Scientific Understanding and the Risk from Extreme Space Weather Mike Hapgood
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Transcript of Scientific Understanding and the Risk from Extreme Space Weather Mike Hapgood
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Scientific Understanding and the Risk from Extreme
Space Weather Mike Hapgood
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Some environment risksFlooding People, homes and infrastructure on flood
plains and coasts
Tsunami People, homes and infrastructure near coast
Volcanoes People, homes and infrastructure on pyroclastic and lava flow lines
Space weather People, homes and infrastructure near a star
• Natural hazards can occur in places that are good to live
• So need to understand and mitigate occasional risk
• Scale and frequency of extreme risks is key concern
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Recent examples of extreme SpW
• Halloween 2003– Recent event
– Well-documented
– Moderate on historical timescale (12th by daily aa)
• 13 March 1989– Big event (3rd by daily aa)
– Impacts on power, drag, etc
– Solar wind state not well known
• 8 Feb 1986– At solar min, but 20th largest
by daily aa
March 1989 event
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12-Mar 13-Mar 14-Mar 15-Mar
Au
rora
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Quebec failure
Aurora over S. England
Auroral E @ Slough
Sudden
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Data: UK Solar System Data Centre
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Some historical extremes• 23 Feb 1956
– SEP event with huge neutron flux at Earth’s surface => hard spectra
– Gold event?
• 1 Sep 1859– Carrington event
– Discovery of solar flares
– Global aurorae
– GIC in telegraph systems
– Huge nitrate production
– The perfect storm
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Carrington event• Carrington event is our canonical example of extreme space weather
– No spacecraft– No electrical power systems – Edison was 12, Tesla only 3
• Repeat will challenge operation of spacecraft & power grids– GIC at lower latitudes where they are not usually seen– Threat to future links to solar power systems in Southern Europe and North
Africa (also wind power on Atlantic margin?)
• US estimates of economic impact– GIC: one to two trillion dollars (NRC workshop, May 2008)– Space: 44 billion dollars from loss of service income, 24 billion dollars in
terms of spacecraft losses (ASR special issue, 2006)
• Something to be scared of!• But also something that can inform us – guide our risk assessments
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Environmental risk & science• Assessment of risk is a standard approach to
mitigate natural hazards ahead of prediction • Public authorities increasing require risk
assessment for wide range of developments, e.g.– design homes to withstand 1 in 100-year risks– higher standards for design of critical infrastructure,
e.g. 1 in 1000-year risks for nuclear reactors
• Risk assessments critically underpinned by scientific knowledge – drives design standards– and hopefully their implementation!
Mike HapgoodESWW5, Brussels, 21 Nov 2008
How is this done for other hazards?Example: 20 July 2007 floods in S. England
• Flooding is a local hazard– Rainfall has local peaks
– Topography channels water
Stream flows statistically independent
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Assessing 100-year flood risk
• Collect data from similar streams, > 500 station-yrs
• Normalise to stream to be assessed
• Get distribution of peak flow vs return time
• Apply corrections for global change
Mike HapgoodESWW5, Brussels, 21 Nov 2008
How to apply to space weather?
• Space weather is global– Data across Earth
are correlated
– So can’t combine
• Can apply ideas to long STP datasets, e.g. aa
• Plot opposite shows the limitations
Binned distribution of 3-hourly aa 1868-2006
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aaF
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1-year risk (*cycle average)
100-year risk??
10-year risk?
• Need other Earth-like planets? (exo-planet AKR?)
• Or wait 500 years!• Statistical modelling of
extremes unreliable
Mike HapgoodESWW5, Brussels, 21 Nov 2008
The importance of physics!
• Modelling of extreme space weather is essential
• Must be physics-based or -guided
• Numerical modelling unreliable outside mean ± stdev– See Tsyganenko 2005 opposite
– Also Roelof & Sibeck m/p
December, Dst – 20 nT, By/Bz 0
Ram 20 nPa
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Towards the physics of extreme events
• How to make a huge auroral oval?– brings auroral effects to mid/low latitudes
– expand polar cap/open field lines?
Make this big:• high V• Bz << 0
Make this small:• time delay?• choke reconnection
outflow in tail?
Mike HapgoodESWW5, Brussels, 21 Nov 2008
How fast can polar cap grow? /t ~ Vsw Bz L
– Take Vsw = 2000 km s-1
– Bz = 50-100 nT
– L ~ 100000 km
/t ~ 107 V• Assume Earth dipole
– 108 Wb/degree
– Pc grows 0.1 deg s-1
– From 70° to 45 ° in 4 mins (would envelope N Europe)
0.E+00
2.E+09
4.E+09
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Latitude (deg)
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)
Mike HapgoodESWW5, Brussels, 21 Nov 2008
What research is needed?
• Response of magnetosphere to extreme inputs:– Needs modelling with comprehensive physics
– What physics would be important at extremes?
– What could limit the response?
• Properties of extreme solar wind– Credible maximum speed?
– Credible maximum Bz?
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Informing decision makers?
• Raise awareness of credible risks from space weather– Stress global nature (no safe zone to supply help)
– Explore risk magnification through impacts on interconnected systems (power, comms, …)
– Risk of creeping dependency via impact on complex systems
• Show the need for risk assessments• Identify the research needed to support good risk
assessment
Mike HapgoodESWW5, Brussels, 21 Nov 2008
SPARES
Mike HapgoodESWW5, Brussels, 21 Nov 2008
What is the problem?• Extreme space weather challenges conventional
institutional thinking – Rare events with huge impact. Institutions struggle with such
hazards unless there is a near-continuous threat (e.g. the Cold War).
– threat magnified by inter-connectedness of modern world. impacts on fundamental infrastructures cascades across economy & society
– creeping dependency: everyday life is supported by complex systems whose safety under stress is not well understood.
– global impact of space weather. No safe place from which help can come – unlike floods, earthquakes, ordinary volcanoes, etc.
• How to proceed? – Develop natural hazard approach– Risk assessment?
Mike HapgoodESWW5, Brussels, 21 Nov 2008
Using L1 warnings
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SW velocity (km s-1)
L1-
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L1 predictions usable