SOLARNET Conference: The Many Scales of the Magnetic Sun

More than 20 years ago most photospheric MHD simulations focused primarily on small patches of granulation with moderate numerical resolution. Over the past 2 decades advances in computing infrastructure have enabled photospheric MHD simulations to cover most magnetic environments from quiet Sun to active Sun. In this talk I review these recent developments and focus primarily on simulations...

The Daniel K. Inouye Solar Telescope is currently acquiring first science data as part of its Operations Commissioning Phase. High-resolution, fast-cadence imaging in the chromospheric Ca II K filter of the Visible Broadband Imager reveals signatures of bright arches emanating radially from the locations of G-band bright points. The G-band bright points denote small-scale magnetic elements...

The Fe I 6173 Å line is widely used to observe the solar photosphere by many instruments. This includes the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) and the Polarimetric and Helioseismic Imager on board the Solar Orbiter. During analysis, this line is often assumed to have formed in Local Thermodynamic Equilibrium (LTE) conditions. However, the UV...

Extreme ultraviolet (EUV) observations of the quiet sun corona have revealed extended regions of reduced emission. These coronal voids are on average around 30% less intense than the quiet Sun and can have sizes corresponding to several supergranular cells. At least the larger of these voids can exist for many hours with their boundaries to the quiet Sun remaining more or less unchanged. The...

Solar events such as flares and coronal mass ejections are the most energetic phenomena affecting interplanetary space in timescales ranging from minutes to a few days. There has been, in recent years, a strong interest in characterizing the processes that inject magnetic energy and helicity in solar active regions (ARs) and the mechanisms that destabilize their magnetic structure leading to...

This study investigates the photospheric and chromospheric flow field in active region NOAA 13096, which consists of pores, sunspots with partial penumbrae, and light bridges. The improved High-resolution Fast Imager (HiFI+) and GREGOR Infrared Spectrograph (GRIS) acquired high-resolution data at the 1.5-meter GREGOR solar telescope at Observatorio del Teide, Izaña, Tenerife, Spain. The...

We have exploited seeing-free and high-quality observations of several small magnetic pores from the High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (PHI) on board the Solar Orbiter spacecraft, during its first close perihelion in March 2022 (at a distance of 0.5 au from the Sun). Only such small magnetic pores, captured at stable observing conditions, could...

We present the results obtained from applying the Self Organizing Map technique to a spectral dataset of monochromatic images acquired by the Interferometric Bidimensional Spectropolarimeter at the Dunn Solar Telescope, along the Ca II 854.2 nm and Hα 656.28 nm lines. This technique allowed us to segment the photospheric and chromospheric penumbra fine structure, revealing the presence of the...

Solar flares sometimes lead to coronal mass ejections that directly affect the Earth's environment. However, a large fraction of flares, especially on solar-type stars, are confined flares. What are the differences in physical properties between confined and eruptive flares? For the first time, we quantify thermodynamic and magnetic properties of hundreds confined and eruptive flares of GOES...

The chromosphere is a dynamic and complex layer where all the relevant physical processes happen on very small spatio-temporal scales. A few spectral lines that can be used as chromospheric diagnostics, give us convoluted information that is hard to interpret without realistic theoretical models. What are the key ingredients that these models need to contain? In this review, we present the...

Spectropolarimetric reconstructions of the photospheric vector magnetic field are intrinsically limited by the 180-degree-ambiguity in the orientation of the transverse component. So far, the removal of such an ambiguity has required assumptions about the properties of the photospheric field, which makes disambiguation methods model-dependent.

The successful launch and operation of Solar...

Open magnetic flux in the photosphere, especially at the poles, presents an important boundary condition for modeling the heliospheric field. The field extrapolated from polar observations is roughly 50% lower than the in-situ measurements (“open flux problem”). Here we present our efforts to characterize biases in the open flux inference and that way explain the discrepancy above. We use a...

For a long time, the study of the evolution of active regions in the solar photosphere has been limited by the transit time of the active regions over the solar disk as seen from Earth. Since its launch in February 2020, ESA/NASA's Solar Orbiter spacecraft provides us, from time to time, with the possibility to see the solar far side. The Polarimetric and Helioseismic Imager (SO/PHI), one of...

While it is being conjectured that a chromospheric canopy plays a role in penumbra formation, it has been difficult to find observational evidence of the connectivity between the photosphere and the chromosphere.

We investigate the existence of a chromospheric canopy as a necessary condition for the formation of a penumbra and aim to find the origin of the inclined magnetic fields....

Fallon Konow - A New Instrument for Synoptic Space Weather Observations
Meetu Verma- Tales of Two Pores – Observed with GREGOR IFU and HiFI
José Roberto Canivete Cuissa - Vortices and Alfvénic pulses in the simulated solar atmosphere
Arooj Faryad - Automatic detection of Ellerman bombs in Halpha using COCOPLOTs
Nikolina Milanović - Thermal structuring and evolution of coronal bright...

The penumbra is an intriguing part of a sunspot where the coupling between magnetic field and plasma is characterized by peculiar physical conditions. Although it has been the focus of many observational and theoretical studies, the processes involved in the formation and decay of a sunspot penumbra are still not fully understood. I will give a brief summary of recent observations leading...

We will review the recent observational results that show the key role played by the vertical component of the magnetic field (B$_\mathrm{ver}$) in the inhibition of convection in the solar photosphere. In sunspots, only regions with B$_\mathrm{ver}$ stronger than a critical value of approximately 1.8 kG (the critical value is dependent on the data used, definition of the umbral boundary,...

Mini-filament eruptions are one of the most common small-scale transients in the solar atmosphere. They are small-scale analogs to solar filaments. They are associated with coronal jets that represent transient, collimated plasma ejections along open fields or far-reaching coronal loops. One particular type is blowout jets. These often come along with erupting loops or twisted filaments at the...

The Interferometric Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope (DST) was employed to capture high spatial resolution spectral scans of a sunspot in the H-alpha line. These scans allowed for the examination of super-penumbral fibrils, including their transverse motions both parallel and perpendicular to the line of sight. Near ubiquitous transverse oscillations of the fibrils...

A quiescent prominence was observed on October 22, 2013 quasi-simultaneously and nearly co-spatially in the Lyman series of hydrogen by SoHO/SUMER and in the Mg II h&k lines by IRIS. Such spectroscopic observations comprising multiple lines offer an excellent opportunity for diagnostics of prominence plasma and the dynamics of its fine structures. However, it also invokes significant...

Abrupt and permanent photospheric magnetic field changes have been observed in many flares. It is believed that such changes are related to the reconfiguration of magnetic field lines, however, the real origin is still unclear. I will present the analysis of 37 flares observed by the Solar Dynamics Observatory (SDO). The characteristics of the magnetic field changes in the flare events are...

The solar ultraviolet (UV) and extreme ultraviolet (EUV) radiations which are major contributors to the solar spectral irradiance (SSI) below 4000 Å, significantly affect the composition and the thermal structure of the Earth's atmosphere. The Magnesium II core-to-wing ratio (also known as the Mg II index) is one of the best proxies for solar activity and UV-SSI variability. To date, the Mg...

The solar chromosphere and corona are heated by the dissipation of magnetic energy that emerges from the photosphere. The outward flux of magnetic energy, or Poynting flux, is therefore important to understand in both qualitative and quantitative terms. It can be computed by taking a cross product of electric and magnetic fields, and in ideal MHD conditions it can be expressed in terms of...

Solar pores are associated with the concetration, dissipation, and transportation of solar magnetic fluxes. Their observable characteristics can provide important constraints to improve models and simulations of magnetic flux emergence and formation. In this work, we have investigated the horizontal movements of solar pores. The goal is to probe possible correlations of observable quantities...

Ellerman bombs (EBs) are compact (~1”) transient brightenings that occur in active regions with enhanced flux emergence. While several studies have examined individual EBs in detail, only a few have done so in large numbers due to the relative difficulty of automatically identifying these features in long time series. We present the first results of our new automated detection algorithm based...

Solar photosphere is seen as a turbulent magnetized medium at small scales. Earlier, we have developed a novel frame-work to characterize small-scale magnetic fields in the photosphere using concepts of stochastic thermodynamics and discovered applicability of the so-called fluctuation relations for evolution of these fields (Gorobets et al. 2016, 2017; Gorobets & Berdyugina 2019).
Here, we...

The non-association of coronal mass ejections with high energetic flares is sparse. For this reason, the magnetic conditions required for the confinedness of major flares is a topic of active research. Using multi-instrument observations, we investigated the evolution and effects of confinedness in an X3.1 flare, which occurred in active region (AR) 12192. The brightenings and decrease of net...

Intermediate stages between pores and sunspots are a rare phenomenon and can manifest with the formation of transient photospheric penumbral-like filaments. Although the magnetic field changes rapidly during the evolution of such filaments, they have not been shown to be connected to magnetic reconnection events yet.

We analyzed observations of a pore in NOAA AR 12739 from the Swedish...

Stellar activity is today the main limitation to detecting Earth-like planets orbiting Sun-like stars with the RV method. The effects of plages and spots strongly modified high-resolution spectra introducing RV signals difficult to model. Part of the problem is related to the absence of good activity proxies for the photospheric faculae and spots active regions.

By using the CaII H&K lines...

We report high frequency and time resolution LOFAR observations in the frequency range of 20-80 MHz, of the type III solar radio bursts which appeared on 8 April 2019. They are accompanied by different fine structures appearing in 20-40 MHz range. We have prepared dynamic spectra produced with the use of LOFAR Solar Imaging Pipeline, and classified the observed phenomena to several generally...

Bald patch (BP) is a magnetic topological feature where U-shaped field lines graze the photosphere. Previous studies often found them in emerging solar active regions (ARs) with patchy flux distribution, or decaying ARs with weaker fields. Here we study the evolution of kilogauss BPs in the delta-penumbral light bridge in AR 12673. The gradual formation spanned ~16 hours, which was accompanied...

The chromosphere is one of the least understood layers of the solar atmosphere, being dominated by ubiquitous, very dynamic fine structures. We here report on high-resolution, 3D, MURaM simulations of the coupling between the solar convection zone, photosphere, chromosphere and corona. These simulations reveal the generation of finely-structured chromospheric features. The features involve...

It has been known for a long time that bright heads of penumbral filaments, penumbral grains (PGs), are moving. Their movements are oriented toward the umbra (inwards) in the inner penumbra and away from the umbra (outwards) in the outer penumbra. The inward motion was first explained by Schlichenmaier et al. (1998, A&A 337, 897) as an apparent motion of the intersection of a rising flux tube...

Chromospheric emission observed using the Ca II K and H resonance lines is generally well correlated with photospheric magnetic fields. However, a fraction of the stronger chromospheric emission is found to originate over regions of low magnetic flux densities in the photosphere. Here we present the results from our recent study which aims at understanding the physical mechanisms responsible...

The Bipolar Magnetic Regions (BMRs) are the strong magnetic feature, consisting of two magnetic polarities separated by a neutral line, observed on the surface of the Sun. They are found to be tilted with the equatorial line, which statistically increases with their latitudes, this is popularly known as Joy’s Law. The thin flux tube model suggests that the magnetic field concentrated in flux...

The Solar Orbiter mission entered its nominal phase at the end of 2021. With ten instruments on board, it will provide a wealth of new data and results in the coming years. For the high-resolution imaging instruments, an accurate knowledge of the pointing direction and its stability, both on short and long time scales, is of crucial importance. We will show measurements of pointing stability...

Coronal Holes (CHs) are regions of the solar atmosphere characterized by “open” magnetic fields from which high-velocity solar fluxes can freely emerge. Photospheric magnetic fields associated with CHs are typically characterized by an imbalance in polarity. The origin of this imbalance and the spatial scales at which this imbalance appears are still debated.
In our work we used the technique...

High-resolution solar observations revealed the existence of small-scale swirling vortices in chromospheric intensity maps and velocity diagnostics. Frequently, vortices have been observed near magnetic flux concentrations, indicating a link between swirls and the evolution of the small-scale magnetic fields. Vortices were also studied with MHD numerical simulations of the solar atmosphere,...

A widely accepted explanation for the origin of the ubiquitous small-scale magnetic field observed on the solar surface is the presence of a small-scale dynamo (SSD) operating in the sub-surface layers of the Sun. To shed light on the functioning of this SSD, a number of numerical studies of a realistic solar atmosphere have been carried out in the past two decades, greatly improving our...

In November 2021, Solar Orbiter started its nominal mission phase. The remote sensing instruments, onboard the spacecraft, acquired scientific data during three observing windows surrounding the perihelion of the first orbit of this phase. The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI) onboard the Solar Orbiter acquired a high-cadence dataset of an...

Solar pores are penumbra-lacking magnetic features that mark two important transitions in the spectrum of magnetohydrodynamic processes: (1) the magnetic field becomes sufficiently strong to suppress the convective energy transport and (2) at some critical point some pores develop a penumbra and become sunspots. Pores are rarely encountered in quiet-Sun images (Verma & Denker 2014, Astron....

Observations of the quiet solar photosphere and chromosphere have revealed the ubiquitous presence of small-scale vortical motions. These features are tightly coupled to the surface magnetic field and extend in the vertical direction, potentially providing a channel for the transport of energy into the upper layers of the solar atmosphere.
We study the dynamics and statistical properties of...