Comparative Study of the Three-dimensional Thermodynamical Structure of the Inner Corona of Solar Minimum Carrington Rotations 1915 and 2081

LLOVERAS, DIEGO; VÁSQUEZ, ALBERTO M.; NUEVO, FEDERICO A.; FRAZIN, RICHARD A.

SOLAR PHYSICS

SPRINGER

Lugar: Berlin; Año: 2017 vol. 292

0038-0938

Using differential emission measure tomography (DEMT) based on time series of EUV images, we carry out a quantitative comparative analysis of the the three-dimensional (3D) structure of the electron density and temperature of the inner corona (r < 1.25 R ) between two specific rotations selected from the last two solar minima, namely Carrington rotations (CR-)1915 and CR- 2081. The analysis places error bars in the results due to systematic uncertainty sources. While the results for CR-2081 are characterized by a remarkable north- ern/southern symmetry, for CR-1915 the southern hemisphere exhibits larger densities and temperatures than the northern one. For both rotations the core region of the streamer belt is found to be populated by structures with temperature decreasing with height (so-called ?down loops? in our previous articles), characterized by plasma β 1, which may be the result of efficient dissipation of Alfv ́en waves at low coronal heights. The comparative analysis reveals that the low latitudes of the equatorial streamer belt of CR-1915 exhibit larger densities than for CR-2081 that cannot be explained by the systematic uncertainties. Also, the southern hemisphere of the streamer belt of CR-1915 is characterized by larger temperatures and density scale heights than for CR-2081. On the other hand, the coronal hole region of CR-1915 shows lower temperatures than for CR-2081. The reported differences are in the range ≈ 10 − 25%, depending on the specific physical quantity and region being compared, as fully detailed in the analysis. For other regions and/or physical quantities the uncertainties do not allow assessment of thermodynamical differences between the two rotations. Future investigation will involve DEMT analysis of other Carrington rotations selected from both epochs, and comparison of their tomographic reconstructions with magnetohydrodynamical simulations of the inner corona.