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Ionospheric Electrodynamics & Low-Earth Orbiting Satellites (LEOS)

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### Ionospheric Electrodynamics&Low-Earth Orbiting Satellites (LEOS)

### The End

J-M Noël, A. Russell, D. Burrell

&

S. Thorsteinson

Royal Military College of Canada

October 7th, 2009

Ubatuba, 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

Satellite Drag

- 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)

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.

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.

Thermospheric Response

horizontal transport

vertical transport

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

Satellite Observations

Schlegel et al, Ann. Geophys., 2005

CHAMP Observations

Schlegel et al, Ann. Geophys., 2005

Liu et al., JGR 2005

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)

Basic Assumptions – Continued

- 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.

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

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

Electrodynamical response

Noël, 2006

Ionospheric Response

Noël, 2006

Thermospheric Response

- A. T. Russell (2005)

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.

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)

Ionospheric Model

- 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))

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