Validating Models of the Corona and Inner Heliosphere

1. Validating Models of the Corona and Inner Heliosphere Discussion Leaders Bart Van Der Holst, Peter MacNeice

2. Objective • To initiate the design and execution of a program of model validation that would enable users and developers of coronal and inner heliospheric models to better understand the relative strengths and limitations of the codes. • Ideally to leave having • identified a set of test problems • settled on a common format for presenting results • agreed on a schedule • Getting these was always going to be an extended multi-stage and multi-year process • Yesterday we made a solid start!

3. The Process • Stage 1 (here) - ‘Buy In’ • Stage 2 (here) – Identify the broad outlines of a set of tests • Stage 3 (next 6 months) – Define the specific details of each test • Stage 4 (6-12 months) – First model runs complete • Stage 5 (Year 2) – Refine problem definitions and rerun • Stage 6 – Final Report

4. Stage 1 – ‘Buy In’ • Well attended and lively debate • Unanimous agreement that the goal is worthy • Issues all centered on whether it can be completed successfully • Consensus seemed to be yes – if the initial effort doesn’t over-reach • Limit the number of test cases • Carefully constrain the model input • Where possible develop tests around well studied datasets • Zoran suggested making this the subject of a SHINE proposal to give the project additional momentum • Philosophy of approach • Focus on science rather than space weather based metrics • Importance of having multiple metrics for each test case • Means to avoid tuning for specific metrics • Critical mass of model developers

5. Potential Model Participants • Inner Heliosphere • PredSci • SWMF • ENLIL • HAF • Wu et al • Arge et al • Jackson et al • Merkin et al • Corona • MHD • PredSci • SWMF • Wu et al • NLFFF • Wiegelmann et al • McTiernan et al • Wheatland et al • Regnier et al • McKay, Yeates, Van Ballegooijen • Potential • DeRosa and Schrijver • Arge et al

6. Stage 2 – Outline of Test Set • Global corona • Full disk EUV and X-ray image reconstruction • Locations of coronal hole boundaries • Size and location of streamer structures • Importance of using multiple lines to avoid over tuning heating functions • Recommended submission of model solution in form of plasma parameters (r,T,v) and a single ‘forward modeling’ application to be used uniformly for all models • Tests should target both solar max and min • Leonard Strachan identified his UVCS database and its synoptic r,T,v maps as a usable measure of ground truth particularly at solar min • Discussion of need for corrections for scattered light • How to make comparison with observation more quantitative • Extract DEM from different classes of features • ‘Line cuts’ through emission maps • CoMP Polarization measurements might also be used as metric • Metric should expose alfven profiles in low coronal solutions • Should use magnetogram data from multiple sources Vo at 2.3 Ro Strachan

7. Stage 2 – Outline of Test Set Merkin • Inner Heliosphere • IMF and plasma parameters • SIR / CIR structure and location • Importance of testing at range of latitudes • Coupled corona and inner heliosphere may be too ambitious • Different coronal models would mean helio components were solving different problems • Can we construct a ‘standardized ‘ inner BC that all competing helio models could use? • Heard about the updated UCSD Heliospheric Tomography model and how it could be used to support the test setup

8. Summary • Will probably limit initial effort to two test cases • Static global corona • Ambient helio structure • I will set up a communication network to keep this dialogue active • In 3 months hope to hold a telecon to propose a specific set of test cases to be defined in greater detail over the following 3 months • Expect to continue this working group next year • I see no reason why we cannot be reporting results of our first iteration then