1 Topics in Space Weather Topics in Space Weather Lecture 14 Space Weather Effects On Technological Systems Robert R. Meier School of Computational Sciences George Mason University CSI 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

Solar Radiation and Plasma Can Affect Earth  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: March 1989: Auroral Oval Solar radiation, magnetospheric and galactic particles ionize and heat Earth’s atmosphere and ionosphere Power System Events 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, F g –2nd term is the drag force –The orbital speed is: FgFg FDFD v 2a

6 Drag, cont. The drag force is C D = 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 –C D = 2.2 for a spherical satellite around 200 km F = rate of change of momentum, L  = air density in Adx A = satellite front surface area v = satellite velocity dx A v mass

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 F D :

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 = C D A/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 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]