The measurement of the Sun's surface motions with a high spatial and temporal resolution is still a challenge. We wish to validate horizontal velocity measurements all over the visible disk of the Sun from Solar Dynamics Observatory/ Helioseismic and Magnetic Imager (SDO/HMI) data. Horizontal velocity fields are measured by following the proper motions of solar granules using a newly developed version of the Coherent Structure Tracking (CST) code. The comparison of the surface flows measured at high spatial resolution (Hinode, 0.1 arcsec) and low resolution (SDO/HMI, 0.5 arcsec) allows us to determine corrections to be applied to the horizontal velocity measured from HMI white light data. We derive horizontal velocity maps with spatial and temporal resolutions of respectively 2.5 Mm and 30 min. From the two components of the horizontal velocity Vx and Vy measured in the sky plane and the simultaneous line of sight component from SDO/HMI dopplergrams v_D, we derive the spherical velocity components (Vr, Vtheta, Vphi). The azimuthal component Vphi gives the solar differential rotation with a high precision (+-0.037km/s) from a temporal sequence of only three hours. By following the proper motions of the solar granules, we can revisit the dynamics of the solar surface at high spatial and temporal resolutions from hours to months and years with the SDO data.
We describe here the application of a machine learning method for flare forecasting using vectors of properties extracted from images provided by the Helioseismic and Magnetic Imager in the Solar Dynamics Observatory (SDO/HMI). We also discuss how the method can be used to quantitatively assess the impact of such properties on the prediction process.
In this paper, we came to conclusion that there is a significant systematic error in the SDO/HMI vector magnetic data, which reveals itself in a significant deviation of the lines of the knot magnetic fields from the radial direction. The value of this deviation demonstrates a clear dependence on the distance to the disk center. This paper suggests a method for correction of the vector magnetograms that eliminates the detected systematic error.
Solar flares with a broadband emission in the white-light range of the electromagnetic spectrum belong to most enigmatic phenomena on the Sun. The origin of the white-light emission is not entirely understood. We aim to systematically study the visible-light emission connected to solar flares in SDO/HMI observations. We developed a code for automatic detection of kernels of flares with HMI intensity brightenings and study properties of detected candidates. The code was tuned and tested and with a little effort, it could be applied to any suitable data set. By studying a few flare examples, we …
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 …
The solar mean magnetic field (SMMF) provided by the Wilcox Solar Observatory (WSO) is compared with the SMMF acquired by the \textit{Helioseismic and Magnetic Imager} (HMI) onboard the \textit{Solar Dynamic Observatory} (SDO). We found that despite the different spectral lines and measurement techniques used in both instruments the Pearson correlation coefficient between these two datasets equals 0.86 while the conversion factor is very close to unity: B(HMI) = 0.99(2)B(WSO). We also discuss artifacts of the SDO/HMI magnetic field measurements, namely the 12 and 24-hour oscillations in SMMF a…
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 several methods towards construction of precursors, which show great promise towards early predictions, of solar flare events in this paper. A data pre-processing pipeline is built to extract useful data from multiple sources, Geostationary Operational Environmental Satellites (GOES) and Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI), to prepare inputs for machine learning algorithms. Two classification models are presented: classification of flares from quiet times for active regions and classification of strong versus weak flare events. We adopt deep learn…
The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) is designed to study oscillations and the mag- netic field in the solar photosphere. It observes the full solar disk in the Fe I absorption line at 6173Å. We use the output of a high-resolution 3D, time- dependent, radiation-hydrodynamic simulation based on the CO5BOLD code to calculate profiles F(λ,x,y,t) for the Fe I 6173Å line. The emerging profiles F(λ,x,y,t) are multiplied by a representative set of HMI filter transmission profiles R_i(λ,1 \leq i \leq 6) and filtergrams I_i(x,y,t;1 \leq i \leq 6) are c…
We compare measurements of horizontal flows on the surface of the Sun using helioseismic time--distance inversions and coherent structure tracking of solar granules. Tracking provides 2D horizontal flows on the solar surface, whereas the time--distance inversions estimate the full 3-D velocity flows in the shallow near-surface layers. Both techniques use HMI observations as an input. We find good correlations between the various measurements resulting from the two techniques. Further, we find a good agreement between these measurements and the time-averaged Doppler line-of-sight velocity, and …
We study properties of waves of frequencies above the photospheric acoustic cut-off of $\approx$5.3 mHz, around four active regions, through spatial maps of their power estimated using data from Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The wavelength channels 1600 Å and 1700 Å from AIA are now known to capture clear oscillation signals due to helioseismic p modes as well as waves propagating up through to the chromosphere. Here we study in detail, in comparison with HMI Doppler data, properties of the power maps, es…
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…
The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carring…
We use SDO/HMI and SOLIS/VSM photospheric magnetic field measurements to model the force-free coronal field above a solar active region, assuming magnetic forces to dominate. We take measurement uncertainties caused by, e.g., noise and the particular inversion technique into account. After searching for the optimum modeling parameters for the particular data sets, we compare the resulting nonlinear force-free model fields. We show the degree of agreement of the coronal field reconstructions from the different data sources by comparing the relative free energy content, the vertical distribution…
We perform an analysis of the line-of-sight (LOS) observables of the SDO/HMI for models of the solar atmosphere heated by precipitating high-energy electrons during solar flares. The radiative hydrodynamic (RADYN) flare models are obtained from the F-CHROMA database. The Stokes profiles for the Fe 6173 A line observed by SDO/HMI are calculated using the radiative transfer code RH1.5D assuming statistical equilibrium for atomic level populations and imposing uniform background vertical magnetic field of various strength. The SDO/HMI observing sequence and LOS data processing pipeline algorithm …
The Sun is the only star where the superficial turbulent convection can be observed at very high spatial resolution. The Solar Dynamics Observatory (SDO) has continuously observed the full Sun from space with multi-wavelength filters since July 2010. In particular, the Helioseismic and Magnetic Imager (HMI) instrument takes high-cadence frames (45 seconds) of continuum intensity in which solar granulation is visible. We aimed to follow the evolution of the solar granules over an activity cycle and look for changes in their spatial properties. We investigated the density of granules and their m…
Using joint observations from Hinode/EIS and the Atmospheric Imaging Array (AIA) on the Solar Dynamics Observatory we explore the asymmetry of coronal EUV line profiles. We find that asymmetries exist in all of the spectral lines studied, and not just the hottest lines as has been recently reported in the literature. Those asymmetries indicate that the velocities of the second emission component are relatively consistent across temperature and consistent with the apparent speed at which material is being inserted from the lower atmosphere that is visible in the SDO/AIA images as propagating co…
Exploding granules constitute the strongest horizontal flows on the quiet Sun and contribute to the structure of the surface horizontal velocity fields which build the large-scale organization of the discrete magnetic field. In this work we explore exploding granule expansion through the observations of the ground-based THEMIS telescope, IRIS, SDO, and the Hinode space-borne instruments, and finally with the magnetohydrodynamics simulation. We evaluate the detection and the expansion of exploding granules at several wavelengths and at various spatial and temporal resolutions. To analyze the di…
White-light (WL) flares have been observed and studied more than a century since the first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial. One of the important facts in addressing the flare energetics is the spatialtemporal correlation between the white-light emission and the hard X-ray radiation, presumably suggesting that the energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares (?greater than or equal to M5) observed simultaneously by the Helioseismic and Magnetic Imager (HMI)…
The SDO/HMI instruments provide photospheric vector magnetograms with a high spatial and temporal resolution. Our intention is to model the coronal magnetic field above active regions with the help of a nonlinear force-free extrapolation code. Our code is based on an optimization principle and has been tested extensively with semi-analytic and numeric equilibria and been applied before to vector magnetograms from Hinode and ground based observations. Recently we implemented a new version which takes measurement errors in photospheric vector magnetograms into account. Photospheric field measure…
We present and discuss results from time-distance helioseismic measurements of meridional circulation in the solar convection zone using 4 years of Doppler velocity observations by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). Using an in-built mass conservation constraint in terms of the stream function we invert helioseismic travel times to infer meridional circulation in the solar convection zone. We find that the return flow that closes the meridional circulation is possibly beneath the depth of $0.77 R_{\odot}$. We discuss the significance of thi…
We report on observations of recurrent jets by instruments onboard the Interface Region Imaging Spectrograph (IRIS), Solar Dynamics Observatory (SDO) and Hinode spacecrafts. Over a 4-hour period on July 21st 2013, recurrent coronal jets were observed to emanate from NOAA Active Region 11793. FUV spectra probing plasma at transition region temperatures show evidence of oppositely directed flows with components reaching Doppler velocities of +/- 100 km/s. Raster Doppler maps using a Si IV transition region line show all four jets to have helical motion of the same sense. Simultaneous observation…
The Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) instruments onboard the Solar Dynamics Observatory satellite produce Doppler velocity and continuum intensity at 6173 A as well as intensity maps at 1600 A and 1700 A, which can be used for helioseismic studies at different heights in the solar photosphere. We perform a Hankel-Fourier analysis in an annulus centered around sunspots or quiet-Sun regions, to estimate the change in power of waves crossing these regions of interest. We find that there is a dependence of power-reduction coefficients on measurement…
Oscillatory Phase and Acoustic Travel-Time Inconsistencies Measured between SDO/HMI and GONG Dopplergrams
Stanford University（斯坦福大学）；Indian Institute of Astrophysics（印度天体物理研究所）；National Solar Observatory（国家太阳观测台）；National Research University TIIAME（塔什干国立研究技术大学）
NASA's Solar Dynamics Observatory is delivering vector field observations of the full solar disk with unprecedented temporal and spatial resolution; however, the satellite is in a highly inclined geostationary orbit. The relative spacecraft-Sun velocity varies by $\pm3$~km/s over a day which introduces major orbital artifacts in the Helioseismic Magnetic Imager data. We demonstrate that the orbital artifacts contaminate all spatial and temporal scales in the data. We describe a newly-developed three stage procedure for mitigating these artifacts in the Doppler data derived from the Milne-Eddin…
As the global magnetic field of the Sun has an activity cycle, one expects to observe some variation of the dynamical properties of the flows visible in the photosphere. We investigate the flow field during the solar cycle by analysing SDO/HMI observations of continuum intensity, Doppler velocity and longitudinal magnetic field. We first picked data at disk center during 6 years along the solar cycle with a 48-hour time step in order to study the overall evolution of the continuum intensity and magnetic field. Then we focused on thirty 6-hour sequences of quiet regions without any remnant of m…
Aims: The statistics of the photospheric granulation pattern are investigated using continuum images observed by Solar Dynamic Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) taken at 6713~Å. Methods: The supergranular boundaries can be extracted by tracking photospheric velocity plasma flows. The local ball-tracking method is employed to apply on the HMI data gathered over the years 2011-2015 to estimate the boundaries of the cells. The edge sharpening techniques are exerted on the output of ball-tracking to precisely identify the cells borders. To study the fractal dimensionality (F…
The solar coronal magnetic field produces solar activity, including extremely energetic solar flares and coronal mass ejections (CMEs). Knowledge of the structure and evolution of the magnetic field of the solar corona is important for investigating and understanding the origins of space weather. Although the coronal field remains difficult to measure directly, there is considerable interest in accurate modeling of magnetic fields in and around sunspot regions on the Sun using photospheric vector magnetograms as boundary data. In this work, we investigate effects of the size of the domain chos…
Measurements of magnetic fields and electric currents in the pre-eruptive corona are crucial to study solar eruptive phenomena, like flare and coronal mass ejections(CMEs). However, spectro-polarimetric measurements of certain photospheric lines permit a determination of the vector magnetic field at the photosphere. Thus, substantial collection of magnetograms relate to the photospheric surface field only. Numerical modeling is carried out by applying state-of-the-art nonlinear force-free field (NLFFF) reconstruction. Cartesian nonlinear force-free field (NLFFF) codes are not well suited for l…
We develop and apply an enhanced regularization algorithm, used in RHESSI X-ray spectral analysis, to constrain the ill-posed inverse problem that is determining the DEM from solar observations. We demonstrate this computationally fast technique applied to a range of DEM models simulating broadband imaging data from SDO/AIA and high resolution line spectra from Hinode/EIS, as well as actual active region observations with Hinode/EIS and XRT. As this regularization method naturally provides both vertical and horizontal (temperature resolution) error bars we are able to test the role of uncertai…
We analyse observations of the X9.3 solar flare (SOL2017-09-06T11:53) observed by SDO/HMI and Hinode/SOT. Our aim is to learn about the nature of the HMI pseudocontinuum Ic used as a proxy for the white-light continuum. From model atmospheres retrieved by an inversion code applied to the Stokes profiles observed by the Hinode satellite we synthesise profiles of the FeI 617.3 nm line and compare them to HMI observations. Based on a pixel-by-pixel comparison we show that the value of Ic represents the continuum level well in quiet-Sun regions only. In magnetised regions it suffers from a simplis…
Observations from the Solar Dynamics Observatory (SDO) have the potential for allowing the helioseismic study of the formation of hundreds of active regions, which would enable us to perform statistical analyses. Our goal is to collate a uniform data set of emerging active regions observed by the SDO/HMI instrument suitable for helioseismic analysis up to seven days before emergence. We restricted the sample to active regions that were visible in the continuum and emerged into quiet Sun largely avoiding pre-existing magnetic regions. As a reference data set we paired a control region (CR), wit…
We analysed line-of-sight magnetic fields and magnetic power spectra of an undisturbed photosphere using magnetograms acquired by the Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamic Observatory (SDO) and the Near InfraRed Imaging Spectrapolarimeter (NIRIS) operating at the Goode Solar Telescope (GST) of the Big Bear Solar Observatory. In the NIRIS data revealed the presence of thin flux tubes of 200-400~km in diameter and of field strength of 1000-2000~G. The HMI power spectra determined for a coronal hole, a quiet sun and a plage areas exhibit the same spectral index of -1 o…
Large scale flows in the Sun play an important role in the dynamo process linked to the solar cycle. The important large scale flows are the differential rotation and the meridional circulation with an amplitude of km/s and few m/s , respectively. These flows also have a cycle related components, namely the torsional oscillations. Our attempt is to determine large-scale plasma flows on the solar surface by deriving horizontal flow velocities using the techniques of solar granule tracking, dopplergrams, and time distance helioseismology. Coherent structure tracking (CST) and time distance helio…
Due to the absence of direct measurement, the magnetic field in the solar corona is usually extrapolated from the photosphere in numerical way. At the moment, the nonlinear force-free field (NLFFF) model dominates the physical models for field extrapolation in the low corona. Recently we have developed a new NLFFF model with MHD relaxation to reconstruct the coronal magnetic field. This method is based on CESE--MHD model with the conservation-element/solution-element (CESE) spacetime scheme. In this paper, we report the application of the CESE--MHD--NLFFF code to \SDO/HMI data with magnetogram…
We use high-resolution images of the sun obtained by the SDO/AIA instrument to study the evolution of the coronal loops in a flaring solar active region. During 15 February 2011 a X-2.2 class flare occurred in NOAA 11158, a $βγδ$ sunspot complex. We identify three distinct phases of the coronal loop dynamics during this event: (i) {\it Slow rise phase}: slow rising motion of the loop-tops prior to the flare in response to slow rise of the underlying flux rope, (ii) {\it Collapse phase}: sudden contraction of the loop-tops with lower loops collapsing earlier than the higher loops, and (iii) {\i…
We take advantage of the HMI/SDO instrument to study the naked emergence of active regions from the first imprints of the magnetic field on the solar surface. To this end, we followed the first 24 hours in the life of two rather isolated ARs that appeared on the surface when they were about to cross the central meridian. We analyze the correlations between Doppler velocities and the orientation of the vector magnetic field finding, consistently, that the horizontal fields connecting the main polarities are dragged to the surface by relatively-strong upflows and are associated to elongated gran…
Time-distance helioseismology is one of the primary tools for studying the solar meridional circulation. However, travel-time measurements of the subsurface meridional flow suffer from a variety of systematic errors, such as a center-to-limb variation and an offset due to the P-angle uncertainty of solar images. Here we apply the time-distance technique to contemporaneous medium-degree Dopplergrams produced by SOHO/MDI and SDO/HMI to obtain the travel-time difference caused by meridional circulation throughout the solar convection zone. The P-angle offset in MDI images is measured by cross-cor…
The physical properties and its contribution to the onset of solar flare are still unclear although chromospheric brightening is considered a precursor phenomenon of flare. Many studies suggested that photospheric magnetic field changes cause destabilization of large-scale coronal structure. We aim to understand how a small photospheric change contributes to a flare and to reveal how the intermediary chromosphere behaves in the precursor phase. We analyzed the precursor brightening of the X1.6 flare on 2014 October 22 in the AR 12192 using the Interface Region Imaging Spectrograph (IRIS) and H…
We present observations of high temperature emission in the core of a solar active region using instruments on Hinode and SDO. These multi-instrument observations allow us to determine the distribution of plasma temperatures and follow the evolution of emission at different temperatures. We find that at the apex of the high temperature loops the emission measure distribution is strongly peaked near 4 MK and falls off sharply at both higher and lower temperatures. Perhaps most significantly, the emission measure at 0.5 MK is reduced by more than two orders of magnitude from the peak at 4 MK. We…
An X1.6 flare occurred in AR 12192 on 2014 October 22 at 14:02 UT and was observed by Hinode, IRIS, SDO, and RHESSI. We analyze a bright kernel which produces a white light (WL) flare with continuum enhancement and a hard X-ray (HXR) peak. Taking advantage of the spectroscopic observations of IRIS and Hinode/EIS, we measure the temporal variation of the plasma properties in the bright kernel in the chromosphere and corona. We found that explosive evaporation was observed when the WL emission occurred, even though the intensity enhancement in hotter lines is quite weak. The temporal correlation…
Active region fan loops in AR 11076 were studied, in search of oscillations, using high cadence spectroscopic observations from EIS on board Hinode combined with imaging sequences from the AIA on board SDO. Spectra from EIS were analyzed in two spectral windows, \FeXII 195.12 Åand \FeXIII 202.04 Åalong with the images from AIA in 171 Åand 193 Åchannels. We find short ($<$3 min) and long ($\approx$9 min) periods at two different locations. Shorter periods show oscillations in all the three line parameters and the longer ones only in intensity and Doppler shift but not in line width. Line profil…
Photospheric magnetic vector maps from two different instruments are used to model the nonlinear force-free coronal magnetic field above an active region. We use vector maps inferred from polarization measurements of the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar Optical Telescope Spectropolarimeter (SP) aboard Hinode. Besides basing our model calculations on HMI data, we use both, SP data of original resolution and scaled down to the resolution of HMI. This allows us to compare the model results based on data from different instruments and to investigate h…
Despite decades of studying the Sun, the coronal heating problem remains unsolved. One fundamental issue is that we do not know the spatial scale of the coronal heating mechanism. At a spatial resolution of 1000 km or more it is likely that most observations represent superpositions of multiple unresolved structures. In this letter, we use a combination of spectroscopic data from the Hinode EUV Imaging Spectrometer (EIS) and high resolution images from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory to determine the spatial scales of coronal loops. We use density measu…
We present a PSF for SDO/HMI and discuss the effects of its removal on the apparent properties of solar surface phenomena in HMI data. The PSF was retrieved from observations of Venus in transit by matching it to the convolution of a model of the venusian disc and solar background with a guess PSF. Observations recorded near in time to the transit of Venus were corrected for instrumental scattered light by the deconvolution with the PSF. Granulation contrast in restored HMI data is greatly enhanced relative to the original data and exhibit reasonable agreement with numerical simulations. Image…
University of Michigan（密歇根大学）；NorthWest Research Associates（西北研究协会）；Lockheed Martin Solar and Astrophysics Laboratory（洛克希德·马丁太阳与天体物理实验室）；Stanford University（斯坦福大学）；NASA GSFC（美国国家航空航天局戈达德太空飞行中心）
We investigate the cross-calibration of the Hinode/SOT-SP and SDO/HMI instrument meta-data, specifically the correspondence of the scaling and pointing information. Accurate calibration of these datasets gives the correspondence needed by inter-instrument studies and learning-based magnetogram systems, and is required for physically-meaningful photospheric magnetic field vectors. We approach the problem by robustly fitting geometric models on correspondences between images from each instrument's pipeline. This technique is common in computer vision, but several critical details are required wh…
Adverse space weather effects can often be traced to solar flares, prediction of which has drawn significant research interests. The Helioseismic and Magnetic Imager (HMI) produces full-disk vector magnetograms with continuous high cadence, while flare prediction efforts utilizing this unprecedented data source are still limited. Here we report results of flare prediction using physical parameters provided by the Space-weather HMI Active Region Patches (SHARP) and related data products. We survey X-ray flares occurred from 2010 May to 2016 December, and categorize their source regions into fou…
Context: Studying the motions on the solar surface is fundamental for understanding how turbulent convection transports energy and how magnetic fields are distributed across the solar surface. Aims: From horizontal velocity measurements all over the visible disc of the Sun and using data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI), we investigate the structure and evolution of solar supergranulation. Methods: Horizontal velocity fields were measured by following the proper motions of solar granules using a newly developed version of the coherent structure tra…
University of Michigan（密歇根大学）；NASA GSFC（美国国家航空航天局戈达德太空飞行中心）；NorthWest Research Associates（西北研究协会）；Lockheed Martin Solar and Astrophysics Laboratory（洛克希德·马丁太阳与天体物理实验室）；Stanford University（斯坦福大学）
Both NASA's Solar Dynamics Observatory (SDO) and the JAXA/NASA Hinode mission include spectropolarimetric instruments designed to measure the photospheric magnetic field. SDO's Helioseismic and Magnetic Imager (HMI) emphasizes full-disk high-cadence and good spatial resolution data acquisition while Hinode's Solar Optical Telescope Spectro-Polarimeter (SOT-SP) focuses on high spatial resolution and spectral sampling at the cost of a limited field of view and slower temporal cadence. This work introduces a deep-learning system named SynthIA (Synthetic Inversion Approximation), that can enhance …
We report the evolution of magnetic field and its energy in NOAA active region 11158 over 5 days based on a vector magnetogram series from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO). Fast flux emergence and strong shearing motion led to a quadrupolar sunspot complex that produced several major eruptions, including the first X-class flare of Solar Cycle 24. Extrapolated non-linear force-free coronal fields show substantial electric current and free energy increase during early flux emergence near a low-lying sigmoidal filament with sheared kilogauss …
Solar magnetic fields are generated in the solar interior and pop up at the solar surface to form active regions. As the magnetic field appears on the surface, it forms various structures like small magnetic elements, pores, and sunspots. The nature of these formation processes is largely unknown. In this contribution we elaborate on the formation of sunspots and particularly on the formation of penumbrae. We report on observations that we obtained at the German VTT on July 4, 2009 on the formation of the spot in AR 11024. This data set is accomplished with data from SOHO/MDI which offers an e…
A major, albeit serendipitous, discovery of the SOlar and Heliospheric Observatory mission was the observation by the Extreme Ultraviolet Telescope (EIT) of large-scale Extreme Ultraviolet (EUV) intensity fronts propagating over a significant fraction of the Sun's surface. These so-called EIT or EUV waves are associated with eruptive phenomena and have been studied intensely. However, their wave nature has been challenged by non-wave (or pseudo-wave) interpretations and the subject remains under debate. A string of recent solar missions has provided a wealth of detailed EUV observations of the…
The uncertainty of measurement of solar diameter is depending on the observational time scale. Full-disc images of SDO/HMI and the images from ground observations in Huairou Solar Observing Station have been analyzed to get the values of solar diameter. The satellite observations reach a very high precision, but the absolute image scale still need to be calibrated. The solar oblateness is a more challenging measurement than the diameter, since the signal amplitude is a few milli-arcseconds. It is a relative measurement, then not affected by the pixel scale calibration required by the diameter …
We present detailed analysis of an extreme ultraviolet (EUV) wave and its interaction with active region (AR) loops observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly and the Hinode EUV Imaging Spectrometer (EIS). This wave was initiated from AR 11261 on 2011 August 4 and propagated at velocities of 430--910 km\s. It was observed to traverse another AR and cross over a filament channel on its path. The EUV wave perturbed neighboring AR loops and excited a disturbance that propagated toward the footpoints of these loops. EIS observations of AR loops revealed that at the tim…
In the quiet solar photosphere, the mixed polarity fields form a magnetic carpet, which continuously evolves due to dynamical interaction between the convective motions and magnetic field. This interplay is a viable source to heat the solar atmosphere. In this work, we used the line-of-sight (LOS) magnetograms obtained from the Helioseismic and Magnetic Imager (HMI) on the \textit{Solar Dynamics Observatory} (\textit{SDO}), and the Imaging Magnetograph eXperiment (IMaX) instrument on the \textit{Sunrise} balloon-borne observatory, as time dependent lower boundary conditions, to study the evolu…
We present plasma diagnostics of an EIT wave observed with high cadence in Hinode/EIS sit-and-stare spectroscopy and SDO/AIA imagery obtained during the HOP-180 observing campaign on 2011 February 16. At the propagating EIT wave front, we observe downward plasma flows in the EIS Fe XII, Fe XIII, and Fe XVI spectral lines (log T ~ 6.1-6.4) with line-of-sight (LOS) velocities up to 20 km/s. These red-shifts are followed by blue-shifts with upward velocities up to -5 km/s indicating relaxation of the plasma behind the wave front. During the wave evolution, the downward velocity pulse steepens fro…
