Ionospheric Electrodynamics & Low-Earth Orbiting Satellites (LEOS)

1. 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

2. 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

3. Most Powerful Solar Flares Ever Recorded

5. Altitude from the surface CHAMP

6. Altitude from the surface Drop of ~300 m in a few days SCISAT 1

7. Altitude ~ 390 km Nov 9-11 2004 ?? July 29 2004 ?? May 28 2003 ??

8. Altitude ~ 710 km

9. 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)

10. Drag Coefficient, CD Moe and Moe, 2005 Average value that is used for most satellites

11. 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.

12. Tools

13. 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.

14. Some Numerical Results

15. Thermospheric Response horizontal transport vertical transport • A. T. Russell (2007), Russell et. al. (2007)

16. Satellite Observations Schlegel et al, Ann. Geophys., 2005

17. CHAMP Observations Schlegel et al, Ann. Geophys., 2005

18. The End Liu et al., JGR 2005

19. FAC and Neutral Densities Neubert & Christiansen, GRL, 2003 Liu et al., JGR 2005

20. STK Simulations of CHAMP OrbitThe Halloween Event

21. 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)

22. 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.

23. STK Modeling of CHAMP Orbit October 26th, 2003 1200 to 1430, separation between sats ~ 20 meters

24. Modeling of CHAMP Orbit November 4th, 2003 1000 to 1330 separation of sats is ~250 km

25. CHAMP accelerations

26. 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.

27. 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.

28. 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

29. Thank YouObrigado

30. Steep Precipitation Pattern

31. Electrodynamical response Noël, 2006

32. Ionospheric Response Noël, 2006

33. More observations from CHAMP

34. Thermospheric Response • A. T. Russell (2005)

37. Halloween 2003 Event Halloween 2003

38. Halloween 2003 EventSOHO

39. 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.

40. CHAMP accelerations

41. CHAMP accelerations

42. 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)

43. 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))