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

[email protected] / [email protected]


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


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

-3000

-2000

-1000

0

1000

2000

3000

4000

12-Mar 13-Mar 14-Mar 15-Mar

Au

rora

l Ele

ctro

jet

ind

ices

(n

T)

AL

AO

AU

AE

Quebec failure

Aurora over S. England

Auroral E @ Slough

Sudden

impuls

Data: UK Solar System Data Centre


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


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


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!


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


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


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

1

10

100

1000

10000

100000

1 10 100 1000 10000

aaF

req

uen

cy in

bin

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


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


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?


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

6.E+09

8.E+09

1.E+10

1.E+10

0 15 30 45 60 75 90

Latitude (deg)

Mag

flu

x p

ole

war

d o

f la

titu

de

(Wb

)


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?


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


SPARES


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?


Using L1 warnings

0

20

40

60

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120

140

0 500 1000 1500 2000 2500 3000

SW velocity (km s-1)

L1-

Ear

th t

ran

sit

tim

e (m

ins)

L1 predictions usable

Scientific Understanding and the Risk from Extreme Space Weather Mike Hapgood

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