Space Weather Effects and Prediction

1. CSI 662 / ASTR 769 Lect. 13 Spring 2007 May 01, 2007 Space Weather Effectsand Prediction • References: • Presentation (main) • Tascione: Chap. 9, Chap. 10, P. 113 – 144 (supplement)

2. Topics • Space Weather Effects • Effects on Spacecraft • Radiation Health Hazard • Effects on ground-based technological systems • Effects on communications and navigations • Space Weather Prediction and Forecasting

3. Space Weather Effects

4. Effects on Spacecraft • Spacecraft Charging • Deep Dielectric Charging • Single Event Effect (SEE) • Single Event Upset (SEU) • Single Event Latchup • Spacecraft dragging

5. Spacecraft Electric Charging • A variation in the electrostatic potential of a spacecraft surface with respect to the surrounding plasma • A resulted electronic discharging causes problems • Spurious electronic switching • Breakdown of thermal coating • Solar cell degradation • Optical sensor degradation • Problems at high altitude (>5 RE), geosynchronous orbit • Caused by magnetotail particle (hot plasma, ~ Kev))

6. Spacecraft Electric Charging Electric charging mechanisms • 1. Particle bombardment • electron (~Kev) penetrating ~micron into a dielectric skin and stick in  negative charge buildup • In a thermal plasma, electrons move faster; more effective than protons on charging

7. Spacecraft Electric Charging Electric charging mechanisms • 2. Photoelectric effects • Electrons escape from the surface  positive charge buildup on the surface The effect of these mechanisms strongly depends on the shape of the spacecraft and the material on the surface. Responsible for about half of all spacecraft anomolies Engineer: design discharge-resistant vehicles

8. Deep Dielectric Charging • Caused by energetic (relativistic) electrons (2-10 Mev) that penetrate deep into the surface • Uneven electric potential between different portions of the inside surface of satellites • Resulting discharging can arc directly into the satellite’s internal electrical circuits • Resulting discharging damages the material Probably caused altitude control problems for GEO satellites Intelsat K, Anik E-1 and Anik E-2 on Jan. 21st and 22nd following a CME

9. Satellite Disorientation • Some Altitude control systems are guided by specific star patterns with the field of view • SEP particle storm produces numerous flashes of light in the optical sensor and confuses the control system • Loss of communication • Loss of satellite power by misalignment of solar panels

10. Single Event Effect (SEE) • Caused by energetic particles and ions (>30 Mev) penetrates spacecraft shielding and interact with the microelectronics (integrated circuits, ICs). • Particles cause direct ionization of silicon materials, producing a burst of electrons • Single Event Upset (SEU) • flips the logic state of a single bit (bit flip) • Rewrite the memory or reboot the system • Single Event Latchup (SEL) • Lead to a permanent high state • Disable the IC

11. Single Event Effect (SEE) • Particle sources • Galactic cosmic ray (GCR) • Solar energetic particles (SEPs) • Radiation belt particles • More SEE events in South Atlantic Anomaly Region SAA

12. Galactic Cosmic Ray (GCR) • Produced by supernova explosion • Mostly particles in Gev, but up to 1021 ev • Isotropically • constant

13. Solar Energetic Particles (SEP) • Accelerated by CME-driven shocks and flare-related magnetic reconnection • Typically 10 Mev to 1 Gev, but up to 100 Gev • Directional nature, more flux if particle path is well-connected by interplanetary magnetic field • Last a few days • Solar cycle variation Astronauts experience “irritating” flashes in the eyes

14. Single Event Effects • Various unplanned events due to faulty commands • Central processing unit (CPU) to halt • Damage to memory • Engineer design: • Error detection and correction (EDAC), additional bit • Memory redundancy

15. Spacecraft Drag • Frictional drag force by atmospheric particles acting on the Low-Earth-Orbit (LEO) satellites • Decrease velocity at perigee results in a decrease in apogee height; orbit becomes more circular • Circular orbits experience the drag at all points; faster orbit decay SMM orbit decay

16. Spacecraft Drag • 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

17. Spacecraft Drag • Abnormally large drag results in sudden orbit changes • Tracking of objects are lost • Accurate pointing becomes difficult; accurate pointing is important for satellite constellations • Heating and expansion during a geomagnetic storm • Heating and expansion by EUV and X-ray emission of strong solar flares Tracking of thousands of space object was lost during the March 13 and 14, 1989 geomagnetic storms. US commands has to re-track these objects. Increased air drag caused the failure of ASCA (Advanced Satellites for Cosmology and Astrophysics) in July 2000. Extra spin moved the solar panel out of proper alignment and reduced the ability to generate power

18. Radiation Health Hazard • When very high energy particles encounter atoms or molecules within the human body, the collisions cause a release of radiation (Bremstrahlung radiation). • The radiation ionizes the surrounding materials, producing a region of dense ionization along its track. • Ionizing radiation can break chemical bonds in biological molecules which result in biological injury. • Radiation exposure results in acute, delayed, or chronic illness, depending on the rate and the accumulative dosage • A person may suffer loss of appetite, digestive failure, brain damage and even death

19. Radiation Health Hazard Quantify the radiation dose Old and SI Unites of Radiation • rad: radiation absorbed dose • RBE: relative biological effectiveness, 1.0 (200 Kev gamma ray, 2.0 (protons)

20. Radiation Health Hazard Recommended Limits to Radiation Exposure

21. Radiation Health Hazard • Earth’s magnetic field produces a factor of ~ ten reduction in total GCR exposure for LEO, e.g., International Space Station orbit • Unshielded interplanetary dose to the blood forming organs (BFO) is ~ 0.6 Sv/year, exceeding the acceptable value • Solar energetic particles pose the greatest short-term threat to astronauts.

22. Radiation Health Hazard • Thin to moderate shielding is effective in reducing the projected equivalent dose rate. • As shield thickness increases, shield effectiveness drops, because of the large number of secondary particles

23. Radiation Health Hazard • Space suit has a small amount of aluminum: stops 10 Mev protons; no extra-vehicle activity during the storm time • Spacecraft typically have several g/cm2 of aluminum shielding. • Storm shelters, ~20g/cm2 or 200 kg/m2 of water equivalent material, Radiation hazard is also a concern for airlines that fly commercial flights routinely over the polar cap.

24. Effects of GIC Geomagnetically Induced Currents (GIC) • During space weather disturbance, enhancement of ionospheric current induces the change of geomagnetic field • The change of geomagnetic field in turn induced a disturbance geo-electric field • This induced electric field drives electric currents in ground-based technological systems • Currents flow through artificial conductors present on the surface • Extended Electric power lines • Telecommunication cables • Extended pipelines • Railway lines

25. Effects of GIC Power System • GIC is a quasi-direct current (DC) (variation in order of minutes) compared with the 50/60Hz alternating current (AC) • GIC flowing through a transformer winding produces extra magnetization • A saturated transform converts energy to heat, then reducing the energy for transmission, and in turn, reducing the voltage • Leading to trip-outs of individual lines to the collapse of the entire system Transformer Failure in March 13-14, 1989 storm, New Jersey

26. Effects of GIC Power System On March 13, 1989, a GIC induced by a great geomagnetic storm caused a nine-hour blackout of the 21GW Hydro Quebec power system, leaving six million costumers without power. “Domino” effect in the collapse of a power system Disaster could be avoided by the preventative actions taken by power grid managers

27. Effects of GIC Pipelines • GIC causes corrosion at points where current flows from the pine into the surrounding soil

28. Effects on Communicationand Navigation Instead of on hardware, this is the effect on signals of radio waves • Radio wave transmission noise • Attenuation • Interruption • Path decay • Scintillation

30. Radio Wave Propagation Mode

31. Sudden Ionospheric Disturbance (SID) • Associated with strong solar flares • Penetration of flare X-rays causes the enhancement density in the D and lower E regions • Results in sharp fadeout of long distance, radio communication on the sunlit side of the Earth • Short lived, ~ 1 hour

32. Polar Cap Absorption (PCA) • Caused by energetic protons from SEP events • Particles guided by open field lines into the polar cap • Increase electron density between 55 and 90 km • Results in communication blackout • PCA is a long-lived effect, ranging from tens of hours to several days Communication blackout in polar cap region

33. Satellite Communication (Satcom) • Use UHF (>300 Mhz) and SHF band to mitigate the ionospheric effects • Primary long-distance communication method since 1970s • Space weather effect on SATCOM • Scintillation in amplitude and phase

34. Scintillation • Scintillation: rapid, usually random variation of the amplitude and phase of transionospheric radiowaves • It is due to abrupt variation in electron density along the signal path which produce rapid signal path variation (phase) and defocusing (amplitude) • It is caused by instability and turbulence • When signal fades exceed the receiver’s fade margin, the signal is temporarily lost

35. Scintillation • Most significant variations occur near the F2-peak between 225 km and 400 km • The scintillation effects are most pronounced in the equatorial (± 20 deg) geomagnetic latitude belt. • It attains maximum density between 2100 L to 0200 L time • The phenomena may persist for 20 minutes to 2 hours at a location

36. Satellite Navigation GNSS: (Global Navigation Satellite System) • GPS (Global Positioning System) • WAAS (Wide Area Augmentation System) • Enroute Oceanic & Domestic • Terminal • Approach (down to category 1 precision) • LAAS (Local Area Augmentation System) • Approach (category 2/3 precision) • Surface (landing)

37. Satellite Navigation

38. Satellite Navigation • Primary Effects on GPS and related systems • Scintillation in amplitude and phase at high latitudes and equatorial latitudes • Time delay and phase distortions arising from the TEC (Total Electron Content) of the ionosphere

39. GPS Errors due to Scintillation

40. Propagation Effects & TEC MKS units are employed. The TEC is in units of electrons/square meter along the ray path, f is the radio frequency (Hz), and HL is the component of the magnetic field along the ray path (ampere-turns/meter). Dual frequency receiver may count for the TEC variation

41. Space Weather Forecasting • Forecast Timeframes • Nowcast: 0 -- 2 hr • Short-term: >2 -- 36 hr • Mid-term: > 36 -- 120 hr • Intermediate term: 5 days – several solar rotation • Long-range: > several solar rotation to solar cycle

42. Space Weather Forecasting • Compared with the terrestrial forecasting, space weather forecasting is still in its infancy. • Terrestrial weather data assimilation • Every 6 hours, measurement of about 10 different parameters taken at 104 to 105 observing points, which are interpolated onto more than 106 points of a three-dimensional grid used by numerical prediction model • Space weather data • Data are sparse, one point outside the magnetosphere (L1), only several points inside the magnetosphere

43. Example • Wang-Sheeley-Arge solar wind model: • Using photospheric surface magnetic field as a boundary condition to predict solar wind speed

44. Example Baker et al [1990] model: forecast > 2 Mev electron at geosynchronous orbit one day in advance Input: solar wind

45. Space Weather Forecasting • NOAA Space Weather Environment Center • http://www.sec.noaa.gov • NASA Community Coordinated Modeling Center • http://ccmc.gsfc.nasa.gov

46. The End