Periodic Reporting for period 3 - SolarALMA (ALMA – The key to the Sun’s coronal heating problem.)
Reporting period: 2019-09-01 to 2021-02-28
Detailed comparisons with numerical simulations are an essential part of the methodology. These comparisons are facilitated through radiative transfer calculations based on the numerical models, producing synthetic ALMA observations. In order to make the required radiative transfer calculations computationally feasible, the Advanced Radiative Transfer code (ART) was developed in cooperation with de la Cruz Rodriguez, Stockholm University, and optimized for performance in the framework of a PRACE Preparatory Access project. ART now performs 100 times more efficient than the codes used before and will have applications that go beyond the SolarALMA project.
Next to the continued contribution to the next generation of numerical codes for 3D simulations of the solar atmosphere, also more established 1D codes have been used in order to give a first impression of the detailed dynamics as it is observable with the currently available ALMA receiver bands. Publications are currently in preparation.
First comparisons of the processed ALMA observations and corresponding simulated data products yield interesting and promising results. The spatial resolution of the observations is high enough for clearly revealing the structure of the mapped atmospheric layer as function of time but also for the detection of small-scale dynamic events. The novel aspect is that these observations now directly indicate the temperature changes connected to such events. The available (and future) data sets allow therefore the anticipated study of chromospheric heating with ALMA, which will be the main focus of the second project half.
The analysis is strongly supported by numerical simulations as they predict the signatures of small-scale processes and how to best detect these in real observations. To this end, large simulation data sets with unprecedented degree of realism are currently in production and will be available for the anticipated analysis. The simulation data will also be used for further optimising the Solar ALMA Pipeline with the aim to optimize the quality of ALMA image sequences and to maximize the accuracy of the measured temperatures.
Furthermore, it is planned to use a novel data inversion code which determines the properties of the gas in the atmospheric layers observed with ALMA. This method provides a complementary way to identify and evaluate heating events and the structure and dynamics of the solar atmosphere as a whole.
Finally, the numerical simulations and tools will be employed for the evaluation of future observing modes for ALMA, especially for polarisation capabilities that will eventually facilitate measurements of the magnetic field in the solar chromosphere, which is in itself a highly anticipated result with large scientific impact.