A5056231060- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Characterization and Applications of Magnetic Nanoparticles
- Geophysics and Gravity Measurements
- Fluid Dynamics and Turbulent Flows
- Magnetic confinement fusion research
- Cosmology and Gravitation Theories
- Laser-Plasma Interactions and Diagnostics
- Electric Motor Design and Analysis
- Nuclear Issues and Defense
- Black Holes and Theoretical Physics
- Sports Dynamics and Biomechanics
- Atmospheric chemistry and aerosols
- Superconducting Materials and Applications
- Oil, Gas, and Environmental Issues
- Field-Flow Fractionation Techniques
- Earthquake Detection and Analysis
- Advanced Neuroimaging Techniques and Applications
- Magnetic and Electromagnetic Effects
- Nanofluid Flow and Heat Transfer
- Laser-induced spectroscopy and plasma
- Fluid dynamics and aerodynamics studies
University of Ioannina
2022-2024
University of St Andrews
2012-2023
National and Kapodistrian University of Athens
2012-2015
St. Andrews University
2012
Andrews University
2010
Instituto de Astrofísica de Canarias
2002-2006
Consejo Superior de Investigaciones Científicas
2004
Numerical experiments of the emergence magnetic flux from uppermost layers solar interior to photosphere and its further eruption into low atmosphere corona are carried out. We use idealized models for initial stratification field distribution below similar those used multidimensional in literature. The energy equation is adiabatic except inclusion ohmic viscous dissipation terms, which, however, become important only at interfaces reconnection sites. Three-dimensional both an unmagnetized a...
We report on three-dimensional (3D) MHD simulations of the formation jets produced during emergence and eruption solar magnetic fields. The interaction between an emerging ambient field in atmosphere leads to (external) reconnection "standard" with inverse Y-shaped configuration. Eventually, low-atmosphere (internal) sheared fieldlines flux region produces erupting rope a jet underneath it. plasma blows out and, moreover, it unwinds as is ejected into outer atmosphere. fast emission cool...
A spectacular manifestation of solar activity is the appearance transient brightenings in far wings H$\alpha$ line, known as Ellerman bombs (EBs). Recent observations obtained by Interface Region Imaging Spectrograph (IRIS) have revealed another type plasma "bombs" (UV bursts) with high temperatures perhaps up to $8\times 10^4$ K within cooler lower atmosphere. Realistic numerical modeling showing such events needed explain their nature. Here, we report on 3D radiative magneto-hydrodynamic...
Using MHD numerical experiments in three dimensions, we study the emergence of a bipolar magnetic region from solar interior into model corona containing large-scale, horizontal field. An arch-shaped concentrated current sheet is formed at interface between rising magnetized plasma and ambient coronal Three-dimensional reconnection takes place along sheet, so that photosphere become magnetically connected, process repeatedly observed recent satellite missions. We show structure evolution how...
Using two-dimensional (2D) magnetohydrodynamic simulations we study the effects of resistive processes in dynamics magnetic flux emergence and its relation to Ellerman bombs other dynamic phenomena Sun. The widely accepted scenario is formation expansion Ω-shaped loops due Parker instability. Since instability has largest growth rate at finite wavelength λp ~ 10H-20H, where H scale height (≈200 km solar photosphere), a number may rise from initial sheet if it sufficiently long. This process...
Aims. We investigate the formation of flux ropes in a emergence region and their rise into outer atmosphere Sun.
<i>Aims. <i/>We investigate the emergence of a "sea-serpent" magnetic field into outer solar atmosphere and connection between undulating fieldlines formation Ellerman bombs.<i>Methods. perform 3D numerical experiments solving time-dependent resistive MHD equations.<i>Results. <i/>A sub-photospheric flux sheet develops undulations due to Parker instability. It rises from convectively unstable layer emerges highly stratified through successive reconnection events along system. Brightenings...
There has been a long-lasting debate on the question of whether or not electric currents in solar active regions are neutralized. That is, main (or direct) coronal connecting region polarities surrounded by shielding return) equal total value and opposite direction. Both theory observations yet fully conclusive regarding this question, numerical simulations have, surprisingly, barely used to address it. Here we quantify evolution during formation bipolar considering three-dimensional...
Ellerman bombs (EBs) and UV bursts are both brightenings related to flux emergence regions specifically magnetic of opposite polarity that meet in the photosphere. These two reconnection-related phenomena, nominally formed far apart, occasionally occur same location at time, thus challenging our understanding reconnection heating lower solar atmosphere. We consider formation an active region, including long fibrils hot dense coronal plasma. The a untwisted sheet, injected $2.5$~Mm below...
Aims.We investigate the effects of varying magnetic field strength and twist a flux tube as it rises through solar interior emerges into atmosphere.
<i>Context. <i/>Models of flux emergence frequently use a twisted cylindrical loop as the initial starting configuration and ignore coupling between radiation field plasma. In these models, axis original tube never emerges through photosphere. Without emerging, it is very difficult to form realistic sunspot.<i>Aims. <i/>The aim toroidal loop, placed beneath solar photosphere study whether system fully into atmosphere. The curvature means that plasma can drain more effectively than in...
Sigmoids are structures with a forward or inverse S-shape, generally observed in the solar corona soft X-ray emission. It is believed that appearance of sigmoid an active region important factor eruptive activity. The association sigmoids dynamic phenomena such as flares and coronal mass ejections (CMEs) make study important. Recent observations sigmoid, obtained X-Ray Telescope (XRT) on board Hinode, showed formation eruption phase high spatial resolution. These revealed topological...
We study the emergence of a toroidal flux tube into solar atmosphere and its interaction with pre-existing field an active region. investigate emission jets as result repeated reconnection events between colliding magnetic fields. perform 3D simulations by solving time-dependent, resistive MHD equations in highly stratified atmosphere. A small region is constructed tube. current structure build up sets when new emerging comes contact ambient The topology around drastically modified during...
Aims. We model the emergence of magnetized plasma from top convection zone to lower corona. investigate eruption coronal flux ropes above emerging regions.
Abstract We have performed 3D MHD simulations to study the effect of partial ionization in process magnetic flux emergence Sun. In fact, we continue previous work, and now focus (1) on fields above solar photosphere (2) eruptive activity that follows into corona. find with (PI), structure emerging field consists arch-like lines very little twist since axis initial rising remains below photosphere. The plasma inside volume is less dense, it moving faster compared fully ionized (FI)...
We present the results of a set three-dimensional numerical simulations magnetic flux emergence from below photosphere and into corona.The corona includes uniform horizontal field as model for pre-existing large-scale coronal system.Cases with different relative orientations upcoming fields are studied.Upon contact, concentrated current sheet shape an arch or bridge is formed at interface which marks positions maximum jump in vector between two systems.Relative angles above 90 degrees yield...
The emergence of magnetic flux from the convection zone into corona is an important process for dynamical evolution coronal field. In this paper we extend our previous numerical investigations, by looking at interaction as initially twisted tube emerges a plane-parallel, Significant differences are found in appearance and depending on relative orientation between rising system any preexisting When systems nearly antiparallel, experiments show substantial reconnection demonstrate clear...
Our aim is to study the photospheric flux distribution of a twisted tube that emerges from solar interior. We also report on eruption new rope when emerging rises into pre-existing magnetic field in corona. To evolution, we use 3D numerical simulations by solving time-dependent and resistive MHD equations. qualitatively compare our results with MDI magnetograms at surface. find consists two regions opposite polarities elongated tails sides polarity inversion line (PIL), depending azimuthal...
We report on a numerical experiment of the recurrent onset helical "blowout" jets in an emerging flux region. find that these are running with velocities ∼100–250 km s−1 and they transfer vast amount heavy plasma into outer solar atmosphere. During their emission, undergo untwisting motion as result reconnection between twisted non-twisted pre-existing magnetic field For first time context blowout jets, we provide direct evidence is associated propagation torsional Alfvén waves corona.
Numerical simulations of kinematic dynamo action in steady and three-dimensional ABC flows are presented with special focus on the difference growth rates between cases single multiple periods prescribed velocity field. It is found that rate (apart from a trivial factor stemming scaling strain wavenumber field) due to differences recycling weakest part magnetic The wavelength classical ABC-flow experiments impose stronger symmetry requirements, which results suppression rate. larger wave...