*************************** ** THE GEM MESSENGER ** *************************** Volume 6, Number 46 September 27, 1996 --------------------------------------------------------------------------- Report on GGCM Campaign Activities at the GEM Snowmass Workshop, June, 1996 --------------------------------------------------------------------------- From wolf at alfven.rice.edu Fri Sep 27 08:31:56 1996 This Workshop marked a transition in leadership of the Geospace General Circulation Model (GGCM) Campaign. George Siscoe and Joel Fedder, who conceived and founded the GGCM effort within GEM, led it through a period when it was "Working Group 5" in the GEM structure and through its transition to a full GEM campaign, are retiring from the official leadership positions, although they may be expected to continue to play active roles informally. Dick Wolf and Michael Hesse will succeed them as Coordinators of the GGCM Campaign. The GGCM-centered sessions were the following: Monday, 6/24, 10:30 am-12:00 noon. GGCM Planning Session. Monday, 6/24, 1:30-3:00 pm. Space Weather Session. Monday, 6/24, 3:30-5:00 pm. GGCM Science Session. Tuesday, 6/25, 8:00 am - 12:00 noon. Joint BL/GGCM "Modeler Challenge" Session. Tuesday, 6/25, 7:30-9:30pm. Continuation of GGCM Planning Session. All of these sessions are summarized below, except for the Tuesday-morning joint session, which is covered in the summary of the Boundary-Layer Campaign. GGCM PLANNING SESSIONS (Dick Wolf, chair) In the final talk of the Plenary Session Monday morning, Dick Wolf described his perception of how the concept of the Geospace General Circulation Model had evolved, from the original formulation of GEM to the present. He discussed the special features of the GGCM concept that distinguish it from other global magnetospheric models. One defining characteristic of the GGCM that was established early in its history was that it would be a modular code, with different approaches used for different regimes of geospace. The modular concept, however, can be interpreted either in a strict sense -- with different codes handling different regions and boundary-condition information passed between them--or in the looser sense of different subroutine packages computing different parameters in different regions. Much of the GGCM-directed research activity in the last few years has been in beginning to develop and couple modules representing different regions and/or parameters. Wolf raised the issue of whether the research had progressed to the point where it was time to begin actually building the GGCM code, defining and building the individual modules as well as the logical structure that would connect them. In his prepared talk, he suggested that the time might not be right for this development, but, in the heated discussion that followed, it quickly became clear that there was strong sentiment of the GEM community for the fastest possible development of the GGCM. Important factors in the perceived urgency were the advent of the National Space Weather Program and the practical need for rapid improvement in forecasts of space weather. Discussion of GGCM planning issues continued through the scheduled Monday morning GGCM planning session and into an additional session Tuesday evening. It was clear that there is a need for a global model that can be widely used by the GEM community to help answer the scientific questions that face magnetospheric physics. One central and contentious issue that arose in the discussions was whether the GGCM should be modular in the strict sense (as defined in the previous paragraph) or should be based on a global MHD code, with program modules correcting or supplementing MHD for various parameters and various regions. Proponents of each side presented their cases at the Tuesday night session. However, after vigorous debate, the majority of those assembled voted to leave the technical decision of basic code design to the proposal-review process. Dick Wolf agreed to assemble a committee to draft a GGCM announcement that would reflect the majority sentiments expressed in the discussions and that people could reference in writing GEM proposals. That committee, which consisted of Jim Drake, Mike Heinemann, Michael Hesse (Co-Chair), John Lyon, Nelson Maynard, George Siscoe, and Dick Wolf (Chair), completed its writing assignment on the required tight time schedule. At the end of July, a draft "Plan for the Development of a Geospace General Circulation Model" was placed on the Web for consideration by the GEM community. A second draft, containing revisions made in response to community comments, was forwarded to the GEM Steering Committee in early September, and it has been endorsed by that Committee. The development plan recommends that the first round of GGCM-development proposals be submitted for the October 1996 GEM solicitation; these proposals would be for short-term concept studies, which would seek to define the computational structure of the GGCM program as well as the institutional structure in which it would be operated and made available to the community. The current version of the Plan can be accessed via the World-Wide Web through the GEM homepage or at the following address: http://jimme.gsfc.nasa.gov/~hesse/GGCM_plan.html SPACE WEATHER SESSION (George Siscoe, chair) For the last several years, the GGCM Campaign has acted as the bridge between the GEM scientific community and the community that is concerned with providing practical forecasts of space weather. Although the focus of that interaction has been in January workshops that have been held in Boulder, this session, which was chaired by George Siscoe, was designed to update the GEM science community at large on activity in the forecasting community. Kent Doggett, who is a forecaster at NOAA's Space Environment Center in Boulder, reported on the Workshop on the Evaluation of Space Weather Forecasts, which was held in previous week in Boulder. This Workshop brought together space scientists, space-weather forecasters, users of space forecasts, and some representatives of the terrestrial-weather forecast community to discuss techniques for systematically evaluating the effectiveness of forecasts. A report on Air Force space weather operations was presented Captain Dave Hembroff, who is a shift commander at the 50th Weather Squadron at Falcon Air Force Base outside Colorado Springs. He reported that new hardware installation of the Magnetospheric Specification Model allows completion of a three-hour run in a few minutes. He summarized the existing space-weather prediction and specification capabilities and the usefulness for customers. He mentioned one satellite-operations customer who was finding that 50WS predictions of activity levels allowed him to make an immediate judgement on whether a given anomaly was environmental in nature -- a major advantage, because the procedure for turning the spacecraft on again after an anomaly is much simpler if the problem is environmental. Howard Singer, of the NOAA Space Environment Center, reported on SEC approaches to improved space weather forcasting. He showed encouraging results of a new algorithm for predicting Ap 3-6 days ahead of time using solar observations. He discussed a proposal for establishing a rapid prototyping center for implementing space weather models. Phil Pratt of the TRW Systems Integration Group described a general computing environment that TRW has developed to facilitate rapid prototyping of models. Transitioning space models to operations has, in the past, sometimes proved to be expensive, time-consuming, and cumbersome. Pratt suggests that this TRW-developed computing environment, which was developed to be useful in a range of applications, could make it easy for a forecast center to implement and test a space-weather model. GGCM SCIENCE SESSION (Michael Hesse, chair) For the last several years, the GGCM science sessions at the June GEM Workshops have served several purposes. They have provided a forum for the planning of, and progress reports on, projects related to development and coupling of computational modules designed to be part of the GGCM. They have also served as an annual scientific meeting for people involved in large-scale magnetospheric theory and modeling and in the theory and modeling of those crucial small-scale processes that affect large-scale dynamics. This year's science session continued in the same tradition. Kolya Tsyganenko presented a scientific talk at the end of the Space Weather Session due to time constraints. He described the latest advance in his magnetic-field-modeling effort, which rests on a large database of spacecraft-measured magnetic fields. His newest models have a well-defined magnetopause and include a data-based prescription for the penetration of the magnetosheath magnetic field through the boundary, as a function of IMF. The latest model is available on the World-Wide Web. Richard Thorne summarized recent work that he has done in collaboration with V. K. Jordanova, R. B. Horne, and Janet Kozyra, calculating ion precipitation rates of ring-current ions by pitch-angle scattering. They are pursuing a very interesting approach to self-consistently representing the effects of small-scale plasma processes in a large-scale computer model of the ring current. Specifically, they utilize the Ring-Current/Atmosphere Interaction Model (RAM) to calculate the particle distribution function for ring-current ions and use that distribution function to calculate linear growth rates for electromagnetic ion cyclotron waves. Then they use the HOTRAY code to follow packets of electromagnetic wave packets through the inner magnetosphere, and calculate the time integral of the linear growth rate. From that, they derive a rough approximation to the wave amplitude and the pitch-angle scattering rate, which is then used in the RAM code to calculate the pitch-angle distribution. W. B. Lyatsky presented a new theoretical interpretation of the down-up-down average observed pattern of Birkeland currents in the midnight sector. He proposes that these currents result from the fact that ions have much more difficulty than electrons in making a sharp turn in the convection pattern - the turn that is implied by the ionospheric electric field pattern near the Harang discontinuity. He suggests that plasma-sheetions and electrons tend to separate in this region, and that the Birkeland currents are required to maintain approximate charge neutrality. Dr. Lyatsky presented a detailed theoretical analysis of this process and its magnetospheric and auroral effects. Harlan Spence reported on an effort at building comprehensive empirical models of the ring current and inner magnetosphere particles and fields. These models combine SCATHA, CRRES, POLAR, and other datasets. The SCATHA dataset is now available online. POLAR crosses the equatorial plane near the peak of the ring-current and provides very valuable information on ring-current dynamics and three dimensional structure of the inner magnetosphere. The synthesized data sets are being sorted by location and geomagnetic "phase" and will provide the core for future semi-empirical models. Frank Cheng reported on recent progress in his effort at theoretical calculation of 3D equilibrium magnetospheric configurations, for a magnetospheric plasma with isotropic pressure. He has developed a 3D quasi-static magnetospheric equilibrium code, the MAG-3D code, which makes use of a new, accurate and efficient numerical procedure based on a flux coordinate system. Employing radial pressure profiles from previous satellite measurements Cheng showed a variety of computed 3D equilibrium configurations for the ring current and inner plasma sheet for both quiet and disturbed times. The Region 2 field-aligned current is shown to be related to the azimuthal magnetic field curvature and plasma pressure gradient. The computed Region 2 field-aligned current is consistent with previous satellite measurements of Iijima and Potemra. Joachim Birn reported briefly on the status of the GEM project to couple the Birn/Hesse tail MHD code with the Rice Convection Model (RCM), using a frictional version of the MHD code that Frank Toffoletto has developed to calculate magnetic equilibria in the RCM's inner-magnetospheric region. The RCM is working effectively with the friction code, but coupling to the tail has not been completed. Birn also reported on some very interesting theoretical results obtained by embedding a particle tracer inside the tail-MHD code; fluxes calculated from Liouville's theorem seem consistent with general observed characteristics of substorm injections at geosynchronous orbit. Frank Toffoletto reported on progress on a GEM project that involves a collaboration between the Rice group and John Lyon at Dartmouth. It centers on embedding the Rice Convection Model inside a global MHD code. Graduate student Michikazu Hojo has completed several RCM runs with plasma and potential boundary conditions and the plasma initial condition taken from a case where the Fedder-Lyon MHD code had reached an approximate steady state. When the RCM is run in the ideal-MHD approximation ( E + vxB = 0), the electric field, plasma distribution, and Birkeland current distribution all change substantially during the RCM run. Region-2 Birkeland currents strengthen, effectively shielding the near-Earth region from the convection electric field. Harry Petschek presented a new physical picture of the growth phase of a substorm. In his picture, reconnection at the dayside magnetopause causes plasma loss and sets up a convection from the nightside to the dayside. The plasma transport thus constitutes a plasma loss from the plasma sheet, which can lead to thinning and subsequently substorm onset. Another way of looking at his scenario is: Imagine that reconnection occurs at the dayside magnetopause, so there is an electric field in the +y direction there. If the electric field is zero or negligible across the tail at x=x1 and along the magnetopause on the flanks, then Faraday's law implies that Bz decreases sunward of x1. Petschek suggests that this mechanism drives Bz to zero in the inner plasma sheet, triggering the onset of the expansion phase. The talks presented in the GGCM science session illustrate how large-scale magnetospheric is moving into an exciting new era, characterized by new ideas and new data. Semi-empirical models continue to improve in sophistication and usefulness. Theoretical models that were developed by different teams for different purposes are now being coupled, to allow investigation of cause-and-effect relationships between different magnetospheric regions and also between plasma processes with very different scale sizes. +-------------------------------------------------------------------------+ |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! | +-------------------------------------------------------------------------+