Related papers: Magnetostatic penumbra models with field-free gaps
Our aim is to model the 3D magnetic field structure of the upper solar atmosphere, including regions of non-negligible plasma beta. We use high-resolution photospheric magnetic field measurements from SUNRISE/IMaX as boundary condition for…
We investigate the existence of magnetohydrostatic equilibria for topologically complex magnetic fields. The approach employed is to perform ideal numerical relaxation experiments. We use a newly-developed Lagrangian relaxation scheme that…
The magnetar magnetosphere is gradually twisted by shearing from footpoint motion, and stored magnetic energy also increases at the same time. When a state exceeds a threshold, flares/outbursts manifest themselves as a result of a…
Context. It is unclear why there is a rather sharp boundary in sunspots between the umbra and the penumbra. Both regions exhibit magnetoconvection, manifesting in penumbral filaments in the penumbra and in umbral dots in the umbra. Aims.…
The magnetic field inside the sunspot umbra, as observed by the Full-disk MagnetoGraph (FMG) onboard the Advanced Space based Solar Observatory (ASO-S), was found to be experiencing a weakening. To address this issue, we employed a method…
We build a single vertical straight magnetic fluxtube spanning the solar photosphere and the transition region which does not expand with height. We assume that the fluxtube containing twisted magnetic fields is in magnetohydrostatic…
Recent numerical simulations and observations of sunspots show a significant amount of opposite polarity magnetic field within the sunspot penumbra. Most of the opposite polarity field is associated with convective downflows. We present an…
Jurcak et al (2018) have reported that, in a sample of more than 100 umbral cores in sunspots, the umbral-penumbral boundary (UPB) is characterized by a remarkably narrowly-defined numerical value (1867 G) of the vertical component of the…
We investigate sharply outlined features recorded in solar magnetic field tracers. It is shown that the magnetic boundaries of a sunspot do not coincide with the photometric ones. Moreover, there is no clear magnetic boundary around…
Context. Existing sunspot simulations fail to reproduce the observed magnetic field distribution due to an artificially increased $B_{hor}$ at the upper boundary. Aims. We explore alternative ways to better reproduce the magnetic and…
Some of the most important technological challenges of today's society, such as fusion reactors for future clean unlimited energy or the next generation of medical imaging techniques, require precise spatial shapes of strong magnetic…
We report on high angular resolution, high precision spectropolarimetric measurements of a decaying sunspot. The spot gradually lost its penumbra during the course of three days. In the late stages of evolution where the only remnant of the…
Inversions of spectropolarimetric observations of penumbral filaments deliver the stratification of different physical quantities in an optical depth scale. However, without establishing a geometrical height scale their three-dimensional…
Measurements of maximum magnetic flux, minimum intensity, and size are presented for 12 967 sunspot umbrae detected on the NASA/NSO spectromagnetograms between 1993 and 2004 to study umbral structure and strength during the solar cycle. The…
In a force-free magnetic field, there is no interaction of field and the plasma in the surrounding atmosphere i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of many magnetic…
The influence of strong, large-scale magnetic fields on the structure and temperature distribution in white dwarf atmospheres is investigated. Magnetic fields may provide an additional component of pressure support, thus possibly inflating…
The generation of magnetic flux in the solar interior and its transport to the outer solar atmosphere will be in the focus of solar physics research for the next decades. One key-ingredient is the process of magnetic flux emergence into the…
Over the past five years, 2010-2015, we have observed, in the near infrared (IR), the maximum magnetic field strengths for 4145 sunspot umbrae. Herein we distinguish field strengths from field flux. (Most solar magnetographs measure flux).…
Electronic and magnetic properties of a system of two charged vacancies in hexagonal shaped graphene quantum dots are investigated using a mean-field Hubbard model as a function of the Coulomb potential strength $\beta$ of the charge…
The formation of sunspots requires the concentration of magnetic flux near the surface. The negative magnetic pressure instability (NEMPI) might be a possible mechanism for accomplishing this, but it has mainly been studied in simple…