Kostas Tziotziou

Academy of Athens · Research Center for Astronomy and Applied Mathematics

We present an analysis of the solar corona visual spectrum, captured during the total solar eclipse of 21 August 2017, in Salem, Oregon USA. The eclipse took place about 2 years before the solar minimum of the 25th solar cycle, that occurred on 2019/2020. The spectra were captured by two slitless spectrographs with different dispersions and include...

Vortex flows, related to solar convective turbulent dynamics at granular scales and their interplay with magnetic fields within intergranular lanes, occur abundantly on the solar surface and in the atmosphere above. Their presence is revealed in high-resolution and high-cadence solar observations from the ground and from space and with state-of-the...

Vortex flows, related to solar convective turbulent dynamics at granular scales and their interplay with magnetic fields within intergranular lanes, occur abundantly on the solar surface and in the atmosphere above. Their presence is revealed in high-resolution and high-cadence solar observations from the ground and from space and with state-of-the...

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operatin...

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operatin...

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operatin...

Context. Chromospheric swirls are related to convectively driven vortex flows and considered to play a significant role in the dynamics and heating of the upper solar atmosphere. It is important to automatically detect and track them in chromospheric observations and determine their properties. Aims. We aim to detect and track chromospheric swirls...

Chromospheric swirls are considered to play a significant role in the dynamics and heating of the upper solar atmosphere. It is important to automatically detect and track them in chromospheric observations and determine their properties. We applied a recently developed automated chromospheric swirl detection method to time-series observations of a...

During totality of the solar eclipse of 20 March 2015, at Svalbard, Norway, the emission spectra of the solar chromosphere and corona were captured with a slitless spectrograph. A very lucky coincidence of a large number of sunspots and Active Regions (ARs) around the solar limb allowed us to observe a number of different spectroscopic effects. Thi...

High-resolution observations have revealed that rotating structures known as “chromospheric swirls” are ubiquitous in the solar chromosphere. These structures have circular or spiral shapes, are present across a broad range of spatial and temporal scales and are considered as viable candidates for providing an alternative mechanism for the heating...

Context. Vortex flows can foster a variety of wave modes. A recent oscillatory analysis of a persistent 1.7 h vortex flow with a significant substructure has suggested the existence of various types of waves within it. Aims. We investigate the nature and characteristics of waves within this quiet-Sun vortex flow, over the course of an uninterrupted...

Vortex flows can foster a variety of wave modes. A recent oscillatory analysis of a persistent 1.7 h vortex flow with a significant substructure has suggested the existence of various types of waves within it. We investigate the nature and characteristics of waves within this quiet-Sun vortex flow to better understand its physics and dynamics. We u...

Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument s...

Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument s...

Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument s...

The main objective of the TechTIDE project (Warning and mitigation Technologies for Travelling Ionospheric Disturbances Effects) is the development of an identification and tracking system for Travelling Ionospheric Disturbances (TIDs) which will issue warnings of electron density perturbations over large world regions. The TechTIDE project has put...

Context. We study the evolution of a small-scale emerging flux region (EFR) in the quiet Sun, from its emergence in the photosphere to its appearance in the corona and its decay. Aims. We track processes and phenomena that take place across all atmospheric layers; we explore their interrelations and compare our findings with those from recent numer...

We study the evolution of a small-scale emerging flux region (EFR) in the quiet Sun, from its emergence to its decay. We track processes and phenomena across all atmospheric layers, explore their interrelations and compare our findings with recent numerical modelling studies. We used imaging, spectral and spectropolarimetric observations from space...

Context . Recently, the appearance, characteristics, and dynamics of a persistent 1.7 h vortex flow, resembling a small-scale tornado, have been investigated with observations both from the ground and from space in a quiet-Sun region in several lines and channels and for the first time in the H α line centre. The vortex flow showed significant subs...

Context . Vortex flows have been extensively observed over a wide range of spatial and temporal scales in different spectral lines, and thus layers of the solar atmosphere, and have been widely found in numerical simulations. However, signatures of vortex flows have only recently been reported in the wings of the H α , but never so far in the H α l...

We investigate the morphology and temporal variability of a quiet Sun network region in different solar layers. The emission in several EUV spectral lines through both raster and slot time series, recorded by EIS/Hinode is studied along with H$\alpha$ observations and high resolution spectropolarimetric observations of the photospheric magnetic fie...

The rather frequent occurrence, and sometimes long duration, of γ-ray events at photon energies above 100 MeV challenges our understanding of particle acceleration processes at the Sun. The emission is ascribed to pion-decay photons due to protons with energies above 300 MeV. We study the X-ray and radio emissions and the solar energetic particles...

A novel integrated prediction system, for both solar flares (SFs) and solar energetic particle (SEP) events is being presented. The Forecasting Solar Particle Events and Flares (FORSPEF) tool provides forecasting of solar eruptive events, such as SFs with a projection to occurence and velocity of coronal mass ejections (CMEs) and the likelihood of...

A new catalogue of 314 solar energetic particle (SEP) events extending over a large time span from 1984 to 2013 has been compiled. The properties as well as the associations of these SEP events with their parent solar sources have been thoroughly examined. The properties of the events include the proton peak integral flux and the fluence for energi...

During the interval 2012 March 7–11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the m...

Ubiquitous small-scale vortices have recently been found in the lower atmosphere of the quiet Sun in state-of-the-art solar observations and in numerical simulations. We investigate the characteristics and temporal evolution of a granular-scale vortex and its associated upflows through the photosphere and chromosphere of a quiet Sun internetwork re...

Solar Energetic Particle (SEP) events related to intense eruptive events on the Sun such as solar flares and coronal mass ejections (CMEs), pose a significant threat for both personnel and infrastructure in stormy space-weather conditions. Of particular concern is the high rate of single event effects on-board spacecraft launchers which can be brou...

Aims. We seek indications or evidence of transmission/conversion of magnetoacoustic waves at the magnetic canopy, as a result of its impact on the properties of the wave field of the photosphere and chromosphere. Methods. We use cross-wavelet analysis to measure phase differences between intensity and Doppler signal oscillations in the Halpha, CaII...

Energetic processes on the Sun accelerate protons to GeV and electrons to tens of MeV energies, resulting in flux enhancements known as Solar Energetic Particle (SEP) events, recorded onboard an wide array of spacecraft within the inner heliosphere. SEP events are typically divided into two basic classes, so-called “gradual” and “impulsive” events....

The Earth’s ionosphere is a magnetoionic medium imbedded in a background neutral atmosphere, exhibiting very interesting refractive properties, including anisotropy, dispersion, and dissipation. As such, it poses a challenge for several radio systems that make use of signal transmission through all or some portion of the medium. It is important the...

Aims. We investigate the free magnetic energy and relative magnetic helicity injection in solar quiet regions. Methods. We use the DAVE4VM method to infer the photospheric velocity field and calculate the free magnetic energy and relative magnetic helicity injection rates in 16 quiet-Sun vector magnetograms sequences. Results. We find that there is...

Solar Energetic Particles (SEPs) result from intense solar eruptive events such as solar flares and coronal mass ejections (CMEs) and pose a significant threat for both personnel and infrastructure in space conditions. In this work, we present FORSPEF (Forecasting Solar Particle Events and Flares), a novel dual system, designed to perform forecasti...

A statistical analysis of the relationship between solar energetic particles (SEPs) and properties of solar flares and coronal mass ejections (CMEs) is presented. SEP events during solar cycle 23 are selected which are associated with solar flares originating on the visible hemisphere of the Sun and at least of magnitude M1. Taking into account all...

We assess the validity of the free magnetic energy - relative magnetic helicity diagram for solar magnetic structures. We used two different methods of calculating the free magnetic energy and the relative magnetic helicity budgets: a classical, volume-calculation nonlinear force-free (NLFF) method applied to finite coronal magnetic structures and...

Solar Energetic Particle (SEP) events resulting from intense eruptive events such as solar flares and coronal mass ejections (CMEs), pose a significant threat for both personnel and infrastructure in stormy space-weather conditions. Of particular concern is the high rate of single event effects on-board spacecraft launchers which can be brought abo...

The Solar Terrestrial Relations Observatory (STEREO) recordings provide an unprecedented opportunity to study the evolution of solar energetic particle (SEP) events from different observation points in the heliosphere, allowing one to identify the effects of the properties of the interplanetary magnetic field (IMF) and solar wind structures on the...

In earlier works we introduced and tested a nonlinear force-free (NLFF) method designed to self-consistently calculate the free magnetic energy and the relative magnetic helicity budgets of the corona of observed solar magnetic structures. The method requires, in principle, only a single, photospheric or low-chromospheric, vector magnetogram of a q...

Context. We present evidence for the conversion and transmission of wave modes on the magnetic flux tubes that constitute mottles and form the magnetic canopy in a quiet Sun region. Aims. Our aim is to highlight the details and the key parameters of the mechanism that produces power halos and magnetic shadows around the magnetic network observed in...

We investigate the free magnetic energy and relative magnetic helicity budgets of solar quiet regions. Using a novel non-linear force-free method requiring single solar vector magnetograms we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 55 quiet-Sun vector magnetograms. As in a previous work on active r...

We study the evolution of the non-potential free magnetic energy and relative magnetic helicity budgets in solar active regions (ARs). For this we use a time-series of a three-dimensional, synthetic AR produced by magnetohydrodynamical (MHD) simulations. As a first step, we calculate the potential magnetic field that has the same normal components...

Transient expulsions of gigantic clouds of solar coronal plasma into the interplanetary space in the form of Coronal Mass Ejections (CMEs) and sudden, intense flashes of electromagnetic radiation, solar flares, are well-established drivers of the variable Space Weather. Given the innate, intricate links and connections between the solar drivers and...

STEREO (Solar TErrestrial RElations Observatory) recordings provide an unprecedented opportunity to identify the evolution of Solar Energetic Particles (SEPs) at different observing points in the heliosphere, which is expected to provide new insight on the physics of solar particle genesis, propagation and acceleration as well as on the properties...

We present a novel nonlinear force-free method designed to calculate the instantaneous free magnetic energy and relative magnetic helicity budgets of a solar region from a single photospheric/chromospheric vector magnetogram of the region. Our objective is to study the role of these quantities in solar eruptions and quiet-Sun dynamics. We apply the...

We investigate the interaction between acoustic oscillations and the fine-scale structures found at the chromospheric network boundaries that form the magnetic canopy. To this end, high precision photospheric magnetograms obtained by SOT/SP on-board the Hinode space mission and time series of high spatial-resolution filtergrams in five wavelengths...

In previous works we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a timeseries of 600 hi...

We investigate the interaction between acoustic oscillations and the fine-scale structures found at the chromospheric network boundaries that form the magnetic canopy. We use high precision photospheric magnetograms obtained by SOT/SP on-board the Hinode satellite and time series of high spatial resolution filtergrams in five wavelengths along the...

Knowledge of the state of the upper atmosphere, and in particular its ionized part, is very important in several applications affected by space weather, especially the communications and navigation systems that rely on radio transmission. To better classify the ionosphere and forecast its disturbances over Europe, a data and model infrastructure pl...

The FP7 COMESEP (COronal Mass Ejections and Solar Energetic Particles: forecasting the space weather impact) project is developing tools for forecasting geomagnetic storms and solar energetic particle (SEP) radiation storms. Here we present preliminary results on a statistical analysis of SEP events and their parent solar activity during Solar Cycl...

SEPServer is a three-year collaborative project funded by the seventh framework programme (FP7-SPACE) of the European Union. The objective of the project is to provide access to state-of-the-art observations and analysis tools for the scientific community on solar energetic particle (SEP) events and related electromagnetic (EM) emissions. The proje...

Magnetic free energy and relative magnetic helicity are two important quantities characterizing solar active regions (ARs). Although the importance of free magnetic energy storage for solar eruptions is widely accepted, the role of magnetic helicity, that quantifies the stress and distortion of the magnetic field compared to its lowest (potential)...

Using a recently proposed nonlinear force-free method designed for single-vector magnetograms of solar active regions, we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 162 vector magnetograms corresponding to 42 different active regions. We find a statistically robust, monotonic correlation between the f...

Solar energetic particle (SEP) events are a key ingredient of solar–terrestrial physics both for fundamental research and space weather applications. Multi-satellite observations are an important and incompletely exploited tool for studying the acceleration and the coronal and interplanetary propagation of the particles. While STEREO uses for this...

In the framework of the EU-funded project ENSEMBLES, an integrated set of high resolution climate model simulations for the present and future climate of Europe has been created, as well as a gridded observational dataset (E-OBS) of daily precipitation and temperature, based on a large number of station data in Europe. This study evaluates the abil...

Expanding on an earlier work that relied on linear force-free (LFF) magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free (NLFF) magnetic structure extending above a single known lower-boundary magnetic field vector. The propose...

Over the last two decades the uninterrupted, high-resolution observations of the Sun, from the excellent range of telescopes aboard many spacecraft complemented with observations from sophisticated ground-based telescopes have opened up a new world producing significantly more complete information on the physical conditions of the solar atmosphere...

SEPServer is set out to make the first database of particle and corresponding EM observations of solar energetic particle (SEP) events over roughly three solar cycles. It will also provide users with results from the scientific analysis of multiple datasets using different observational and simulation based methods. Therefore, SEPServer will lead t...

The solar chromosphere is a very inhomogeneous and dynamic layer of the solar atmosphere that exhibits several phenomena on a wide range of spatial and temporal scales. High-resolution and long-duration observations, employing mostly lines, such as Halpha, the Ca II infrared lines and the Ca II H and K lines, obtained both from ground-based telesco...

The chromosphere is an inhomogeneous and highly dynamic layer of the solar atmosphere. New high resolution observations have revealed that it consists mainly of fine-scale structures which are directly related to the magnetic field. In this work we use multi-wavelength observations to study oscillatory phenomena in the quiet Sun and their relation...

During an eleven year cycle the Sun goes from quiet conditions at minimum to levels of high activity at maximum. In the latter case, energetic phenomena such as coronal mass ejections (CMEs) and solar flares (SFs) accompanied by explosive releases of mass, magnetic flux and solar energetic particles (SEPs) are common. Damaging effects, as a result...

We use a dataset of simultaneous image sequences obtained by Hinode/SOT with the Ca II H filter, as well as in Ha+-0.2A. SOT was looking at the SW solar limb. The high temporal and spatial resolution allows us to study the structure and dynamics of spicules seen at the different filters. Individual spicules have been selected and intensity and velo...

The intensities of Solar Energetic Particles (SEPs) are strongly affected by the variations in the level of solar activity, the characteristics of the solar wind and the properties of the interplanetary magnetic field that enable the acceleration and propagation of SEPs throughout the heliosphere. The study of SEPs at different latitudes and under...

Climate changes in the Mediterranean region, related to a significant increase in temperature and changes in precipitation patterns, can potentially affect local economies. Agriculture and tourism are undoubtedly the most important economic sources for Greece and these may be more strongly affected by changing future climate conditions. Climate cha...

Aims: We explore the differences in the measurement of the magnetic field of the quiet solar photosphere provided by the Michelson Doppler Imager (MDI) onboard SoHO and the SpectroPolarimeter (SOT/SP) onboard Hinode and the ensuing implications for the extrapolated chromospheric magnetic field and the determination of the location of the magnetic c...

Aims: Our aim is to gain a better understanding of the interaction between acoustic oscillations and the small-scale magnetic fields of the Sun. To this end, we examine the oscillatory properties of a network region and their relation to the magnetic configuration of the chromosphere. We link the oscillatory properties of a network region and their...

We analyze the temporal behavior of a solar quiet region using a set of multi-wavelength observations obtained during a coordinated campaign. The observations were acquired by the ground-based Dutch Open Telescope (DOT), the Michelson Doppler Imager (MDI) on-board SOHO and the UV filters of the Transition Region and Coronal Explorer (TRACE). A larg...

Context. We investigated the solar origin of Solar Particle Events (SPEs) which occurred during four time periods of the 23rd solar cycle with intense solar activity and were detected by the Standard Radiation Environment Monitor (SREM) onboard the INTEGRAL satellite. SREM is a second generation ESA particle radiation monitor, already flying onboar...

Context. We investigate the oscillatory behavior of the quiet solar chromosphere and its discrete components in terms of oscillation properties, i.e. network and internetwork. For this purpose, we use a time series of high resolution filtergrams at five wavelengths along the Halpha profile, obtained by the Dutch Open Telescope. Aims: We aim to gain...

The Standard Radiation Environment Monitor (SREM) belongs to a second generation of instruments in a program established by the European Research and Technology Centre (ESTEC) of the European Space Agency (ESA) to provide minimum intrusive particle radiation detectors on ESA spacecrafts for space weather applications. SREM detects high-energy elect...

Solar Particle Events (SPEs) of the 23rd Solar Cycle detected by the ESA Standard Radiation Environment Monitor (SREM) onboard the INTEGRAL satellite have been studied in order to find their connection to solar sources. X-ray, optical and radio data of solar flares that were observed by several space-based instruments during the aforementioned sola...

This review focuses on the solar chromosphere, a very inhomogeneous and dynamic layer that exhibits phenomena on a large range of spatial and temporal scales. High-resolution observa-tions from existing telescopes (DST, SST, DOT), as well as long-duration observations with Hinode's SOT employing lines such as the Ca II infrared lines, the Ca II HK...

We use time series of G-band and Ca II H filtergrams obtained by SOT on-board Hinode, as well as Halpha filtergrams in 5 wavelengths along the line profile obtained by the Dutch Open Telescope during a coordinated campaign. Our goal is to study the oscillatory behavior of a network region as seen at different heights of the solar atmosphere and to...

Precipitation patterns are expected to alter in response to global climate change. Many climate models project declining mean precipitation over much of the Mediterranean region and changes in the seasonal distribution of rainfall and its intensity. In this study, regional climate models have been used to investigate potential future changes in ext...

Context. We examine oscillatory phenomena in a solar network region from multi-wavelength observations obtained by the ground-based Dutch Open Telescope (DOT) and by the Coronal Diagnostic Spectrometer (CDS) on the spacecraft Solar and Heliospheric Observatory (SoHO). The observations were obtained during a coordinated observing campaign in October...

A long solar filament was observed simultaneously in the Hα line by THEMIS/MSDP and in selected EUV lines by the Coronal Diagnostic Spectrometer on SOHO. Co-alignment of optical and EUV images reveals that the dark EUV filament is much more extended than the Hα filament. Assuming that the EUV filament represents Lyman continuum absorption of the ba...

We have studied spicules observed at the northern solar limb by using simultaneous high resolution image sequences. The images were obtained by Hinode/SOT (in the Ca II H passband) and TRACE (in the 1600 Å passband) during a coordinated campaign. Both data sets were reduced and then carefully co-aligned in order to compare the observed patterns in...

We examine oscillatory phenomena in a solar network region from multi-wavelength, observations obtained by the ground-based Dutch Open Telescope (DOT), and by instruments on the spacecraft Solar and Heliospheric Observatory (SoHO). The observations were obtained during a coordinated observing campaign on October 14, 2005. The temporal variations of...

We study the influence of atmospheric seeing due to terrestrial atmospheric turbulence on cloud model parameters obtained from Halpha observations with Beckers' cloud model. The analysis indicates that atmospheric seeing does not affect the velocity determination, but does influence significantly the determination of the Doppler width when velocity...

We study the contrast of fine structures (mottles), found in a quiet-Sun network region and close to a filament, observed by the SOHO/SUMER spectrograph. The observations were made during August 29 -- 30, 1996, in several chromospheric, transition-region and coronal EUV lines. The contrasts of the fine-scale structures were obtained in the differen...

High resolution optical spectra of chromospheric spicules obtained in the H? line are studied together with slit-jaw filtergrams. The spectra were recorded along a vertical slit parallel to the solar limb with the HSFA2 (Horizontal-Sonnen-Forschungs-Anlage) Solar Spectrograph at Ondrejov Observatory on August 19, 2007 and show H? line profiles take...

Context.Atmospheric seeing due to terrestrial atmospheric turbulence is a process that distorts solar ground-based observations.Aims.We study the influence of atmospheric seeing on ${\rm H\alpha}$ cloud model inversions.Methods.We use Beckers' cloud model which assumes a constant source function to obtain physical parameters from observed quiet-Sun...

Spectral inversion techniques based on the cloud model are extremely useful for the study of properties and dynamics of various chromospheric cloud-like structures. Several inversion techniques are reviewed based on simple (constant source function) and more elaborated cloud models, as well as on grids of synthetic line profiles produced for a wide...

We present observations of a solar quiet region obtained by the ground-based Dutch Open Telescope (DOT), and by instruments on the spacecraft SOHO and TRACE. The observations were obtained during a coordinated observing campaign on October 2005. The aim of this work is to present the rich diversity of fine-scale structures that are found at the net...

Context: Sunspots exhibit a wide range of oscillatory phenomena within their umbrae and penumbrae. Aims: We investigate the behavior of intensity and Doppler velocity oscillations in the umbra and the penumbra to study sunspot oscillations and their associations. Methods: Simultaneous, high-cadence (8 s), two-dimensional, Ca II 8542 Å and Halpha 65...

The temporal variation of a loop system that appears to be changing rapidly is examined. The analyzed data were obtained on 15 May 1999, with the Transition Region and Coronal Explorer (TRACE) during an observing campaign and consist of observations in the Fe ix/Fe x 171 Å and Fe xii 195 Å passbands taken at a cadence of ∼10 min. The special intere...

We present methods for estimating different physical properties of dark mottles from observations obtained with the MSDP spectrograph mounted on the 50 cm refractor of the Pic du Midi Observatory and on THEMIS (Tenerife). We also present studies of their dynamical evolution and estimates of the role they play in the mass balance and heating of the...

Umbral oscillations and running penumbral (RP) waves are studied with simultaneous, two-dimensional, high cadence (8 sec), dual-line sunspot observations in Ca II 8542 Å and Halpha , obtained with the MSDP spectrograph on the German VTT in Tenerife. Doppler velocity and intensity images are used to investigate the physical characteristics of umbral...

Context.Umbral flashes (UFs) and running penumbral (RP) waves are believed to be closely related oscillatory phenomena of sunspots.Aims.We investigate the association of UFs and RP waves to see whether the latter are a visual pattern created by a common source with UFs or a trans-sunspot wave driven by UFs.Methods.Simultaneous, two-dimensional, dua...

We study the broadening of EUV line widths as we move from the disk through and off the solar limb. This broadening maximizes at approximately 10 Mm above the limb. We use one raster scan and two time series obtained by SUMER/SoHO to examine a possible correlation between this phenomenon and spicule activity. It appears that spicule presence leads...

We report on our observations made during the SOHO-GBO campaign in October 2005. In particular, we focus on Hα mottles observed with the Dutch Open Telescope (DOT) and quiet Sun regions seen in O V 629 Å and N V 1238 Å lines by SOHO/SUMER. Hα data provide us with the diagnostics of the Hα line opacity and this can be correlated with the opacity of...

We analyze time series scans of the solar limb performed by the spectrometer SUMER on-board the SoHO satellite. The analyzed dataset consists of observations obtained in the C III 977 Å line. After applying the standard SUMER data reduction procedure, we perform a one line Gaussian fit to the profiles to obtain different parameters for each pixel w...

Mottles and spicules are the most prominent, short-lived, dynamic features residing at the quiet Sun chromospheric network and constitute what is known as chromospheric fine structure. We are reporting a comprehensive study of the dynamical characteristics and physical properties of such structures, from multi-wavelength observations, using line in...