Solar Physics最新文献

This study investigates penumbrae and light bridges based on photospheric and chromospheric flow fields and photospheric magnetic fields in active region NOAA 13096. The improved High-resolution Fast Imager (HiFI+) and the GREGOR Infrared Spectrograph (GRIS) acquired high-resolution imaging and spectropolarimetric data at the 1.5-meter GREGOR solar telescope at the Observatorio del Teide, Izaña, Tenerife, Spain. Background-Subtracted Activity Maps (BaSAMs) have been used to locate areas of enhanced activity, Local Correlation Tracking (LCT) provides horizontal proper motions, and near-infrared full-Stokes polarimetry offers access to magnetic fields and line-of-sight velocities. The results show that the decaying active region is characterized by a triangular region between the three leading, positive-polarity sunspots with unfavorable conditions for penumbra formation. This region has a spongy appearance in narrow-band H(alpha ) images, shows signs of enhanced activity on small spatial scales, is free of divergence centers and exploding granules, lacks well-ordered horizontal flows, has low flow speeds, and is dominated by horizontal magnetic fields. Umbral cores are inactive, but the interface between pores and penumbral filaments often shows enhanced activity. Moat flows and superpenumbrae are almost always observed, when penumbral filaments are present, even in very small penumbral sectors. However, evidence of the moat flow can also be seen around pores, surviving longer than the decaying penumbral filaments. Light bridges have mainly umbral temperatures, reaching quiet-Sun temperatures in some places, show strong intensity variations, and exhibit weak photospheric horizontal flows, while narrow-band H(alpha ) flow maps show substantial inflows.

With the steady improvement of the observing capabilities and numerical simulations, an efficient data management of large data volumes has become mandatory. The Institute for Solar Physics (KIS) has developed the Science Data Centre (SDC), a data infrastructure to store, curate, and disseminate science-ready data from the German solar-observing facilities and other partner institutions. The SDC was also conceived to create and disseminate higher-level data products of added value like inversions from spectropolarimetric data. The SDC archive infrastructure consists of a back-end based on the Rucio science data-management and MongoDB systems and a front-end web interface that allows the user to search and discover data based on search parameters like instrument, date, wavelength range, and target. The SDC archive also provides data access via API and TAP services. The SDC currently offers access to 1299 science-ready datasets from the GRIS instrument at the GREGOR telescope (Tenerife) since 2014, a set of 610 spectra from the LARS at the Vacuum Solar Telescope (VTT, Tenerife) and 202 404 full-disc solar images from the Chromospheric Telescope (ChroTel). The SDC also offers to the community Milne–Eddington inversions of the GRIS spectropolarimetric archived data that can be downloaded as well as tools for data visualization and advanced analysis (e.g., GRISView tool). Many SDC activities have been carried out within the framework of large international data projects like the Horizon 2020 ASTERICS and ESCAPE EU-funded projects under the FAIR (Findable, Accessible, Interoperable, Reusable) principles. New and planned SDC activities include the ingestion of solar data from GREGOR context imaging instruments, flare observations from Ondřejov Observatory (Czech Republic), archiving and dissemination of in-house magnetohydrodynamic simulations, and creation of high-level data products using machine learning. The KIS Science Data Centre is a state-of-the-art data-management infrastructure that curates, archives, and provides access to ground-based science-ready spectropolarimetric and imaging solar data. SDC also provides advanced data visualization and analysis tools and invites data providers to publish their data to the solar and broader (astro)physics community via the SDC data archive.

The study of the solar corona is a prominent focus in the field of solar physics. However, conducting ground-based observations of the corona is a challenging task due to the interference caused by the diffused sky brightness, which obscures the faint coronal signal. As a result, such observations are primarily carried out during total solar eclipses. The requirement of a sky-brightness level as low as (10^{-6}) times the solar disk brightness ((B_{odot })) is met by few places on Earth, and currently there are only two sites hosting solar observatories that satisfy this criterion, Mauna Loa and Haleakala, both located in Hawaii. Nevertheless, another candidate coronagraphic site was discovered in the Concordia Station at Dome C plateau, Antarctica ((simeq 3300) m a.s.l.). In this article, we show the last results of the Extreme Solar Coronagraphy Antarctic Program Experiment (ESCAPE) during the 38th summer campaign of the Italian Piano Nazionale di Ricerche in Antartide (PNRA). Here, we report a model for estimating the air column, which allows for the first time to account for variations in the Sun’s altitude above the horizon during different observation periods, and we use it to compare the obtained results with previous campaigns. Our results confirm that Dome C is an ideal coronagraphic site with the required sky-brightness level, reaching (1.0-0.7times 10^{-6}B_{odot }) in optimal conditions.

The first adiabatic exponent profile, noted ({{Gamma }_{1}}), computed along adiabatic coordinates ((T), (rho )), is in the focus of our study. Under conditions of almost fully ionized hydrogen and helium, the ({{Gamma }_{1}}) profile is quite sensitive to heavy elements ionization. ({{Gamma }_{1}}) decreases in regions where an element is partially ionized. The recent helioseismic structural inversion is obtained with an accuracy better than ({{10}^{-4}}) in the most of the adiabatic convective zone that allows to study ionization variations. The aim is to determine the major heavy elements content in the solar convective zone. The method of our research is synthesis of the (Gamma _{1}) profile, which is based on a linear combination of the contributions of individual heavy elements. The idea of the approach was proposed and justified by Baturin et al. (2022). We find the best approximation of the inverted profile ({{Gamma }_{1}}) adjusting the abundances of major elements (C, N, O, Ne), meanwhile the abundances of elements heavier than neon are fixed. We synthesize the theoretical ({{Gamma }_{1}}) profile using the SAHA-S equation of state, and are able to reproduce the inverted profiles with an accuracy of ((1-2)cdot {{10}^{-5}}). Total mass fraction of heavy elements found with this method is (Z=0.0148pm 0.0004). The oxygen logarithmic abundance is (8.70pm 0.03), carbon (8.44pm 0.04), nitrogen (8.12pm 0.08), and neon (8.17pm 0.09). The obtained estimations of oxygen and carbon agree with spectroscopic abundances by Asplund, Amarsi, and Grevesse (2021).

The aim of this work is to study the dispersion of acoustic waves in the rarefied high-temperature plasma of the solar corona and its role in propagating intensity disturbances (PDs) occurring in this region. We believe that a multi-periodicity in wavelet spectra, recorded when observing PDs in coronal holes and loops, is due to a result of the combined effect of dispersion and damping of compression waves. Observations show the presence of continuous spectra, where periods are distinguished by suitable maxima. The shape of the spectra is characteristic of localized disturbances. This study is based on our previously proposed clear model of nonadiabatic waves in high-temperature plasma, which takes into account the properties of thermal conduction, radiative cooling, and constant heating. Thermal conduction forms a local minimum of group speed, separating groups of waves with short and long periods. Waves of the first group have strong dispersion and weak damping while waves of the second group have the opposite properties. This effect leads to the fact that the initial pulse disturbance eventually acquires a form in which the indicated groups are clearly separated. Two maxima appear in the wavelet spectrum which determine the short period (P_{s}) and the long period (P_{l}). Two groups of waves with dominant periods propagate at the same speed, which is less than the sound speed. We assume that the form of PDs can indeed arise in the corona under the influence of small-scale disturbances in the lower atmosphere. The speed of the observed disturbances is also less than the sound speed. This is usually explained by the projection effect, but can also be explained by the fact that PDs propagate with a group speed. The time signals in the corona recorded by observing PDs bear little resemblance to the superposition of just a few harmonic components. The observed periods are not regular, they can change several times during the entire observation time (often 2 – 3 hours). We propose to consider PDs as a sequence of independent pulse disturbances. Two periods occur only in a given pulse, the duration of which is on the order of a long period (P_{l}), often 20 – 30 minutes. They may change in the next pulse, since they depend on the length of the initial pulse formed at the boundary of the corona and the lower atmosphere.

We investigate the angular rotation velocities of stable recurrent sunspot groups characterized by a leading unipolar sunspot with an initially well-developed penumbra, similar to the H or J types in the Zürich classification. These structures are tracked for two (class I) or three (class II) solar rotations. The Debrecen Photoheliographic Data sunspot catalogue (1977 – 2017) used in this study provides the daily positions and areas of observable sunspots and sunspot groups with great precision. This allows the calculation of the angular rotation synodic velocities from a least-squares fit to the sunspot positions over a given disk passage. After converting to sidereal coordinates, the velocities were used to obtain the solar rotation parameters via a least-squares fit to the solar differential rotation law. Comparison is made with the solar differential rotation laws obtained in two previous studies considering the same classes of sunspot groups, and over comparable time periods, using the data from the Greenwich Photoelectric Results (GPR) catalogue. We find that, on average, the sunspots exhibit a braking tendency, aligning with previous findings. The common results across the three studies, when examined in the context of simulations for sunspot formation and evolution, suggest a scenario in which recurrent unipolar sunspots are anchored at a shallow subsurface layer. The observed braking effect is attributed to gradual fragmentation, leading to disconnection and a transition to dynamics increasingly influenced by surface flows.

In the immediate sunspots’ vicinity—their superpenumbra—3-minute line-of-sight (LOS) velocity oscillations dominate in the photosphere and chromosphere. Oscillations of similar periods are also registered in the transition region and lower corona above active regions. This work aims to clarify whether these LOS velocity oscillations are manifestations of Alfvénic waves in the lower solar atmosphere. The study is based on the analysis of three sunspots using data from instruments on board the Solar Dynamics Observatory. Additional observations of another sunspot were carried out at the ground-based Automated Solar Telescope. We use narrow-band frequency filtration (5.6 – 5.8 mHz) of the LOS velocity, magnetic field, and intensity signals of the Fe i 6173 Å spectral line. For the analysis, we use a 90-minute long time series. We conclude that the 3-minute oscillations in the LOS velocity signals result from magnetoacoustic waves rather than Alfvénic waves. However, oscillations registered in magnetic field signals indicate that Alfvénic waves may be present already in the photosphere. Further research requires simultaneous observations of LOS velocity, magnetic field strength, spectral line width, and intensity carried out at two heights of the solar atmosphere.

In this article, recent advances concerning the knowledge of solar opacity are presented. We first review a few laser and Z-pinch iron-opacity measurements performed in France, Germany, and the USA over the past decades. Interpretation of laser experiments on neighboring elements such as chromium, nickel, and copper are also considered. Several theoretical issued raised by these experimental spectra are then addressed and discussed, such as configuration interaction, highly-excited states, line broadening, and two-photon absorption.

The Polarimeter to UNify the Corona and Heliosphere (PUNCH) will image macroscopic features of the inner heliosphere and also admit sufficiently high spatial resolution to probe scales of turbulence within the upper end of the inertial range, close to the integral scale. As PUNCH is an imager, its measurements will relate differently to the underlying turbulent environment of the outer corona and inner heliosphere from more familiar in situ samples. We present a numerical study that combines magnetohydrodynamic simulations of turbulence together with FORWARD-modeling synthesis of white-light data via the FORWARD code. We show that (i) the “usual” turbulence scalings are modified by the integration along the LOS in an optically thin medium, and (ii) those scalings are still linked to the original properties of the turbulent field. This study is a first step in the process of analyzing and understanding the unprecedented information that PUNCH will provide.

A reliable data analysis center plays a crucial role in the successful execution of a space mission. The Science Operation and Data analysis Center (SODC) of Advanced Space-based Solar Observatory (ASO-S) is a bridge between the science team of ASO-S and data users (Huang et al. 2019). ASO-S plays a crucial role in understanding the solar eruptions (such as flares and coronal mass ejections) and the magnetism behind them. In this article, we outline the current status of ASO-S, as well as its data products and analysis software. These resources aid in the enhanced understanding of solar magnetism and its associated energetic eruptions.