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A Quasi-periodic Propagating Wave and Extreme-ultraviolet Waves Excited Simultaneously in a Solar Eruption Event
摘要： Quasi-periodic fast-propagating (QFP) magnetosonic waves and extreme-ultraviolet (EUV) waves were proposed to be driven by solar flares and coronal mass ejections (CMEs), respectively. In this Letter, we present a detailed analysis of an interesting event in which we find that both QFP magnetosonic waves and EUV waves are excited simultaneously in one solar eruption event. The co-existence of the two wave phenomena offers an excellent opportunity to explore their driving mechanisms. The QFP waves propagate in a funnel-like loop system with a speed of 682–837 km s-1 and a lifetime of 2 minutes. On the contrary, the EUV waves, which present a faster component and a slower component, propagate in a wide angular extent, experiencing reflection and refraction across a magnetic quasi-separatrix layer. The faster component of the EUV waves travels with a speed of 412–1287 km s-1, whereas the slower component travels with a speed of 246–390 km s-1. The lifetime of the EUV waves is ～15 minutes. It is revealed that the faster component of the EUV waves is cospatial with the first wavefront of the QFP wave train. The QFP waves have a period of about 45 ± 5 s, which is absent in the associated flares. All of these results imply that QFP waves can also be excited by mass ejections, including CMEs or jets.
关键词： Sun: oscillations,waves,Sun: flares,Sun: corona,Sun: magnetic fields
更新于2025-09-23 15:22:29
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Solar total and spectral irradiance reconstruction over the last 9000 years
摘要： Context. Changes in solar irradiance and in its spectral distribution are among the main natural drivers of the climate on Earth. However, irradiance measurements are only available for less than four decades, while assessment of solar influence on Earth requires much longer records. Aims. The aim of this work is to provide the most up-to-date physics-based reconstruction of the solar total and spectral irradiance (TSI/SSI) over the last nine millennia. Methods. The concentrations of the cosmogenic isotopes 14C and 10Be in natural archives have been converted to decadally averaged sunspot numbers through a chain of physics-based models. TSI and SSI are reconstructed with an updated SATIRE model. Reconstructions are carried out for each isotope record separately, as well as for their composite. Results. We present the first ever SSI reconstruction over the last 9000 years from the individual 14C and 10Be records as well as from their newest composite. The reconstruction employs physics-based models to describe the involved processes at each step of the procedure. Conclusions. Irradiance reconstructions based on two different cosmogenic isotope records, those of 14C and 10Be, agree well with each other in their long-term trends despite their different geochemical paths in the atmosphere of Earth. Over the last 9000 years, the reconstructed secular variability in TSI is of the order of 0.11%, or 1.5 W m?2. After the Maunder minimum, the reconstruction from the cosmogenic isotopes is consistent with that from the direct sunspot number observation. Furthermore, over the nineteenth century, the agreement of irradiance reconstructions using isotope records with the reconstruction from the sunspot number by Chatzistergos et al. (2017, A&A, 602, A69) is better than that with the reconstruction from the WDC-SILSO series (Clette et al. 2014, Space Sci. Rev., 186, 35), with a lower χ2-value.
关键词： solar-terrestrial relations,Sun: faculae, plages,Sun: activity,Sun: magnetic fields
更新于2025-09-23 15:22:29
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Structural properties of the solar flare-producing coronal current system developed in an emerging magnetic flux tube
摘要： The activity of a magnetic structure formed in the solar corona depends on a coronal current system developed in the structure, which determines how an electric current flows in the corona. To investigate structural properties of the coronal current system responsible for producing a solar flare, we perform magnetohydrodynamic simulation of an emerging magnetic flux tube which forms a coronal magnetic structure. Investigation using fractal dimensional analysis and electric current streamlines reveals that the flare-producing coronal current system relies on a specific coronal current structure of two-dimensional spatiality, which has a sub-region where a nearly anti-parallel magnetic field configuration is spontaneously generated. We discuss the role of this locally generated anti-parallel magnetic field configuration in causing the reconnection of a three-dimensional magnetic field, which is a possible mechanism for producing a flare. We also discuss how the twist of a magnetic flux tube affects structural properties of a coronal current system, showing how much volume current flux is carried into the corona by an emerging flux tube. This gives a way to evaluate the activity of a coronal magnetic structure.
关键词： magnetohydrodynamics (MHD),Sun: magnetic fields,Sun: corona,methods: numerical,Sun: flares
更新于2025-09-23 15:21:01
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Latitude dependence of the solar granulation during the minimum of activity in 2009
摘要： Context. Knowledge of the latitude variation of the solar granulation properties (contrast and scale) is useful to better understand interactions between magnetic field, convection, differential rotation, and meridional circulation in the solar atmosphere. Aims. We investigated the latitude dependence of the contrast and scale of the solar granulation, with the help of HINODE/SOT blue continuum images taken in the frame of the HOP 79 program, along the central meridian and along the equator on a monthly basis in 2009 during the last solar minimum of activity. Methods. We selected the sharpest images in latitude and longitude intervals. The selected images in all the N-S and E-W scans taken in 2009 were combined to get statistically reliable results. Results. The contrast of the solar granulation decreases towards the poles and the scale increases, but not regularly since a perturbation occurs at around 60? where both quantities return close to their values at the disk center. Conclusions. Such a latitude variation in a period of minimum of activity (2009), is probably not due to magnetic field, neither the quiet magnetic field at the surface, nor the strong magnetic flux tubes associated with active regions, which could be embedded more or less deeply in the convection zone before they reach the surface. The decrease in contrast and increase in scale towards the pole seem to be related to the differential rotation and the perturbation around 60? to the meridional circulation.
关键词： Sun: evolution,Sun: granulation,Sun: rotation,Sun: interior,Sun: magnetic fields
更新于2025-09-23 15:19:57
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An open-source, massively parallel code for non-LTE synthesis and inversion of spectral lines and Zeeman-induced Stokes profiles
摘要： With the advent of a new generation of solar telescopes and instrumentation, interpreting chromospheric observations (in particular, spectropolarimetry) requires new, suitable diagnostic tools. This paper describes a new code, NICOLE, that has been designed for Stokes non-LTE radiative transfer, for synthesis and inversion of spectral lines and Zeeman-induced polarization profiles, spanning a wide range of atmospheric heights from the photosphere to the chromosphere. The code features a number of unique features and capabilities and has been built from scratch with a powerful parallelization scheme that makes it suitable for application on massive datasets using large supercomputers. The source code is written entirely in Fortran 90/2003 and complies strictly with the ANSI standards to ensure maximum compatibility and portability. It is being publicly released, with the idea of facilitating future branching by other groups to augment its capabilities.
关键词： Sun: photosphere,polarization,Sun: abundances,radiative transfer,Sun: chromosphere,Sun: magnetic fields
更新于2025-09-19 17:15:36
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Spatial deconvolution of spectropolarimetric data: an application to quiet Sun magnetic elements
摘要： Context. One of the difficulties in extracting reliable information about the thermodynamical and magnetic properties of solar plasmas from spectropolarimetric observations is the presence of light dispersed inside the instruments, known as stray light. Aims. We aim to analyze quiet Sun observations after the spatial deconvolution of the data. We examine the validity of the deconvolution process with noisy data as we analyze the physical properties of quiet Sun magnetic elements. Methods. We used a regularization method that decouples the Stokes inversion from the deconvolution process, so that large maps can be quickly inverted without much additional computational burden. We applied the method on Hinode quiet Sun spectropolarimetric data. We examined the spatial and polarimetric properties of the deconvolved profiles, comparing them with the original data. After that, we inverted the Stokes profiles using the Stokes Inversion based on Response functions (SIR) code, which allow us to obtain the optical depth dependence of the atmospheric physical parameters. Results. The deconvolution process increases the contrast of continuum images and makes the magnetic structures sharper. The deconvolved Stokes I profiles reveal the presence of the Zeeman splitting while the Stokes V profiles significantly change their amplitude. The area and amplitude asymmetries of these profiles increase in absolute value after the deconvolution process. We inverted the original Stokes profiles from a magnetic element and found that the magnetic field intensity reproduces the overall behavior of theoretical magnetic flux tubes, that is, the magnetic field lines are vertical in the center of the structure and start to fan when we move far away from the center of the magnetic element. The magnetic field vector inferred from the deconvolved Stokes profiles also mimic a magnetic flux tube but in this case we found stronger field strengths and the gradients along the line-of-sight are larger for the magnetic field intensity and for its inclination. Moreover, the discontinuity between the magnetic and non magnetic environment in the flux tube gets sharper. Conclusions. The deconvolution process used in this paper reveals information that the smearing induced by the point spread function (PSF) of the telescope hides. Additionally, the deconvolution is done with a low computational load, making it appealing for its use on the analysis of large data sets.
关键词： Sun: photosphere,techniques: polarimetric,methods: statistical,methods: data analysis,Sun: magnetic fields,techniques: spectroscopic
更新于2025-09-19 17:15:36