E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 The statistical importance of narrow CMEs Open questions to be addressed by SECCHI Eva Robbrecht, David Berghmans, Ronald Van der Linden SIDC – Royal Observatory of Belgium Look! Our capricious sun!

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 What are Coronal mass ejections? Plasma clouds leaving the Sun Observationally defined as a new, discrete, bright feature moving radially outward in the coronagraphic field of view (Hundhausen 1984, Munro 1979, Schwenn 1985) Many other bright features observed in white light: waves and shocks Observational characterisation of CME: Principal angle Angular width Speed: 100  2000 km/s Mass estimate: g Severe projection effects Thomson scattering Parameter measurements Halo CMEs Empirical cone model angle width Halo CME

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 CACTus = software for CME detection top: Polar transformed C2 image Bottom: CACTus CME detection in green θ r

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 The CACtus software t r Automated detection of CMEs in time-sequences Aim of software: Detect appearance of CME + measure important parameters  width, angle, speed  NEW: Propagation direction! Application: -Real-time  space weather -Post processing  catalog of all events - -Available via SolarSoft Data: - LASCO C2/C3: Qkl and LZ - COR2 total B: beacon and LZ (A & B) Requirements: cadence! CME speed transit time min. cadence km/s  4hrs in fov COR2  2 images/hr km/s  2hrs in fov COR2  4 images/hr km/s  1hr in fov COR2  8 images/hr

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Validation of the method Very good agreement Sigma ~ 10 ° Good agreement for θ < 120 ° Large sigma  definition? Halo CMEs CACTus CDAW Principal angleAngular width

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Statistical analysis of CMEs during solar cycle 23 CACTus CME catalog: 1997 – June 2006 Data: LASCO C2/C3 CACTus application to whole dataset CME rate over solar cycle Statistics of CME parameters

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March CME rate during cycle 23 Conclusions [1] Solar Cycle well retrieved! N max =3*N min Delay of 6-12 monthsWhy? Observed in several activity indicators 1-4 mth: chromospheric and coronal emission lines mth: flare rates Monthly and monthly smoothed rates

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March CME rate during cycle 23 Conclusions [2] Large discrepancy CACTus - CDAW! N CDAW = ½ N CACTus N narrow = ½ N CACTus Monthly and monthly smoothed rates

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Statistical analysis of CMEs during solar cycle 23 CACTus CME catalog: 1997 – June 2006 Data: LASCO C2/C3 Data: LASCO C2/C3 CACTus application to whole dataset CACTus application to whole dataset CME rate over solar cycle CME rate over solar cycle Statistics of CME parameters

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 CME width distribution

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 CME width CDAW: lognormal distribution  log(θ) ~ N(μ,σ) with μ ≈ 30 ° CACTus: Power-law distribution  5/3  CME has no typical size!  CME process is scale invariant! Well-known result for other types of magnetic field restructuring: E.g. Flare energy distribution (Crosby et al., 1993) Occurs frequently in nature: earthquakes, avalanche of snow, epidemic disease, stock market Why are small events systematically excluded by human? instrumental effect, morphology, `detection saturation’ during solar max? = 1 order of magnitude Movie What are they? Where are they formed? What is the driver? Is CME process scale invariant?

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 CME latitude distribution

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Latitude difference distribution

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Latitude difference distribution

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Narrow events: Discussion Are they physically different from “classical CMEs”? Does there exist a smallest CME? i.e. cutoff value Narrow events occur frequently at “quiet sun” latitudes = Position of (mid-latitude) coronal hole boundaries Number and position vary according to solar cycle Are they the “liliputters” of the global magnetic field restructuring? i.e. are they gradually untying the magnetic field? Can they trigger “avalanche” CMEs?

E. Robbrecht – SIDC- Royal Observatory of Belgium 8 March 2007 Conclusions CME rate follows solar cycle is delayed to w.r.t. sunspot rate: 6-12 months We find much more outflow due to better instruments and new techniques Discussion on CME concept (cfr. Pluto is not a Planet anymore) Statistics of CME parameters obtained by CACTus differ significantly from classical CME statistics Statistical importance of narrow events (< 40 °) Neglected by observer Obey the observable CME definition Power law in CME width parameter power ~ suggests that CME process is scale invariant occur at mid-latitudes and active region latitude