SHINE 2000

The contents below include the Scientific Agenda, Workshop Recap, and Working Group I report.

Scientific Agenda

The program featured working groups devoted to two key space weather issues:

Working Group I: Coronal Mass Ejections (CMEs) and Prominence Eruptions

[co-leaders: J. Klimchuk and J. Gurman]

The CME Working Group focused its discussions around two overarching questions: Are there physically distinct classes of CMEs? How can observations be better used to test the theoretical models? We will examine the observational evidence for different CME classes, including distinctions based on:

• CME morphology and speed
• Pre-eruption configuration (sigmoids, neutral lines, etc.)
• Role of prominences
• Lower coronal response (“waves,” arcades, dimmings)

We compared and contrasted the physical attributes and observational signatures of CME models involving:

• Sheared bipolar arcades
• Flux ropes (magnetic, buoyancy, and photospheric drivers)
• Multipolar systems

Working Group II: Interplanetary Connections

[co-leaders: P. Riley and T. Zurbuchen]

The focus of Working Group II was the link between detectable solar phenomena and interplanetary CME manifestations and whether they depend upon solar cycle phase. Specifically, Is this solar cycle “misbehaving?” Why have we not seen in recent months more activity at Earth, given the apparent CME inputs at the Sun? Discussions will begin with a comparison of solar/terrestrial linkages during the rising phases of solar cycles 22 and 23, preparatory to consideration of potential contributory factors, which include:

• Incomplete understanding of coronal indicators of CMEs (eg. disappearing/eruptive filaments, X-ray dimmings, halos, etc.)
• Intrinsic differences among CMEs
• Systematic changes in the ambient global solar wind background

Scientific Organizing Committee

N. Crooker (Chair), J. Feynman, J. Kunches, J. Linker, J. Luhmann, S. Martin, V. J. Pizzo, J. Steinberg, and D. Webb.

Workshop Recap

The SHINE 2000 summer workshop was held June 14-17 at Caesar’s Palace, Lake Tahoe, immediately preceding the meeting of the Solar Physics Division of the American Astronomical Society (who chose the location).  Undeterred by the long walk through the gaming tables between the hotel rooms and the conference rooms, 72 solar and heliospheric physicists participated in a number of lively sessions.  Barbara Thompson (GSFC) kept the poster previews on schedule with the threat of her dart gun, in spite of competing drummers in the next room, and later, competition between the two working groups was heightened with bribes of beer and nachos and a Jeep Cherokee door prize.  The competition between the working groups has since continued on the internet, where each is vying for the flashiest web page (click on SHINE 2000 at http://www.sec.noaa.gov/shine).

            Scientifically the workshop was highly successful.  As introductory material, excellent reviews on coronal mass ejection (CME) observations, theory, and terrestrial linkages were given by Joan Burkepile (HAO), Spiro Antiochos (NRL), and Chris Russell (UCLA).  Most of the time thereafter was devoted to sessions of the two working groups:  Working Group 1 on CMEs, led by Jim Klimchuk (NRL) and Joe Gurman (GSFC) and Working Group 2 on Interplanetary Connections, led by Thomas Zurbuchen (UMich) and Pete Riley (SAIC).

            The working group sessions were as unstructured as possible, allowing ample time for discussion.  Perhaps the most surprising outcome of this format is the perception that an extraordinary amount of backtracking must be done to reach a consensus view.  A participant comes to the table with a level of understanding on a certain issue which s/he assumes is shared by the community and discovers that often this is not at all true.  Finding the common level was deemed a necessary step backwards in order to make forward progress.

            Working Group 1 addressed three main questions:  1) What is the observational evidence for multiple classes of CMEs, 2) what are the fundamental physical differences among the various CME initiation models that have been proposed, and 3) what are the key observations that can discriminate among the models?

            The first question turned out to be an excellent example of how much backtracking is needed to reach a consensus view.  Published observational studies [e.g., Sheeley et al., 1999; Andrews and Howard, 2000] provided what was thought by some to be smoking-gun evidence that there are two kinds of CMEs:  those that start slowly and accelerate through the coronagraph (SOHO/LASCO) field of view and those that pass through at constant speed.  Participants in the working group sessions on this topic, however, were bombarded with exceptions to and arguments against the two-type rule.

            Leading the discussion of the second two questions, which are knottier, required arduous labor on the part of Jim Klimchuk.  Under his persevering guidance, however, the group came up with a workshop product in the form of the table below.  In essence it is a communication from theorists to observers to indicate what kinds of measurements are needed to discriminate between models for CME initiation.  A variety of models have been proposed, and they can be classified in several different ways based on their physical attributes [e.g., Forbes, 2000; Klimchuk, 2000].  The table presents one such classification of five distinct model types:  1) Breakout [e.g., Antiochos, 1998; Antiochos, DeVore, and Klimchuk, 1999]; 2) Flux Rope [Forbes and Isenberg, 1991; Amari et al., 2000; Wu et al., 2000]; 3) Tether Cutting [Sturrock et al. 1984; Moore et al. 2000]; 4) Flux Injection [Chen, 1989; Krall, Chen, and Santoro, 2000]; and 5) Mass Loading [Wolfson and Saran, 1998; Low, 1999].  The table columns list observables that can be used to test the models.  1) Is a multipolar magnetic field required, or is a simple bipolar field sufficient?  2) Does the pre-eruption configuration necessarily contain a flux rope?  3) Must the field be appreciably sheared near the neutral line?  4) Must there be a converging flow toward the neutral line in the period leading up to the eruption?  5) Is reconnection required, and if so, does it occur before or after the onset of the eruption?  (This refers to vigorous reconnection with strong heating.)  6) Does the reconnection take place above or below the sheared core field/flux rope/prominence?  7) Are there requirements on the existence and/or distribution of mass?

Observational Tests of CME Initiation Models (Y = “yes,” NR = “not required”)
Model	Multi-Polar	Flux Rope	Sheared NL	Converg-ing Flow	Recon. Timing	Recon. Location	Mass Distribution
Breakout	Y	NR	Y	NR	at/before	above	NR
Flux Rope	NR	Y	Y	Y(1) NR(2)	after(1) at/after(2)	below	NR
Tether Cutting	NR	NR	Y	NR	at/before	below	NR
Flux Injection	NR	Y	NR	NR	NR	NR	NR
Mass Loading	NR	NR	NR	NR	NR	NR	cavity and/or prominence

(1) – Forbes and Isenberg [(1991]

(2) – Amari et al. [2000]

            From the Working Group 1 discussion came the most memorable SHINE 2000 quote, obviously from a theorist:  “Don’t be fooled by what you see!”

            Following the example of the GEM community, each working group set challenges for the coming year.  For Working Group 1 these are:  1) Determine observationally whether there are two distinct classes of CMEs, as possibly suggested by acceleration profiles, 2) Better define and quantify the observational predictions of the models, and 3) Devise and execute focused observational studies to test the models.

            A separate challenge was issued by Ron Turner (ANSER), who announced an “All Clear Competition.”  To emphasize the importance of accurate forecasts of geomagnetically calm conditions, Ron will award a prize (a tube of Clearasil) to the person who can correctly forecast the most clear days over the period of the competition.  This might sound easy:  since most days are clear, why not predict that every day will be storm free?  The catch is that any storm occurring on a day forecast to be clear means immediate disqualification from the competition!  Interested competitors should contact Ron at [/cdn-cgi/l/email-protection [email protected]]

            Working Group 2 began with a brainstorming session to gauge interests.  A wide variety of questions were raised, nearly one for each participant.  These were broadly grouped into five topics:  1) solar cycle anomalies, 2) global connectivity and morphology, 3) CME evolution to 1 AU, 4) signatures of interplanetary CMEs (ICMEs), and 5) CME geoeffectiveness.  The first topic reflected the question the group advertised well in advance of the workshop, “Is this solar cycle misbehaving?”  Why do we not see more geomagnetic activity at Earth given the apparently large number of CMEs at the Sun and ICMEs detected in space?  Participants were asked to prepare their responses in advance and, as a result, the matter was dispatched in record time.  Nearly everyone agreed that the observations were within the bounds of the range of past solar cycle patterns and that the apparent disparity may just reflect our improved ability to detect CMEs and ICMEs.

            Working Group 2 quickly moved on to the remaining topics, repeatedly backtracking to find common ground.  At the last session they agreed upon two challenges in the form of questions to the community for the coming year:  1) What is different about the solar sources of simple ICMEs, like magnetic clouds, compared to complex ICMEs, and 2) Are there two classes of ICMEs which reflect the two apparent classes of CMEs (accelerating and constant speed)?  Both of these challenges reflect the surprisingly provocative idea discussed in Working Group 1 that CMEs can be classified into distinct types.

            SHINE 2000 closed with some agency reports and discussion of joint activities with CEDAR and GEM.  Both groups have been warmly supportive of SHINE’s fledgling efforts, and the SHINE community looks forward to future joint efforts.

References:

Amari, T., J. F. Luciani, Z. Mikic, and J. Linker, A twisted flux rope model for coronal mass ejections and two-ribbon flares, Astrophys. J. (Lett.), 529, L49-L52, 2000.
Andrews, M. D., and R. A. Howard, A two type classificatioin of LASCO coronal mass ejection, Space Sci. Rev., in press, 2000.
Antiochos, S. K., The magnetic topology of solar eruptions, Astrophys. J. (Lett.), 502, L181-L184, 1998.
Antiochos, S. K., C. R. DeVore, and J. A. Klimchuk, A model for solar coronal mass ejections, Astrophys. J., 510, 485-493, 1999.
Chen, J., Effects of toroidal forces in current loops embedded in a background plasma, Astrophys. J., 338, 453-470, 1989.
Forbes, T. G., A review of the genesis of coronal mass ejections, J. Geophys. Res., 105, 23,153-23,165, 2000.
Forbes, T. G., and P. A. Isenberg, A catastrophe mechanism for coronal mass ejections, Astrophys. J., 373, 294-307, 1991.
Klimchuk, J. A., Theory of Coronal Mass Ejections, in Space Weather (AGU Monograph Series), edited by P. Song, G. Siscoe, and H. Singer, AGU, Washington, 2000, in press.
Krall, J., J. Chen, and R. Santoro, Drive mechanisms of erupting solar magnetic flux tubes, Astrophys. J., 539, 964-982, 2000.
Low, B. C., Coronal mass ejections, flares, and prominences, in Solar Wind Nine, CP471, edited by S. R. Habbal, R. Esser, J. V. Hollweg, and P. A. Isenberg, pp. 109-114, Am. Inst. Physics, Woodbury, NY, 1999.
Moore, R. L., A. C. Sterling, H. S. Hudson, and J. R. Lemen, Onset of the magnetic explosion in solar flares and coronal mass ejections, Astrophys. J., submitted, 2000.
Sheeley, Jr., N. R., J. H. Walters, Y.-M. Wang, and R. A. Howard, Continuous tracking of coronal outflows:  Two kinds of coronal mass ejections, J. Geophys. Res., 104, 24,739-24,767, 1999.
Sturrock, P. A., P. Kaufman, R. L. Moore, and D. F. Smith, Energy release in solar flares, Solar Phys., 94, 341-357, 1984.
Wolfson, R., and S. Saran, Energetics of coronal mass ejections:  role of the streamer cavity, Astrophys. J., 499, 496-503, 1998.
Wu, S. T., W. P. Guo, S. P. Plunkett, B. Schmieder, and G. M. Simnett, Coronal mass ejections (CMEs) initiation:  models and observations, J. Atmos. Solar Terr. Phys., 62, 1489-1498, 2000.

Working Group Reports

Working Group II information is not available as the original info was at an external link that is no longer live.

Working Group 1 (Coronal Mass Ejections): Observational Tests of CME Initiation Models

SHINE 2000 Working Group 1
J. Klimchuk
2000 November 1

led by Jim Klimchuk and Joe Gurman, addressed three main questions during the SHINE 2000 meeting in Lake Tahoe:

1. What is the observational evidence for multiple classes of CMEs?
2. What are the fundamental physical differences among the various CME initiation models that have been proposed?
3. What are the key observations that can discriminate among the models?

Progress was made on all of these questions, especially the last (see below), but in the end it was clear that much more work needs to be done before definitive answers are available. This “work in progress” status is reflected in the three challenges that we set for ourselves for the coming year:

1. Determine observationally whether there are two distinct classes of CMEs, as possibly suggested by acceleration profiles.
2. Better define and quantify the observational predictions of the models.
3. Devise and execute focussed observational studies to test the models.

A separate challenge was issued by Ron Turner, who announced an “All Clear Competition.” To emphasize the importance of accurate forecasts of geomagnetically calm conditions, Ron will award a prize to the person who can correctly forecast the most clear days over the period of the competition. Might sound easy: since most days are clear, why not predict that every day will be storm free? The catch is that any storm occurring on a day forecast to be clear means immediate disqualification from the competition! Interested competitors should contact Ron.

1. The models

A variety of models for CME initiation have been proposed, and they can be classified in several different ways based on their physical attributes (e.g., Forbes 2000; Klimchuk 2000). The table below presents one such classification that was developed at the SHINE 2000 Workshop. It identifies five distinct types of CME initiation model:

1. Breakout ( Antiochos 1998; Antiochos, DeVore, and Klimchuk 1999)
2. Flux Rope ( Forbes and Isenberg 1991; Amari et al. 2000; Wu et al. 2000)
3. Tether Cutting ( Sturrock et al. 1984; Moore et al. 2001)
4. Flux Injection ( Chen 1989; Krall, Chen, and Santoro 2000)
5. Mass Loading ( Wolfson and Saran 1998; Low 1999).

Only representative papers are cited. Additional references can be found in the Forbes and Klimchuk reviews.

2. The Observables

The table also lists a number of observables that can be used to test the models:

1. Is a multipolar magnetic field required, or is a simple bipolar field sufficient?
2. Does the pre-eruption configuration necessarily contain a flux rope?
3. Must the field be appreciably sheared near the neutral line?
4. Must there be a converging flow toward the neutral line in the period leading up to the eruption?
5. Is reconnection required, and if so, does it occur before or after the onset of the eruption? (This refers to vigorous reconnection with strong heating.)
6. Does the reconnection take place above or below the sheared core field/flux rope/prominence?
7. Are there requirements on the existence and/or distribution of mass?

Y in the table signifies “yes,” and NR signifies “not required.” Readers should consult the original references for a detailed interpretation of the table entries.

3. The Matrix

See the table above in the Workshop Recap.

4. References

Amari, T., J. F. Luciani, Z. Mikic, and J. Linker, A twisted flux rope model for coronal mass ejections and two-ribbon flares, Astrophys. J. (Lett.), 529, L49-L52, 2000
Antiochos, S. K., The magnetic topology of solar eruptions, Astrophys. J. (Lett.), 502, L181-L184, 1998
Antiochos, S. K., C. R. DeVore, and J. A. Klimchuk, A model for solar coronal mass ejections, Astrophys. J., 510, 485-493, 1999
Chen, J., Effects of toroidal forces in current loops embedded in a background plasma, Astrophys. J., 338, 453-470, 1989
Forbes, T. G., A review on the genesis of coronal mass ejections, J. Geophys. Res., 105, 23153-23165, 2000
Forbes, T. G., and P. A. Isenberg, A catastrophe mechanism for coronal mass ejections, Astrophys. J., 373, 294-307, 1991
Klimchuk, J. A., Theory of Coronal Mass Ejections, in Space Weather (AGU Monograph Series), edited by P. Song, G. Siscoe, and H. Singer, AGU, Washington, 2000, in press
Krall, J., J. Chen, and R. Santoro, Drive mechanisms of erupting solar magnetic flux tubes, Astrophys. J., 539, 964-982, 2000
Low, B. C., Coronal mass ejections, flares, and prominences, in Solar Wind Nine, CP471, edited by S. R. Habbal, R. Esser, J. V. Hollweg, and P. A. Isenberg, pp. 109-114, Am. Inst. Physics, Woodbury, NY, 1999
Moore, R. L., A. C. Sterling, H. S. Hudson, and J. R. Lemen, Onset of the magnetic explosion in solar flares and coronal mass ejections, to be published in Astrophys. J., 2001.
Sturrock, P. A., P. Kaufman, R. L. Moore, and D. F. Smith, Energy release in solar flares, Solar Phys., 94, 341-357, 1984
Wolfson, R., and S. Saran, Energetics of coronal mass ejections: role of the streamer cavity, Astrophys. J., 499, 496-503, 1998
Wu, S. T., W. P. Guo, S. P. Plunkett, B. Schmieder, and G. M. Simnett, Coronal mass ejections (CMEs) initiation: models and observations, J. Atm. and Solar Terrestrial Phys., in press, 2000