Ionospheric Electrodynamics & Low-Earth Orbiting Satellites (LEOS) J-M Noël, A. Russell, D. Burrell & S. Thorsteinson Royal Military College of Canada October 7 th, 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

Most Powerful Solar Flares Ever Recorded

CHAMP Altitude from the surface

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

Altitude ~ 390 km Nov ?? May ?? July ??

Altitude ~ 710 km

Satellite Drag a drag is the in-track acceleration (m/s 2 ) C D is the drag coefficient v sat is the satellite velocity (m/s) v n is the neutral wind (m/s) A is the cross-sectional area (m 2 ) ρ is the neutral number density (m -3 )

Drag Coefficient, C D Moe and Moe, 2005 Average 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 C D, 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, 2003Liu et al., JGR 2005

STK Simulations of CHAMP Orbit The 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, to 1430, separation between sats ~ 20 meters

Modeling of CHAMP Orbit November 4 th, to 1330separation 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 You Obrigado

Steep Precipitation Pattern

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 Event SOHO

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

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