1. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 Jonathan Constable Mentors: Anthony Yeates and Piet Martens

2. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 Contents: 1.Motivation for the project 2.Description of the model 3.Choice of simulation periods 4.SOHO (LASCO) and STEREO (SECCHI) observations 5.Simulation results 6.Discussion 7.References

3. Credit: G.L. Slater and G.A. Linford; S.L. Freeland; Yohkoh Soft X-Ray Telescope Classic CME observed by the Large Angle Spectrometric Coronagraph (LASCO) C2 field of view, onboard the Solar and Heliospheric Observatory (SOHO) Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 1. Motivation: a)Approximately 11 year solar cycle over which the rate of Coronal Mass Ejections (CMEs) varies significantly; Schwabe, 1843 Hale et al,1919 Yashiro et al, 2004 b) Mackay, D. H. & van Ballegooijen, A. A., 2006; Models of the large-scale corona. I. Formation, Evolution, and liftoff of magnetic flux ropes. c)A.R. Yeates and D.H. Mackay 2009; Initiation of Coronal Mass Ejections in a Global Evolution Model d)Can we extend this work to cover significant phases of solar cycle 23?

4. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 2. Description of the model: Two parts, the lower boundary at the photosphere and the corona. The lower boundary at the photosphere is evolved by the: 1.Emergence of new magnetic flux from below the photosphere. 1 2.Large scale flows due to differential and meridionial rotation. 1 3.Dispersal of magnetic flux by small scale convection cell. 2 4.Cancellation of magnetic flux at polarity inversion lines. 2 The corona evolves in response to the emerging magnetic flux and the changing photospheric boundary conditions. 1.Yeates et al, 2008 2.Sheeley, N. R. 2005 Model inputs: We use U.S. National Solar Observatory, Kitt Peak radial synoptic magnetograms for each Carrington rotation within our simulation periods.

5. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 3. Choice of simulation periods: Four periods chosen: Period 1CR1948.5 to CR195417 th Apr 1999 – 11 th Oct 1999“Rising Phase” Period 2CR1974.5 to CR198026 th Mar 2001 – 19 th Sept 2001“Solar Maximum” Period 3CR2018.5 to CR20248 th Jul 2004 – 2 nd Jan 2005“Declining Phase” Period 4CR2067.5 to CR20736 th Mar 2008 – 30 th Aug 2008“Solar Minimum” Stop Press! Period 5CR1911.5 to CR191712 th Jul 1996 – 4 th Jan 1997“Solar Minimum 22” Period 6CR1962.5 to CR19683 rd May 2000 – 27 th Oct 2000“Solar Maximum B” Key: Red – CDAW 27day histogram, Blue – CACTus 27 day histogram, Grey – Monthly sunspot number Period 1 Period 2 Period 3 Period 4

6. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 4. SOHO (LASCO) and STEREO (SECCHI) observations: CDAW cycle 23 CACTus cycle 23 Key: Black – Histogram of 27 day CME rate Red – Monthly sunspot number Yellow – Histogram of data gap duration 15° ≤ apparent width < 270° 10° ≤ apparent width < 270° 5° ≤ apparent width < 270° “Very Poor Event”, “Poor Event” and “Marginal Case” removed Legend: - CDAW observation - CACTus observation - Simulation result

7. Simulated Yeates et al 2009 CR1948.5 to CR1954 (Period 1 – “Rising Phase”) Simulated random twists (-1 to 1) Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 5. Simulation Results: Comparison with Yeates & Mackay 2009 General trends consistent. Differences could be due to the choice of newly emerging bipoles (119 Yeates et al 2009 as opposed to 117 in our simulation). Comparison with Pevtsov et al 1995 Where: x Β = αΒ

8. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 5. Simulation Results: Period 1 Period 2 Period 3 Period 4 Key: Black – simulation results Red – CDAW observations Blue – CACTus observations

9. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 5. Simulation Results: CDAW: Period 1 Period 2 Period 3Period 4

10. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 5. Simulation Results: CACTus: Period 1 Period 2 Period 3Period 4

11. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 6. Conclusions: We were able to produce consistent results compared to Yeates & Mackay 2009 with reasonable accuracy. Our simulations show variation over the solar cycle, with more eruptions per day at solar maximum and over a greater range of latitudes, than our simulations produced at solar minimum. We see the 50% of observed CMEs as in Yeates & Mackay 2009, however over the solar cycle, our simulation produces only about 30% of the observed CMEs. This could be due to: Random bipole twists compared to a step function for twist. Less twist on average should produce fewer eruptions. We need better observations of magnetic helicity. There are significant uncertainties in the apparent latitudes of CMEs in the observations used. Plus CACTus detects “ghost CMEs” where the supporting pylon for the occulting disk is located (-30° latitude / 120° central position angle) The model does not easily reproduce multiple CMEs in a short timeframe.

12. Jonathan A. Constable University of St Andrews Solar REU Presentation 2009 A flux rope model for CME initiation over solar cycle 23 7. References: Yeates, A. R., & Mackay, D. H.: 2009, ApJ, 699, 1024 Mackay, D. H., & van Ballegooijen, A. A.: 2006, ApJ, 641, 577 Hale, G. E., Ellerman, F., Nicholson, S. B., & Joy, A. H.: 1919, ApJ, 49, 153, 1919 Schwabe, S. H.: 1843, Astronomische Nachrichten, 20, 495, 1843 Yashiro, S. et al: 2004, JGR, 109, A07105, doi:10.1029/2003JA010282 Yeates, A. R., Mackay, D. H., & van Ballegooijen, A. A.: 2008, Solar Physics, 247, 103 Sheeley, N. R.: 2005, Living Rev. Solar Physics, 212, 165 van Ballegooijen, A. A., Priest, E. R., Mackay, D. H.: 2000, ApJ, 539, 983 Pevtsov, A. A., Canfield, R. C., Metcalf, T. R.: 1995, ApJ, 440, L109-L112 Nandy, D., Mackay, D. H., Canfield, R. C., Martens, P. C. H.: 2008, Journal of atmospheric and solar- terrestrial physics, 70, 605