Tomography of the Solar Corona with the Metis Coronagraph I: Predictive Simulations with Visible Light Images

ALBERTO M. VASQUEZ; FEDERICO A. NUEVO; FEDERICA FRASSATI; ALESSANDRO BEMPORAD; RICHARD A. FRAZIN; MARCO ROMOLI; NISHTHA SACHDEVA; WARD B. MANCHESTER IV

SOLAR PHYSICS

SPRINGER

Lugar: Berlin; Año: 2022 vol. 297 p. 120 - 141

0038-0938

{The emph{Solar Orbiter/Metis} coronagraph records full-Sun visible-light polarized brightness ($pB$-) images of the solar corona. This work investigates the utility of a synoptic observational program of emph{Metis} for tomographic reconstruction of the three-dimensional (3D) distribution of the electron density of the global solar corona. During its lifetime, the mission´s distance to the Sun will range over $approx 0.3,-,1.0,m AU$, while its solar-latitude will span $approxpm 33deg$. The limitations that this orbital complexity poses on tomographic reconstructions are explored in this work. Using the predicted orbital information of emph{Solar Orbiter} and 3D-MHD simulations of the solar corona using the Alfvén Wave Solar atmosphere Model, time series of synthetic emph{Metis} $pB$-images were computed and used as data to attempt tomographic reconstruction of the model. These numerical experiments were implemented for solar-minimum and solar-maximum conditions. In both cases, images were synthesized from three orbital segments, corresponding to extreme geometrical conditions of observation by emph{Metis}: aphelion, perihelion, and maximum solar latitude. The range of heights that can be reconstructed, the required data-gathering period, and the accuracy of the reconstruction, are discussed in detail for each case. As a general conclusion, a emph{Metis} synoptic observational program with a cadence of at least four images~day$^{-1}$ provides enough data to attempt tomographic reconstructions during the whole lifetime of the mission, a requirement well within the two to three hour cadence of the current synoptic program. This program will allow implementation of tomography experimenting with different values for the cadence of the time series of images used to feed reconstructions. Its cadence will also provide continuous opportunities to select images avoiding highly dynamic events, which compromise the accuracy of tomographic reconstructions.}