Fibrils are thin elongated features visible in the solar chromosphere in and around magnetized regions. Because of their visual appearance they have been traditionally considered a tracer of the magnetic field lines. To our best knowledge, this common conception has never been actually put to test, probably because a proper empirical determination of the chromospheric magnetic field is very challenging, requiring high-resolution spectro-polarimetry in chromospheric lines. In this work we challenge that notion for the first time by comparing their orientation to that of the magnetic field, obtained via high-resolution spectro-polarimetric observations of Ca II lines. The transverse (i.e., projected on the plane of the sky) component of the magnetic field, which is what we are interested in for this work, is determined solely by the observed linear polarization signals (Stokes Q and U profiles). Unfortunately, such signals are typically very weak and their observation presents numerous challenges. In order to extract a clear signal above the noise we select by hand a small segment along the direction of a fibril and average the Stokes Q and U profiles spatially to improve the signal-to-noise ratio. From the profiles thus obtained we can determine the azimuth of the magnetic field on the plane of the sky. Our measurements suggest that fibrils are mostly oriented along the magnetic field direction, however we find evidence of misalignment in some cases.
Advertised on
References
2011, A&A, 527, L8.
It may interest you
-
It is well known that fullerenes – big, complex, and highly resistant carbon molecules with potential applications in nanotechnology – are mostly seen in planetary nebulae (PNe); old dying stars with progenitor masses similar to our Sun. Fullerenes, like C60 and C70, have been detected in PNe whose infrared (IR) spectra are dominated by broad unidentified IR (UIR) plateau emissions. The identification of the chemical species (structure and composition) responsible for such UIR emission widely present in the Universe is a mystery in astrochemistry; although they are believed to be carbon-richAdvertised on
-
Dark matter is an invisible substance that makes up more than eighty percent of the matter content of the universe. We know of its existence due to its gravitational influence, being a key ingredient to understand everything from the large-scale evolution of the universe to the formation of galaxies like the Milky Way, of which we are part of . However, very little is known about its nature, which constitutes one of the greatest unsolved problems in contemporary physics. The fuzzy dark matter model has recently been studied as a promising candidate. In this model , it is postulated that darkAdvertised on
-
In the 90s, the COBE satellite discovered that not all the microwave emission from our Galaxy behaved as expected. Part of this signal was later assigned to a fresh new emission component, spatially correlated with the Galactic dust emission, which showed greater importance in the microwave range of frequencies. It has been named since as “anomalous microwave emission”, or AME. The current main hypothesis to explain the AME origin is that it is emitted by small dust particles which undergo fast spinning movements. In Fernández-Torreiro et al. (2023), we study the observational properties ofAdvertised on