Space Weather Forecasting

Space Weather Forecasting David Jackson and Edmund Henley Suzy Bingham, Emily Down, Siegfried Gonzi, Mike Marsh STFC Introductory Solar System Plasmas Summer School 28 August 2018, University of Exeter

Contents A Quick Intro to Space Weather Met Office Space Weather Operations Centre (MOSWOC) Rationale and Services How do we observe space weather? How do we forecast space weather? Way forward and issues More and better (and coupled) models More data (including L1/L5 missions) Crown copyright Met Office 2

Solar eruptions Space Weather generally refers to changing conditions on the Sun, in the solar wind, and in Near-Earth space (magnetosphere, ionosphere and thermosphere) Coronal mass ejections (CMEs)..that can influence the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health. Solar flares Much of it is intimately linked to these solar eruptions Sophie Murray (TCD) Solar energetic particles

Space weather affects us all Impacts on power grids, satellites, aviation, GNSS, comms,. crown copyright

Eruption Type How do the solar eruptions connect to the impacts? Physical impacts CME 1-3 days to travel to Earth If geoeffective (Bz<0) can cause geomagnetic storms within Earth s atmosphere Geomagnetically induces currents (GICs) Increased ionospheric ionisation Heating in thermosphere Aurorae! Tech. impacts GICs => disruption to electricity grid, railways, pipelines GNSS and HF comms disruption Satellite drag / issues with orbital tracking Satellite damage eg surface charging Solar energetic particles crown copyright ~few mins to ~1 day to reach Earth Increased radiation levels Increased ionisation in polar atmosphere Flares Reaches Earth in 8 mins Radio noise Increased ionisation and heating Radiation health impacts astronauts, flight crew, passengers Satellite and avionics damage incl deep charging HF comms disruption over poles HF (and other) comms disruption (sunlit Earth) Some minor satellite tracking issues

Met Office Space Weather Operations Centre (MOSWOC) 24/7 Operations Forecasts to 4 days ahead to meet UK Gov / Critical National Infrastructure / Industry requirements : CMEs Geomagnetic storms Flares Solar energetic particles (protons and electrons) Set up in response to National Risk Register Met Office owns risk on behalf of UK Government (Dept of Business, Energy and Innovation Strategy (BEIS))

Space Weather The Dynamic Space Environment Space Weather Types and Arrival Times from Sun Solar Wind Electromagnetic Radiation & Energetic Charged Particles and Charged Plasma Galactic Cosmic Radiation Challenges: Difficult to forecast accurately Short warning time to prepare once we have certainty about speed and size of events Days Geomagnetic Storms Hours/Mins Solar radiation Storms Minutes Solar Flares / Radio Blackout SECRET // UKEO E: robert.seaman@metoffice.gov.uk DII: METO-MET-INT-1

How do we even start? Need to observe and assess current state first good for alerts / warnings Then can use this as basis for forecasts human-based, empirical and numerical Crown copyright Met Office

How do we observe space weather? Crown copyright Met Office

Location of satellites Not to scale STEREO AHEAD SUN DSCOVR (ACE) & SOHO SDO EARTH L1 92 million miles 1 m miles L1 ORBIT GOES STEREO BEHIND

CMEs Near solar maximum: ~3 CMEs/day. Near solar minimum: ~1 CME/5days. CME mass speed Range 10 11-4 10 13 g 200-3000km/s transit time 12-60h kinetic energy 2 10 30 erg CME propagation detected by coronagraphs: at L1 (NASA SOHO) precessing (NASA/ESA STEREO were 2; now only 1)

In situ observations of CMEs ACE and DSCOVR obs at L1 indicate CME hitting Earth Plasma speed jump due to ballistic CME. Need to know magnetic field. If Bz < 0 in CME, geomag storm can be very large This is only definitive observation only gives us ~30 mins lead time!!!!

Coronal Holes These are regions of open magnetic field lines in the Sun s corona These lead to high speed solar wind streams. Impacts Geomagnetic storms (CH/CME interaction can enhance these storms) Enhanced high energy electron flux (near Earth) Observations SDO EUV images (for location and size)

Geomagnetic Storms Storms indicated on the Earth s surface via magnetometer obs Large db/dt will lead to large geomagnetic induced currents and impact on eg power grids This effect is typically described via the Kp index a global index based on 13 worldwide stations Kp=9 (or G5) storm is what we are really worried about We receive Kp nowcasts and forecasts from BGS and NOAA We also receive magnetometer measurements from 3 UK sites from BGS to monitor local impact

Space Weather is usually linked to Active regions Big, bad, and ugly! We monitor ARs using SDO magnetograms and white light images Also ground based (GONG) magnetograms

Solar Analysis First the forecasters do a solar analysis (based on SDO data) AR classification and CH identification This identifies if there are complex ARs likely to give CMEs, flares, SEPs AR analysis drives the flare forecast CHs => High Speed Stream and geomagnetic storm forecast Manual Coronal Hole analysis being replaced by automated methods (CHIMERA: Tadhg Garton, TCD)

Solar flares GOES 15 in eclipse Classification of solar flare strength based on GOES X-ray flux measurements Impacts X20 (Extreme;,1 / solar cycle) complete HF blackout on sunlit side of Earth for several hours M1 (Minor; 2000 / solar cycle) Weak or minor HF degradation on SSoE. Occasional loss of radio contact GOES Class A B C M X Peak flux [W m 2 ] 10 8 10 7 10 6 10 5 10 4 Occur in active regions around sunspots: Several flares/day around solar max. ~1/week around solar min. Location and structure measured by imagers (typically EUV) we usually use NASA SDO

Solar radiation storms High Energy Electron Flux Usually linked to CHs Observations GOES >2MeV electron flux (for monitoring near Earth fluxes) Associated with solar flares (rapid onset) or CMEs (gradual onset) Can be seen as snow in coronagraph images Near Earth impact seen in GOES proton flux observations S5 (extreme) Flux / particles: 10 5 pfu; < 1 / cycle Airline passengers / crew may be exposed to increased radiation; Some satellites may suffer temporary outages due to memory impacts. Some aircraft electronic systems may experience single event effects (SEE) => upsets or unexpected behaviour S3 (strong) 10 3 pfu; 10 / cycle Radiation hazard avoidance recommended for astronauts on EVA; passengers & crew in high-flying aircraft at high latitudes may be exposed to radiation risk. Some SEE risk HF comms affected at high lats

How do we forecast space weather? Crown copyright Met Office

All Forecasts are categorical and probabilistic Using categories helps by Indicating action affected user may need to take. Since forecasts are hard, may make forecast information more usable than more quantitative forecast Have already introduced categories for flares (M and X class) and radiation storms (S3 and S5 class) Active / very active categories of high energy electron fluence For geomagnetic storms use G index (KP 5) Probabilistic forecasts indicate level of uncertainty also useful for interpretation (focus on geomagnetic storms and flares in the following)

Geomagnetic storm & CME forecasting Forecasters analyse images to identify CMEs and CHs and use WSA Enlil & persistence model to predict HSSs, CMEs Geomagnetic storm forecasts are limited as Bz is unknown other than L1 (DSCOVR/ACE observations) Kp forecasts from BGS are statistical no knowledge of current situation (eg CMEs) So forecasters rely on their experience to interpret the information they have available

Solar wind / CME forecast model: WSA Enlil Models solar wind speed & density (IMF modelled but no Bz input). Predicts CME arrival times at Earth. Inputs: (GONG) solar magnetograms to model coronal magnetic field and provide inner BCs for Enlil. CME parameters input into Enlil (from CAT) Run every 2hrs Forecasts: average error: +/- 7 hrs; lead time: CME transit time a few hrs Ensemble prediction system now operational

CH influence CHs influence solar wind and thus geomagnetic storms How do we assess impact? CH perturbations should be picked up in magnetograms and thus WSA Enlil initial conditions Use recurrence CH size can grow / shrink from one solar rotation (27 days) to the next Solar wind persistence model very good

Flare Forecast Statistical models link complexity of ARs with probability of occurrence of different classes of flares Forecasters use experience to modify this before issuing forecast MOSWOC issued forecasts better than raw ones Murray et al (2015)

RPSS Forecast Verification RPSS Solar Flares SRSs issued every 6 hrs for each classified AR 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00-0.05-0.10-0.15-0.20-0.25-0.30-0.35 Need to know how good forecasts are to drive further improvement NRT verification in operation / being developed Rolling 12-monthly RPSS values (x) with 90% bootstrapped CIs for each day of the geomag storm forecast (Mar-Oct 2016). Day 1,2,3 & 4 are indicated by solid, long dashed, short dashed and dotted lines, respectively. International praise and demand

Way forward and Issues Crown copyright Met Office

Toward Sun-Earth coupled modelling Solar wind (interplanetary space) Magnetosphere Radiation belts Photosphere (solar surface) Corona (solar atmosphere) Upper / lower atmosphere coupling (via whole atmosphere UM) Thermo / ionosphere coupling Ionosphere Thermosphere Middle and Lower atmosphere GOAL: Coupled Sun-to-Earth models with DA for much-enhanced forecast capacity

Sun-to-Earth modelling What s missing? ----------------------------------------------- No coupling! ------------------------------------------ CME prediction coronal magnetic field modelling What ARs shall be eruptive? Flare prediction, AR tracking CH and filament identification Bz prediction DA / IPS data SEP propagation Strength of storms / substorms No magnetosphere model! Ionospheric scintillation Thermosphere modelling Thermo / ionosphere coupling Upper / lower atmosphere coupling (whole atmosphere model) SEP initiation ---------------------------------------------- Forecast verification in development ----------------------------------------------- Opinion of MOSWOC Scientists, Forecasters, Managers

Other (WSA) Enlil developments WSA initialised with GONG m/graphs Do this better using DA ADAPT ADAPT gives ensemble solutions possible ensemble of ambient solar wind forecasts Also trialling NLFFF model (Durham / St Andrews) 1 st step to CME prediction but major research needed IPS ground based solar wind obs to drive Enlil Possibly also new Bz measurements 10X in advance of current Carl Henney (AFRL)

SEPs: SPARX High energy electrons: Towards Coupled Modelling BAS RB model? Physics-based, not confined to GEO Magnetosphere: SWMF (Michigan) being implemented and tested Will enable Magnetosphere / Ionosphere coupling Thermosphere / ionosphere: Extended UM (to ~150 km) in development + coupling to TIEGCM

The observation network Apart from DSCOVR and GOES, all observations science not operational Risk to CME monitoring since SOHO and STEREO beyond planned lifetime. Solutions: L1 and L5 operational missions planned Alternative observations ground based radio telescopes (IPS) Magnetosphere has similar issues quite a lot of GEO obs but few elsewhere Ionosphere well observed but thermosphere and radiation not Observation requirements defined via WMO but more concerted efforts needed L5 mission will replicate and enhance STEREO: c/graph HI m/graph EUV imager Solar wind (U,r,B)

Summary Space Weather related to solar eruptions and impacts health and technology so on UK NRR =>MOSWOC monitors / forecasts SpWx for UK How do we observe and forecast space weather? Issues More and better (and coupled) models needed but lots of underpinning research and improved understanding needed More operational data (including L1/L5 missions) urgently needed 32 Crown copyright Met Office

Extra slides

National risk register The UK government response guide Catastrophic Coastal floods Electricity failure Pandemic flu Significant Transport accidents Effusive volcano Severe space weather Moderate Industrial accidents Heavy snow & low temps Minor Impact Volcanic ash Limited Likelihood Public disorder Drought Industrial action Low Medium low Medium Medium high High

Active region classification Zpc format: Z modified Zürich class (general distribution, size) p primary penumbra shape c interior spot compactness Combined: α unipolar β bipolar γ mixing of polarities δ opposite polarity umbrae within one penumbra Larger and more complex ARs typically give you the strongest flares and biggest CMEs AR classification can drive some models Crown copyright Met Office

Other models used D-RAP: HF absorption due to flares, SEPs OVATION Aurora Forecast Model Bernese: TEC (ionosphere): GNSS impacts Nowcast version operational and 3 day forecast version being tested

SEPs / Proton flux Forecasts based on active region analysis assessment of NRT data from GOES

Electron flux Relativistic Electron Forecast Model (REFM) Forecasts of >2 MeV flux at GEO up to 3 days ahead Driven by L1 data ACE / DSCOVR Statistical model trained on historical data Issued forecasts based on: REFM forecasts assessment of CHs assessment of NRT data from GOES