Space Weather Forecasting - Need and Importance

Transcription

1 Coronal Magnetic Field Measurements: Space Weather Forecasting Needs D.N. Baker Laboratory for Atmospheric and Space Physics Department of Astrophysical and Planetary Sciences Department of Physics University of Colorado - Boulder

2 A conference is a gathering of important people who individually can do nothing, but who, together, can conclude that nothing can be done. Fred Allen

3 Questions to Address: Space Weather Practical View 1. If one could make accurate, timely measurements of magnetic field above solar surface, how might this information be used to make better space weather forecast models? a. How would/could limb observations best be used for SWx? b. How would/could on-disk observations in coronal holes, active regions, etc. be used for SWx? 2. What should be the key properties of physicsbased models of the corona intended for space weather forecasting purposes?

4 Take Away Message for Space Weather Forecasting 1. Need to have interplanetary magnetic field orientation at 1 AU 2. Need the north-south direction of the magnetic field near Earth 3. Need the B z component of the upstream interplanetary magnetic field Oh, and by the way, did I mention the need for the IMF B z component??

5 Outline of Presentation Overview of Space Weather Concerns Solar Energetic Particles Radiation Belt Energization Geomagnetic Storms (Power Grid, etc.) Present Modeling: WSA-ENLIL Summary and Future Directions

6 Risk Assessment Should Answer Three Basic Questions: What can happen? How likely is it to happen? What are the consequences if it does happen?

7 The Societal and Economic Impacts of Severe Space Weather Events May 22-23, 2008 in DC Approximately 80 attendees from academia, industry, government, and industry associations Association reps aggregated data and helped avoid concerns about proprietary or competitionsensitive data Analyses in specific areas; e.g., GPS, power industry, aviation, military systems, human and robotic exploration beyond low- Earth orbit Econometric analysis of value of improved SpaceWx forecasts [

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9 Solar Cycle Characteristics Solar Max: Major, non-recurrent geomagnetic storms (caused by CMEs) Approach to Solar Min: Recurrent storms and high radiation belt flux (due to high-speed streams) Solar Min: Quiet magnetospheric conditions [Baker et al., Space Weather, 2009]

10 ashington Post raphic

11 Coronal Mass Ejection - Earth Impact Courtesy of NASA

12 Solar events are observable 12

13 Heliophysics Research Missions with Realtime Space Weather Utility 13

14 High-Energy Ion Effects D.N. Baker How to Cope with Space Weather, Science, 297, 1486, 2002

15 The Active Sun: July 2000 SOHO-EIT, 07:00 UT

16 Background Due to Solar Particles SOHO EIT, 13:28 UT

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19 High-Energy Electrons

20 Energetic Electrons: Deep-Dielectric Charging 1. Electrons bury themselves in the insulator 4. Electrons build up faster than they leak off 2. Electrons slowly leak out of the insulator 5. Discharge (electrical spark) that damages or destroys the material 3. Influx of electrons increases to levels higher than the leakage rate

21 SAMPEX Radiation Belt Electrons: 2-6 MeV

22 MHD Simulation of a Strong Storm [Courtesy M. Wiltberger]

23 MHD/Particle Simulations of Energetic Electron Trapping 60 kev test electrons, constant M Started 20 R E downtail, 15s intervals Evolves naturally under MHD E and B fields Removed from simulation at magnetopause Color coded by energy Elkington, Baker, Wiltberger [2004]

24 Relativistic Electrons & Geomagnetic Storms Recovery phase Increased fluxes Energization Main phase Flux dropout Adiabatic field change & particle loss Flux changes Decrease or no change in about 50% of storms - GEO data [See Kanekal et al., 2004; Reeves et al., 2003]

25 1994 High Speed Stream Control Strong electron acceleration in the approach to sunspot minimum White arrows indicate 27-day recurrent events: High-speed solar wind streams

26 Formation of a Corotating Interaction Consider a radius vector from the Sun (say a vertical line) As the Sun rotates slow wind, then fast wind, and again slow wind is emitted and travels radially outward The solar magnetic field is pulled outward by the wind and wrapped into spiral lines Slow wind is more tightly wrapped than fast wind The fast wind overtakes the slow wind and begins to interact with it along an interface that has shape intermediate between the slow and fast spirals Because of the imbedded fields the two streams do not interpenetrate Region (CIR) [R. L. McPherron]

27 Magnetospheric Activity for Streams in 1995 Magnetospheric Activity for Streams in 2004 Equ Flow Equ Flow P dyn (np)) Epoch Time (days) P dyn (np)) Epoch Time (days) GSM Ey (mv/m) Epoch Time (days) Epoch Time (days) GSM Ey (mv/m) Epoch Time (days) Epoch Time (days) ap (nt) ap (nt) Sym-H (nt) Epoch Time (days) Sym-H (nt) Epoch Time (days) Epoch Time (days) Epoch Time (days)

28 GOES Electron Fluxes in Cycles #22 & #23 In cycle #22 years 1994 and 1995 fluxes were low before CIRs, exhibited strong dropouts before the interface, and large enhancements after In cycle #23 the fluxes were 10 x higher before the interface, had about the same size dropout, and showed a weaker enhancement after the interface Something is different between the two cycles. The fluxes are higher in cycle #23, but not as strongly enhanced at an interface Compare log10(ele flux) Quartiles of All Streams in log10(ele flux) 1994 log10(ele flux) 1995 log10(ele flux) 1996 Compare log10(ele flux) Quartiles of All Streams in log10(ele flux) 2003 log10(ele flux) 2004 log10(ele flux) log10(ele flux) log10(ele flux) Epoch Time (days) Epoch Time (days)

29 We have developed models that go from Sun to magnetosphere B sun ( τ < t) Mount Wilson Observatory Solar Magnetograms Baker et al. [1990] Method in use at NOAA/SWPC V ( t) = f ( B ( τ t), R) < SW sun J ( t) = F( V ( τ t), L) e < SW SAMPEX

30 GEO MeV Electron Prediction Filter J e ( t) = h V 1 ( t 1) + h 2 V ( t 2) h T V ( t T ) h 2 V ( t) = δ ( t) J e h 1 h T h 0 Days Since Solar Wind Impulse [Baker et al., 1990]

31 R E MeV Filter h t (L) From Vassiliadis et al., 2002

32 RBSP Real-Time Rad Belt Forecasting Use SDO, SOHO, and WSA-ENLIL to forecast Earth-impacting events: Then compare forecasted radiation belt response with RBSP (esp. REPT) obs. Current ACE Measurements V Solar Boundary Measurements WSA/ENLIL Propagation Lead Time of 3-4 Days V Linear Filter J e (Daily averaged MeV Electron Flux) Current MeV Electron Flux measurements J e

33 WSA-ENLIL Solar Wind Forecast Model Daily synoptic solar maps WSA Pre-processing of synoptic maps Potential field source surface (PFSS) + Heliospheric current sheet (HCS) Mapping to ENLIL inner boundary or L 1 ENLIL Generation of inner boundary from WSA Propagation of SW structures with MHD code in heliosphere Post-processing of simulation for < ~1 AU prediction Current Solar Wind Conditions Space Weather Forecast Real-time Inputs Coupled Coronal Heliospheric model Output Products Ambient modeled conditions and cone model extension

34 Model-Data Comparison (M1 Flyby) [Baker et al., JGR, 2009]

35 Coronal Mass Ejections August 2011

36 Forecasting Space Weather Conditions Baker - Advisory Council March 2010

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39 Wide Area Augmentation System (October 2003) Ionosphere disturbances impact vertical error limits, defined by the FAA s Lateral Navigation/Vertical Navigation (LNAV/VNAV) specification to be no more that 50 meters. Commercial aircraft unable to use WAAS for precision approaches.

40 The Interdependencies of Society

41 Low Frequency/High Consequence: Increasing Power Grid Vulnerability The grid is becoming increasingly vulnerable to space weather events Future Directions in Satellitederived Weather and Climate Information for the Electric Energy Industry Workshop Report Jun 2004 $1-2 trillion 4-10 years Potential loss due to widespread power grid Blackout following severe geomagnetic storm Recovery time from a widespread power grid Blackout following severe geomagnetic storm Source: National Academy Workshop on the Societal and Economic Impacts of Severe Space Weather Events held in Washington, D.C., May 2008.

42 Oxford Dictionaries: (noun) A mainly black swan with white flight feathers which is common in Australia and Tasmania and has been introduced elsewhere An unpredictable or unforeseen event, typically one with extreme consequences Nassim Nicholas Taleb, 2007: A black swan is a highly improbable event with three principal characteristics: - It is unpredictable; - It carries a massive impact; and - After the fact, we concoct an explanation that makes it appear less random, and more predictable, than it was. 42

43 On the probability of occurrence of extreme space weather events American Geophysical Union, SPACE WEATHER, VOL. 10, S02012 Pete Riley, Predictive Science, San Diego, USA Dst = -850nT Carrington estimate from Siscoe et al. Estimation Techniques for Rare Events: Event Trees Similarity Judgments Time To Event Extrapolation from Frequent Events Used measured data from 746 geomagnetic storms over 46 years Time-stationary conservative assumption: no solar cycle influence Best data fit is a power law distribution Extreme events have a higher probability than intuitive probability beliefs 12% probability of Carrington Event exceeding -850 nt over the next decade s Log (Probability that an event will exceed some severity Log (Severity of the space weather event) 43

44 Are CME events black swans? Taleb, 2007: A black swan is a highly improbable event with three principal characteristics: It is unpredictable; No. Both estimable and observable. It carries a massive impact; Yes. Power grid failures. Aviation, communications, navigation assets. After the fact, we concoct an explanation that makes it appear less random, and more predictable, than it was. No excuses - a solvable policy and investment problem. 44

45 Summary and Conclusions Knowledge of the interplanetary magnetic field from the Sun to Earth is crucially important for space weather forecasting The general direction, strength, and polarity of the IMF (as from ENLIL) is useful for many SWx purposes such as Solar Energetic Particle (SEP) forecasting Radiation belt forecasts depend greatly on IMF B z knowledge The highest need in SWx forecasting is to get CME arrival and geo-effectiveness right: Again B z is key! To be really useful, coronal field information feeding heliospheric model must be quite current and accurate Important SWx forecasting progress may be possible using probabilistic methods until nirvana is reached

46 Thanks-Questions?