Dr Suzana de Souza e Almeida Silva, 


Dr Juie Shetye 
Zooming into the solar chromosphereThe solar chromosphere serves as a bridging layer between the photosphere and the corona. This dynamic layer is filled with a plethora of features that vary in time and space. With the advent of highresolution groundbased observations we can discover new features. We use some of the World’s biggest solar telescopes to zoom into this layer and it reveals never seen before dynamics. Here I present detailed observations of two science topics that are guided by observations. I show a statistical study of spicules, which are longthin grasslike features observed on the sun. These events wigglejiggle and sway around their axes or along a common centre of mass to create wavelike motions on the Sun. These waves can travel with speeds on 100s of km per second to energise the solar chromosphere. The second example I show are swirlingwhirling events, that look like Tornadoes on the Earth. These churn the matter from the Lowe photosphere to the chromosphere. Studying the behaviour of such events is vital in understanding a decade long question in the solar physics, that tells us how the Sun’s atmosphere is heated. In addition, the current work presented already tests the limits of current telescopes in terms of the temporal and spatial resolution. The answer to exploring the depth of chromosphere lies in building nextgeneration solar physics observatories such as DKIST that have 3 times more spatial resolution than CRISP and much higher temporal resolution. 

Dr Iulia Chifu 
3D solar coronal loop reconstructions with machine learningThe magnetic field plays an essential role in the initiation and evolution of different solar phenomena in the corona. The structure and evolution of the 3D coronal magnetic field are still not very well known. A way to ascertain the 3D structure of the coronal magnetic field is by performing magnetic field extrapolations from the photosphere to the corona. In previous work, it was shown that by prescribing the 3Dreconstructed loops’ geometry, the magnetic field extrapolation produces a solution with a better agreement between the modeled field and the reconstructed loops. This also improves the quality of the field extrapolation. Stereoscopy, which uses at least two view directions, is the traditional method for performing 3D coronal loop reconstruction. When only one vantage point of the coronal loops is available, other 3D reconstruction methods must be applied. Within this work, we present a method for the 3D loop reconstruction based on machine learning. Our purpose for developing this method is to use as many observed coronal loops in space and time for the modeling of the coronal magnetic field. Our results show that we can build machinelearning models that can retrieve 3D loops based only on their projection information. Ultimately, the neural network model will be able to use only 2D information of the coronal loops, identified, traced, and extracted from the extremeultraviolet images, for the calculation of their 3D geometry. 

Dr Kostas Tziotziou 
Detection of smallscale chromospheric vortices and their intricate dynamicsSmallscale vortex motions are detected at various spatial and temporal scales in the solar atmosphere, from the photosphere to the low corona. They often exhibit complex structure and dynamics and, as largely magnetic structures, can foster a variety of oscillations and wave modes. Despite, however, recent advancements in observational and theoretical studies, as well as in simulations and modelling, their proper detection, especially in chromospheric lines such as Hα and Ca II 8542 Å is still an open issue, and their structure and dynamics remain poorly understood. We present a novel automated method of chromospheric swirl detection based on their morphological characteristics that nicely complements previous LCTrelated approaches. We further discuss in detail the intricate dynamics of a persistent smallscale vortex flow with significant substructure, observed with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish Solar Telescope (SST), as well as oscillations and observational signatures of different types of waves within it and their propagation characteristics. Both discussed aspects, better detection leading to a more precise estimation of their occurrence rate and wave identification and their properties, are key elements for accurately assessing the role of vortex structures in the energy budget of the solar atmosphere. 

Dr Érico Rempel 
Dynamical Systems Approach to Solar Physics: From Lyapunov Exponents to Lagrangian Coherent StructuresDynamical systems, or chaos theory, has enjoyed huge success in the analysis of systems described by ordinary differential equations, such as nonlinear oscillators, chemical reactions, electronic devices, population dynamics, etc. Usually, in the dynamical systems approach, one is concerned with the identification of the basic building blocks of the system under investigation and how they interact with each other to produce the observable dynamics, as well as how they can be manipulated to produce a desired output, in the cases where control is pursued. Examples of those building blocks are unstable equilibrium and periodic solutions, nonattracting chaotic sets and their manifolds, which are special surfaces in the phase space that basically control the dynamics, guiding solutions in preferred directions. Despite its success in those areas, many still think that the theory has limited value when applied to fully developed turbulence, like observed in solar convection, due to the infinite dimension of the phase space. In this talk, we show that this difficulty can be overcome by adopting a Lagrangian reference frame, where the phase space for each fluid particle becomes threedimensional and the building blocks of the turbulence can be efficiently extracted by appropriate numerical tools. We reveal how finitetime Lyapunov exponents, a traditional measure of chaos, can be used to detect attracting and repelling timedependent manifolds that divide the fluid in regions with different behavior. These manifolds are shown to accurately mark the boundaries of granules in observational data from the photosfere. In addition, stagnation points and vortices detected as elliptical Lagrangian coherent structures complete the set of building blocks of the photospheric turbulence. Such structures are crucial for the trapping and transport of mass and energy in the solar plasma. 

Dr Mijie Shi 
Coronal loop model heated by transverse waves against radiative lossesIn the quest to solve the longstanding coronal heating problem, it has been suggested that coronal loops could be heated by waves. Despite the accumulating observational evidence of the possible importance of coronal waves, still very few 3D MHD simulations exist that show significant heating by MHD waves. In this seminar, I will present our recent 3D coronal loop model heated by transverse waves against radiative cooling. The coronal loop is driven at the footpoint by transverse oscillations and subsequently the induced KelvinHelmholtz instability deforms the loop crosssection to a fully turbulent state. Wave energy is transferred to smaller scales where it is dissipated, overcoming the internal energy losses by radiation. These results open up a new avenue to address the coronal heating problem. 

Dr Richard Morton 
A new seismology of the coronaThe Coronal Multichannel Polarimeter (CoMP) instrument has proved itself invaluable for the study of propagating kink waves in the corona. After making the initial discovery back in 2007, CoMP has been able to provide a number of insights into the properties of the kink waves. The kink mode is found to be present throughout the corona and appears to be continuous. The widespread and reliable presence means that the propagating kink mode can make a fantastic tool for magnetoseismology. While CoMP shows a persistent Doppler velocity signal related to the propagating kink mode, the continuous transverse motions of the coronal structures can also be detected with Solar Dynamics Observatory (SDO/AIA). However the scale of the displacements are at the edge of the SDO's capabilities, requiring careful measurements to be able to study them and exploit them for seismology. In this talk I discuss the new possibilities for coronal seismology using the propagating kink mode, demonstrating how we’ve used both CoMP and SDO/AIA to measure the young solar wind, the density structure in a coronal hole and provide the first estimates for the global coronal magnetic field. 

Dr Petr Heinzel 
Partial ionization of hydrogen plasma in the solar atmosphere  a nonLTE modeler's viewBased on our extensive experience with the nonLTE radiativetransfer modeling of different atmospheric structures (chromosphere, flares, prominences, CMEcores), I will demonstrate the importance of partial hydrogen ionization and review the most relevant atomic processes. I will also discuss the role of nonequilibrium ionization of hydrogen. 

Prof Francisco Guzman 
A code that solves the equations of MHD coupled to radiationOur code is based on a finite volume discretization, uses highresolution shockcapturing flux formulae of the HLL class. Concerning the MHD part, we use the divergence cleaning method to preserve the nonmonopoles constraint. For radiation, at the moment, we use the M1 closure relation within the gray body approximation. The evolution equations for radiation become stiff for high opacities, for which we use an implicitexplicit evolution method, which allows the use of a standard integration timestep. We present our code's status and mention the solar physics scenarios where we expect to produce some applications. 

Dr Inigo Arregui 
Bayesian coronal seismologyCoronal seismology is based on the remote diagnostics of physical conditions in the solar corona by comparison between model predictions and observations of wave activity. Our lack of direct access to the physical system of interest makes information incomplete and uncertain so our conclusions are at best probabilities. Bayesian inference is increasingly being employed in the area, following a general trend in solar and astrophysical research. In this seminar, I first justify the use of a Bayesian probabilistic approach to seismology diagnostics and explain its philosophy and methodology. Then, I report on recent results that demonstrate its feasibility and advantage in applications to coronal loops, prominences and extended regions of the corona. To finish, I suggest other areas of current interest where the use of Bayesian methods could contribute to improve our understanding on the structure, dynamics and heating of the corona. 

Prof George Haller 
Objective material barriers to the transport of momentum and vorticityI discuss a recent theory for material surfaces that maximally inhibit the diffusive transport of a dynamically active (i.e., velocitydependent) vector field, such as the linear momentum, the angular momentum or the vorticity, in threedimensional unsteady flows. These diffusion barriers provide physicsbased, observerindependent boundaries of dynamically active coherent structures. Instantaneous limits of these Lagrangian diffusion barriers mark objective Eulerian barriers to shortterm active transport. I show how active diffusion barriers can be identified with active versions of Lagrangian coherent structure (LCS) diagnostics. In comparison to their passive counterparts, however, active LCS diagnostics require no significant fluid particle separation and hence provide substantially higherresolved Lagrangian and Eulerian coherent structure boundaries from shorter velocity data sets. I illustrate these results on twodimensional turbulence and threedimensional wallbounded turbulence. 

Dr Rekha Jain 
Frequency power spectra of Alfvén waves in a solar coronal arcade: Discrete or Continuous?In this talk I will present theoretically computed frequency power spectra for shear Alfvén waves excited in a solar coronal arcade. I investigate two separate perturbations, a cosinemodulated Gaussian perturbation and an impulsive driver. The arcade is assumed to consist of potential magnetic field lines embedded in stratified plasma. In principle, the nature of the frequency power spectra can constrain the size and the type of driver. 

Dr Isabell Piantschitsch 
A new method for estimating global coronal wave properties from their interaction with solar coronal holesGlobal coronal waves (CWs) and their interaction with coronal holes (CHs) result, among other effects, in the formation of reflected and transmitted waves. Observations of such events provide us with measurements of different CW parameters, such as phase speed and intensity amplitudes. However, several of these parameters are provided with only intermediate observational quality, other parameters, such as the phase speed of transmitted waves, can hardly be observed in general. We present a new method to estimate crucial CW parameters, such as density and phase speed of reflected as well as transmitted waves, Mach numbers and density values of the CH's interior, by using analytical expressions in combination with basic and most accessible observational measurements. The transmission and reflection coefficients are derived from linear theory and subsequently used to calculate estimations for phase speeds of incoming, reflected and transmitted waves. The obtained analytical expressions are validated by performing numerical simulations of CWs interacting with CHs. This new method enables to determine in a fast and straightforward way reliable CW and CH parameters from basic observational measurements which provides a powerful tool to better understand the observed interaction effects between CWs and CHs. 

Dr Jonathan Higham 
Modal Decompositions: What are they, why should we use them and how?The dynamics of natural systems are often complex and highly nonlinear, understanding these procedures is difficult as their dynamics and complexities are usually intertwined and colluded. Whilst we might be able to identify these systems using sets of nonlinear equations, determining the individual process is underlying a complex mechanism are nontrivial. Over the past few decades, there has been much work to develop data driven methods to extract coherent features either in space or in time. Two prominent methods are the proper orthogonal decomposition and the dynamic mode decomposition; in this seminar these two methods will be introduced, the underpinning mathematics and algorithms will be outlined, and variants of the algorithms and methods will also be described. However, much of the seminar will focus on applying these methods, using them at all different scales from idealised smallscale laboratory experiments to largescale realworld applications. The primary aim of this seminar will be to equip you with an arsenal of spatially and temporally orthogonal tools which you can use to elucidate the complex features from your data sets. 

Dr Nitin Yadav 
Vortex Flows in the Solar AtmosphereVortex flows exist over various spatial and temporal scales throughout the solar atmosphere and are of great importance due to their potential in twisting the magnetic field lines and hence facilitating Poynting flux transport. Recent advances in both, observational techniques and numerical simulations, have enabled us to detect a multitude of smallscale vortices in the solar atmosphere. Smaller vortices are suggested to play an important role in the solar atmospheric heating, however, their physical properties remain poorly understood due to limited resolution in observations. Hence, it is crucial to investigate them using highresolution simulations since they are more abundant and faster rotating flows than the larger vortices. Using MHD simulations, we explored the the relationship between vortex flows at different spatial scales, analyze their physical properties, and investigate their contribution to Poynting flux transport from the lower to the upper layers of the solar atmosphere. We found that a large vortex, as seen at low spatial resolution, consists of a large number of smaller vortices, when seen at high spatial resolution. Statistically, they have higher densities and higher temperatures than the average values at the same geometrical height. Their Poynting flux contribution is more than adequate to compensate for the radiative losses in the chromosphere indicating their possible role in the solar atmospheric heating. 

Dr Matheus AguiarKriginsky Silva 
Ubiquituous hundredGauss magnetic fields in solar spiculesEven though they were observed for the first time in the 19th century, the nature of spicules is not well understood because they are are thin and elongated chromospheric jets and therefore their study is limited to the resolution of the instruments used. Every time a step forward in the quality of the observations of the lower chromosphere is taken, the interest in spicules sparks. Most recently, the advent of the Hinode telescope provided highresolution images of spicules that allowed for a better comprehension of their nature and behavior. Studies regarding their magnetic field have been also undertaken, but most of them did not have the ideal spatial/temporal resolution needed to give definitive results. This study is aimed to provide a step forward in this matter, with observations in the Ca II 854.2 nm line taken with the CRISP instrument at the Swedish 1meter Solar Telescope in La Palma. The sensitivity of the Ca II 854.2 nm line to the magnetic field is exploited and the Weak Field Approximation (WFA) is used to estimate the lineofsight component of the magnetic field of spicules both offlimb and on the solar disk. The WFA must be used carefully, since there are conditions that need to be met for it to be applicable. This consideration is assessed in every pixel, and a Bayesian approach is taken to infer the lineofsight magnetic field component from the WFA equations. It is established that magnetic fields over 100 G are abundant, and the reason for the failure of previous studies to conclude this is carefully studied and is speculated to lie in the poor temporal/spatial resolution of the observations used. 

Dr Suzana de Souza e Almeida Silva04.06.2020 at 16:00 via Google Hangouts Meet 
Dynamics of the Vortex Tubes in the Solar AtmosphereWe use a state of the art vortex detection method, Instantaneous Vorticity Deviation, to define and locate threedimensional vortices in magnetoconvections simulations performed by the MURaM code. The detected vortices extend from the photosphere to the low chromosphere. The dynamics across the vortical flows at different height levels are investigated through radial profiles. We found that the vortices present similar dynamics at all height levels, with nonuniform angular rotational velocity and eddy viscosity effects. The vortices intensify the magnetic field, and in turn, the vortex dynamics are affected by the magnetic field. On the other hand, our findings hint that kinematic vortices need to present high tangential velocities at different height levels to overcome the magnetic tension and generate magnetic vortices. 

Dr José Juan González Avilés21.05.2020 at 16:00 via Google Hangouts Meet 
Numerical studies of jet formation in the solar atmosphereUsing the Newtonian CAFE MHD code to perform 2.5D and 3D resistive MHD
simulations in the solar atmosphere, we show that magnetic reconnection may
be responsible for the formation of jets with some characteristics of Type II
spicules and cool coronal jets. We numerically model the photospherecorona region
using the C7 atmosphere model. The initial magnetic configuration in the 2.5D case
consists of two symmetric neighboring loops with opposite polarity, used to support
reconnection. In the 3D case, the initial magnetic configuration is extrapolated up to
the solar corona region from a dynamic realistic simulation of the solar photospheric
magnetoconvection model that mimics the quietSun.


Dr Rahul Sharma07.05.2020 at 16:00 via Google Hangouts Meet 
Complex 3D dynamics of solar spicule structuresSun’s outer atmosphere is a million degree hotter than it’s visible surface, which is not understood with any of the known laws of thermodynamics and remains an intriguing problem for the astrophysics in general. It is now believed that most of the energy dissipation phenomenon occurs at the interface region in between solar chromosphere and corona, which is a highly dynamic, gravitationally stratified, nonlinear, inhomogeneous environment. Observed dynamics of thin magnetic fluxtube structures in this layer, reflects the confined magnetohydrodynamic (MHD) wavemodes (kink, sausage and torsional Alfven). For the first time, the evolution of the resultant transverse displacement of the observed flux tube structures, estimated from perpendicular velocity components, is analyzed along with crosssectional width, photometric and azimuthal shear/torsion variations, to accurately identify the confined wavemode(s). In my talk, I will discuss the observational evidence of pulselike nonlinear kink wavemode(s), as indicated by the strong coupling in between kinematic observables, with a frequencydoubling, tripling aspect, supported by mutual phase relations centered around 0 and +180 (Sharma et al. 2018). The 3D ensemble of the observed dynamic components revealed complexities pertinent to the accurate identification and interpretation of e.g. linear/nonlinear, coupled/uncoupled MHD wavemodes in the observed waveguides (spicules). 

Mr Abdulaziz Alharbi23.04.2020 at 16:00 via Google Hangouts Meet 
Waves in TwoFluid Gravitationally Stratified PlasmasThe temperature in the lower part of solar atmosphere is not high enough for a complete ionisation of the plasma. Therefore, this environment region is made up of electrons, positive ions and neutrals that interact through short and long range collisions in the presence of the magnetic field. Due to the low temperature, the gravitational scaleheight is also short, meaning that perturbations will be affected by gravity. Here we study the spatial and temporal evolution of slow magnetoacoustics waves propagating in a stratified magnetic flux tube. In the twofluid plasma the dynamics of neutrals and charged species has to be studied separately. Our analysis shows that the dynamic is described by a system of coupled KleinGordon equations that are solved in the strongly ionised limit. For the mentioned two species we study the changes in the cutoff frequency for a range of physical parameters. Asymptotic solutions to the governing equations are obtained for a harmonic driver. Our results reveal that ionacoustic and neutralsacoustic slow modes show a different damping scale. 

Mr Yasir Aljohani09.04.2020 at 16:00 via Google Hangouts Meet 
Identifying magnetohydrodynamic vortex tubes in the Sun's photosphereVortex flows in the solar photosphere are fundamentally important for the generation of magnetohydrodynamic (MHD) waves which propagate to the upper layers of the solar atmosphere. Vortex tubes are formed as coherent magnetic field structures in the solar atmosphere, e.g. twisted magnetic flux tubes. In this presentation, I will discuss the method of Lagrangian Averaged Vorticity Deviation (LAVD) developed by Haller (2016) to identify vortex flows, namely the center of circulation and their boundary, then I will present the algorithmic technique I have developed to check whether a structure detected by the LAVD method is a true vortex or not and how to determine the rotational direction(clockwise or anticlockwise). In addition, I will apply these methods to MURaM magnetoconvection simulation data to detect and track the evolution of both 2D vortices and 3D vortex tubes in the solar photosphere. 

Mr Abdulrahman Albidah26.03.2020 at 16:00 via Google Hangouts Meet 
Multifaceted approach to decomposing and identifying individual magnetohydrodynamic (MHD) wave modes in sunspots and poresHigh resolution observations of pores and sunspots show a rich and complex variety of oscillatory temporal and spatial behaviour. To decompose this data into individual magnetohydrodynamic (MHD) wave modes is nontrivial and requires a multifaceted approach. Here we take a threepronged approach of combining Fourier analysis, Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD). The Fourier omegak power spectrum provides us with a useful overall view of the particular temporal and spatial scales of interest but does not provide any crosspixel correlation. In this regard, POD classifies modes that are orthogonal in space but places no restrictions on their frequencies. DMD has no such restrictions in space but classifies modes that are orthogonal in time, i.e., identified modes cannot have the same frequency. Each of these complementary techniques have their particular strengths which we will illustrate with synthetic data. 

Dr Viktor Fedun12.03.2020 at 16:00 in F28 (Hicks Building) 
Vortex motions in the solar atmosphereSolar photosphere vortices have the potential to form coherent magnetic field structures, e.g. twisted magnetic flux tubes and, therefore, may play a key role in the transport of energy and momentum from the lower atmosphere into the upper solar atmosphere. In this talk I will review existing methods for their identification and discuss our approach, which is based on Gamma detection and LAVD of intergranular photospheric intensity vortices. I will also present new mechanism for the generation of magnetic waveguide from the lower solar atmosphere to the corona. This waveguide appears as the result of interacting perturbations (initially generated by photospheric vortex motions) in neighbouring magnetic flux tubes (modelled in the framework of selfsimilar approach). 

Dr Ben Snow06.03.2020 at 16:00 in F28 (Hicks Building) 
Mode conversion of twofluid shocks in a partiallyionised, isothermal, stratified atmosphereThe plasma of the lower solar atmosphere consists of mostly neutral particles, whereas the upper solar atmosphere is mostly ionised particles and electrons. A shock that propagates upwards in the solar atmosphere therefore undergoes a transition where the dominant fluid is either neutral or ionised. An upwards propagating shock also passes a point where the sound and Alfven speed are equal. At this point the energy of the acoustic shock can separated into fast and slow components. How the energy is distributed between the two modes depends on the angle of magnetic field. Twofluid numerical simulations are performed of a wave steepening into a shock in an isothermal, partiallyionised atmosphere. The collisional coefficient is varied to investigate the regimes where the plasma and neutral species are weakly, strongly and finitely coupled. The propagation speeds of the compressional waves hosted by neutral and ionised species vary, therefore velocity drift between the two species is produced as the plasma attempts to propagate faster than the neutrals. This is most extreme for a fastmode shock. We find that the collisional coefficient drastically changes the features present in the system, specifically the mode conversion height, type of shocks present, and the shock widths. In the finitelycoupled regime fastmode shock widths can exceed the pressure scale height leading to a new potential observable of twofluid effects in the lower solar atmosphere. 

Dr Sandra Milena Conde Cuellar27.02.2020 at 16:00 in F28 (Hicks Building) 
Oscillation of coronal loops associated with flaring eventsLoops are fascinating structures that bring us a lot of information about the exchange of energy in the solar atmosphere. Oscillations and waves represent one of the most fascinating events in the loops, which also plays a key role in the study of coronal seismology. It is not clear how the disturbances are excited, however, there are several candidates, e.g., flares, emerging flux, and eruptions. In this talk, I present a summary of oscillations observed in different active regions in the presence of flares and other events. This analysis has been done with data provided by IRIS, SDO and GOES15 spacecraft. We have found excitation sources of some disturbances in lower heights of the solar atmosphere. This matches with oscillations found in the top and the footpoints of the coronal loops. We used this information together with semiempirical models to study the distribution of physical variables in the loops. 

Dr Shahin Jafarzadeh13.02.2020 at 16:00 in F28 (Hicks Building) 
Magnetoacoustic Waves in the Lower Solar Atmosphere at High ResolutionFibrillar structures of different appearances and/or properties have ubiquitously been observed throughout the Sun's chromosphere. They are often thought to map the magnetic fields, and are likely rooted in smallscale magnetic elements in the solar photosphere. Here, we present properties of magnetohydrodynamicwave dynamics in various fibrillar structures as well as in small magnetic elements in the low solar atmosphere, at highspatial resolution, from the SUNRISE balloonborne observatory as well as the Swedish Solar Telescope. Our analysis reveals the prevalence of kink and sausage waves in both types of magnetic structures, propagating at similar high frequencies. The estimated energy flux carried by the observed waves is marginally enough to heat the chromosphere (and perhaps the corona). Furthermore, such waves are compared with temperature fluctuations in the fibrils from hightemporal resolution observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS) explorer, simultaneously observed at several millimetre and ultraviolet bands of, e.g., ALMA 1.3 mm as well as IRIS Mg II h & k, Si IV, and C II spectral lines, from which, physical properties of the fibrillar structures are also discussed. 

Dr Tom Van Doorsselaere05.12.2019 at 16:00 in F28 (Hicks Building) 
Waves and seismology of poresIn this seminar, I will discuss several aspects of waves in pores. These concentrations of magnetic field similar to miniature sunspots are wave guides for MHD waves. In contrast to waves in coronal loops, they are resolved across the wave guide, but it is harder to know what happens further along the magnetic field. I will discuss mode identification by using wave amplitude ratios, calculation of their energy fluxes as could be used for coronal heating, and resonant absorption of slow waves. An outlook to future work is also included. 

Mr Farhad Allian21.11.2019 at 16:00 in F28 (Hicks Building) 
A New Analysis Procedure for Detecting Periodicities within Complex Solar Coronal ArcadesCoronal loop arcades form the building blocks of the hot and dynamic solar atmosphere. In particular, their oscillations serve as an indispensable tool in estimating the physical properties of the local environment by means of seismology. However, due to the nature of the arcade's complexity, these oscillations can be difficult to analyze. In this talk, I will present a novel imageanalysis procedure based on the spatiotemporal autocorrelation function that can be utilized to reveal 'hidden' periodicities within EUV imagery of complex coronal loop systems. 

Dr Norbert Magyar07.11.2019 at 16:00 in F28 (Hicks Building) 
Simulations of MHD waves in structured plasmasIt is well known that in an infinite and homogeneous plasma, there are three types of waves: fast, slow, and Alfven. However, richer dynamics appear in MHD once inhomogeneities are considered.The solar corona and solar wind is often seen to be highly structured, most probably even way below the current resolving capabilities of imaging instruments. The structuring of the plasma gives rise to some wellknown phenomena such as surface and body modes, reflection/refraction of waves, phase mixing, resonant absorption and so on. The nonlinear implications of structuring are less wellknown, though. In a series of numerical simulations, we will review the basic dynamics of waves supported by structures, and will connect these findings to the generation of turbulence in a structured plasma. 

Mr Yuyang Yuan24.10.2019 at 16:00 in F28 (Hicks Building) 
The Solar Spicule Tracking CodeIn this talk I will explain and demonstrate the Solar Spicule Tracking Code (SSTC) that I have developed. This code has the ability to automatically detect and track the motion spicules in imaging data. I will specifically demonstrate the code working with images obtained using the H alpha line from the CRisp Imaging SpectroPolarimeter (CRISP) based at the Swedish Solar Telescope. 

Ms Anwar Aldhafeeri10.10.2019 at 16:00 in F28 (Hicks Building) 
Solar atmospheric magnetohydrodynamic wave modes in magnetic flux tubes of elliptical crosssectional shapeThe approach to understanding and analysing the behaviour of MHD we observed in the solar atmosphere is to find a relevant wave solution for the MHD equations. Therefore many previous studies focused on deriving a dispersion relation equation and solving this equation for a cylindrical tube. We know perfectly well that sunspots and pores do not have an ideal circular crosssection. Therefore, any imbalance in waveguide’s diameters, even if very small, will move the study of the problem from the cylindrical coordinates to elliptical coordinates. Thus the emphasis on knowing the properties and what type of wave modes exist in elliptical waveguides are much more critical than studying them in cylindrical coordinates. In this talk, I will start by deriving the dispersion relation in a compressible flux tube with elliptical crosssectional shape. I will then solve the dispersion equation and discuss the solution of dispersion equation and how the ellipticity of tube effects the solutions with applications to coronal and photospheric conditions. However, the information we get from the dispersion diagram does not give the full picture of how we can observe a wave, and how much the wave mode changes when the crosssectional shape of waveguide changes. Therefore I will present some visualisations of eigenfunctions of MHD wave modes and explain how the eccentricity effects each MHD wave mode. 

Dr Dave Jess30.05.2019 at 14:00 in LT10 (Hicks Building) 
Resonance Cavities: A wave amplification mechanism above highly magnetic sunspotsThe solar atmosphere provides a unique astrophysical laboratory to study the formation, propagation, and subsequent dissipation of magnetohydrodynamic (MHD) waves across a diverse range of spatial scales. The concentrated magnetic fields synonymous with sunspots allow the examination of guided magnetoacoustic modes as they propagate upwards into the solar corona, where they exist as ubiquitous 3minute waves readily observed along loops, plumes and fan structures. While cuttingedge observations and simulations are providing insights into the underlying wave generation and damping mechanisms, the insitu amplification of magnetoacoustic waves as they propagate through the solar chromosphere has proved difficult to explain. Here we provide observational evidence of a resonance cavity existing above a magnetic sunspot, where the intrinsic temperature stratification provides the necessary atmospheric boundaries responsible for the resonant amplification of these waves. Through comparisons with highresolution numerical MHD simulations, the geometry of the resonance cavity is mapped across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1300–2300 km. This brings forth important implications for nextgeneration groundbased observing facilities, and provides an unprecedented insight into the MHD wave modelling requirements for laboratory and astrophysical plasmas. 

Dr Peter Wyper16.05.2019 at 16:00 Room K14 (Hicks Building) 
Reconnection, Topology and Solar EruptionsThe majority of free energy in the solar corona is stored within sheared magnetic field structures known as filament channels. Filament channels spend most of their life in force balance before violently erupting. The largest produce powerful solar flares and coronal mass ejections (CMEs), whereby the filament channel is bodily ejected from the Sun. However, a whole range of smaller eruptions and flares also occur throughout the corona. Some are ejective, whilst others are confined. Recently it has been established that coronal jets are also typically the result of a filament channel eruption. The filament channels involved in jets are orders of magnitude smaller than the ones which produce CMEs. In this talk I will start by considering these tiny, jet producing eruptions. I will introduce our MHD simulation model that well describes them and then discuss what jets can tell us about solar eruptions in general. Specifically, I will argue that many different types of eruption can be understood by considering two defining features: the scale of the filament channel and its interaction via reconnection with its surrounding magnetic topology. 

Dr Suzana de Souza e Almeida Silva13.05.2019 at 13:00 Room LT9 (Hicks Building) 
Lagrangian Coherent Structures: Overview and applications in solar physicsLagrangian coherent structures (LCS) is a newly developed theory which describes the skeleton of turbulent flows. LCS act as barriers in the flow, separating regions with different dynamics and organizing the flow into coherent patterns. This talk will introduce some concepts of LCT techniques as well as recent application to solar physics problems. 

Dr Youra Taroyan02.05.2019 at 16:00 Room K14 (Hicks Building) 
Amplification of magnetic twists during prominence formationSolar prominences are dense magnetic structures that are anchored to the visible surface known as the photosphere. They extend outwards into the Sun’s upper atmosphere known as the corona. Twists in prominence field lines are believed to play an important role in supporting the dense plasma against gravity as well as in prominence eruptions and coronal mass ejections (CMEs), which may have severe impact on the Earth and its near environment. We will use a simple model to mimic the formation of a prominence thread by plasma condensation. The process of coupling between the inflows and the twists will be discussed. We show that arbitrarily small magnetic twists should be amplified in time during the mass accumulation process. The growth rate of the twists is proportional to the mass condensation rate. 

Prof Philippa Browning18.04.2019 at 16:00 Room K14 (Hicks Building) 
Plasma heating and particle acceleration by magnetic reconnection in solar and stellar flaresIn this talk, I will describe recent models of plasma heating and nonthermal particle acceleration in flares, focussing on the role of twisted magnetic flux ropes as reservoirs of free magnetic energy. First, using 2D magnetohydrodynamic simulations coupled with a guidingcentre testparticle code, I will describe magnetic reconnection and particle acceleration in a largescale flaring current sheet, triggered by an external perturbation – the “forced reconnection” scenario. I will show how reconnection is involved both in creating twisted flux ropes, and in their merger, how this depends on the nature of the driving disturbance, and how particles are accelerated by the different modes of reconnection. Moving to 3D models, showing how fragmented current structures in kinkunstable twisted loops can both heat plasma and accelerate charged particles. Forward modelling of the observational signatures of this process in EUV, hard Xrays and microwaves will be described, and the potential for observational identification of twisted magnetic fields in the solar corona discussed. Then, coronal structure with multiple twisted threads will be considered, showing how instability in a single unstable twisted thread may trigger reconnection with stable neighbours, releasing their stored energy and causing an "avalanche" of heating events, with important implications for solar coronal heating. This avalanche can also accelerate electrons and ions throughout the structure. Many other stars exhibit flares, and I will briefly discuss recent work on modelling radio emission in flares in young stars (T Tauri stars). In particular, the enhanced radio luminosity of these stars relative to scaling laws for the Sun and other Main Sequence stars will be discussed. 

Dr Peter Keys21.03.2019 
Smallscale magnetic field evolution with high resolution observationsSmallscale magnetic fields, ubiquitous across the solar surface, manifest as intensity
enhancements in intergranular lanes and, thus, often receive the moniker of magnetic bright
point (MBP). MBPs are frequently studied as they are considered as a fundamental building block
of magnetism in the solar atmosphere. The theory of convective collapse developed in the late
70’s and early 80’s is often used to explain how kilogauss fields form in MBPs. The dynamic
nature of MBPs coupled with these kilogauss fields means that they are frequently posited as a
source of wave phenomena in the solar atmosphere.


Dr Patrick Antolin07.03.2019 
Transverse MHD Waves and associated dynamic instabilities in the solar atmosphereA large amount of recent simulations and analytical work indicate that standing transverse MHD waves in loops should easily lead to the generation of dynamic instabilities at their edges, and in particular of the KelvinHelmholtz kind. While a direct observation of these transverse waveinduced KelvinHelmholtz rolls (or TWIH rolls) is still lacking, the forward modelling of these simulations give us an indication of what to look for in next generation instrumentation, and which currently observed features could actually be the result of TWIKH rolls. In this talk I will go through some of these results, comparing observations with various instruments with simulations of coronal loops, prominences and spicules. 

Dr. Mark Wrigley28.02.2019 
1201 Alarm ProjectThe 1201 Alarm Project is the restoration, exhibition and sharing of materials recorded in 1969 of the Apollo moon landings from a domestic television. The talk will review the Apollo flight plan, the recording technologies of the day and the impact that it had on the speaker. The materials will form the basis for an exhibition celebrating the 50th anniversary of moon landings to be held at the National Science and Media Museum in Bradford, Yorkshire.


Prof. Valery Nakariakov31.01.2019 venue LT1, Hicks Building 
The effect of thermal misbalance on compressive oscillations in solar coronal loopsFast and slow magnetoacoustic waves are a promising tool for the seismological diagnostics of physical parameters of various plasma structures in the corona of the Sun. In particular, compressive waves can provide us with information about the thermodynamic equilibrium in the coronal plasma, and hence the heating function. Compressive perturbations of the thermodynamic equilibrium by magnetoacoustic waves can cause the misbalance of the radiative cooling and unspecified heating. The effect of the misbalance is determined by the derivatives of the combined heating/cooling function with respect to the plasma density and temperature, and can lead to either enhanced damping of the compressive oscillations or their magnification. Moreover, in the regime of strong misbalance, compressive MHD waves are subject to wave dispersion that can slow down the formation of shocks and can cause the formation of quasiperiodic wave trains. 

Ms. Hope Thackray29.11.2018 venue LTD 
Fast MHD modes of a two (and three) shell semicylindrical waveguideThe modelling of coronal loop structures has long been pursued as a means of determining physical properties of the Sun's corona. Here, a 3D semicylindrical waveguide is proposed, representing a coronal loop arcade anchored in the photosphere. By considering the eigenfunctions formed at the interface of a sharp density discontinuity (represented by "twoshell" and subsequently "threeshell" density structures), we show that waves are elliptically polarised, and that small changes in density contrast between shells can drastically affect the presence of eigenmodes. Since observational information has restrictions on resolution, the implication is that two similarly determined density structures may produce vastly different estimations of potential eigenmodes. 

Dr. Istvan Ballai22.11.2018 venue LT2 
Introduction to multiple scaling methods to solve differential equations with applications to plasma physics. Part II: Nonlinear partial differential equationsIn the second part of my seminar I will focus on nonlinear partial differential equations that can be obtained from the MHD equations. Using the multiple scale technique I will present a method to obtain the Kortewegde VriesBurgers equation in a nonideal plasma in the presence of Hall currents. Using simple methods, I will find solutions to the limiting cases of shock waves and solitons. 

Dr. Istvan Ballai15.11.2018 venue K14 
Introduction to multiple scaling methods to solve differential equations with applications to plasma physics. Part I: Ordinary linear differential equationsMany of the equations we encounter in our research on solar and space plasma physics
dynamics contain essential physical constraints (nonlinearity, singularities, complex domains
of interest, complex boundary conditions, etc.) that makes difficult to find exact solutions.
Therefore, in order to obtain information about solutions of equations, we are forced to use
approximative methods, numerical solutions, or both. The most important approximation methods
are the perturbation methods, where the solutions are represented by the first few terms of an expansion.


Mr. Samuel Skirvin1.11.2018 
Properties of Alfvénic waves in the solar chromosphereIn the first part of my talk I will discuss the results of investigation of the properties of transverse waves existing in spicules using the automated wave tracking code NUWT. Analysing a distancetime diagram at an altitude of 7 Mm relative to the solar limb produces the measured distribution of properties such as wave amplitude, period and velocity amplitude. In the second part of the talk I will provide an overview of the rescent studies on the effect of initial flow profiles on the dynamics of solar jets. 

Dr. Gary Verth18.10.2018 
Introduction to the SunThis talk will be an introduction to the science required to understand the Sun and its atmosphere. It is primarily intended for students starting their postgraduate research in plasma, solar, or magnetospheric physics. Due to the introductory nature of the talk, it would also be suitable for any interested nonspecialists. 

Dynamic Sun III 

Dynamic Sun II 


Dynamic Sun I 


ESPOS, 25.02.2021 
Detection and dynamics of the vortex tubes in the solar atmosphereWe present the stateofart detection method of threedimensional vortices and apply it to realistic magnetoconvections simulations performed by the MURaM code. The detected vortices extend from the photosphere to the low chromosphere, presenting similar behaviour at all height levels. The vortices concentrate the magnetic field, and thereby the plasma dynamics inside the vortex is considerably influenced by the Lorentz force. Rotational motions also perturb the magnetic field lines, but they lead to only slightly bent flux tubes as the magnetic field tension is too high for the vortex flow to significantly twist the magnetic lines. We find that twisted magnetic flux tubes are created by shear motions in regions where plasmaβ>1, regardless of the existence of flow vortices. 

ESPOS, 7.11.2019 
MHD wave modes in the solar magnetic flux tubes with elliptical crosssectionMany previous studies of MHD modes in the magnetic flux tubes were focussed on deriving a dispersion relation for cylindrical waveguides. However, from observations it is well known that, for example, the crosssectional shape of sunspots and pores are not perfect circles and can often be much better approximated by ellipses. From a theoretical point of view, any imbalance in a waveguide’s diameters, even if very small, will move the study of the problem from cylindrical to elliptical coordinates. In this talk, I will therefore describe a model that predicts the MHD wave modes that can be trapped and propagate in a compressible magnetic flux tube with an elliptical crosssection embedded in a magnetic environment. I will discuss the resultant dispersion relations for body and surface modes, then then I will show how the ellipticity of a magnetic flux tube effects these solutions (with specific applications to the coronal and photospheric conditions). From a practical point of view the information from these dispersion diagrams does not show how these MHD modes will manifest themselves in observational data. Therefore, I will also present several visualisations of the eigenfunctions of these MHD wave modes and explain how the eccentricity effects each wave mode. 

ESPOS, 4.10.2018 
Surface waves and instabilities in the presence of an inclined magnetic fieldWhile surface waves propagating at tangential discontinuities have been studied in great detail, few studies have been dedicated to the investigation of the nature of waves at contact discontinuities, i.e. plasma discontinuity, where the background magnetic field crosses the interface between two media. In this talk, I will show that, by introducing magnetic field inclination, the frequency of waves is rendered complex, where the imaginary part describes wave attenuation, due to lateral energy leakage. We investigate the eigenvalue and initial value problem and determine the conditions of transition from contact to tangential discontinuity. Finally, I will present an investigation into the effect of magnetic field inclination on magnetic RayleighTaylor instability. 

Sheffield Space Initiative 

Following the fantastic success of the SunbYte mission (2017), the Sheffield Space Initiative (SSI) was founded to further engage University of Sheffield students in the science and engineering challenges involved in the exploration of Space and now consists of four exciting projects, i.e. SunbYte, SunrIde, MoonWorks and ROV Avalon. Working with the world’s largest professional Engineering Institution (IET), UK Students for the Exploration and Development of Space (UKSEDS), National Aeronautics and Space Administration (NASA), European Space Agency (ESA), UK Space Agency (UKSA), Institution of Mechanical Engineers (IMechE), Sheffield Engineering Leadership Academy (SELA), the University of Sheffield Space Society and a number of Faculty of Engineering and Science departments, the SSI aims to inspire the next generation of Space Engineers and Scientists. 
Solar Spicule Tracking Code (SSTC)version 1.0 

Solar Spicule Tracking Code version 1.0 (SSTC v1.0, written in MatLab) is designed for
automated detection, tracking and analysis of solar spicules properties (also applicable for
coronal loop and other curvilinear features detection in the solar atmosphere). The code works
best with hiresolution observational solar imaging data. The choice of either photospheric,
chromospheric or coronal spectral lines depends on the particular features to be identified
and analysed. As an output, the code provides information on individual spicules/loops detected
as well as overall statistics. A gradient contour method is used to constrain identified spicule/loop
boundaries as well as their axis (the spicule/loop ``spine''). Detection results may be influenced by
quality of current observational data (DKIST data will be tested by the authors when available). The
level of accuracy of the code can be improved by adding more points along the spicule/loop ``spine''
(if the detection region has a particularity high density of spicules/loops). This will also provide a
more accurate time evolution of the spicules/loops. To improve robustness, Machine Learning (ML) will
be implemented in the next version of the code. Data processing time of current version depends on user
computing facilities (i.e. number of CPU cores, GPU performance) used. 
Sheffield Dispersion Diagram Code (SDDC)version 1.0 

Sheffield Dispersion Diagram Code version 1.0 (SDDC v1.0, written in Python)
is designed to produce the dispersion diagram for magnetoacoustic magnetohydrodynamic (MHD) wave modes within a solar application.
The motivation for developing this method comes from the analytical requirement to derive a dispersion relation
in order to previously produce a dispersion diagram. In order to do this, simple models or specific case studies
are considered so that the mathematics becomes more manageable. Consideration of more complicated models
and solving the set of MHD equations result in a differential equation with no known analytic solution. However
using the shooting method, the roots of the equation can be found. Therefore more complicated models and plasma
structuring can be investigated in more depth using this method than could be conduction through theory alone. 
version 2.0 

Sheffield Dispersion Diagram Code version 2.0 (SDDC v2.0, written in Python) is designed to produce the dispersion diagram for magnetoacoustic magnetohydrodynamic (MHD) wave modes within a solar application. The version explained in this manual build on the previous v1.0 which was very much the spine of the code. This version is much more streamlined and contains additional features which improve the accuracy of the results and additional files for analysis of results. The improvements made in SDDC v2.0 include:Viktor Fedun (ACSE), v.fedun at sheffield.ac.uk Gary Verth (SoMaS), g.verth at sheffield.ac.uk 
Wave Mode Analysis Code (WMAC)version 1.0 

Wave Mode Analysis Code version 1.0 (WMAC v1.0, written in MatLab 2019a) is prepared to analyse solar data
as it is dealing with the techniques of Proper Orthogonal Decomposition (POD), developed by Pearson (1901),
and Dynamic Mode Decomposition(DMD), initially developed by Schmid (2010). The POD is a mathematical
technique that identifies modes that are orthogonal in space and it provides a clear ranking of the modes in terms
of their contribution (Higham et al. 2018). While DMD identities temporal orthogonality and it does not rank the
modes in any way. If it is assumed that modes are temporally orthogonal, i.e., different modes cannot have identical
frequencies, then DMD with a search criteria offers an optimal methodology to identify coherent mode structure
from, for example, intensity snapshots. In this manual we apply the POD and DMD in an intensity time series of a
sunspot data to identify MHD wave mode. 
Code for Vortex Flow Analysis (CVFA)version 1.1 
CVFA v1.1 code and data, zip (26MB) 
Code for Vortex Flow Analysis version 1.1 (CVFA v1.1, written in MatLab 2019a). Vortex flows in the solar photosphere are fundamentally
important for the generation of magnetohydrodynamic (MHD) waves which propagate to the upper layers of the solar atmosphere.
Vortex tubes are formed as coherent magnetic field structures in the solar atmosphere, e.g. twisted magnetic flux tubes.
In this manual, we explain a code of Lagrangian Averaged Vorticity Deviation (LAVD) Haller et al. 2016 adopted to
identify vortex flows (the center of circulation and 3D vortex boundary) in the solar atmosphere data, Additional algorithmic
technique were developed to check whether a structure detected by the LAVD method is a true vortex or not and how to
determine the rotational direction (clockwise or anticlockwise).
Also, we applied these methods to the MuRaM magnetoconvection simulation data to detect and track the evolution
of 2D vortices in the solar photosphere. 
Tool for Analysis of Oscillatory Modes (TAOM)version 1.0 

The Tool for Analysis of Oscillatory Modes (TAOM) version 1.0 (TAOM v1.0, written in MatLab) is designed to detect and trace
the boundary of binary image of sunspots umbra (or other feature for which boundary can be traced) and then calculate the eigenmodes and
eigenfunctions of the shape of the input sunspots image with implies a fixed boundary condition using discrete Laplacian in MatLab. The
code scans parameter space for eigenvalues and orthogonal eigenvectors that match the boundary conditions for any given crosssectional
shape. Also this code is designed to find the best elliptical (or other shape) approximation of the sunspot and calculate the
eigenmodes/eigenfunctions and provides the comparison between the umbra of the sunspots and elliptical membrane. This code work
with binary image only. 
Vortex Detection Code (VDC)version 1.0 
VDC v1.0 zip (30KB)Use the main function "gamma_identification_for_vortex_demo.m" to run VDC v1.0 manual (4.1MB)

The Vortex Detection Code (VDC) version 1.0 (VDC v1.0, written in MatLab)
is designed to detect and identify the vortex flow motions in the 2D numericalor observational
solar data. Code is based on implementation of Gamma functions Graftieaux et al. 2001
and new algorithm for more accurate tracking of the vortex boundary.
The code is fully tested on the numerical datagenerated by SolarBox code. 
