Search Publications
Enhancing SDO/HMI images using deep learning
Asensio Ramos, A.; Díaz Baso, C. J.
Context. The Helioseismic and Magnetic Imager (HMI) provides continuum images and magnetograms with a cadence better than one per minute. It has been continuously observing the Sun 24 h a day for the past 7 yr. The trade-off between full disk observations and spatial resolution means that HMI is not adequate for analyzing the smallest-scale events…
Persistent magnetic vortex flow at a supergranular vertex
Bellot Rubio, Luis R.; Gošić, Milan; Requerey, Iker S. +1 more
Context. Photospheric vortex flows are thought to play a key role in the evolution of magnetic fields. Recent studies show that these swirling motions are ubiquitous in the solar surface convection and occur in a wide range of temporal and spatial scales. Their interplay with magnetic fields is poorly characterized, however.
Aims: We study th…
The magnetic nature of umbra-penumbra boundary in sunspots
Jurčák, J.; Schlichenmaier, R.; Rezaei, R. +2 more
Context. Sunspots are the longest-known manifestation of solar activity, and their magnetic nature has been known for more than a century. Despite this, the boundary between umbrae and penumbrae, the two fundamental sunspot regions, has hitherto been solely defined by an intensity threshold. Aim. Here, we aim at studying the magnetic nature of umb…
Properties of the inner penumbral boundary and temporal evolution of a decaying sunspot
Gömöry, P.; Jurčák, J.; Kuckein, C. +3 more
Context. It has been empirically determined that the umbra-penumbra boundaries of stable sunspots are characterized by a constant value of the vertical magnetic field.
Aims: We analyzed the evolution of the photospheric magnetic field properties of a decaying sunspot belonging to NOAA 11277 between August 28-September 3, 2011. The observation…
Measuring the Wilson depression of sunspots using the divergence-free condition of the magnetic field vector
Solanki, S. K.; Lagg, A.; Löptien, B. +1 more
Context. The Wilson depression is the difference in geometric height of unit continuum optical depth between the sunspot umbra and the quiet Sun. Measuring the Wilson depression is important for understanding the geometry of sunspots. Current methods suffer from systematic effects or need to make assumptions on the geometry of the magnetic field. …
Heating of the solar photosphere during a white-light flare
Kleint, Lucia; Kašparová, Jana; Jurčák, Jan +1 more
Context. The Fe I lines observed by the Hinode/SOT spectropolarimeter were always seen in absorption, apart from the extreme solar limb. Here we analyse a unique dataset capturing these lines in emission during a solar white-light flare.
Aims: We analyse the temperature stratification in the solar photosphere during a white-light flare and co…
Occurrence and persistence of magnetic elements in the quiet Sun
Gošić, M.; Bellot Rubio, L.; Giannattasio, F. +3 more
Context. Turbulent convection efficiently transports energy up to the solar photosphere, but its multi-scale nature and dynamic properties are still not fully understood. Several works in the literature have investigated the emergence of patterns of convective and magnetic nature in the quiet Sun at spatial and temporal scales from granular to glo…
Does the solar granulation change with the activity cycle?
Ichimoto, K.; Utz, D.; Hanslmeier, A. +1 more
Context. Knowledge of the variation of the solar granulation properties (contrast and scale) with the 11-yr activity cycle is useful for a better understanding of the interaction between magnetic field and convection at global or local scales. A varying granulation may also contribute to irradiance variations and affect the p-mode damping rates an…
Temperature gradient in the solar photosphere. Test of a new spectroscopic method and study of its feasibility for ground-based telescopes
Chiavassa, A.; Faurobert, M.; Carbillet, M. +2 more
Context. The contribution of quiet-Sun regions to the solar irradiance variability is currently unclear. Some solar-cycle variations of the quiet-Sun physical structure, such as the temperature gradient, might affect the irradiance. The synoptic measurement of this quantity along the activity cycle would improve our understanding of long-term irra…
Analysis of unresolved photospheric magnetic field structure using Fe I 6301 and 6302 lines
Lozitsky, V. G.; Browning, P. K.; Gordovskyy, M. +1 more
Context.Early magnetographic observations indicated that the magnetic field in the solar photosphere has an unresolved small-scale structure. Near-infrared and optical data with extremely high spatial resolution show that these structures have scales of a few tens of kilometres, which are not resolved in the majority of solar observations. Aims.Th…