1. Multi-Point Observations of The Solar Corona for Space weather Acknowledgements The forecasting data was retrieved from NOAA SWPC products and SIDC PRESTO messages. Predicting CMEs A relationship exist between an active region’s physical properties and the activity emanating from that region. This relationship is highly complex and current techniques are not sufficiently accurate enough to provide direct warnings of CMEs, based on active region observations alone. Time (Day/UT) Cumulative Time (Days) EventPrediction Predicted Time (Day/UT) 07/20120.000Flare maximum 08/08520.527CME glancing blow10 th 08/15000.783Shock arrival at Earth08 th 1800-2100 08/15000.783G1 - G2 stormsEarly hours 9 th 08/19450.981Geo. A-index >= 2010th 08/22001.075Active geomagnetic storm09 th -10 th 09/07001.450 CME Shockwave at STEREO A 09/22002.075CME arrival at Earth10 th (mid-day) 10/06002.408CME arrival at ACE 10/06232.424 Geomagnetic sudden impulse 10 th 0645-0745 10/06272.427Geomagnetic K-index of 410 th 0640-0745 10/08002.408Geomagnetic K-index of 4 A list of past CME events were selected for investigation, on the basis that each event had certain features enabling the analysis of different aspects of CME based space weather forecasting. Solar activity forecasting accuracy was evaluated by comparing descriptive predictions and forecasted solar flare probabilities with information of actual events. Geomagnetic activity forecasting was investigated by chronologically combining forecasts with physical data, and discerning how certain parameters affected the forecasting. Deductions were made about several aspects of CME based space weather forecasting;  Predicting if a solar eruption will occur.  Estimating the energy of an eruption.  Determining the presence of a CME.  Predicting CME arrival time at Earth and the associated geomagnetic storm intensity. A list of advantages was produced for Lagrangian points L4 and L5, from a CME based space weather service perspective. L4 and L5 Advantages Both the Sun and Earth are in view.  Track and observe the evolution of CMEs as they head towards Earth. CMEs heading towards Earth will be viewed on the East/West limb of the Sun.  Easier to detect in coronagraph and EUV images.  Projection effects are reduced compared to the L1 vantage point. Combine with imagery from L1 to produce stereoscopic images.  Better CME speed and trajectory estimates.  Important for CME modelling techniques. Additional viewpoint for imaging solar disk features that indicate the presence of a CME, such as EIT waves and post eruption arcades. Earth can suffer a delayed glancing blow from CMEs heading directly towards L4/L5, due to the curved nature of the CME front.  Measurement of CME properties at L4/L5 leads to better predictions for geomagnetic storm intensity and time of arrival at Earth. L4 advantages Provide coronagraph and EUV imagery of active regions beyond the west limb.  Detect eruptions and warn about possible geoeffective solar energetic particle events. L5 advantages Magnetogram, EUV and coronagraph images of active regions and their associated activity, before they rotate onto to the Earth-facing side of the Sun.  Gain 4 days of active region information.  Use extra data to improve solar activity forecasting. Magnetogram images of active regions at extreme easterly locations.  Easier to deduce active region properties, compared with L1 images. Coronal mass ejections (CMEs) are huge burst of magnetised plasma ejected from active regions on the Sun. Interacting with the Earth’s magnetosphere, they can cause geomagnetic storms affecting many of the key systems on which our society relies, therefore forecasting the arrival time and intensity of these CMEs is critical. This is currently done using remote and in situ data from spacecraft at multiple locations within the Sun-Earth system. The main instruments used in the forecasting are coronagraphs and Extreme Ultraviolet (EUV) imagers, in combination with in situ measurements of solar wind and magnetic field parameters. This study was conducted in order to determine the advantages and disadvantages of several different vantage points in space, for the forecasting of CME occurrence, intensity and time of arrival at Earth. Conclusions Solar Flare Forecasted Probabilities and Actual Events Timeline of CME Associated Events and Predictions CME and Active Region Observations CME trajectory Mainly determined using coronagraph data, but the location of the flare on the solar disk can also give a good insight into where the CME is heading. STEREO coronagraphs have several advantages when in a position close to L4/L5.  Useful in determining if a CME will have a direct hit or glancing blow with the Earth.  Quickly determine if a CME is heading directly towards or away from the Earth → Difficult if L1 is the only vantage point. CME time of arrival predictions Very difficult for CMEs that have been decelerated by pre- existing structures in the ambient solar wind. High dependence on coronagraph imagery for CME speed estimation. Speed estimation also important for determining if several CMEs will combine to produce stronger geomagnetic storms. SOHO coronagraph images can become contaminated leading to unreliable CME velocity estimation → STEREO coronagraphs did not appear to be as susceptible. Precise arrival time and measurement of CME magnetic field orientation can only be made after a CME reaches ACE at L1.  Short lead time (30-60 minutes).  Magnetic field orientation vital for predicting geomagnetic storm intensity Solar wind measurements along the Sun-Earth line only available from ACE → Limited insight into solar wind upstream. ACE solar wind measurements can be contaminated resulting in a loss of valuable data → Change in detector type or location needed. Features on the Solar Disk indicative of CME occurrence EIT Wave Eruption energy Gained from measuring the X-ray output of a solar flare. Correlation exists between CME and Flare energy. X-ray output measurements performed by GOES and readily available. Confirmation of CME presence Deduced mainly from coronagraph and EUV imagery. When multiple flares occurred but only one CME was visible in coronagraph imagery → Number of CMEs determined through the presence of coronal dimming, EIT waves and post eruption arcades. SpacecraftSOHOSTEREO A and BACEGOES Vantage PointL1 Orbiting the Sun ahead/behind the Earth and moving away at 22° per year L1 Geosynchronous orbit Coronagraph  EUV imager  Solar wind speed, temperature and density measurements  Magnetic field measurements  X-ray flux  Main Spacecraft Associated with CME based Space Weather Forecasting East limb West limb Stephen Legg SSA-SWE Segment, ESA/ESAC, Madrid, Spain; University of Manchester, United Kingdom AbstractMethod Understanding of Forecasting Top: Coronagraph and EUV 304 Å images of a CME from the west limb of the Sun; Bottom: Magnetogram images of an active region as it rotates across the solar disk. CoronagraphEUV Magnetogram Post Eruption Arcade Left: EIT wave shown in EUV imagery; Right: The first appearance of a post eruption arcade is shown by the black arrow. A plot of forecasted flare probability against the actual intensity of the flares that occurred, for active region 10930. X and M-class flare probabilities are shown by the blue and red bars respectively. The yellow markers show the intensity of the flares that occurred.