]:FLC = 0.4[1+0.8sin(2pi×(MLT-3)/24)]

N is LFM density in cm -3 reduced to thefraction of density above instrum ental EMIN

= 50eV, based on the MHD temp erature.

S120 is LFM Poynting flux in mW/m 2 at 120km altitude; 0.245 maps from 120 to 4000km alt.

Temp erature 0.1 + 9.2×(0.24×S120)0.35 [eV] Strangeway [private commu nication]

Parallel energy E// [eV ] = Eth + ePhi [V] wherePhi[V] =1500[V /µAm -2] ×(J// - 0.33)2 [µA m -2]

Lyons [1981]Threshold current 0.33 µA/m 2

Polar WindH+ flux

0 < SZA < 90: F1000 = 2×108 cm -2s-1

90 < SZA < 110:F1000 = 2 ×10 (̂8-(SZA-90)/20×2.5)110< SZA < 180: F1000 = 2×105.5 

Su et al., [1998] solar zenith angle (SZA)dependence.

All fluxes at 1000 km altitude

Local scalings used to drive ionospheric outflows [Taken from Moore et al., 2007]

Ionospheric Outflow Driven by MHD Condition

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Simulation of Auroral Wind and Polar Wind Outflow

O+

Violation of 1st adiabatic invariant

Strong non-adiabatic acceleration

Test-particle code of Delcourt

Calculation of Density and Temperature from Test-Particle Trajectories

€

nj(t)= nij(t)i∑ =dA

VjFi(ti)cosαi(ti)Tiji

∑kT||j(t)=2E||j(t)=2 Eij(t)i

∑ cos2αij(t)kT⊥j(t)=E⊥j(t)=2 Eij(t)i

∑ sin2αij(t)nj: density at bin j

Ej: energy at bin j

Σ: sum over all ions passing through bin j from t-Δt to t+Δt

dA: area of the source surface allocated to each particle

Vj: volume of bin j (1 RE3)

Fi: ion source flux

Tij: residence time of ion i in bin j

Eij: average energy of ion i in bin j

α ij: average pitch angle of ion i in bin j

The entire simulation space is divided into bins of 1 RE

3 volume.

The Comprehensive Ring Current Model (CRCM)

Ring CurrentPhase Space Density

MagnetosphericElectric Field

Field AlignedCurrent

IonosphericElectric Field

Ionospheric ConductivityCross Polar Cap Potential Drop

Charge ExchangeDrift Losses

Boundary ConditionSolar, Polar, Auroral Winds

LFMMagnetic Field

Ring Current Formed by Solar Wind Ions

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Ring Current Formed by Auroral O+ Ions

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Ionospheric Particles Contribution to Ring Current Energy Content

0 100

1 1031

2 1031

3 1031

4 1031

5 1031

6 1031

8 12 16 20 24 28 32 36

solar-wind sourceauroral-wind sourcepolar-wind source

hour

Ring Current Particle Energy

Nov 20 Nov 21

Ionospheric ion outflow contributes significantly to the ring current particle and energy content during this event.

Simulated ionospheric Potential

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Auroral conductivity includes effects due to precipitating electrons and field-aligned potential drop

Effect of Ionospheric Conductivity on Electric Potential

Hardy Auroral ConductivityLFM Auroral Conductivity

Strong field at sharp conductivity gradient

Effect of Ionospheric Conductivity on Ring Current Development

Hardy Auroral ConductivityLFM Auroral Conductivity

Relatively strong pressure in the post-midnight sector due to high auroral conductivity.

Summary

The global magnetospheric configuration and ring current development during the storm on 20-21 November 2003 are simulated using the combined tool: LFM + Delcourt-particle-code + CRCM

Particles from solar wind (H+), auroral wind (O+) and polar wind (H+) are considered as sources of ring current ions.

Auroral wind and polar wind outflow characteristics are driven by instantaneous MHD conditions at the ionosphere.

Contribution of auroral O+ to the ring current is comparable or higher than that of the solar wind source. Contribution from the polar wind is negligible.

Strong auroral conductivity and sharp gradient produce high ring current flux in the post-midnight sector.