Fredagskollokvium: Chromospheric inversions and new insights into flares from IRIS

Bart De Pontieu — Lockheed Martin Solar & Astrophysics Laboratory, Palo Alto

Prof. Bart De Pontieu,Lockheed Martin Solar & Astrophysics Laboratory, Palo Alto. Credits: Bart De Pontieu

The Interface Region Imaging Spectrograph (IRIS) is a NASA Small Explorer that is focused on high-resolution ultraviolet observations of the chromosphere, transition region, and flaring corona. I will provide an overview of several different results based on IRIS data. I will show a new approach, based on machine learning techniques and the Stockholm Inversion Code (STiC), that provides, in a matter of a few minutes (instead of millions of minutes),  temperatures, densities, velocities and non-thermal motions as a function of height for any IRIS map of the Mg II h & k lines. In the second part of my talk, I will also discuss the non-thermal broadening of the Fe XXI 1354 A line during flares, and show that the excessive broadening during flares cannot be explained by superposition of evaporative flows on unresolved and neighboring field lines, a commonly proposed mechanism. If there is time, I will also briefly discuss recent observations of plage using IRIS and ALMA.

Optically thick IRIS spectra of the Mg II h & k lines (left) can be inverted to yield information about the low solar atmosphere. The inversion process is computationally cumbersome, but can be dramatically sped up by using machine learning techniques (e.g. k-means) that group similar spectra into groups (colorful image on the right).
Optically thick IRIS spectra of the Mg II h & k lines (left) can be inverted to yield information about the low solar atmosphere. The inversion process is computationally cumbersome, but can be dramatically sped up by using machine learning techniques (e.g. k-means) that group similar spectra into groups (colorful image on the right).
Publisert 6. des. 2018 07:18 - Sist endret 30. apr. 2019 16:00