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Ionospheric Electrodynamics & Low-Earth Orbiting Satellites (LEOS)

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Ionospheric Electrodynamics&Low-Earth Orbiting Satellites (LEOS)

J-M Noël, A. Russell, D. Burrell

&

S. Thorsteinson

Royal Military College of Canada

October 7th, 2009

Ubatuba, Brazil

- 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

Altitude from the surface

CHAMP

Altitude from the surface

Drop of ~300 m

in a few days

SCISAT 1

Altitude ~ 390 km

Nov 9-11

2004 ??

July 29

2004 ??

May 28

2003 ??

Altitude ~ 710 km

- 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)

Moe and Moe, 2005

Average value that is used

for most satellites

- 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.

- 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

horizontal transport

vertical transport

- A. T. Russell (2007), Russell et. al. (2007)

Schlegel et al, Ann. Geophys., 2005

Schlegel et al, Ann. Geophys., 2005

The End

Liu et al., JGR 2005

Neubert & Christiansen, GRL, 2003

Liu et al., JGR 2005

STK Simulations of CHAMP OrbitThe Halloween Event

- 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.

1200 to 1430, separation between sats ~ 20 meters

1000 to 1330separation of sats is ~250 km

- 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.

- 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.

- Complete the coupling of the thermospheric model:
- Transcar – ionospheric model
- Blelly et al., 1996

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

- Transcar – ionospheric model
- Comprehensive Coupled 2 – D Model
- De Boer et al., 2009 submitted

Thank YouObrigado

Noël, 2006

Noël, 2006

- A. T. Russell (2005)

Halloween 2003 Event

- 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.

- There are 2 kinds of FAC
- Electric Fields
- Ionospheric and thermospheric responses.
- How these responses affect satellite orbits.

- 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))