Properties of Magneto-Hydrodynamic Waves in the Solar Photosphere with Hinode
Daisuke Fujimura, Saku Tsuneta
备注：
50 pages, 10 Postscript images, accepted for publication in ApJ.(There are some changes in version 2 of our paper. Equations (65), (66), (68) in page 40 are corrected. Figure 9 is replaced with new one following the corrected equations. The calculated parameters in pages 32, 33, 42 are corrected.)
We report the observations of the magneto-hydrodynamic waves propagating along magnetic flux tubes in the solar photosphere. We identified 20 isolated strong peaks (8 peaks for pores and 12 peaks for inter-granular magnetic structure) in the power spectra of the l.o.s. (line-of-sight) magnetic flux, the l.o.s. velocity, and the intensity for 14 different magnetic concentrations. The observation is performed with the spectro-polarimeter of the Solar Optical Telescope aboard the \emph{Hinode} satellite. The observed phase relation between the magnetic and the photometric intensity fluctuation would not be consistent with that caused by the opacity effect, if the magnetic field strength decreases with height along the oblique line of sight. We suggest that the observed fluctuations are due to longitudinal (sausage mode) and/or transverse (kink mode) MHD waves. The observed phase relation between the fluctuations in the magnetic flux and the velocity is consistent with the superposition of the ascending wave and the descending wave reflected at chromosphere/corona boundary (standing wave). Even with such reflected waves, the residual upward Poynting flux is estimated to be $2.7 \times 10^{6}$ erg cm$^{-2}$ s$^{-1}$ for a case of the kink wave. Seismology of the magnetic flux tubes is possible to obtain various physical parameters from the observed period and amplitude of the oscillations.
A new three-dimensional model of the solar photosphere is presented in this paper and made publicly available to the community. This model has the peculiarity that it has been obtained by inverting spectro-polarimetric observations, rather than from numerical radiation hydrodynamical simulations. The data used here are from the spectro-polarimeter onboard the Hinode satellite, which routinely delivers Stokes I, Q, U and V profiles in the 6302 A spectral region with excellent quality, stability and spatial resolution (approximately 0.3"). With such spatial resolution, the major granular compone…
In this work, we focus in the magnetic evolution of a small region as seen by Hinode-SP during the time interval of about one hour. High-cadence LOS magnetograms and velocity maps were derived, allowing the study of different small-scale processes such as the formation/disappearance of bright points accompanying the evolution of an observed convective vortical motion.
Aims. Convective collapse, a theoretically predicted process that intensifies existing weak magnetic fields in the solar atmosphere, was first directly observed in a single event by Nagata et al. (2008) using the high resolution Solar Optical Telescope (SOT) of the Hinode satellite. Using the same space telescope, we performed a statistical analysis of convective collapse events. Methods. Our data sets consist of high resolution time series of polarimetric spectral scans of two iron lines formed in the lower photosphere and filter images in Mg I b2 and Ca II H, spectral lines that are formed i…
Magnetohydrodynamic (MHD) waves have been considered as energy sources for heating the solar chromosphere and the corona. Although MHD waves have been observed in the solar atmosphere, there are a lack of quantitative estimates on the energy transfer and dissipation in the atmosphere. We performed simultaneous Hinode and IRIS observations of a sunspot umbra to derive the upward energy fluxes at two different atmospheric layers (photosphere and lower transition region) and estimate the energy dissipation. The observations revealed some properties of the observed periodic oscillations in physica…
We study the observational signature of flux emergence in the photosphere using synthetic data from a 3D MHD simulation of the emergence of a twisted flux tube. Several stages in the emergence process are considered. At every stage we compute synthetic Stokes spectra of the two iron lines Fe I 6301.5 Å and Fe I 6302.5 Å and degrade the data to the spatial and spectral resolution of Hinode's SOT/SP. Then, following observational practice, we apply Milne-Eddington-type inversions to the synthetic spectra in order to retrieve various atmospheric parameters and compare the results with recent Hino…
In this work we follow a series of papers on high-resolution observations of small-scale structures in the solar atmosphere \citep[][Cabello et al., in prep]{Balmaceda2009, Balmaceda2010, Vargas2011, Palacios2012, Domingo2012, Vargas2015}, combining several multi-wavelength data series. These were acquired by both ground-based (SST) and space-borne (Hinode) instruments during the joint campaign of the Hinode Operation Program 14, in September 2007. Diffraction-limited SST data were taken in the G-band and G-cont, and were restored by the MFBD technique. Hinode instruments, on the other hand, p…
White-light emissions were observed from an X1.7 class solar flare on 27 January 2012, using three continuum bands (red, green, and blue) of the Solar Optical Telescope (SOT) onboard the Hinode satellite. This event occurred near the solar limb, and so differences in locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regi…
Doppler Velocity Variation near the Solar Limb in the Solar Photosphere Observed with Hinode
The University of Tokyo（东京大学）；National Astronomical Observatory of Japan（日本国立天文台）；National Institute for Fusion Science（核聚变科学研究所）；The Graduate University for Advanced Studies, SOKENDAI（综合研究大学院大学）
本研究利用Hinode卫星数据分析了太阳临边附近Fe I 630.15 nm谱线，发现颗粒对流导致朝向临边的红移增加，且颗粒谱线形成区域比颗粒间区域更厚。
The \ion{Fe}{i} lines observed by the Hinode/SOT spectropolarimeter were always seen in absorption, apart from the extreme solar limb. Here we analyse a unique dataset capturing these lines in emission during a solar white-light flare. We analyse the temperature stratification in the solar photosphere during a white-light flare and compare it with the post-white-light flare state. We used two scans of the Hinode/SOT spectropolarimeter to infer, by means of the LTE inversion code Stokes Inversion based on Response function (SIR), the physical properties in the solar photosphere during and after…
Context. Magnetic Bright Points (MBPs) are small-scale magnetic features in the solar photosphere. They may be a possible source of coronal heating by rapid footpoint motions that cause magnetohydrodynamical waves. The number and size distribution are of vital importance in estimating the small scale-magnetic-field energy. Aims. The size distribution of MBPs is derived for G-band images acquired by the Hinode/SOT instrument. Methods. For identification purposes, a new automated segmentation and identification algorithm was developed. Results. For a sampling of 0.108 arcsec/pixel, we derived a …
Magnetic null points can be located numerically in a potential field extrapolation or their average density can be estimated from the Fourier spectrum of a magnetogram. We use both methods to compute the null point density from a quiet Sun magnetogram made with Hinode's NFI and from magnetograms from SOHO's MDI in both its high-resolution and low-resolution modes. All estimates of the super-chromospheric column density (z>1.5 Mm) agree with one another and with the previous measurements: 0.003 null points per square Mm of solar surface.
In our studies of the dynamics and energetics of the solar atmosphere, we have detected, in high-quality observations from Hinode SOT/NFI, ubiquitous small-scale upflows which move horizontally with supersonic velocities in the quiet Sun. We present the properties of these fast moving upflows (FMUs) and discuss different interpretations.
We present properties of intensity oscillations of a sunspot in the photosphere and chromosphere using G~band and CaIIH filtergrams from Hinode. Intensity power maps as function of magnetic field strength and frequency reveal reduction of power in Gband with increase in photospheric magnetic field strength at all frequencies. In CaIIH, however, stronger fields exhibit more power at high frequencies particularly in the 4.5 mHz-8.0 mHz band. Power distribution in different locations of the active region show that the oscillations in CaIIH exhibit more power in comparison to that of Gband. We als…
Three-dimensional magnetohydrodynamic simulations of the surface layers of the Sun intrinsically produce a predominantly horizontal magnetic field in the photosphere. This is a robust result in the sense that it arises from simulations with largely different initial and boundary conditions for the magnetic field. While the disk-center synthetic circular and linear polarization signals agree with measurements from Hinode, their center-to-limb variation sensitively depends on the height variation of the horizontal and the vertical field component and they seem to be at variance with the observed…
We have developed an inversion procedure designed for high-resolution solar spectro-polarimeters, such as Hinode/SP or DKIST/ViSP. The procedure is based on artificial neural networks trained with profiles generated from random atmospheric stratifications for a high generalization capability. When applied to Hinode data we find a hot fine-scale network structure whose morphology changes with height. In the middle layers this network resembles what is observed in G-band filtergrams but it is not identical. Surprisingly, the temperature enhancements in the middle and upper photosphere have a rev…
We have derived the temporal power spectra of the horizontal velocity of the solar photosphere. The data sets for 14 quiet regions observed with the Gband filter of Hinode/SOT are analyzed to measure the temporal fluctuation of the horizontal velocity by using the local correlation tracking (LCT) method. Among the high resolution (~0.2") and seeing-free data sets of Hinode/SOT, we selected the observations whose duration is longer than 70 minutes and cadence is about 30 s. The so-called k-ω diagrams of the photospheric horizontal velocity are derived for the first time to investigate the tempo…
To investigate the penumbral plasma flow on a small scale, spectropolari- metric data of sunspots recorded by HINODE was used. Maps of Doppler velocities were created by evaluating the bisector in the line-wing, thereby visualizing the flow pattern in the low photosphere where the Evershed effect is most pronounced. In penumbrae close to the disk center, the vertical component of the Evershed flow dominates. The latter consists of a series of elongated up-flow patterns extending radially through the entire center-side penumbra at a constant azimuth. Along this structure, strong up-flows appear…
Recent spectro-polarimetric observations have provided detailed measurements of magnetic field, velocity and intensity during events of magnetic field intensification in the solar photosphere. We consider the temporal evolution of the relevant physical quantities for three cases of magnetic field intensification in a numerical simulation. We determine the evolution of the intensity, magnetic flux density and zero-crossing velocity derived from the synthetic Stokes parameters by taking into account the spectral and spatial resolution of the spectropolarimeter (SP) on board Hinode. The three eve…
We present the first interpretation of the Stokes profile asymmetries measured in the FeI 630 nm lines by SOT/SP, in both quiet Sun internetwork (IN) and network regions. The inversion is carried out under the hypothesis of MISMA, where the unresolved structure is assumed to be optically thin. We analyze a 29.52"x31.70" subfield carefully selected to be representative of the properties of a 302"x162" quiet Sun field-of-view at disk center. The inversion code is able to reproduce the observed asymmetries in a very satisfactory way. The inversion code interprets 25% of inverted profiles as emerg…
Various theoretical and observational results have been reported regarding the presence/absence of net electric currents in the sunspots. The limited spatial resolution of the earlier observations perhaps obscured the conclusions. We have analyzed 12 sunspots observed from Hinode (SOT/SP) to clarify the issue. The azimuthal and radial components of magnetic fields and currents have been derived. The azimuthal component of the magnetic field of sunspots is found to vary in sign with azimuth. The radial component of the field also varies in magnitude with azimuth. While the latter pattern is a c…
A magnetic field is force-free if there is no interaction between the magnetic field and plasma in surrounding atmosphere i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. Computation of various magnetic parameters such as magnetic energy, gradient of twist of sunspot fields and any kind of extrapolations, heavily hinge on the force-free approximation of the photospheric sunspot magnetic fields. Thus it is important to inspect the force-freeness of sunspot fields. The force-freeness of sunspot magnetic fields has been examined earlier by some resea…
Since May 1, 2010, we have been able to study (almost) continuously the vector magnetic field in the Sun, thanks to two space-based observatories: the Solar Dynamics Observatory (SDO) and Hinode. Both are equipped with instruments able to measure the Stokes parameters of Zeeman-induced polarization of photospheric line radiation. But the observation modes, the spectral lines, the spatial, spectral and temporal sampling, and even the inversion codes used to recover magnetic and thermodynamic information from the Stokes profiles are different. We compare the vector magnetic fields derived from o…
We present the first Hinode/EIS observations of 5 min quasi-periodic oscillations detected in a transition-region line (He II) and five coronal lines (Fe X, Fe XII, Fe XIII, Fe XIV, and Fe XV) at the footpoint of a coronal loop. The oscillations exist throughout the whole observation, characterized by a series of wave packets with nearly constant period, typically persisting for 4-6 cycles with a lifetime of 20-30 min. There is an approximate in-phase relation between Doppler shift and intensity oscillations. This provides evidence for slow magnetoacoustic waves propagating upwards from the tr…
We investigate the evolution of 5 granular-scale magnetic flux cancellations just outside the moat region of a sunspot by using accurate spectropolarimetric measurements and G-band images with the Solar Optical Telescope aboard Hinode. The opposite polarity magnetic elements approach a junction of the intergranular lanes and then they collide with each other there. The intergranular junction has strong red shifts, darker intensities than the regular intergranular lanes, and surface converging flows. This clearly confirms that the converging and downward convective motions are essential for the…
Solar granules are bright patterns surrounded by dark channels called intergranular lanes in the solar photosphere and are a manifestation of overshooting convection. Observational studies generally find stronger upflows in granules and weaker downflows in intergranular lanes. This trend is, however, inconsistent with the results of numerical simulations in which downflows are stronger than upflows through the joint action of gravitational acceleration/deceleration and pressure gradients. One cause of this discrepancy is the image degradation caused by optical distortion and light diffraction …
We investigated the role of photospheric plasma motions in the formation and evolution of polar magnetic patches using time-sequence observations with high spatial resolution. The observations were obtained with the spectropolarimeter on board the Hinode satellite. From the statistical analysis using 75 magnetic patches, we found that they are surrounded by strong converging, supergranulation associated flows during their apparent life time and that the converging flow around the patch boundary is better observed in the Doppler velocity profile in the deeper photosphere. Based on our analysis …
The satellite Hinode has recently revealed penumbral structures with a magnetic polarity opposite to the main sunspot polarity. They may be a direct confirmation of magnetic field lines and mass flows returning to the solar interior throughout the penumbra, a configuration previously inferred from interpretation of observed Stokes profile asymmetries. The paper points out the relationship between the reverse polarity features found by Hinode, and the model Micro-Structured Magnetic Atmospheres (MISMAs) proposed for sunspots. We show how the existing model MISMAs produce strongly redshifted rev…
Inversion techniques applied to the radiative transfer equation for polarized light are capable of inferring the physical parameters in the solar atmosphere (temperature $T$, magnetic field ${\bf B}$, and line-of-sight velocity $v_{\rm los}$) from observations of the Stokes vector (i.e., spectropolarimetric observations) in spectral lines. Inferences are usually performed in the $(x,y,τ_c)$ domain, where $τ_c$ refers to the optical-depth scale. Generally, their determination in the $(x,y,z)$ volume is not possible due to the lack of a reliable estimation of the gas pressure, particularly in re…
Recent studies undoubtedly demonstrate that the magnetic field in the photosphere and corona is an intermittent structure, which offers new views on the underlying physics. In particular, such problems as the existence in the corona of localized areas with extremely strong resistivity (required to explain magnetic reconnection of all scales) and the interchange between small and large scales (required in study of the photosphere/corona coupling), to name a few, can be easily captured by the concept of intermittency. This study is focused on simultaneous time variations of intermittency propert…
We investigate the importance of ambipolar diffusion and Hall currents for high-resolution comprehensive ('realistic') photospheric simulations. To do so we extended the radiative magnetohydrodynamics code \emph{MURaM} to use the generalized Ohm's law under the assumption of local thermodynamic equilibrium. We present test cases comparing analytical solutions with numerical simulations for validation of the code. Furthermore, we carried out a number of numerical experiments to investigate the impact of these neutral-ion effects in the photosphere. We find that, at the spatial resolutions curre…
Context: The expansion of network magnetic fields with height is a fundamental property of flux tube models. A rapid expansion is required to form a magnetic canopy. Aims: We characterize the observed expansion properties of magnetic network elements and compare them with the thin flux tube and sheet approximations, as well as with magnetoconvection simulations. Methods: We used data from the Hinode SOT NFI NaD1 channel and spectropolarimeter to study the appearance of magnetic flux concentrations seen in circular polarization as a function of position on the solar disk. We compared the observ…
Helioseismic and magnetohydrodynamic waves are abundant in and above sunspots. Through cross-correlating oscillation signals in the photosphere observed by the SDO/HMI, we reconstruct how waves propagate away from virtual wave sources located inside a sunspot. In addition to the usual helioseismic wave, a fast-moving wave is detected traveling along the sunspot's radial direction from the umbra to about 15 Mm beyond the sunspot boundary. The wave has a frequency range of 2.5 - 4.0 mHz with a phase velocity of 45.3 km/s, substantially faster than the typical speeds of Alfven and magnetoacoustic…
High-resolution observations of the solar photosphere have recently revealed the presence of elongated filamentary bright structures inside sunspot umbrae. These features, which have been called umbral filaments (UFs), differ in morphology, evolution, and magnetic configuration from light bridges that are usually observed to intrude in sunspots. To study an UF observed in the leading sunspot of active region NOAA 12529, we have analyzed spectro-polarimetric observations taken in the photosphere with the spectropolarimeter (SP) aboard the Hinode satellite. High-resolution observations in the up…
This is a follow-up investigation of a magnetic-flux cancellation event at a polarity inversion line (PIL) on the Sun observed with the spectropolarimeter on board Hinode. Anomalous circular polarization (Stokes V) profiles are observed in the photosphere along the PIL at the cancellation sites. Kubo et al. (2010) previously reported that the theoretically expected horizontal fields between the canceling opposite-polarity magnetic elements in this event are not detected at granular scales. We show that the observed anomalous Stokes V profiles are reproduced successfully by adding the nearly sy…
Using numerical simulations of the magnetised solar photosphere carried out with the radiative magneto-hydrodynamic code, MURaM, and detailed spectro-polarimetric diagnostics of the simulated photospheric 6302A FeI line, spectro-polarimetric signatures of Alfven waves in magnetised intergranular lanes of the simulated solar photosphere were analysed at different positions at the solar disk. The torsional Alfven waves in the intergranular lanes are horizontal plasma motions, which do not have a thermal perturbation counterpart. We find signatures of Alfven waves as small-scale line profile Dopp…
The solar photosphere is the visible surface of the Sun, where many bright granules, surrounded by narrow dark intergranular lanes, are observed everywhere. The granular pattern is a manifestation of convective motion at the photospheric level, but its velocity structure in the height direction is poorly understood observationally. Applying bisector analysis to a photospheric spectral line recorded by the Hinode Solar Optical Telescope, we derived the velocity structure of the convective motion in granular regions and intergranular lanes separately. The amplitude of motion of the convective ma…
Small-scale magnetic fields in the solar photosphere can be identified in high-resolution magnetograms or in the G-band as magnetic bright points (MBPs). Rapid motions of these fields can cause magneto-hydrodynamical waves and can also lead to nanoflares by magnetic field braiding and twisting. The MBP velocity distribution is a crucial parameter for estimating the amplitudes of those waves and the amount of energy they can contribute to coronal heating. The velocity and lifetime distributions of MBPs are derived from solar G-band images of a quiet sun region acquired by the Hinode/SOT instrum…
We analyze spectropolarimetric data taken with the Hinode spacecraft in quiet solar regions at the disk center. Distorted redshifted Stokes $V$ profiles are found showing a characteristic evolution that always follows the same sequence of phases. We have studied the statistical properties of these events using spectropolarimetric data from Hinode/SP. We also examined the upper photosphere and the low chromosphere using Mg i b2 and Ca ii h data from Hinode. Finally, we have applied the SIRGAUSS inversion code to the polarimetric data in order to infer the atmospheric stratification of the physi…
We present G-band and Ca II H observations of NOAA AR 10930 obtained by Hinode/SOT on 2006 December 6 covering an X6.5 flare. Local Correlation Tracking (LCT) technique was applied to the foreshortening-corrected G-band image series to acquire horizontal proper motions in this complex beta-gamma-delta active region. With the continuous high quality, spatial and temporal resolution G-band data, we not only confirm the rapid decay of outer penumbrae and darkening of the central structure near the flaring neutral line, but also unambiguously detect for the first time the enhancement of the sheare…
To study the structure of spatially unresolved features of the solar photosphere, we calculated the Stokes profiles of seven photospheric iron lines using two-dimensional nonstationary MHD models of solar granulation for various amounts of magnetic flux (0, 10, 20, 30 mT). We investigate variations in the absolute wavelength shifts and bisectors of the I profiles, as well as variations in the zero-crossing wavelength shifts, amplitude and area asymmetry of the V profiles as functions of magnetic field strength and time. The center-to-limb variations of the Stokes profiles are analyzed. The iro…
We investigate the generation mechanisms of MHD Poynting flux in the magnetised solar photosphere. Using radiative MHD modelling of the solar photosphere with initial magnetic configurations that differ in their field strength and geometry, we show the presence of two different mechanisms for MHD Poynting flux generation in simulations of solar photospheric magneto-convection. The weaker mechanism is connected to vertical transport of weak horizontal magnetic fields in the convectively stable layers of the upper photosphere, while the stronger is the production of Poynting flux in strongly mag…
Light bridge (LB) is bright structure crossing the umbra of sunspots and associated to the breakup or assembly of sunspots. In this paper, a LB is presented and studied using the observatory data obtained by {\it Hinode} satellites. Force-free factor ($α$) and the z-component of current ($J_{z}$) and tension force ($T_{z}$) are calculated basing on the vector magnetograms observed by Spectro-Polarimeter (SP) of the Solar Optical Telescope (SOT) on board {\it Hinode}. It is found that the amplitudes of $α$ and $J_{z}$ of LB are generally larger than those of umbra. It is found that there are tw…
Modeling the interface region between solar photosphere and corona is challenging, because the relative importance of magnetic and plasma forces change by several orders of magnitude. While the solar corona can be modeled by the force-free assumption, we need to take care about plasma forces (pressure gradient and gravity) in photosphere and chromosphere, here within the magneto-hydro-static (MHS) model. We solve the MHS equations with the help of an optimization principle and use vector magnetogram as boundary condition. Positive pressure and density are ensured by replacing them with two new…
The removal of magnetic flux from the quiet-sun photosphere is important for maintaining the statistical steady-state of the magnetic field there, for determining the magnetic flux budget of the Sun, and for estimating the rate of energy injected into the upper solar atmosphere. Magnetic feature death is a measurable proxy for the removal of detectable flux. We used the SWAMIS feature tracking code to understand how nearly 20000 detected magnetic features die in an hour-long sequence of Hinode/SOT/NFI magnetograms of a region of quiet Sun. Of the feature deaths that remove visible magnetic flu…
Given the difficulty in directly determining prominence physical parameters from observations, prominence seismology stands as an alternative method to probe the nature of these structures. We show recent examples of the application of magnetohydrodynamic (MHD) seismology techniques to infer physical parameters in prominence plasmas. They are based on the application of inversion techniques using observed periods, damping times, and plasma flow speeds of prominence thread oscillations. The contribution of Hinode to the subject has been of central importance. We show an example based on data ob…
To elucidate the flare trigger mechanism, we have analyzed several flare events which were observed by Hinode/Solar Optical Telescope (SOT), in our previous study. Because of the limitation of SOT field of view, however, only four events in the Hinode data sets have been utilizable. Therefore, increasing the number of events is required for evaluating the flare trigger models. We investigated the applicability of data obtained by the Solar Dynamics Observatory (SDO) to increase the data sample for a statistical analysis of the flare trigger process. SDO regularly observes the full disk of the …
Aims: The interactions of velocity scales on the Sun's surface, from granulation to supergranulation are still not understood, nor are their interaction with magnetic fields. We thus aim at giving a better description of dynamics in the mesoscale range which lies between the two scales mentioned above. Method: We analyse a 48h high-resolution time sequence of the quiet Sun photosphere at the disk center obtained with the Solar Optical Telescope onboard Hinode. The observations, which have a field of view of 100 \arcsec$\times$ 100 \arcsec, typically contain four supergranules. We monitor in de…
Low-amplitude Doppler-shift oscillations have been observed in coronal emission lines in a number of active regions with the EUV Imaging Spectrometer (EIS) on the Hinode satellite. Both standing and propagating waves have been detected and many periods have been observed, but a clear picture of all the wave modes that might be associated with active regions has not yet emerged. In this study, we examine additional observations obtained with EIS in plage near an active region on 2007 August 22--23. We find Doppler-shift oscillations with amplitudes between 1 and 2 km/s in emission lines ranging…
We perform radiative magnetohydrodynamic calculations for the solar quiet region to investigate the dependence of statistical flow on magnetic properties and the three-dimensional (3D) structure of magnetic patches in the presence of large-scale flow that mimics differential rotation. It has been confirmed that strong magnetic field patches move faster in the longitudinal direction at the solar surface. Consequently, strong magnetic patches penetrate deeper into the solar interior. The motion of the deep-rooted magnetic patches is influenced by the faster differential rotation in the deeper la…
The results of 2D MHD simulations of solar magnetogranulation are used to analyze the horizontal magnetic fields and the response of the synthesized Stokes profiles of the FeI 1564.85 nm line to the magnetic fields. Selected 1.5-h series of the 2D MHD models reproduces a region of the network fields with their immediate surrounding on the solar surface with the unsigned magnetic flux density of 192 G. According to the magnetic field distribution obtained, the most probable absolute strength of the horizontal magnetic field at an optical depth of tau_5 = 1 (tau_5 denotes tau at lambda = 500 nm)…
It is generally believed that the evolution of magnetic helicity has a close relationship with solar activity. Before the launch of SDO, earlier studies have mostly used MDI/SOHO line of sight magnetograms and assumed that magnetic fields are radial when calculating magnetic helicity injection rate from photospheric magnetograms. However, this assumption is not necessarily true. Here we use the vector magnetograms and line of sight magnetograms, both taken by HMI/SDO, to estimate the effects of non-radial magnetic field on measuring magnetic helicity injection rate. We find that: 1) The effect…
The high-resolution pictures of the solar photosphere from space based 50 cm Solar Optical Telescope (SOT) on-board Hinode spacecraft, are now routinely observed. Such images of a delta-sunspot in NOAA 10930 were obtained by Hinode during 13 December 2006 while a X-class flare occurred in this active region. Two bright ribbons were visible even in white light and G-band images apart from chromospheric Ca II H images. We register the sunspot globally using cross-correlation technique and analyse local effects during flare interval. We find that during flare the penumbral filaments show lateral …
We report the first observation of multiple-periodic propagating disturbances along a fan-like coronal structure simultaneously detected in both intensity and Doppler shift in the Fe XII 195 A line with the EUV Imaging Spectrometer (EIS) onboard Hinode. A new application of coronal seismology is provided based on this observation. We analyzed the EIS sit-and-stare mode observation of oscillations using the running difference and wavelet techniques. Two harmonics with periods of 12 and 25 min are detected. We measured the Doppler shift amplitude of 1-2 km/s, the relative intensity amplitude of …
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$α$ observations and high resolution spectropolarimetric observations of the photospheric magnetic field. The photospheric magnetic field is extrapolated up to the corona showing a multitude of large and small scale structures. We show for the first time that the smallest magnetic structures both at the network and the internetwork contribute significantl…
Context. High-resolution observations of the solar photosphere reveal the presence of fine structures, in particular the so-called magnetic bright points (MBPs), which are small-scale features associated with strong magnetic field regions of the order of kilogauss (kG). It is especially relevant to study these magnetic elements, which are extensively detected at all moments of the solar cycle, in order to establish their contribution to the behaviour of the solar atmosphere, and ultimately a plausible role within the coronal heating problem. Aims. We aim to characterise the size and velocity d…
We report on G-band emission observed by the Solar Optical Telescope onboard the Hinode satellite in association with the X1.5-class flare on 2006 December 14. The G-band enhancements originate from the footpoints of flaring coronal magnetic loops, coinciding with non-thermal hard X-ray bremsstrahlung sources observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. At the available 2 minute cadence, the G-band and hard X-ray intensities are furthermore well correlated in time. Assuming that the G-band enhancements are continuum emission from a blackbody, we derived the total radia…
Solar ultraviolet (UV) bursts are small-scale compact brightenings in transition region images. The spectral profiles of transition region lines in these bursts are significantly enhanced and broadened, often with chromospheric absorption lines such as Ni~{\sc{ii}} 1335.203 and 1393.330 Å superimposed. We investigate the properties of several UV bursts using a coordinated observation of the Interface Region Imaging Spectrograph (IRIS), Solar Dynamics Observatory (SDO), and \textit{Hinode} on 2015 February 7. We have identified 12 UV bursts, and 11 of them reveal small blueshifts of the Ni~{\sc…
