*************************** ** THE GEM MESSENGER ** *************************** Volume 4, Number 17 September 14, 1994 ------------------------------------------------ REPORT ON 1994 SNOWMASS WORKSHOP - GGCM WORKSHOP ------------------------------------------------ WG 5: GGCM ASSEMBLY George Siscoe and Joel Fedder Working Group 5 comprises three Sub Working Groups: SWG 1: The Core Unit--Dick Wolf, leader SWG 2: The Boundary Unit--Bill Lotko, leader SWG 3: The Tail/Substorm Unit--Michael Hesse, leader This year's WG 5 sessions met on Wednesday, June 29. They emphasized two activities: 1. applications to space weather, and 2. integrating GGCM components. The morning and afternoon session were preceded by talks by Rita Sagalyn and Ron Zwickl on the needs of the military and civilian forecasting communities for numerical specification and prediction codes. In the morning, Sub Working Groups 1 and 2 ran parallel sessions to discuss space weather applications. In the afternoon Sub Working Groups 1 and 3 ran a joint session to discuss "marriages" between the core code and other codes. This session was followed by parallel sessions of Sub Working Groups 2 and 3 to discuss procedures for testing boundary layer and substorm models by "wedding" them to the core code. George Siscoe began the proceedings by reminding everyone of WG 5's fourfold goals: 1. organize activity leading to a generalized general circulation model; 2. identify intermediate GEM milestones; 3. bring into being intermediate GEM products; and 4. complete a prototype GEM-GGCM during or before 1996 (the Eastman Challenge). He noted that the following progress has occurred in defining WG 5's specific tasks: The WG has taken a decision to build a modularized GGCM (i.e., RCM-like vs. global MHD-like, though hybrids are possible). It has defined "modules" to be stand-alone, special-purpose, regional codes. (These are also intermediate GEM products.) It has defined "prototype GGCM" (in reference to the Eastman Challenge) to be a GGCM with applications. It has created the three sub working groups listed above. It has assigned the core unit the task of developing an advanced prediction code (e.g., a value-added MSFM) capable of being transitioned into forecast operations. It has assigned the two other units the tasks of wedding boundary and substorm models to the core code to provided a global context for evaluating their consequences. It has added as a task the developing of special-purpose "space weather" codes capable of being transitioned into forecast operations. It has declared that the completion of an instance of any of these tasks constitutes satisfying the Eastman Challenge. The WG sessions dealt with information aimed at performing these tasks. The last task mentioned-- developing space weather codes--was the focus of the morning session. Rita Sagalyn described the "space weather" component of the program she directs at Phillips Laboratory (PL). The space weather work at PL has produced a suite of computer codes for use at the Air Force Space Forecast Center. These codes are the first numerical codes ever developed for operational space weather forecasting. Together they constitute an integrated set that covers space from the sun though the heliosphere to the magnetosphere and thence to the ionosphere and thermosphere. One of these codes is of particular interest to the GEM community. This is the Magnetosphere Specification and Forecast Model (MSFM) developed under an Air Force contract to John Freeman and Dick Wolf at Rice University. The MSFM has been completed, delivered, and made available for public use. But because it takes time to render the code security tight for DoD use, its operational deployment at AFSFC might be delayed one or more years. Nonetheless, GEM could adopt the MSFM now as a core module for a prototype GGCM. The GEM community could then develop value-added products to augment and extend it. Such value-added contributions would be encouraged by Phillips Laboratory. Sagalyn went on to note that the MSFM needs a real-time solar wind data stream, which at present does not exist. To bring one into existence, she has been working with NASA and the Air Force to configure the WIND spacecraft for real-time duty. Such duty entails issues of risk and tracking cost that still need to be resolved, but her efforts have induced NASA to make WIND physically able to transmit data in real time. She has also secured a promise of a minimum of two hours of real time data each day, which will at least serve for demonstration and testing purposes. She stressed that even with real-time solar wind data, the MSFM will permit forecasts valid for approximately one hour. To make longer forecasts, one needs information on conditions upstream from the solar-wind weather station. For this she is proposing a joint Air Force-NASA mission to detect on-coming CMEs by their characteristic coronograph signature (a sun-centered, expanding halo). This could give reliable warnings a day in advance. The morning SWG 1 session dealt with the environmental specification and forecasting possibilities for the inner magnetosphere and ionosphere. The focus was on algorithms that already exist and on improvements that could be made to existing algorithms. John Freeman gave a demonstration of the MSFM, which, as noted above, is available now. The MSFM takes a number of near-real-time inputs and predicts particle fluxes in the tens-to-hundreds-of-keV range throughout the inner magnetosphere. It also predicts precipitation fluxes and ionospheric potentials, from which, given a conductivity model, ionospheric currents can be predicted. The model's "cludges" have been set to maximize the accuracy of predictions at geosynchronous orbit of particle fluxes. These predictions are of greatest use to the Air Force, and hence, they have been tested most; indeed, the model's ionospheric predictions have not been tested. This fact led Gary Erickson to propose a program to test the MSFM's ionospheric predictions to see if they can be used to forecast ground induced currents (GICs). These are the currents that surge in power lines and give power companies trouble. For this a code would need to be developed to go from the present MSFM ionospheric output to a GIC forecast for a specific power network. The testing and the code could constitute a value-added product by the GEM program. To pursue this idea, Dick Wolf has set up an e-mail discussion group. To get in it, e-mail to wolf at spacvax.rice.edu. Jay Albert described a different sort of addition to the MSFM that he is implementing at Phillips Lab. This is a radiation belt model based on the extensive library of CRRES radiation belt data. Xinlin Li described a successfully-tested approach that he and Mary Hudson are pursuing at Dartmouth to model the dynamical creation of radiation belts by invoking phase coherence of drift-orbiting particles and the E field of a transiting shock wave. David Sibeck described the GIC warning algorithm that Larry Zanetti has developed at APL. It uses real-time auroral imaging data from the Freja satellite and an empirical ionospheric current model to predict if and when a power grid will rotate under an active current system. This algorithm is in operation now. Lou Lee reminded everyone that the MSFM is relatively low tech compared to the possibilities inherent in hybrid codes like the one being developed at the University of Alaska by Dan Swift. With this reminder, the audience, looking back to the first talk, had a view of both the starting points and the ends points in an evolution of operational codes, which, if the history of numerical tropospheric forecasting is a guide, will probably take decades to advance through. The morning SWG 2 session dealt with predicting the magnetospheric boundary and the ground level geomagnetic consequences of its motions. Chris Russell and David Sibeck took turns describing their models of the shape of magnetospheric boundary and its dependence on solar wind parameters. Despite their different formulations, they give very similar shapes everywhere but in the tail and at high latitudes where data are sparse. Howard Singer spoke for the operational forecasting community. They simply want the best model. The improvements that they regard as most crucial have to do with predicting extreme events, for which neither the Russell nor Sibeck model has been tested. They are also concerned with the problem of how best to display the model predictions in an operational environment. Regarding the question of the ground level geomagnetic consequences of magnetopause motions, Sibeck noted that the region 1 current system mainly causes the boundary to move in response to a change in IMF Bz. Thus, one must determine the ground level effects of region 1 currents to answer the question for this type of motion. Russell presented data on the ground level magnetic perturbations caused by changes in solar wind ram pressure. He finds that the perturbations fits the theoretical square- root-of-pressure law fairly well, but that the amplitude has a strong local time dependence with maximum amplitude at noon. These kinds of results have yet to make their way into operational GIC forecasting procedures. The theme of operational forecasting continued into the afternoon with Ron Zwickl's talk on the needs of space weather forecasters and their customers in the commercial sector. He noted that SEL's Space Environment Services Center has customers who are interested in forecasts up to days or weeks in advance or even longer. The long-term types of forecasting fall in the areas of solar and heliospheric physics. The type of forecasting that magnetospheric physics can lead to is called nowcasting at SEL, that is, specifying the state of the magnetosphere up to about an hour in advance. For nowcasting services, SESC relies primarily on real-time global activity indices, especially Kp. But to advance beyond index-based nowcasting, SEL recognizes the need for, and is developing capability in, physically based, quantitative models. These will be of two types. Models that give maps of the particle environment at geosynchronous orbit, from which forecasters can issue warnings on surface charging, deep dielectric charging, and radiation damage. The other type of model will give maps of the low-altitude electromagnetic environment. These will let forecasters issue warnings on GICs and changing field conditions. Zwickl concluded by saying that SEL is preparing to move SESC's nowcasting capability from reliance on global indices to computer aided analyses of quantitative, physically based magnetospheric weather maps. After Zwickl's talk, the theme of the afternoon session switched to GGCM assembly and its application to science issues. SWG 1 and SWG 3 held a joint session on the physical coupling between the tail and the inner magnetosphere, and, more specifically, on how to represent that coupling in terms of numerical models. Two projects were described to merge the Rice Convection Model with MHD models. One, which was discussed already at the preceding Fall AGU/GEM mini-workshop, involves imbedding the RCM within the Fedder-Lyon global MHD model. The goal of this project is to build a merged model that displays the exclusive strengths of its two component models. The MHD model gives a B field that is mutually consistent with the particle pressure; the RCM gives particle pressures that are consistent with guiding center--i.e., non MHD--drifts in a given B field. The merged model should give a B field that is mutually consistent with particle pressures determined by guiding center drifts. The plans for the merger have matured enough since December to form the basis for a GEM proposal. The other, new project involves merging the Birn-Hesse MHD tail model with the RCM. The goal again is to build a merged model that displays the exclusive strengths of its component models. In this case the exclusive strength of the MHD model is its ability to simulate substorm-like reconnection in the tail. A merged model might possess this ability and the ability simultaneously to model substorm injection events, for which guiding center drift formalism is needed. Harlan Spence described a third project that merges his and Margaret Kivelson's particle distribution functions for the plasma sheet and low-latitude boundary layer with Margaret Chen's ring current model. The merged model should give the relative contributions of the two source populations modeled by Spence and Kivelson to the ring current population modeled by Chen. Spence described this as a low-tech version of the global MHD-RCM merger project. As a way to help implement the merging of models that reside at separated sites, John Lyon proposed setting up an internet line for exchanging data and images. After this session, SWG 3 continued meeting to discuss substorms in the context of global models. The question posed was whether global models can guide the development of substorm models by testing their global consequences. Joel Fedder noted that to some extent global models need smaller scale models to get the physics right. He pointed in particular to the need MHD models have for correct models of ionospheric conductivity. He affirmed the value of embedding local substorm models within global models citing that global models can give the inductive E fields that appear to be an essential part of the substorm process. Amitava Bhattacharjee advised that we need to get the microphysics right in substorm models. For this more emphasis should be put on developing transport models to connect the microphysics with the macrophysics. Gary Erickson described a substorm model that was, in effect, inspired by a combination of RCM and MHD thinking. It entails a chain of cause and effect that goes like this: particle drifts generate field-aligned currents, which create parallel electric fields, which cause pressure to vary along field lines, and this leads to ballooning, and ultimately to tearing. Erickson intends to try to embed his model in the RCM to test it in the manner that this session advocated. Dan Weimer displayed two targets that substorm models should shoot for. One is the shape of the AL index for isolated substorms. It is remarkably repeatable and could serve as a simple diagnostic for testing models. The other target is the behavior of the B field at geosynchronous orbit. It too is repeatable and could be used either to test models or as an input for models. Returning to the question posed at the beginning of the session, we note that no one seems to have addressed it directly. Perhaps we will see the first results of an attempt to embed a local substorm model in a global magnetospheric model at the next Snowmass workshop. The afternoon SWG 2 session featured an overview talk by Joel Fedder. The question posed was how do boundary layers behave in a global MHD model? The main points are these: Current closure is very complex. This finding casts doubt on a program that attempts to isolate a separate boundary layer component out of a global system. The second point relates to northward IMF: For it the LLBL is a closed-field-line dynamo; the downstream wall of the cusp is also a dynamo--an interesting, new result; and the magnetopause current layer lies mostly outside the topological boundary. The third point relates to the southward IMF: For it the LLBL between 8 and 16 MLT is an open-field-line load; on the flanks, it is a closed-field-line dynamo; and region 1 currents leave the ionosphere on closed field lines. The lessons and questions for boundary-layer modelers are several: Quantitative, physics-based LLBL models all assume closed field lines; open field line models need to be developed. The cusp is a dynamically interesting place, why are there no quantitative, physics-based models for it? How can one combine an open LLBL and a close LLBL in a single local LLBL model? etc. These results, lessons, and questions are preparatory to the real project of SWG 2, which is to embed a local boundary layer model in a global magnetospheric model to test its global consequences. This was the first Snowmass meeting of WG 5 under its three subgroup structure. How did it go? It seems clear that the project of merging models with the RCM is advancing well and that there are other merging projects are also moving along (e.g., Spence's model and Chen's model). Also the MSFM has been introduced as a GEM community resource. Value- added modifications of it could be the quickest answer to the Eastman Challenge. The projects of embedding substorm models and boundary layer models in the core (RCM) model is moving more slowly. Perhaps it is more difficult. This means we should push harder until we get one example to see how well the concept works. We learned a lot at this workshop. There is now a sense of motion toward definite near-term goals. This sense of an accessible, near-term goal arises in part because we have identified space weather as one of the applications that defines a prototype GGCM. To continue this motion, we are holding the second "Boston College" meeting of WG5 in Boulder at the Space Environment Laboratory--thanks to arrangements made by Ron Zwickl--on January 12 and 13, 1995. There will be more information on this meeting in a later newsletter. +-------------------------------------------------------------------------+ |To add name to the mailing list, send a message to: guan at igpp.ucla.edu | |For message to whole GEM mailing list, send to: gem at igpp.ucla.edu | |For message to a specific working group (BL Campaign), send to: | | gem_field at igpp.ucla.edu (WG1); gem_boundary at igpp.ucla.edu (WG2); | | gem_current at igpp.ucla.edu (WG3); gem_data at igpp.ucla.edu (WG4) | | gem_ggcm at igpp.ucla.edu (WG5) | | gem_chair at igpp.ucla.edu (WG chairs, Odile and W. Lotko) | |GEM Bulletin Board: telnet terra.igpp.ucla.edu; user name: gem or GEM | | contents: GEM Messengers, magnetic indices, IMF data | |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! | +-------------------------------------------------------------------------+