SHINE 1999

Meeting Summary

SHINE Joins GEM and CEDAR Summer Workshop Series

Killer Electrons summary presentation

A long-standing gap in workshop coverage of the solar-terrestrial physics field was filled this summer. The grass-roots organization SHINE, an acronym for Solar Heliospheric INterplanetary Environment, held its first stand-alone workshop, SHINE 99, in conjunction with those of its sister organizations, GEM (Geospace Environment Modeling) and CEDAR (Coupling, Energetics, and Dynamics of Atmospheric Regions). Together these groups reflect the interests of the three subsections of AGU’s Space Physics and Aeronomy Section: Solar and Heliospheric Physics, Magnetospheric Physics, and Aeronomy, respectively. SHINE 99 took place at the Regal Harvest House in Boulder on June 14-17, simultaneously with the CEDAR workshop in Boulder and during the week prior to the GEM workshop in Snowmass. Joint sessions between the three groups were held on June 18 and June 19 in Boulder. Like the GEM and CEDAR workshops, SHINE 99 was sponsored by the National Science Foundation. Support for its members, however, is broad-based, reflecting the fact that SHINE is a community-wide organization.

SHINE 99 opened with agency reports from NSF, NASA, and AFOSR explaining how SHINE’s activities fit in to their larger programs. SHINE is an affiliation of researchers dedicated to promoting enhanced understanding of and predictive capabilities for solar disturbances that propagate to Earth. Thus the group’s primary focus on space weather makes SHINE a vehicle for agency participation in the National Space Weather Program.

The scientific program of SHINE 99 focused on four broad topics: 1) coronal mass ejection (CME) genesis, 2) CME solar signatures and geoeffectiveness, 3) solar wind propagation, and 4) energetic particles. An invited tutorial, an invited review, and a working group were associated with each topic. The tutorials covered basic concepts, the reviews covered recent developments, and the working groups discussed topics on the frontiers of research. In the capable hands of working group leaders Sara Martin, Dave Webb, Vic Pizzo, and Joan Feynman, this program structure helped guide participants toward identification of the most pressing problems in their areas of expertise.

Under topic 1, an ultimate goal is to predict when a CME will occur. Competing mechanisms involving newly emerging flux, flux rope formation, and filament eruption were discussed. Terry Forbes pointed out that the key to reaching this goal lies in the ability to test theoretical 3D magnetic configurations against observations, especially from vector magnetographs, at accuracies yet to be achieved. Good vector magnetograph measurements are also crucial input to MHD simulations of CME initiation, as noted by Zoran Mikic. Joan Burkepile reported progress using white light data. She showed that CMEs appear to form very close to the surface and begin to accelerate low in the corona at ~1.5 solar radii.

Under topics 2 and 3, an ultimate goal is to predict the time of arrival of a CME and whether or not it will be geoeffective. Observational research addressing this issue is still focused on event studies, but some important results were agreed upon: A halo (Earth-directed) CME accompanied by detectable solar surface activity is nearly always followed 2.5-5 days later by a magnetic storm at Earth; halo CMEs usually produce magnetic cloud signatures (smooth field rotation, high field strength, low temperature) at 1 AU, suggesting that a magnetic flux rope is a common internal characteristic; ionic composition data provide important information on the source characteristics of ejecta; the most geoeffective events appear to be associated with complex multiple transient structures interacting with each other and with the ambient stream structure, a point made long ago by Len Burlaga and strongly supported by recent results. In addition to these points of agreement, a number of forecasting tools were described. Of note, Sara Martin presented a scheme for forecasting specific flux rope parameters at 1 AU using empirical information from solar filament eruptions.

Jack Gosling and Simon Plunkett both discussed a major stumbling block for forecasting tools, a lack of ability to determine not only the speed of CMEs at launch but also the rate of change of speed as CMEs propagate to Earth. Theoretical efforts to address this problem again focus on MHD simulations. These, however, still require knowledge about the most fundamental of solar wind problems, those of coronal heating and solar wind acceleration. Jon Linker explained that a promising approach which works around those problems is to parameterize with sub-grid scale models constrained by observations. Pete Riley reviewed the status of “inverse mapping” methods, or the use of models to trace interplanetary flow structures back to their coronal source. He outlined plans for making available to the community a user-friendly scheme based on a 2D MHD model, which would offer significant advantages over the kinematic projections commonly applied. In conjunction with the inverse mapping discussion, several participants stressed the importance of developing better approximate methods for tracing the flow topology within 30 solar radii of the Sun.

Under topic 4, an ultimate goal is to predict the occurrence of energetic particle events. Discussion focused on the processes that produce protons and ions in the energy range from 10 MeV/nucl to GeVs/nucl. This energy range is hazardous for both instruments and astronauts. Ed Cliver and Don Reames reviewed evidence for the now broadly-accepted paradigm that CME shocks, not flares, are the sources of the major particle events. Marty Lee discussed models for acceleration of the particles at the shock, and this year’s AGU Fred Scarf award winner, David Lario, described work on the release and transport of particles from the shock acceleration region. Both problems are challenging, but significant progress has been made. Shock acceleration, release, and transport have been satisfactorily modeled for proton energies up to about 15 MeV. For higher energies, up to 500 MeV, shock acceleration and transport in the solar wind are theoretically reasonable, but whether realistic shocks can produce the observed intensities has not yet been demonstrated quantitatively. Shock acceleration for the most hazardous events does not preclude flare acceleration for other events. In the past, flare-accelerated particles were clearly distinguished from shock-accelerated particles by their composition signatures; but Dick Mewaldt described recent ACE data which suggest that this distinction may not be as clear as previously thought.

In addition to the main program, poster papers, introduced at a lively preview session conducted by JoAnn Joselyn, were conveniently displayed in the refreshments room throughout the meeting. Poster highlights included three-dimensional models of solar filaments, several evaluations of the reliability of halo CMEs as predictors of geomagnetic storms, pilot projects for predicting storms from large-scale coronal field changes and filament eruptions, MHD models of CME initiation by emerging flux and CME distortion in the solar wind, and radio techniques for tracking CMEs.

A total of 65 people participated in SHINE 99, including four students and six postdocs. The level of excellence of the tutorials and reviews and the workshop atmosphere facilitated lively interactions. Of particular note, a number of younger scientists were especially vocal. These aspects , encouraged by the National Science Foundation, set workshops like SHINE 99 apart from other scientific meetings. SHINE summer workshops will now be held annually, and plans for SHINE 2000 are underway. Working groups on selected topics will be formed in advance via e-mail, and the Steering Committee welcomes participation in this activity by all interested solar and/or heliospheric physicists.

Organizational aspects of SHINE are handled by its Steering Committee. Current members are V. Pizzo, NOAA Space Environment Center, Chair; N. Crooker, Boston University; J. Feynman, Jet Propulsion Laboratory; J. Linker, Science Applications International Corp.; J. Luhmann, UC Berkeley; S. Martin, Helio Research; J. Steinberg, Los Alamos National Laboratory; D. Webb, Boston College.