The Aditya-L1 is the first space-based solar observatory of the Indian Space Research Organization (ISRO). The spacecraft will carry seven payloads providing uninterrupted observations of the Sun from the first Lagrangian point. Aditya-L1 comprises four remote sensing instruments, viz. a coronagraph observing in visible and infrared, a full disk imager in Near Ultra-Violet (NUV), and two full-sun integrated spectrometers in soft X-ray and hard X-ray. In addition, there are three instruments for in-situ measurements, including a magnetometer, to study the magnetic field variations during energetic events. Aditya-L1 is truly a mission for multi-messenger solar astronomy from space that will provide comprehensive observations of the Sun across the electromagnetic spectrum and in-situ measurements in a broad range of energy, including magnetic field measurements at L1.

Accurate atomic data for line wavelengths, energy levels, line broadening such as hyperfine structure and isotope structure, and f-values, particularly for the line rich iron group elements, are needed for stellar astrophysics applications, and examples of recent measurements are given. These atomic data are essential for determination of elemental abundances in astronomical objects. With modern facilities, telescopes and spectrographs, access to underexplored regions (IR, UV, VUV), and improved stellar atmosphere models (3D, NLTE), and extremely large datasets, astronomers are tackling problems ranging from studying Galactic chemical evolution, to low mass stars and exoplanets. Such advances require improved accuracy and completeness of the atomic database for analyses of astrophysical spectra.

The relative abundances of the radionuclides in the solar system at the time of its birth are crucial arbiters for competing hypotheses regarding the birth environment of the Sun. The presence of short-lived radionuclides, as evidenced by their decay products in meteorites, has been used to suggest that particular, sometimes exotic, stellar sources were proximal to the Sun’s birth environment. The recent confirmation of neutron star - neutron star (NS-NS) mergers and associated kilonovae as potentially dominant sources of r-process nuclides can be tested in the case of the solar birth environment using the relative abundances of the longer-lived nuclides. Critical analysis of the 15 radionuclides and their stable partners for which abundances and production ratios are well known suggests that the Sun formed in a typical massive star-forming region (SFR). The apparent overabundances of short-lived radionuclides (e.g. 26Al, 41Ca, 36Cl) in the early solar system appears to be an artifact of a heretofore under-appreciation for the important influences of enrichment by Wolf-Rayet winds in SFRs. The long-lived nuclides (e.g. 238U, 244Pu, 247Cr, 129I) are consistent with an average time interval between production events of 108 years, seemingly too short to be the products of NS-NS mergers alone. The relative abundances of all of these nuclides can be explained by their mean decay lifetimes and an average residence time in the ISM of ∼200 Myr. This residence time evidenced by the radionuclides is consistent with the average lifetime of dust in the ISM and the timescale for converting molecular cloud mass to stars.

The magnetic flux emergence can help understand the physical mechanism responsible for solar atmospheric phenomena. Emerging magnetic flux is frequently related to eruptive events, because when emerging they can reconnected with the ambient field and release magnetic energy. We will use a physic-based model to reconstruct the evolution of the solar emission based on the configuration of the photospheric magnetic field. The structure of the coronal magnetic field is estimated by employing force-free extrapolation NLFFF based on vector magnetic field products (SHARPS) observed by HMI instrument aboard SDO spacecraft from Sept. 29 (2013) to Oct. 07 (2013). The coronal plasma temperature and density are described and the emission is estimated using the CHIANTI atomic database 8.0. The performance of the our model is compared to the integrated emission from the AIA instrument aboard SDO spacecraft in the specific wavelengths 171Å and 304Å.

ChemiX is a Bragg crystal spectrometer that will fly on the two Interhelioprobe spacecraft due for launch in 2025 and 2026. The spacecraft perihelion will be only 0.3 a.u. and the orbit inclination up to 30°, and so instruments on board will have a close view of solar active regions and flares and regions near each solar pole. The ChemiX X-ray spectrometer, built by a consortium of groups led by the Space Research Centre, Polish Academy of Sciences, will fly on each of the spacecraft, and observe X-ray spectra in the 1.5 - 9 Å range. Spectral lines in this range include resonance lines of helium-like and hydrogen-like ions of elements such as Fe, Ca, Ar, S, and Si, with less abundant elements such as K and Cl represented by weaker lines which the high sensitivity of ChemiX should be able to detect. The free–free and free–bound continua should also be detected since instrumental background will be eliminated. Three of the seven channels of ChemiX will be in a “dopplerometer” arrangement by which spatial and spectral shifts present in flare impulsive stages can be disentangled.

We present results of analysis of the spectra collected with Polish instrument RESIK flown on CORONAS-F satellite. RESIK was the bent crystal spectrometer, measuring spectra in the spectral range 3.3 - 6.1 Å with a high cadence during flares. The emission lines as well as the continuum observed by RESIK are formed in hotter (T > 3 MK) plasmas of active regions and flares. RESIK observed various types of flares: from X-ray class B and C up to strongest flares of X-class, for both, short and long duration events. The analysis of absolute and relative spectral intensities of the lines and continuum observed for 33 events allowed for determining the plasma elemental composition with subsequent detailed study of time changes of the temperature structure of the sources described in terms of the differential emission measure (DEM). As an example we present the typical DEM evolutionary patterns for the C1.9 flare (SOL2002-12-26T08:35) and discuss its thermodynamics.

The solar abundances of Fe and of the CNO elements play an important role in addressing a number of important issues such as the formation, structure, and evolution of the Sun and the solar system, the origin of the chemical elements, and the evolution of stars and galaxies. Despite the large number of papers published on this issue, debates about the solar abundances of these elements continue. The aim of the present investigation is to quantify the impact of photospheric magnetic fields on the determination of the solar chemical abundances. To this end, we used two 3D snapshot models of the quiet solar photosphere with a different magnetization taken from recent magneto-convection simulations with small-scale dynamo action. Using such 3D models we have carried out spectral synthesis for a large set of Fei, Ci, Ni, and Oi lines, in order to derive abundance corrections caused by the magnetic, Zeeman broadening of the intensity profiles and the magnetically induced changes of the photospheric temperature structure. We find that if the magnetism of the quiet solar photosphere is mainly produced by a small-scale dynamo, then its impact on the determination of the abundances of iron, carbon, nitrogen and oxygen is negligible.

This is a sketch of a 321D approximation which is nonlocal, and thus has nonzero fluxes of KE (to be published in more detail elsewhere). We plan to add this as an option to MESA. Inclusion of KE fluxes seems to help resolve the solar abundance problem (Asplund et al.2009). Smaller cores may ease the explosion problems with core collapse supernova simulations.

I present a personal view of Wojtek Dziembowski's scientific career, derived mainly from my direct interactions with Wojtek. Necessarily this presentation is biased towards the earlier days, partly because we interacted more then, and partly because the presentation after mine is by a local admirer who has been much more involved than I with Wojtek's later work.

We investigate first ionization potential (FIP) bias levels in an anemone active region (AR) - coronal hole (CH) complex using an abundance map derived from Hinode/EIS spectra. The detailed, spatially resolved abundance map has a large field of view covering 359″ × 485″. Plasma with high FIP bias, or coronal abundances, is concentrated at the footpoints of the AR loops whereas the surrounding CH has a low FIP bias, ~1, i.e. photospheric abundances. A channel of low FIP bias is located along the AR's main polarity inversion line containing a filament where ongoing flux cancellation is observed, indicating a bald patch magnetic topology characteristic of a sigmoid/flux rope configuration.

The Sun is used as the fundamental standard in chemical abundance studies, thus it is important to know whether the solar abundance pattern is representative of the solar neighborhood. Albeit at low precision (0.05 – 0.10 dex) the Sun seems to be a typical solar-metallicity disk star, at high precision (0.01 dex) its abundance pattern seems abnormal when compared to solar twins. The Sun shows a deficiency of refractory elements that could be due to the formation of terrestrial planets. The formation of giant planets may also introduce a signature in the chemical composition of stars. We discuss both planet signatures and also the enhancement of neutron-capture elements in the solar twin 18 Sco.

We present a new determination of the solar nitrogen abundance making use of 3D hydrodynamical modelling of the solar photosphere, which is more physically motivated than traditional static 1D models. We selected suitable atomic spectral lines, relying on equivalent width measurements already existing in the literature. For atmospheric modelling we used the co5bold 3D radiation hydrodynamics code. We investigated the influence of both deviations from local thermodynamic equilibrium (non-LTE effects) and photospheric inhomogeneities (granulation effects) on the resulting abundance. We also compared several atlases of solar flux and centre-disc intensity presently available. As a result of our analysis, the photospheric solar nitrogen abundance is A(N) = 7.86 ± 0.12.

The mean abundances of Mg, Si, Ca, Ti, Cr, and Fe based on both strong and weak lines of α Cen A are determined by matching the observed line profiles with those synthesised from stellar atmospheric models and comparing these results with a similar analysis for the Sun. There is good agreement between the abundances from strong and weak lines.

Strong lines should generally be an excellent indicator of abundance and far easier to measure than the weak lines normally used. Until the development of the Anstee, Barklem, and O'Mara (ABO) theory for collisional line broadening, the uncertainty in the value of the damping constant prevented strong lines being used for abundance determinations other than in close differential analyses.

We found that α Cen A has a mean overabundance of 0.12 ± 0.06 dex compared to solar mean abundances. This result agrees remarkably well with previous studies that did not use strong lines or the ABO theory for collisional line broadening. Our result supports the conclusion that reliable abundances can be derived from strong lines provided this new theory for line broadening is used to calculate the van der Waals damping.

The observed uniform rotation of the Sun's radiative interior can be explained by the presence of a global-scale interior magnetic field, provided that the field remains confined below the convection zone. In high latitudes, such magnetic confinement is possible by means of persistent downwelling, driven by the convection zone's turbulent stresses.

In the spirit of the symposium and the theme of the session of this presentation, “Our solar system after Galileo, the grand vision,” I review briefly a relatively recently discovered phenomenon in the solar system – existence of atmospheres on certain moons, including Io, one of the four moons Galileo discovered four centuries ago. The origin of such atmospheres is discussed, and comparisons are made between various gassy moons.

Asteroseismology is a powerful tool to derive stellar parameters, including the helium content and internal helium gradients, and the macroscopic motions which can lead to lithium, beryllium, and boron abundance variations. Precise determinations of these parameters need deep analyses for each individual stars. After a general introduction on helio and asteroseismology, I first discuss the solar case, the results which have been obtained in the past two decades, and the crisis induced by the new determination of the abundances of heavy elements. Then I discuss asteroseismology in relation with light element abundances, especially for the case of main sequence stars.

In this review we discuss possible systematic errors inherent in classical 1D LTE abundance analyses of late-type stars for the light elements (here: H, He, Li, Be and B). The advent of realistic 3D hydrodynamical model atmospheres and the availability of non-LTE line formation codes place the stellar analyses on a much firmer footing and indeed drastically modify the astrophysical interpretations in many cases, especially at low metallicities. For the Teff-sensitive hydrogen lines both stellar granulation and non-LTE are likely important but the combination of the two has not yet been fully explored. A fortuitous near-cancellation of significant but opposite 3D and non-LTE effects leaves the derived 7Li abundances largely unaffected but new atomic collisional data should be taken into account. We also discuss the impact on 3D non-LTE line formation on the estimated lithium isotopic abundances in halo stars in light of recent claims that convective line asymmetries can mimic the presence of 6Li. While Be only have relatively minor non-LTE abundance corrections, B is sensitive even if the latest calculations imply smaller non-LTE effects than previously thought.

For more than 140 years the chemical composition of our Sun has been considered typical of solar-type stars. Our highly differential elemental abundance analysis of unprecedented accuracy (~0.01 dex) of the Sun relative to solar twins, shows that the Sun has a peculiar chemical composition with a ≈20% depletion of refractory elements relative to the volatile elements in comparison with solar twins. The abundance differences correlate strongly with the condensation temperatures of the elements. A similar study of solar analogs from planet surveys shows that this peculiarity also holds in comparisons with solar analogs known to have close-in giant planets while the majority of solar analogs without detected giant planets show the solar abundance pattern. The peculiarities in the solar chemical composition can be explained as signatures of the formation of terrestrial planets like our own Earth.

Study of solar oscillations has provided us detailed information about solar structure and dynamics. These in turn provide a test of theories of stellar structure and evolution as well as theories of angular momentum transfer and dynamo. Some of these results about the solar structure and its implication on the recent revision of heavy element abundances are described. Apart from these the solar cycle variations in the rotation rate and its gradients are also discussed.

The solar chemical composition has recently undergone a drastic revision, in particular in terms of the C, N, O and Ne abundances that have been lowered by almost a factor of two. In this invited review I will describe the different compounding reasons for this change (3D model atmospheres, non-LTE line formation, improved atomic/molecular data) and discuss some astrophysical implications thereof, which fall under both good (solar neighborhood) and bad (helioseismology) news. The most recent literature regarding the solar O abundance is surveyed and a critical evaluation whether or not these support the low solar abundance scale is presented. Finally I venture to make some predictions to what the real solar O abundance may be.