Search Publications
Stokes inversion based on convolutional neural networks
Asensio Ramos, A.; Díaz Baso, C. J.
Context. Spectropolarimetric inversions are routinely used in the field of solar physics for the extraction of physical information from observations. The application to two-dimensional fields of view often requires the use of supercomputers with parallelized inversion codes. Even in this case, the computing time spent on the process is still very…
Photospheric magnetic structure of coronal holes
Temmer, Manuela; Veronig, Astrid; Hofmeister, Stefan J. +2 more
In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at ±25 G. We find tha…
Hinode EIS line widths in the quiet corona up to 1.5 R⊙
Mason, H. E.; Del Zanna, G.; Gupta, G. R.
We present an analysis of several Hinode Extreme-ultraviolet Imaging Spectrometer (EIS) observations of coronal line widths in the quiet Sun, up to 1.5 R⊙ radial distances. Significant variations are found, which indicates no damping of Alfvén waves in the quiescent corona. However, the uncertainties in estimating the instrumental width…
A comparison between solar plage and network properties
Solanki, S. K.; Lagg, A.; van Noort, M. +1 more
Aims: We compare the properties of kG magnetic structures in the solar network and in active region plage at high spatial resolution.
Methods: Our analysis used six SP scans of the solar disc centre aboard Hinode SOT and inverted the obtained spectra of the photospheric 6302 Å line pair using the 2D SPINOR code.
Results: Photospheri…
Solar microflares: a case study on temperatures and the Fe XVIII emission
Del Zanna, G.; Mitra-Kraev, U.
In this paper, we discuss the temperature distribution and evolution of a microflare, simultaneously observed by Hinode's X-Ray Telescope (XRT), its Extreme Ultraviolet Imaging Spectrometer (EIS), as well as the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO). Using EIS lines, we find that during peak emission the …
Superstrong photospheric magnetic fields in sunspot penumbrae
Solanki, S. K.; Lagg, A.; van Noort, M. +2 more
Context. Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions. These superstrong penumbral fields are even larger than the strongest umbral fields on record and appear to be associated with supersonic d…
Exploring the damping of Alfvén waves along a long off-limb coronal loop, up to 1.4 R⊙
Mason, H. E.; Del Zanna, G.; Gupta, G. R.
The Alfvén wave energy flux in the corona can be explored using the electron density and velocity amplitude of the waves. The velocity amplitude of Alfvén waves can be obtained from the non-thermal velocity of spectral line profiles. Previous calculations of the Alfvén wave energy flux with height in active regions and polar coronal holes have pro…
Observations of solar small-scale magnetic flux-sheet emergence
Bello González, N.; Borrero, J. M.; Fischer, C. E. +1 more
Aims: Two types of flux emergence were recently discovered in numerical simulations: magnetic loops and magnetic sheet emergence. While magnetic loop emergence has been documented well in recent years using high-resolution full Stokes data from ground-based telescopes as well as satellites, magnetic sheet emergence is still an understudied pr…
Chromospheric observations and magnetic configuration of a supergranular structure
Leenaarts, Jorrit; Robustini, Carolina; de la Cruz Rodríguez, Jaime +1 more
Context. Unipolar magnetic regions are often associated with supergranular cells. The chromosphere above these regions is regulated by the magnetic field, but the field structure is poorly known. In unipolar regions, the fibrillar arrangement does not always coincide with magnetic field lines, and polarimetric observations are needed to establish …
Measuring relative abundances in the solar corona with optimised linear combinations of spectral lines
Buchlin, Éric; Zambrana Prado, Natalia
Context. Elemental abundances in some coronal structures differ significantly from photospheric abundances, with a dependence on the first ionization potential (FIP) of the element. Measuring these FIP-dependent abundance biases is important for coronal and heliospheric physics.
Aims: We aim to build a method for optimal determination of FIP …