Topics in Space Weather Lecture 14

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Topics in Space Weather Lecture 14

Space Weather Effects On Technological Systems
Robert R. Meier School of Computational
Sciences George Mason University rmeier_at_gmu.edu CS
I 769 29 November 6 December 2005
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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

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Solar Radiation and Plasma Can Affect Earth
Solar radiation, magnetospheric and galactic
particles ionize and heat Earths 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
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Effect of Drag on Satellite Orbits

• Assume elliptical orbit
• a semi-major axis
• m satellite mass
• M Earth mass gtgt m
• G gravitational constant
• Calculate change in a resulting from drag
• Expressions derived from Keplers Laws

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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
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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
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Drag, cont.

• The total energy is
• The orbital period is

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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
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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

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Decay of Elliptical Orbit
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A Simple Example Decay Rate of the Solar Max
Mission (SMM) Satellite
Courtesy, J. Lean
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Another Example Same Satellite 30 Years Apart
Emmert et al. 2004
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Secular Trend from 27 Objects from 1966 - 2001
Emmert et al. 2004
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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