Transcript CH12: Space Weather Effects
Introduction to Space Weather Space Weather Effects April 26, 2012
Jie Zhang Copyright ©
CSI 662 / PHYS 660 Spring, 2012
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Part 1: Sun
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Part 2: Heliosphere
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Part 3: Magnetosphere
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Part 4: Ionosphere
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Part 5: Space Weather Effects
Roadmap
CH12: Space Weather Effects
CSI 662 / PHYS 660 Apr. 26, 2012
CH12: Space Weather Effects
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CH12.1 Society and Economic Impact
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CH12.2 Effects on Spacecraft
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CH12.3 Effects on Human
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CH12.4 Effects on ground-based technological system
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CH12.5 Effects on communications and navigations
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CH12.6 Space Weather Prediction and Forecasting
CH12: Space Weather Effects
References and Reading Assignment:
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Chapter 13 of Deleres D. Knipp book “Understanding Space Weather and The Physics Behind It”
2009 Space Weather Enterprise Forum May 19-20, 2009 Washington, D.C.
2012 Space Weather Enterprise Forum June 05, 2012 National Press Club Washington, D.C.
Is the solar minimum over?
Nov. 19, 2009
A “gentle” solar maximum?
April 26, 2012
CH12.1 Society and Economic Impact
The Society Interdependence
Economy Impact
• • • •
Repair damaged S/C: $50-70 M Replace commercial S/C: $250-300 M Cost of major power blackout: $4-10 B Extreme storm (“1859 Carrington event”): $1-2 Trillion
CH12.2 Effects on Spacecraft
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Spacecraft Surface Charging Deep Dielectric Charging Single Event Effect (SEE)
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Single Event Upset (SEU)
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Single Event Latchup Spacecraft dragging
Spacecraft Surface Charging
• A variation in the
electrostatic potential of a spacecraft
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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
Responsible for about half of all spacecraft anomalies.
Spacecraft Surface 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 -> negative charge buildup • Particularly during satellite eclipses
Spacecraft Surface Charging
Electric charging mechanisms
2. Photoelectric effects • Electrons escape from the surface positive charge buildup on the surface
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 attitude control problems for GEO satellites Intelsat K, Anik E-1 and Anik E 2 on 2007 Jan. 21 st and 22 nd following a CME
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
Single Event Effect (SEE)
• More SEE events in South Atlantic Anomaly Region
SAA
Single Event Effect
• Various unplanned events due to faulty commands • Central processing unit (CPU) to halt • Damage to memory
Engineer design:
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Error detection and correction (EDAC), additional bit
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Memory redundancy
Spacecraft Drag
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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
Spacecraft Drag
• Heating and expansion of the thermosphere during a geomagnetic storm • Heating and expansion of the thermosphere by EUV and X-ray emission of strong solar flares • Abnormally large drag results in sudden orbit changes • Tracking of objects are lost • Accurate pointing becomes difficult; accurate pointing is important for satellite constellations
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.
Satellite Disorientation
• Some attitude 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 by misalignment of antenna • Loss of satellite power by misalignment of solar panels
CH12.3 Effects on Human
• 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
Radiation Health Hazard
Quantify the radiation dose Old and SI Unites of Radiation
Deposition Old Unit 1 rad = 10 mJ/kg Equivalent dose Rem=RBE X rad SI Unit 1 Gray (Gy) = 100 rad = 1 J/kg 1 Sievert (Sv) = quality Factor (QF) X Gray •
rad: radiation absorbed dose
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RBE: relative biological effectiveness, 1.0 (200 Kev gamma ray, 2.0 (protons)
Radiation Health Hazard
Recommended Limits to Radiation Exposure Exposure
Astronaut Exposure
Maximum Dose (Sv)
50 mSv in one year
Equivalent Dose (rem)
~5 rem in one year ~0.5 rem in one year Public Exposure in the US Occupational Exposure Early-fetus Exposure 5 mSv in one year 50 mSv in one year 0.5 mSv/month ~5 rem in one year Typical Chest X-ray Natural Background 0.05-0.01 mSv ~1 mSv in one year ~0.05 rem in one month ~0.005-0.001 rem ~0.1 rem in one year
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.
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
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/cm 2 of aluminum shielding.
• Storm shelters, ~20g/cm 2 or 200 kg/m 2 of water equivalent material,
Radiation hazard is also a concern for airlines that fly commercial flights routinely over the polar cap.
(Continued on May 3, 2012)
CH12.4 Effects on ground-based technological system
Effects of GIC
Geomagnetically Induced Current (GIC) http://en.wikipedia.org/wiki/File:GIC_generation.jpg
Effects of GIC
Geomagnetically Induced Current (GIC)
• During space weather disturbances, enhancement of ionospheric current induces the change of geomagnetic field • The change of geomagnetic field in turn induces a disturbance geo-electric field • This induced electric field drives electric currents in ground based technological systems, .e.g, 6 V / km • Electric currents flow through artificial conductors present on the surface • Extended electric power lines • Telecommunication cables • Extended pipelines • Railway lines
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 transformer converts energy to heat, 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
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.
Disaster could be avoided by the preventative actions taken by power grid managers
Effects of GIC
Pipelines
• GIC causes corrosion at points where current flows from the pipe into the surrounding soil
CH12.5 Effects on Communication and Navigation
Radio Wave Propagation Mode
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
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
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
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
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.
• The phenomena may persist for 20 minutes to 2 hours at a location
Satellite Navigation
GNSS: (Global Navigation Satellite System) – GPS (Global Positioning System) (USA) – GLONASS (Russia) – Galileo (Europe) – Northern Star (China)
Satellite Navigation
GPS Errors due to Scintillation
Satellite Navigation • Primary Effects on GPS and related systems
– Time delay and phase distortions arising from the TEC (Total Electron Content) of the ionosphere • 1 TECU = 10 16 electrons/m 2 • 1 TECU increases the path length by ~ 0.16 m – Scintillation in amplitude and phase at high latitudes and equatorial latitudes
Propagation Effects & TEC
Effect Faraday Rotation Group-Path-Delay Phase Advance Doppler Shift Units Radians Seconds Radians Hz Formulae 2.97 x 10 -2 f -2 H L * TEC 1.34 x 10 -7 f -2 * TEC 8.44 x 10 -7 f -1 * TEC 1.34 x 10 -7 f -2 * d/dt TEC Time Delay Dispersion Phase Dispersion Seconds/Hz Radians/Hz -2.68 -8.44 x x 10 10 -7 -7 f f -3 -2 * TEC * 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
WASS
– WAAS (Wide Area Augmentation System) • A network of reference stations on the ground • Significantly increase the accuracy, ~ order of cm • Spacecraft approaching and landing
CH12.6 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
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 10 4 to 10 5 observing points, which are interpolated onto more than 10 6 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