Letters of Intent for 2015

LoI 2015-201
Focus Meeting: Observations and 3D numerical models: exploring the common ground

Date: 4 August 2015 to 6 August 2015
Location: IAU General Asssembly, Honolulu, United States
Contact: Fernando Moreno-Insertis (fmi@iac.es)
Coordinating division: Division E Sun and Heliosphere
Chair of SOC: Fernando Moreno-Insertis (Instituto de Astrofisica de Canarias)
Chair of LOC: ()



- Solar magnetoconvection. Photospheric velocity and magnetic fields. Photospheric jets. Vortices. Convective intensification of the magnetic field. The surface dynamo problem.

- Magnetic flux emergence from the solar interior to the atmosphere: models and observations of active region formation. Sunspot models. Link to 3D models of the deep layers of the convection zone.

- Stellar magnetoconvection: 3D models for different stellar types and comparison with observations. The atomic abundance problem.

- The solar chromosphere. Spicules and chromospheric jets. The NLTE radiation transfer and ionization non-equilibrium problems in models and observations; interpretation of Halpha, He I 10830 and other chromospheric lines in the light of 3D models. Hall and ambipolar diffusion models. Advances in the theory of chromospheric heating.

- The solar corona: EUV/Xray jets and minor solar eruptions. Flares and CME's. Coronal vortices. Topological questions (null points, bald patches, QSLs) and their identification in observations. Magnetic field extrapolation of observed regions.

- Techniques for comparison of 3D models and observations: a-posteriori radiation transfer and creation of synthetic observations from models. Techniques to account for instrumental effects and limitations. Useful observational proxies for the solar and stellar velocity and magnetic fields for comparison with models.

- Future challenges for the joint work of observers and modellers. Opportunities opened up by Solar Orbiter, ATST, Solar-C.



In recent years, large 3D numerical models of structures and processes in the solar atmosphere (photosphere, chromosphere, transition region and corona) are being used to produce synthetic observations that can be compared directly to real observations. This includes imaging, spectropolarimetry, and diagnostics of physical quantities. This research is being fostered by the availability of very high spatial, spectral and time resolution observations of those layers from different missions (SoHO, Trace, Hinode, RHESSI, Sunrise, SDO, Stereo, Hi-C, IRIS) and ground-based facilities. Simultaneously, the availability of PetaFlop-class Supercomputing installations and the development of massively parallel radiation-MHD codes with increasingly realistic thermodynamics and material properties permit the calculation of theoretical models with unprecedented closeness to the actual Sun. Detailed 3D modeling is also being carried out for magnetoconvection flows in stars of different types, with important implications for the understanding of stellar observations and determination of atomic abundances.

Although not new, this approach is going through a phase of very fast expansion and deepening. A meeting specifically devoted to the exploration of the common ground between observers and modelers as well as between solar and stellar modeling, is necessary and can help advance in this field. We are not aware of any recent international meeting specifically devoted to the interaction of numerical modelers and observers targeting techniques and direct comparison of their results.

At the time of submission of this LoI, ten established scientists in this field, both theoreticians dealing with 3D numerical models and observers, from institutions in different continents, have already agreed to be in the SOC of the proposed Focus Meeting if approved by the IAU.