Fredagskollokvium: Tiago Pereira, The Multispectral Sun

Abstract: In a dark matter Universe the Sun is just another insignificant star.
Yet its proximity allows for detailed observations well outside of the
reach of other branches of Astrophysics. In this talk I will focus on
the multispectral nature of the Sun. The Sun changes dramatically when
observed at different wavelengths, from slowly evolving very hot diffuse
plasma to very dynamic cooler regions, and bubbling activity from
convection. Understanding the connection between these regions is
crucial for many problems in solar physics. With some examples from my
work I will show how observations are required at high spatial,
spectral, and temporal resolution. Increasingly complex observations
bring problems of their own, both technical and conceptual. NASA's new
IRIS mission aims to fill a much needed gap in multispectral
observations, but its observations are complex and their diagnostic
information not immediately obvious. I will give an overview of IRIS
with some of its just-released data, and discuss how we used 3D
simulations to understand the formation of its spectra and images.