I: Session C3 Thermal Studies : Techniques

1. I: Session C3Thermal Studies : Techniques Chair(s): Mark Weber & Paul Boerner Status: draft

2. Guidelines to group leads • Assess the task definitions in appendix A (‘AIA Science Plan’) in the 2004 Concept Study Report (CSR). In particular: • Science/task descriptions in Ch. A1.1 • Summaries in Table A2 • Identify required changes from, and additions to, the ‘AIA Science Plan’ • Evaluate the status of that plan, and formulate changes, if needed. • You may add as many pages to this document as you need, but: • Add pages under the same headings: please, do not change the roman numerals in the page titles, please add ‘a, b, c, d, …’ • Resources: • AIA home: http://aia.lmsal.com/ • AIA CSR summary: http://aia.lmsal.com/public/CSR.htm • CSR: https://aia.lmsal.com/doc?cmd=vcur&proj_num=AIA00435 • Proposal: https://aia.lmsal.com/doc?cmd=vcur&proj_num=AIA00341

3. Schedule • 17 November 2005: draft sheets I, II to teams, requesting input for sheets III and IV • 24 November 2005: completed sheets I-IV for review to teams, requesting input for sheets V-VI • 8 December 2005: team input received for sheets V-VI • 19 December 2005: draft of sheets VII-VIII to teams • 9 January 2006: team comments received for sheets VII-VIII • 6 February 2006: draft ‘Science plans’ on meeting website, with sheets IX-X filled out by team leads (or teams after telecons) • 13-17 February 2006: discussions during science team meeting discuss and complete pages IX-X. • 17 February: completed ‘Science plans’ on line.

4. IIa: Science questions and tasks (from CSR) • Primary scientific questions: • Objective 2: Study coronal heating and irradiance, and the origins of the thermal structure and coronal emission, to understand the basic properties of the solar coronal plasma and field, and the spatially-resolved input to solar spectral irradiance. • SDO/AIA science tasks: • Task 2B: Characterize the physical properties of coronal structures

5. IIb: Science questions and tasks (DEM recovery) • DEM recovery offers a description of the thermal structure along a line of sight, which allows us to: • distinguish overlapping structures in the optically-thin corona • distinguish between plasma motion and heating • identify the location and magnitude of heating and cooling events • track plasma topology and connectivity • relate morphology and dynamics observed in the corona with AIA to irradiance observed with EVE

6. IIIa: Science context • There are a number of upcoming advances that should leave us in a better position to do thermal studies when SDO launches than we are now: • Observations with broader spectral (and thermal) coverage, particularly from SOLAR-B EIS and XRT; also GOES-N SXI, STEREO SECCHI • Gradual improvements in spectral codes and databases • Faster computers and larger displays, which will facilitate the computation and visualization of DEM data products • Improvements in the software and techniques that enable the analytic combination of multiple instrument datasets (e.g. TRACE, MDI, EIT, CDS…)

7. IIIb: Science context (cont.) • SDO should advance our understanding of coronal thermal structure even further: • AIA is designed for DEM recovery, with more EUV bandpasses than have ever been available from a high-resolution imager • High spatial resolution is required in order to study the thermal properties of elemental structures • High cadence allows studies of the evolution of coronal structures at the shortest relevant timescale

8. IVa: Science investigation • Uncertainties in spectral models are a major obstacle • databases rely on tabulated measurements of abundance, ionization balance, etc., which may not be correct or constant • spectral databases do not have complete catalogues of coronal emission lines • Another major obstacle is the scaling of the computation • difficult to compute, analyze and display DEMs for the whole volume of AIA observations

9. IVb: Science investigation • Additional obstacles: • instability of DEM inversion in the presence of error and uncertainty • range of possible DEM solutions and uniqueness of recovered DEM must be estimated and understood • optical depth of plasma is difficult to accommodate in large scale, automated codes • going from LOS DEM to a description of thermal structure in a volume element not always trivial

10. V: Implementation: general • In order to improve our ability to do useful thermal studies, we need: • A DEM working group that will • foster a broader understanding of the need for, and difficulty of, DEM analysis • reach a consensus on many implementation issues • Improvements to spectral models and databases • These will allow us to work towards a standard DEM recovery code that will provide easily understood uncertainty estimates, temperature maps, and LOS discrimination

11. VI: Implementation: AIA+HMI • DEM inversion requires AIA observations: • in all EUV bandpasses • near-simultaneous • Cadence of ~1 minute • Full dynamic range (longest exposures possible without saturating) • Simultaneous HMI observations to enable study of topology/connectivity • requires co-alignment with AIA • Simultaneous EVE observations for cross-calibration

12. VII: AIA (+HMI+EVE) data products • Critical data products: • SDO data: • AIA observations in EUV bandpasses • Desireable data products • SDO data: • HMI observations of magnetic field • EVE observations for cross-calibration • Supporting data from other observatories: • EIS spectra for cross-calibration • STEREO images to distinguish 3-D structure

13. VIIIa: AIA (+HMI+EVE) data production • Open question: should there be a DEM data product in the pipeline? • computationally intensive • could implement linear inversion or lookup table • numerous knobs must be set almost arbitrarily • parameterization of DEM (range, resolution in T space) • spectral code and assumptions (abundance, pressure, etc) • conduct DEM recovery study to optimize these settings • difficult to include other observations in the pipeline

14. VIIIb: AIA (+HMI+EVE) data production • If we do have a standard DEM product, we will need to decide: • how comprehensively it will be produced • full-disk, full-resolution per-pixel DEMs? • bin pixels, sum over multiple exposures • run DEM recovery routine selectively • how to display the recovered DEM • temperature maps • error bars/level of certainty

15. IXa: Business plan: Resources • AIA can be used for thermal studies in 2 ways: for quicklook T maps, and for more careful/detailed DEM reconstruction. • It would be useful to supply 2 DEM data/code products: • A pipeline DEM/Temperature map data product; • A set of software tools to allow expert users to perform DEM reconstruction

16. IXb: Business plan: Resources • The pipeline data product should: • Be clear and usable by experts and non-experts • Supply information that is not available in the standard images • Allow users to identify features, events, and regions that warrant for further study • The DEM reconstruction software package should allow users to: • Tweak a variety of atomic parameters (abundance, charge state, etc.) and a priori constraints (smoothness, etc.) • Include observations from other instruments, and from models • Understand the uncertainties in the recovered DEM

17. Xa: Business plan: Implementation • Develop a “white paper” and work with people who calculate and measure atomic physics properties to reduce atomic uncertainties in the AIA bandpasses • Hold workshops to develop an understanding of the problem of DEM reconstruction with AIA • ~30 participants, incl. representatives of the instrument, spectral codes, and modeling teams • Focused on DEM reconstruction problems (not spectral codes): • Inversion algorithms • Uncertainties • Data pipeline realities • Preliminary meeting adjacent to SPD 2006; identify problems and have volunteers work on them • Follow-up meeting in Feb 2007

18. Xb: Business plan: Implementation • The Pipeline Product: Do we need a DEM data product in the pipeline? This fundamental question is still unanswered • Survey community to determine how it would be used, and how useful it would be (May 2006) • Based on the study of how practical DEM reconstruction is (see Xa), develop and test methods to determine how it could be implemented (Early-mid 2007) • Spatial resolution (number of DEM pixels) • Inversion technique • Standard set of “atomic physics” assumptions