McKenzie, David E.; Auchère, Frédéric; Kano, Ryouhei; Ishikawa, Ryohko; Trujillo Bueno, Javier; del Pino Alemán, Tanausú; Okamoto, Takenori J.; Song, Donguk; Yoshida, Masaki; Rachmeler, Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage, Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge, Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.; Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán, Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit
Routine ultraviolet imaging of the Sun's upper atmosphere shows the spectacular manifestation of solar activity; yet we remain blind to its main driver, the magnetic field. Here we report unprecedented spectropolarimetric observations of an active region plage and its surrounding enhanced network, showing circular polarization in ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We infer the longitudinal magnetic field from the photosphere to the very upper chromosphere. At the top of the plage chromosphere the field strengths reach more than 300 gauss, strongly correlated with the Mg II $k$ line core intensity and the electron pressure. This unique mapping shows how the magnetic field couples the different atmospheric layers and reveals the magnetic origin of the heating in the plage chromosphere.
Magnetism, Polarization and Radiative Transfer in Astrophysics
Magnetic fields pervade all astrophysical plasmas and govern most of the variability in the Universe at intermediate time scales. They are present in stars across the whole Hertzsprung-Russell diagram, in galaxies, and even perhaps in the intergalactic medium. Polarized light provides the most reliable source of information at our disposal for the