*************************** ** THE GEM MESSENGER ** *************************** Volume 7, Number 30 July 21, 1997 *********************************************************************** 1997 GEM SNOWMASS REPORT: GGCM Working Group 1: GGCM Spine *********************************************************************** From: Jimmy Raeder Working group 1 of the GGCM campaign met on Wednesday, 18 June to discuss how the GEM community should proceed in developing a community geospace general circulation model (GGCM). Several speakers presented their views on what a GGCM spine might look like and whether a global MHD based approach or a modular based approach should be taken. Joachim Birn stressed that the GGCM should be the focus for the community and should not be exclusive. He advocated using a global MHD model as a spine, mostly because a modular approach seemed unrealistic and because global MHD models do already most of what is expected from the GGCM. However, smaller models should also have their place for problems that do not require a GGCM and where more sophistication beyond MHD is needed. Jim Drake remarked that although MHD is constraining, kinetic physics can be added, for example in modeling the ring current. Bill Lotko commented that the GGCM should not only be as inclusive as possible, but should also become an ongoing activity within GEM, especially by including observationalists. He also emphasized that the MHD and modular approaches are not necessarily exclusive since a global MHD model may hold other modules together in a self consistent way. Gary Erickson proposed that both approaches should be taken. A global MHD model would be better suited to study global properties, while a modular approach would be better suited to study detailed basic processes. He presented a list of modules that already exist or that could be easily adapted for a modular spine. He also emphasized that the modular approach would take considerably longer to implement. Janet Luhmann added that two different spines would have the additional advantage to create competition between the models. Michael Hesse remarked that there was obviously a convergence between the two approaches because most of the modules could also be used with a MHD spine. Antonius Otto pointed out that the two basic goals for a GGCM are science and forecasting, but that public relations is also an important consideration (Bob Clauer mentioned that the more appropriate term would be `service to society'). He gave a perspective from the local modelers view, noting that neither approach would be well suited to treat directly processes at the dayside magnetopause, like FTE's, patchy reconnection, or Kelvin Helmholtz waves. However, local models that can treat these processes may be easier to combine with a global MHD spine. Mike Heinemann advocated a purely modular approach. He proposed a model that is based around a stress balanced magnetosphere model and driven through the Spreiter/Stahara magnetosheath model. Such a model would be structurally complete. However, time delays between different regions of the model would be crucial and need to be worked out. He also went through the issues raised in the appendix of the GGCM planning document (http://jimme.gsfc.nasa.gov/~hesse/GGCM_plan.html) and discussed which approach (MHD or modular) would be best suited in addressing these issues. Robert Winglee pointed out that a GGCM would essentially need to be able to solve the problems outlined in the National Space Weather Program (NSPW) implementation plan (http://www.geo.nsf.gov/atm/nswp/nswp.htm), and that only a global MHD approach seems feasible. However, other models, like the Tsyganenko, RCM, Toffoletto-Hill, Weimer, or IZMEM have their place because they need far fewer resources and are therefore better suited for some of the space weather goals. Jeff Hughes pointed out that the GGCM is part of GEM, and not the NSPW. There were three more presentations in the morning session, focusing on tools for supporting and possibly developing a GGCM: Bob Clauer presented the Upper Atmospheric Research Collaboratory (UARC). UARC is a web based tool that is now used by all radars to share and visualize data, among other things. UARC may be used, or at least serve as the prototype, for a distributed GGCM center. The UARC url is: http://www.sils.umich.edu/UARC/Overview.html. Terry Onsager presented the NOAA Rapid Prototyping Center (RPC) which could be used for GGCM prototyping and verifying. The RPC provides standardized model input and output and various visualizations. So far the RPC has been used with three different models. Mike Heinemann presented PL-GEOSPACE, a graphics based master program for models and visualization. PL-GEOSPACE is used by the Air Force for rapid prototyping of geospace models. In the afternoon session several global MHD modelers briefly presented their latest results: Bill White showed initial results from the Integrated Space Weather Prediction Model (ISM), an effort by the Defense Special Weapons Agency to develop a comprehensive model of geospace. The model is unique in that it solves the coupled plasma - neutral equations all the way down to the ionosphere. The model also includes several modules such as an inner magnetospheric module based on the Rice Convection Model that overrides the MHD, a solar energetic particle model, and a Vlasov field line model. Tamas Gombosi presented initial results from his new, adaptive grid MHD model. He has modeled the solar corona as well as Earth's magnetosphere and hopes to eventually model the solar wind from the corona all the way to Earth's ionosphere. He also made the controversial suggestion that all MHD modelers publish the details of their numerical algorithms, so that the community could get a better idea of how the codes work. Jimmy Raeder presented results from a simulation of the MAY 19/20 substorms, including the first direct comparisons of simulated with observed ground magnetograms. Michael Wiltberger showed a comparison of the May 15, 1996 substorm with a global MHD simulation, including an animation showing tail reconnection and the dipolarization of the near earth field. Robert Winglee showed results from a simulation of the January 10, 1997 events and compared them with POLAR images. *********************************************************************** July 16, 1996 Jimmy Raeder (jraeder at igpp.ucla.edu) Frank Toffoletto (toffo at rice.edu) +-------------------------------------------------------------------------+ |To add name to the mailing list, send a message to: editor at igpp.ucla.edu | |For message to whole GEM mailing list, send to: gem at igpp.ucla.edu | | | |URL of GEM Home Page: http://igpp.ucla.edu/gem/Welcome.html | |Please update your e-mail address. | |CAUTION: Do not send messages to gem at igpp.ucla.edu unless you want | | your message to go to everyone in the GEM mailing list! | +-------------------------------------------------------------------------+