Ionospheric Electrodynamics & Low-Earth Orbiting Satellites (LEOS)
description
Transcript of 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