The idea of the working group is to review the challenges faced over the last 80 years, to develop strategies for making real progress, and to set about refuting some of the tens of recipes prescribing how, the corona might be heated. We have an embarrassingly large number of model recipes, in part because instruments are ill-suited following the journey of ordered, large-scale energy, down through the decades of scales where the irreversible dissipation of magnetic energy into heat occurs. In attempting to refute certain pictures, we hope to develop a much more direct path towards identifying how this journey is made.

The working group will address the following main themes: It is designed to expose the bare essence of coronal heating mechanisms, focusing on those studies which describe the physics of the journey that magnetic energy must make from large driving scales to dissipation. The main goal is to break loose from incremental related research and to identify new approaches. Here are some draft ideas for themes:

1. Define the essence of the problem

2. Identify true challenges, versus apparent challenges, which have clouded our ability to make breakthroughs, and see where limits of technology lie now

3. Develop a strong methodology stressing the need to refute models, and seeking probabilistic (Bayesian?) solutions to examine multiple models probabilistically against (future) information-rich data. Find the likelihoods of multiple theories being compatible with data.

4. Guided by advances in MHD theory, including turbulence, identify novel measurements capable of rejecting models, through spectroscopic and polarimetric signatures unique to, for example, anisotropic and aligned turbulent structures (“eddies”). Directions for immediate
attention might include

a. measuring the flow of magnetic energy through the chromosphere

b. Studies of “robust’’ predictions from ideal MHD, from turbulence resonant absorption, of Parker’s spontaneous current sheets, all under the umbrella of ideal MHD. Challenge with the best observations and identify further observations

c. Identify the processes first breaking the frozen-field condition

d. Seek spectroscopic signatures of anisotropic dynamics (waves, cascades,..)