Chromospheric response to emergence of internetwork magnetic fields

Abstract:

Internetwork (IN) magnetic fields are weak, short-lived, but highly dynamic magnetic structures that emerge all over the Sun. They bring an enormous amount of magnetic flux and energy to the solar surface. Therefore, IN fields are of paramount importance for maintenance of the QS magnetism. Since these fields are ubiquitous, they may have a substantial impact on the energetics and dynamics of the solar atmosphere. In this work, we use coordinated, high-resolution, multiwavelength observations obtained with the Interface Region Imaging Spectrograph (IRIS) and the Swedish 1 m Solar Telescope (SST) to follow the evolution of IN magnetic loops as they emerge into the photosphere. The footpoints of the emerging IN bipoles are clearly visible as they appear in the photosphere and rise up through the solar atmosphere, as seen in SST magnetograms taken in the Fe I 6173 Å and Mg I b2 5173 Å lines, respectively. Our polarimetric measurements, taken in the Ca II 8542 Å line, provide the first direct observational evidence that IN fields are capable of reaching the chromosphere. Moreover, using IRIS data, we describe in detail how individual IN bipoles affect the dynamics and energetics of the chromosphere and transition region.