jonathan a. constable university of st andrews solar reu presentation 2009 a flux rope model for cme...

Jonathan A. Constable University of St Andrews Solar REU Presentation 2009

A flux rope model for CME initiation over solar cycle 23

Jonathan ConstableMentors: Anthony Yeates and Piet Martens



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

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)



1. Motivation:a) Approximately 11 year solar cycle

over which the rate of Coronal Mass Ejections (CMEs) varies significantly;Schwabe, 1843Hale et al,1919Yashiro 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?



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, 20082. 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.



3. Choice of simulation periods:Four periods chosen:Period 1 CR1948.5 to CR1954 17th Apr 1999 – 11th Oct 1999 “Rising Phase”Period 2 CR1974.5 to CR1980 26th Mar 2001 – 19th Sept 2001 “Solar Maximum”Period 3 CR2018.5 to CR2024 8th Jul 2004 – 2nd Jan 2005 “Declining Phase”Period 4 CR2067.5 to CR2073 6th Mar 2008 – 30th Aug 2008 “Solar Minimum”

Stop Press!Period 5 CR1911.5 to CR1917 12th Jul 1996 – 4th Jan 1997 “Solar Minimum 22”Period 6 CR1962.5 to CR1968 3rd May 2000 – 27th Oct 2000 “Solar Maximum B”

Key: Red – CDAW 27day histogram, Blue – CACTus 27 day histogram, Grey – Monthly sunspot number

Peri

od 1

Peri

od 2

Peri

od

3

Peri

od 4



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

Simulated Yeates et al 2009

CR1948.5 to CR1954 (Period 1 – “Rising Phase”)

Simulated random twists (-1 to 1)



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

α

Where: x Β = αΒΔ



5. Simulation Results:

Period 1 Period 2

Period 3 Period 4

Key: Black – simulation results

Red – CDAW observations

Blue – CACTus observations



5. Simulation Results:CDAW:

Period 1 Period 2

Period 3 Period 4



5. Simulation Results:CACTus:

Period 1 Period 2

Period 3 Period 4



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.



7. References:

Yeates, A. R., & Mackay, D. H.: 2009, ApJ, 699, 1024

Mackay, D. H., & van Ballegooijen, A. A.: 2006, ApJ, 641, 577Hale, 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, 165van 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

jonathan a. constable university of st andrews solar reu presentation 2009 a flux rope model for cme...

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