lect13

Space Weather Effectsand Prediction: 

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

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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

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Space Weather Effects

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

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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))

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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

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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

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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

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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

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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

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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

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

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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

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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

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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

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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  = air density in Adx A = satellite front surface area v = satellite velocity dx A v mass Spacecraft Drag

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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 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 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.

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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

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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)

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Radiation Health Hazard Recommended Limits to Radiation Exposure

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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.

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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

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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.

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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

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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

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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

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

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Effects on Communication and Navigation Instead of on hardware, this is the effect on signals of radio waves Radio wave transmission noise Attenuation Interruption Path decay Scintillation

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Radio Wave Propagation Mode

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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

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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

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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

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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

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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

Satellite Navigation: 

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)

Satellite Navigation: 

Satellite Navigation

Satellite Navigation: 

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

GPS Errors due to Scintillation: 

GPS Errors due to Scintillation

Propagation Effects & TEC: 

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

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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

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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

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

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

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

The End: 

The End