1. Extreme Space Weather Warning System Andrew Fazakerley (1), Chris Arridge (1), Dhiren Kataria (1), Jonny Rae (1), Matthew Stuttard (2) (1) Mullard Space Science Laboratory, University College London (2) Airbus D&S (but this is not an official Airbus presentation!) SEREN Bz Workshop Abingdon July 2014 Solar wind power input to the magnetosphere/unit area: P = V sw B IMF 2 µ 0 sin 4 (θ /2) Perreault and Akasofu 1978

2. ENLIL vs ACE Are forecasts adequate? Accurate V and B are needed for several types of predictive models of space weather effects Random example interval (Oct-Nov 2009) Solar wind speed –Incorrectly indicates speeds over 400 km/s –Peaks at wrong times Interplanetary magnetic field –Magnitude badly wrong –Peaks at wrong times –(direction also matters…) ENLIL ACE ENLIL ACE 1.6 1.4 1.2 1.0 0.8 0.6 B(nT)

3. Multi-spacecraft Extreme Space Weather Warning System Interplanetary Coronal Mass Ejections (ICMEs) Earth L5 Sun L1 Sub-L1 Possibility of magnetic cloud, which may have prolonged geoeffective B ICME can drive geoeffective sheath SEPs often associated with sheath Hazard Potential sudden magnetospheric compression possible prolonged geoeffective B radiation belt enhancements Forecasting needs measurements at L5: active regions (caution) L5: Earthward ICME (clear risk) L1 or Sub-L1: n, V, B test for geoeffective plasma (alert)

4. Multi-spacecraft Extreme Space Weather Warning System Stream Interaction Regions (SIR) and High Speed Streams (HSS) Prolonged HSS related to radiation belt enhancements SIRs can be geoeffective Hazard Potential Radiation belts sudden compression of magnetosphere Forecasting needs measurements at L5: near-equatorial coronal holes and measure fast streams (caution) L1 or Sub-L1 : n, V, B test for geoeffective plasma (alert) Earth L5 Sun L1 Sub-L1

5. Multi-spacecraft Extreme Space Weather Warning System L5 space weather observatory Some studies & proposals: Akioka et al, J. CRL, 2005 Vourlidas et al., Gopalswamy et al., White papers for Heliophysics Decadal Survey 2010 EASCO Gopalswamy et al., JASTP, 2011 RESCO, CAS-ESA Workshop 2013 INSTANT, CAS-ESA Workshop 2013 WATCHER, CAS-ESA Workshop 2013 Very long distance communication: 1 AU L5 Active Region L5 Time T Time T + 6 days L1 No Active Regions Time T Time T + 6 days Average direction of CMEs that produce Earth- affecting SEPs is best observed from L1 Average direction of geoeffective CMEs (GEO) is well observed from L5 (Gopalswamy et al)

6. Multi-spacecraft Extreme Space Weather Warning System Predictive value of L5 solar wind and IMF data for Earth? ICMEs Data from 2 months when STEREO-B (red) was at L5 and ACE (black) was at L1. ICMEs from L1 (yellow) and from L5 (blue) based on published ACE/STEREO lists few, if any, are seen at both locations

7. Multi-spacecraft Extreme Space Weather Warning System Predictive value of L5 solar wind and IMF data for Earth? SIRs Data from 2 months when STEREO-B (green) was at L5 and ACE (black) was at L1. STEREO data shifted 5 days. Velocity profile is quite similar SIRs from L1 (yellow) and from L5 (blue) based on published ACE/STEREO lists – only a few overlap ICMEs often appear at only one spacecraft Most of the enhanced |B| and n events are ICMEs or SIRs

8. Multi-spacecraft Extreme Space Weather Warning System Sub-L1 Measure solar wind/IMF near the sun- Earth line significantly earlier than from L1 Distant Retrograde Orbit Scenarios St Cyr et al, JASTP, 2000 St Cyr et al Decadal Survey 2010 Cranfield MSc Group Project 2012 MSSL study & student projects 2012-4 St Cyr et al Sp W Experts Mtg 2014 Airbus UK informal study, MagAlert, 2014 Non-Keplerian Orbit Scenarios Solar Sail: Sunjammer (Geostorm) Ion engine Heliocentric Ring inside 1 AU Needs >10 spacecraft…

9. Multi-spacecraft Extreme Space Weather Warning System Sub-L1 Distant Retrograde Orbit type mission: UK studies: revisiting the St Cyr et al. (JASTP, 2000) “Space Weather Diamond” concept and explore feasibility of a UK mission launch scenarios orbits communications challenges number of spacecraft most cost-effective operational approach A more sophisticated Concurrent Design Facility study is under discussion Credit. C Arridge,MSSL Credit. MagAlert, Airbus

10. Multi-spacecraft Extreme Space Weather Warning System Sub-L1 Sunjammer: state of the art solar sail Solar sail –Largest area solar sail, by factor 7: 1,200m 2 –Lowest mass solar sail, by factor 10: ~ 50 kg, –Thrust ~ 0.01N Small mass spacecraft bus and payload, as well as sail Current status –Possible test flight in 2018 There are limits on how far Sun-ward a sail can get, while sitting near the Sun-Earth line, related to sail mass/unit area For Sunjammer the limit is ~ 0.018 AU (2,747,100 km) (multiple sails in halo orbit around that distance can improve warning time, in theory, Heiligers and McInnes 2014; but comms issue tough in low mass spacecraft)

11. Multi-spacecraft Extreme Space Weather Warning System Extreme Interplanetary Coronal Mass Ejection Event STEREO-A (Liu et al, Nature Comm, 2014) Peak speed at STEREO ~2,246 km/s; Average speed ~ 2,150 km/s Transit time across 1 AU: ~19 hours Peak magnetic field magnitude ~109 nT Predicted minimum D st = -598/1,154 nT, comparable to Carrington Event estimates By chance, strongest Bz north, not south Best possible warning times for n, V, Bz: L1 (0.01 AU) 11 min Sunjammer (0.018 AU) 20 min DRO (0.1 AU)110 min (~2 hours) (best case)

12. Multi-spacecraft Extreme Space Weather Warning System Summary Concept for operational extreme space weather warning satellite system Satellites in different places are complementary In combination, they could provide a graduated space weather alert system Share costs of elements/ops internationally? Some Possible Discussion Points Limited information on statistics of 3D spatial scales, forms of ICME magnetic clouds: DRO constellation data would improve stats and models Even non-MC ICMEs can drive a geoeffective sheath (piled up solar wind) How does prediction effectiveness of in situ data fall with increasing distance away from the Sun- Earth line? how does this vary with heliocentric distance? scale of solar wind structure? Earth L5 Sun L1 Sub-L1