Topics in Space Weather Lecture 14

1. Topics in Space WeatherLecture 14 Space Weather Effects On Technological Systems Robert R. Meier School of Computational Sciences George Mason University rmeier@gmu.edu CSI 769 29 November & 6 December 2005

2. Topics • Meier • Introductory comments • Drag effects on orbiting space objects • Thermospheric density decreases due to greenhouse gas cooing • Goodman • Introduction to Space Weather & Technological Systems • Telecommunication Systems and Space Weather Vulnerabilities • Large Storms and Impacts upon Systems • Modeling and Compensation Methods used in Practice • Prediction Systems & Services

3. Solar Radiation and Plasma Can Affect Earth • Solar radiation, magnetospheric and galactic particles ionize and heat Earth’s atmosphere and ionosphere March 1989: Auroral Oval Power System Events • spacecraft drag, collisions, loss • communications & navigation • aurora • currents induced in power grids • spacecraft detector upsets • hazards to humans in space • ozone depletion in major events • speculated climate impacts LASCO Detector: 1997-11-06 www.nas.edu.ssb/cover.html Lecture 14

4. Effect of Drag on Satellite Orbits • Assume elliptical orbit a = semi-major axis m= satellite mass M = Earth mass >> m G = gravitational constant • Calculate change in a resulting from drag • Expressions derived from Kepler’s Laws

5. Drag, cont. The dynamical equation to be solved is • 1st term on the rhs is the centripetal acceleration, Fg • 2nd term is the drag force • The orbital speed is: FD Fg v 2a

6. Drag, cont. • The drag force is • CD = drag coefficient • Accounts for • Momentum transfer on all sides • Fluid flow around satellite • Turbulent effects • Is a function of speed, shape, air composition, and aerodynamic environment • CD = 2.2 for a spherical satellite around 200 km F = rate of change of momentum, L A mass v dx  = air density in Adx A = satellite front surface area v = satellite velocity

7. Drag, cont. • The total energy is: • The orbital period is:

8. Drag, cont. • The work done by drag is: • The rate of change of energy due to drag is: • The rate of change of orbital period is: Solving for da/dt & substituting for FD:

9. Drag, cont. • Eliminating da/dt from the last two equations on slide 10, and substituting in for the drag force leads to: • The relative change in orbital period over 1 rev is: • The rate of change of period depends on B = CDA/m (the ballistic coefficient) • If orbital parameters and the ballistic coefficient are known, the average atmospheric density can be determined

10. Decay of Elliptical Orbit

11. A Simple Example: Decay Rate of the Solar Max Mission (SMM) Satellite Courtesy, J. Lean

12. Another Example: Same Satellite 30 Years Apart Emmert et al. [2004]

13. Secular Trend from 27 Objects from 1966 - 2001 Emmert et al. [2004]

14. Secular Trend • Density decreases consistent with theoretical predictions of greenhouse gas increases with thermospheric GCMs • Heating of troposphere • Cooling of stratosphere, mesosphere and thermosphere • Observation: • Emmert et al. [J. Geophys Res., 109, A02301, 2004] • Theory: • Roble, R. G., and R. E. Dickinson [Geophys. Res. Lett., 16, 1441– 1444, 1989]