ionospheric electrodynamics & low-earth orbiting satellites (leos)

Ionospheric Electrodynamics

&Low-Earth Orbiting

Satellites (LEOS)J-M Noël, A. Russell, D. Burrell

& S. Thorsteinson

Royal Military College of CanadaOctober 7th, 2009Ubatuba, Brazil

Outline

• An extreme example of space weather– Halloween 2003 Event and it’s effect on LEOs orbits.

• Numerical models– Neutral atmosphere – HLTIM– Electrodynamic – Electro– Ionospheric – Transcar

• Some numerical Results• Implications for satellite orbits

– predictions• Concluding remarks

Most Powerful Solar Flares Ever Recorded

Ranking Date X-Ray Class

1 November 4th, 2003 X28+ (est. closer to X45 (Thomson et. al, 2004)

2 April 2nd, 2001 X20.0 2 August 16th, 1989 X20.0 3 October 28th, 2003 X17.2 4 September 7th, 2005 X17 5 March 6th, 1989 X15.0 5 July 11th, 1978 X15.0 6 April 15th, 2001 X14.4 7 April 24th, 2004 X13.0 7 October 19th, 1989 X13.0

CHAMP

Altitude from the surface

SCISAT 1

Altitude from the surface

Drop of ~300 m in a few days

Altitude ~ 390 km

Nov 9-11 2004 ??

May 28 2003 ??

July 29 2004 ??

Altitude ~ 710 km

Satellite Drag

2

2

1nsatDdrag vvACa

•adrag is the in-track acceleration (m/s2)•CD is the drag coefficient•vsat is the satellite velocity (m/s)•vn is the neutral wind (m/s)•A is the cross-sectional area (m2)•ρ is the neutral number density (m-3)

Drag Coefficient, CD

Moe and Moe, 2005Average value that is used for most satellites

What we want to study

• Thermospheric responses to ionospheric electric fields.– Electric fields can vary substantially in both

space and time.

• How does the thermospheric responses affect satellite orbits?– Variation in CD, ρ and v (not just only ρ)

– In this talk we will concentrate on ρ.

Tools

High Resolution High Latitude Thermospheric Model

• Thermospheric Model – A. T. Russell– based on the 2-D model of Chang and St.-

Maurice (1991)– solves the Navier-Stokes equations – several upgrades have been incorporated into

the model e.g. new cooling rates, stretched vertical grid, more realistic initial conditions.

Some Numerical Results

Thermospheric Response

A. T. Russell (2007), Russell et. al. (2007)vertical transport

horizontal transport

Satellite Observations

Schlegel et al, Ann. Geophys., 2005

CHAMP Observations

Schlegel et al, Ann. Geophys., 2005

The End

Liu et al., JGR 2005

FAC and Neutral Densities

Neubert & Christiansen, GRL, 2003 Liu et al., JGR 2005

STK Simulations of CHAMP OrbitThe Halloween Event

Basic Assumptions

• Severe space weather simulation– large ambient electric field in the ionosphere-

thermosphere, 100 mV/m, 0.5° half-width centered at 70°, ramped from 0 to 100 linearly in 1000 seconds.

• Use MSIS as a base neutral atmosphere– Add density perturbations obtained from the

thermospheric model (HLTIM – Russell)

• Assumed that the thermosphere is symmetric.– i.e. no variation in the East-West direction.

• The latitudinal distribution is the same for the southern hemisphere as it is for the northern hemisphere.

Basic Assumptions – Continued

STK Modeling of CHAMP Orbit October 26th, 2003

1200 to 1430, separation between sats ~ 20 meters

Modeling of CHAMP Orbit November 4th, 2003

1000 to 1330 separation of sats is ~250 km

CHAMP accelerations

Concluding Remarks

• Space weather plays a important role in the decay rates of satellite orbits via:→ increases in the electrodynamical response

→ increases frictional heating

→ increases the thermospheric densities in the vicinity of orbiting satellites.

Concluding Remarks

• Small-scale auroral structures having intense electrodynamics should not be neglected when simulating satellite orbits to determine their projected lifetimes.

• We have made an attempt to simulate the effects of the small-scale structures on satellites for the first time.

What’s Next?

• Complete the coupling of the thermospheric model:– Transcar – ionospheric model

• Blelly et al., 1996

– Electro – electrodynamic model • Noel et al., 2001, 2005

• Comprehensive Coupled 2 – D Model– De Boer et al., 2009 submitted

Thank YouObrigado

Steep Precipitation Pattern

arctan2

arctanarctan)(

xxxf

Electrodynamical response

Noël, 2006

Ionospheric Response

Noël, 2006

More observations from CHAMP

Thermospheric Response

A. T. Russell (2005)

Halloween 2003

Halloween 2003 Event

Halloween 2003 EventSOHO

What we want to study

• Current systems and electric fields in the vicinity and inside auroral arcs– There are 2 kinds of FAC

• FAC driven by the magnetosphere.

• FAC associated with divergences in Pedersen currents.– They are known to produce FACs on the edges of arcs.

• Electric Fields• Ionospheric and thermospheric responses.• How these responses affect satellite orbits.

CHAMP accelerations

CHAMP accelerations

Electrodynamic Model (Electro)

• 2-dimensional model based on divergence-free current density.

• computes the electric potential, electric fields and current densities.

Noël, (1999), Noël et al. (2001, 2005)

• Transcar – transport (Blelly et al., 1996)– computes the time evolution of the ionosphere

(composition, energetics and transport).– 1-dimensional along the magnetic field line. – electron energy spectrum – electron heating due to waves (Dimant and

Milikh, (2003), Noel et al. (2005))

Ionospheric Model