Solar Physics最新文献

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.

The problem of coronal heating is one of the fundamental problems of solar physics. At present, it is again attracting great interest due to the appearance of a large amount of observational data of high spatial and temporal resolution. These data made it possible to diagnose plasma parameters from observations of waves and oscillations in coronal magnetic structures and, moreover, to introduce analytical constraints on the coronal heating function. In this paper, we propose an approach allowing us to impose constraints on the heating function based on data on the gravitational stratification of the solar atmosphere. The developed algorithm is applied to the altitude profiles of temperature and density in several regions of the solar corona obtained from direct modeling of EUV radiation from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). Assuming that the heating function is a power function of temperature and density, we determine the domain of power-index constraints allowing us to realize the observed altitude profiles. The obtained results are combined with the conditions of stability for the entropy and magnetoacoustic modes, to narrow the region of possible parameters further.

Decades of in-situ solar-wind measurements have clearly established the variation of solar-wind physical parameters. These variable parameters have been used to classify the solar-wind magnetized plasma into different types, leading to several classification schemes being developed. These classification schemes, while useful for understanding the solar wind’s originating processes at the Sun and early detection of space weather events, have left open questions regarding which physical parameters are most useful for classification and how recent advances in our understanding of solar-wind transients impact classification. In this work, we use neural networks trained with different solar-wind magnetic and plasma characteristics to automatically classify the solar wind in coronal hole, streamer belt, sector reversal and solar transients such as coronal mass ejections comprised of both magnetic obstacles and sheaths. Furthermore, our work demonstrates how probabilistic neural networks can enhance the classification by including a measure of prediction uncertainty. Our work also provides a ranking of the parameters that lead to an improved classification scheme with (sim 96%) accuracy. Our new scheme paves the way for incorporating uncertainty estimates into space-weather forecasting with the potential to be implemented on real-time solar-wind data.

At high frequencies beyond the acoustic cut-off, a peak-like structure is visible in the solar power spectrum. Known as the pseudo-modes, their frequencies have been shown to vary in anti-phase with solar magnetic activity. In this work, we determined temporal variations in these frequencies across the solar disc, with the aim of identifying any potential latitudinal dependence of pseudo-mode frequency shifts. We utilised nearly 22 years of spatially resolved GONG data for all azimuthal orders, (textit{m}), for harmonic degrees (0leq lleq 200), and determined shifts using the resampled periodogram method. Periodogram realisations were created from overlapping, successive 216 day-long segments in time, and cropped to 5600 – 6800 μHz. Cross-correlation functions were then repeatedly generated between these realisations to identify any variation in frequency and the uncertainty. We categorised each mode by its latitudinal sensitivity and used this categorisation to produce average frequency shifts for different latitude bands (15^∘ and 5^∘ in size) which were compared to magnetic proxies, the (F_{mathrm{10.7}}) index and GONG synoptic maps. Morphological differences in the pseudo-mode shifts between different latitudes were found, which were most pronounced during the rise to solar maximum where shifts reach their minimum values. At all latitudes, shift behaviour was strongly in anti-correlation with the activity proxy. Additionally, periodicities shorter than the 11-year cycle were observed. Wavelet analysis was used to identify a periodicity of four years at all latitudes.

The Spectro-Polarimeter (SP) is a new instrument installed at the upgraded Andrei B. Severny Solar Tower Telescope (STT) at the Crimean Astrophysical Observatory. The instrument is a traditional echelle slit dual-beam spectropolarimeter with temporal modulation of the polarization. STT-SP provides simultaneous spectropolarimetric observations of the Sun within three 15 Å wide spectral ranges around photospheric Fe I 5250 Å, Fe I 5324 Å, and chromospheric Mg I b2 5172 Å spectral lines. The spectral resolution of the instrument reaches 70,000 with the seeing-constrained slit width of 1 arcsec. The field-of-view of STT-SP is 200 arcsec allowing one to map a moderate size active region within a single raster scan. The instrument will provide new opportunities in the analysis of magnetic fields and thermodynamics of the lower atmosphere of the Sun. In this paper we describe the optical design of STT-SP and present the preliminary results acquired during the commissioning of the instrument.

The torsional Alfvén wave is highly regarded as the carrier of the energy from the photosphere to the corona in the solar atmosphere. This paper presents a comprehensive linear analysis of the wave behavior and energy transfer within an open, twisted, divergent magnetic flux tube configuration, considering the impact of wave guide structure on the propagation of these waves using the magneto-hydrodynamic approach. The study shows that waves with frequencies between 0.001 Hz and 1 Hz can effectively penetrate the transition region, with the most efficient energy transfer occurring in the 0.1 Hz to 1 Hz frequency range. The research findings suggest that waves with certain intermediate frequencies are able to transmit energy to the coronal region of the Sun, contributing to its active heating.