We present results of a global survey of single-pixel intensity power spectra from a 12-hour time period on 26 June 2013 in a 1600x1600 pixel region from four channels of the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument. We extract single-pixel time series from a derotated image sequence, fit models to the power spectra of these time series, and study the spatial dependence of the model parameters. Two power spectra models are considered: i) a three-parameter power-law + tail model and ii) a power-law + tail model + three-parameter localized Lorentzian, the latter to model periodicity. Spectra are well-described by at least one of these models for all pixel locations, with the spatial distribution of best-fit model parameters shown to provide new and unique insights into turbulent, quiescent and periodic features in the EUV corona and upper photosphere. Findings include: individual model parameters correspond clearly and directly to visible solar features; detection of numerous quasi-periodic three- and five-minute oscillations; observational identification of concentrated magnetic flux as regions of largest power-law indices [n]; identification of unique spectral features of coronal holes and filaments; identification of sporadic and pervasive five-minute oscillations throughout the corona; detection of the known global ~4.0-minute chromospheric oscillation; "coronal bullseyes" appearing as radially decaying periodicities over sunspots and sporadic foot-point regions; and "penumbral periodic voids" appearing as broad rings around sunspots in 1600 and 1700 Å in which spectra contain no statistically significant periodic component.
In order to better understand the plasma supply and leakage at active regions, we investigated physical properties of the upflows from edges of active region NOAA AR10978 observed with the EUV Imaging Spectrometer (EIS) onboard Hinode. Our observational aim is to measure two quantities of the outflows: Doppler velocity and electron density.
Solar corona, the last main layer of the atmosphere of the Sun, is detectable in the EUV and X-ray. The corona is expanding into space up to millions of kilometers and is observable during the eclipse. The temperature is increasing about millions of Kelvin. The investigation of this layer is significant for solar physicists because it is dynamic and features. Active regions (AR) and solar mass ejections (CMEs) are the important features in the solar corona. In this research, the solar limb and coronal width is studied from full-disk images at $284 Å$ taken by SOHO/EIT during eleven-year period…
Solar extreme ultraviolet (EUV) waves are spectacular propagating disturbances with EUV enhancements in annular shapes in the solar corona. These EUV waves carry critical information about the coronal magnetised plasma that can shed light on the elusive physical parameters (e.g. the magnetic field strength) by global solar coronal magneto-seismology. EUV waves are closely associated with a wide range of solar atmospheric eruptions, from violent flares and coronal mass ejections (CMEs) to less energetic plasma jets or mini-filament eruptions. However, the physical nature and driving mechanism o…
We re-examine the physical relationship between Extreme-UltraViolet (EUV) waves and type II radio bursts. It has been often thought that they are two observational aspects of a single coronal shock wave. However, a lack of their speed correlation hampers the understanding of their respective (or common) natures in a single phenomenon. Knowing the uncertainties in identifying true wave components from observations and measuring their speeds, we re-examine the speeds of EUV waves reported in previous literature and compare these with type II radio bursts and Coronal Mass Ejections (CMEs). This c…
A previous work of ours found the best agreement between EUV light curves observed in an active region core (with evidence of super-hot plasma) and those predicted from a model with a random combination of many pulse-heated strands with a power-law energy distribution. We extend that work by including spatially resolved strand modeling and by studying the evolution of emission along the loops in the EUV 94 A and 335 A channels of the Atmospheric Imaging Assembly on-board the Solar Dynamics Observatory. Using the best parameters of the previous work as the input of the present one, we find that…
Recent progress in obtaining high spatial resolution images of the solar corona in the extreme-ultraviolet (EUV) with Hinode, TRACE, SDO and recent Hi-C missions and soft X-ray (SXR) bands opened a new avenue in understanding the solar coronal heating, the major goal of solar physics. The data from EUV/SXR missions suggest that solar corona is a non-uniform environment structured into active regions (AR) represented by bundles magnetic loops heated to temperatures exceeding 5 MK. Any viable coronal heating model should be capable of reproducing EUV and SXR emission from coronal active regions …
Understanding the density structure of the solar corona is important for modeling both coronal heating and the solar wind. Direct measurements are difficult because of line-of-sight integration and possible unresolved structures. We present a new method for quantifying such structure using density-sensitive EUV line intensities to derive a density irregularity parameter, a relative measure of the amount of structure along the line of sight. We also present a simple model to relate the inferred irregularities to physical quantities, such as the filling factor and density contrast. For quiet Sun…
We investigate the high-speed ($v >$ 1000 km s$^{-1}$) extreme-ultraviolet (EUV) wave associated with an X1.2 flare and coronal mass ejection (CME) from NOAA active region 11283 on 2011 September 6 (SOL2011-09-06T22:12). This EUV wave features peculiar on-disk signatures, in particular we observe an intermittent "disappearance" of the front for 120 s in SDO/AIA 171, 193, 211 Å data, whereas the 335 Å filter, sensitive to hotter plasmas (T$\sim$2.5 MK), shows a continuous evolution of the wave front. The eruption was also accompanied by localized coronal dimming regions. We exploit the multi-po…
We present detailed EUV spectra of 4 large solar flares: M5.6, X1.3, X3.4, and X17 classes in the spectral ranges 176-207 Å and 280-330 Å. These spectra were obtained {by the slitless} spectroheliograph SPIRIT aboard the CORONAS-F satellite. To our knowledge these are the first detailed EUV spectra of large flares obtained with spectral resolution of $\sim 0.1$ Å. We performed a comprehensive analysis of the obtained spectra and provide identification of the observed spectral lines. The identification was performed based {on the calculation} of synthetic spectra (CHIANTI database was used), wi…
The detailed observational analysis of a homologous Extreme-ultraviolet (EUV) wave event is presented to study the driving mechanism and the physical property of the EUV waves, combining high resolution data taken by the Solar Dynamics Observatory and the Solar TErrestrial RElations Observatory. It is observed that four homologous EUV waves originated from the same active region AR11476 within about one hour, and the time separations between consecutive waves were of 8 - 20 minutes. The waves showed narrow arc-shaped wavefronts and propagated in the same direction along a large-scale transequa…
We study a coronal mass ejection (CME) associated with an X-class flare, whose initiation is clearly observed in low corona with high-cadence, high-resolution EUV images, providing us a rare opportunity to witness the early evolution of an energetic CME in detail. The eruption starts with a slow expansion of cool overlying loops (~1 MK) following a jet-like event in the periphery of the active region. Underneath the expanding loop system a reverse S-shaped dimming is seen immediately above the brightening active region in hot EUV passbands. The dimming is associated with a rising diffuse arch …
The physical properties responsible for the formation and evolution of the corona and heliosphere are still not completely understood. 3D MHD global modeling is a powerful tool to investigate all the possible candidate processes. To fully understand the role of each of them, we need a validation process where the output from the simulations is quantitatively compared to the observational data. In this work, we present the results from our validation process applied to the wave turbulence driven 3D MHD corona-wind model WindPredict-AW. At this stage of the model development, we focus the work t…
Using detrended fluctuation analysis (DFA) and rescaled range (R/S) analysis, we investigate the scaling properties of EUV intensity fluctuations of low-latitude coronal holes (CHs) and neighboring quiet-Sun (QS) regions in signals obtained with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instrument. Contemporaneous line-of-sight SDO/Helioseismic and Magnetic Imager (HMI) magnetic fields provide a context for the physical environment. We find that the intensity fluctuations in the time series of EUV images present at each spatial point a scaling symmetry over the rang…
Extreme ultraviolet (EUV) coronal dimmings are often observed in response to solar eruptive events. These phenomena can be generated via several different physical processes. For space weather, the most important of these is the temporary void left behind by a coronal mass ejection (CME). Massive, fast CMEs tend to leave behind a darker void that also usually corresponds to minimum irradiance for the cooler coronal emissions. If the dimming is associated with a solar flare, as is often the case, the flare component of the irradiance light curve in the cooler coronal emission can be isolated an…
The reflection, refraction, and transmission of large-scale extreme ultraviolet (EUV) waves (collectively, secondary waves) have been observed during their interactions with coronal structures such as active regions (ARs) and coronal holes (CHs). However, the effect of the total reflection of EUV waves has not been reported in the literature. Here, we present the first unambiguous observational evidence of the total reflection of a quasi-periodic EUV wave train during its interaction with a polar CH. The event occurred in NOAA AR 12473, located close to the southeast limb of the solar disk, an…
We report the first unambiguous observational evidence in the radio range of the reflection of a coronal shock wave at the boundary of a coronal hole. The event occurred above an active region located at the northwest limb of the Sun and was characterized by an eruptive prominence and an extreme-ultraviolet (EUV) wave steepening into a shock. The EUV observations acquired by the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory(SDO) and the Extreme Ultraviolet Imager (EUVI) instrument on board the Solar TErrestrial RElations Observatory(STEREO-A) were used t…
Solar extreme ultraviolet (EUV) waves are large-scale propagating disturbances in the corona. It is generally believed that the vital key for the formation of EUV waves is the rapid expansion of the loops that overlie erupting cores in solar eruptions, such as coronal mass ejections (CMEs) and solar jets. However, the details of the interaction between the erupting cores and overlying loops are not clear, because that the overlying loops are always instantly opened after the energetic eruptions. Here, we present three typical jet-driven EUV waves without CME to study the interaction between th…
The solar corona is the origin of very dynamic events that are mostly produced in active regions (AR) and coronal holes (CH). The exact location of these large-scale features can be determined by applying image-processing approaches to extreme-ultraviolet (EUV) data. We here investigate the problem of segmentation of solar EUV images into ARs, CHs, and quiet-Sun (QS) images in a firm Bayesian way. On the basis of Bayes' rule, we need to obtain both prior and likelihood models. To find the prior model of an image, we used a Potts model in non-local mode. To construct the likelihood model, we co…
In this paper, we report the observed temporal correlation between extreme-violet (EUV) emission and magneto-acoustic oscillations in a EUV moss region, which is the footpoint region only connected by magnetic loops with million-degree plasma. The result is obtained from a detailed multi-wavelength data analysis to the region with the purpose of resolving fine-scale mass and energy flows that come from the photosphere, pass through the chromosphere and finally heat solar transition region or the corona. The data set covers three atmospheric levels on the Sun, consisting of high-resolution broa…
The outer solar atmosphere, the corona, contains plasma at temperatures of more than a million K, more than 100 times hotter that solar surface. How this gas is heated is a fundamental question tightly interwoven with the structure of the magnetic field in the upper atmosphere. Conducting numerical experiments based on magnetohydrodynamics we account for both the evolving three-dimensional structure of the atmosphere and the complex interaction of magnetic field and plasma. Together this defines the formation and evolution of coronal loops, the basic building block prominently seen in X-rays a…
Spectroscopic diagnostics of solar coronal plasmas critically depends on the uncertainty in the measured line intensities. One of the main sources of uncertainty is instrumental scattered light, which is potentially most important in low-brightness areas. In the solar corona, such areas include polar and equatorial coronal holes, which are the source regions of the solar wind; instrument-scattered light must thus pose a significant obstacle to studies of the source regions of the solar wind. In this paper we investigate the importance of instrument-scattered light on observations of equatorial…
Coronal bright points (CBPs) as characteristics of the solar corona are small-scale bright features ubiquitously observed at extreme ultraviolet passbands. Here, we focused on time series of CBPs in the periods of their lifetimes. We used Solar Dynamic Observatory (SDO) / Atmospheric Imaging Assembly (AIA) taken at 171 and 193 Å. Using image processing methods, CBPs were extracted from data and tracked during their lifetimes. We found that CBPs observed in 171 Åhave more lifetimes than those of observed at 193 Å. CBPs at 171 Åare more fluctuated in intensity and appeared as highly density numb…
We investigate the scaling properties of the long-range temporal evolution and intermittency of SDO/AIA intensity observations in four solar environments: an active region core, a weak emission region, and two core loops. We use two approaches: the probability distribution function (PDF) of time series increments, and multifractal detrended fluctuation analysis (MF-DFA). Noise taints the results, so we focus on the 171 Angstrom waveband , which has the highest signal-to-noise ratio. The lags between pairs of wavebands distinguish between coronal versus transition region (TR) emission. In all p…
Reconstructing the Local Twist of Coronal Magnetic Fields and the Three-Dimensional Shape of the Field Lines from Coronal Loops in EUV and X-Ray Images
We investigate a global extreme-ultraviolet (EUV) wave associated with a coronal mass ejection (CME)-driven shock on 2017 September 10. The EUV wave is transmitted by north- and south-polar coronal holes (CHs), which is observed by the Solar Dynamics Observatory (SDO) and Solar Terrestrial Relations Observatory A (STEREO-A) from opposite sides of the Sun. We obtain key findings on how the EUV wave interacts with multiple coronal structures, and on its connection with the CME-driven shock: (1) the transmitted EUV wave is still connected with the shock that is incurvated to the Sun, after the sh…
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…
On 2014 October 30, a band-splitted type II radio burst associated with a coronal mass ejection (CME) observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) occurred over the southeast limb of the Sun. The fast expansion in all directions of the plasma front acted as a piston and drove a spherical fast shock ahead of it, whose outward progression was traced by simultaneous images obtained with the Nançay Radioheliograph (NRH). The geometry of the CME/shock event was recovered through 3D modeling, given the absence of concomitant stereoscopic observation…
Signatures of localised particle acceleration at a global coronal shock wave
Dublin City University（都柏林城市大学）；Dublin Institute for Advanced Studies（都柏林高等研究院）；Observatoire de Paris（巴黎天文台）；PSL Research University（PSL研究大学）；CNRS（法国国家科学研究中心）；Sorbonne Université（索邦大学）；Université Paris Cité（巴黎西岱大学）
The origin of the activity in the solar corona is a long-standing problem in solar physics. Recent satellite observations, such as Hinode, Solar Dynamics Observatory (SDO), Interface Region Imaging Spectrograph (IRIS), show the detail characteristics of the solar atmosphere and try to reveal the energy transfer from the photosphere to the corona through the magnetic fields and its energy conversion by various processes. However, quantitative estimation of energy transfer along the magnetic field is not enough. There are mainly two reason why it is difficult to observe the energy transfer from …
We present observations of a powerful solar eruption, accompanied by an X8.2 solar flare, from NOAA Active Region 12673 on 2017 September 10 by the Solar Ultraviolet Imager (SUVI) on the GOES-16 spacecraft. SUVI is noteworthy for its relatively large field of view, which allows it to image solar phenomena to heights approaching 2 solar radii. These observations include the detection of an apparent current sheet associated with magnetic reconnection in the wake of the eruption and evidence of an extreme-ultraviolet wave at some of the largest heights ever reported. We discuss the acceleration o…
This study entails the fourth part of a global flare energetics project, in which the mass $m_{\mathrm{cme}}$, kinetic energy $E_{\mathrm{kin}}$, and the gravitational potential energy $E_{\mathrm{grav}}$ of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. The EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The mo…
We carry out an analysis of the evacuated mass from three coronal dimming regions observed by the {\it Atmospheric Imaging Assembly} (AIA) on board the {\it Solar Dynamics Observatory}. The three events are unambiguously identified with white-light coronal mass ejections (CMEs) associated in turn with surface activity of diverse nature: an impulsive (M-class) flare, a weak (B-class) flare and a filament eruption without a flare. The use of three AIA coronal passbands allows applying a differential emission measure technique to define the dimming regions and identify their evacuated mass throug…
The EUV (100-912 Å) is a spectral region notoriously difficult to observe due to attenuation by neutral hydrogen gas in the interstellar medium. Despite this, hundreds to thousands of nearby stars of different spectral types and magnetic activity levels are accessible in the EUV range. The EUV probes interesting and complicated regions in the stellar atmosphere like the lower corona and transition region that are inaccessible from other spectral regions. In this white paper we describe how direct EUV observations, which require a dedicated grazing-incidence observatory, cannot yet be accuratel…
A comparison between a Coronal Hole (CH) and the adjacent Quiet-Sun (QS) has been performed using spectroscopic diagnostics of Hinode/ the EUV Imaging Spectrometer (EIS). Coronal funnels play an important role in the formation and propagation of the nascent fast solar wind. Applying Gaussian fitting procedures to the observed line profiles, Doppler velocity, intensity, line width (FWHM) and electron density have been estimated over CH and adjacent QS region of a North Polar Coronal Hole (NPCH). The aim of this study is to identify the coronal funnels based on spectral signatures. Excess width …
Improving Solar EUV Irradiance Modeling with Differential Emission Measure Informed Spectra
University of Colorado at Boulder（科罗拉多大学博尔德分校）；Cooperative Institute for Research in Environmental Sciences, University of Colorado（科罗拉多大学环境科学研究合作研究所）；NOAA National Centers for Environmental Information（美国国家海洋和大气管理局国家环境信息中心）；Southwest Research Institute（西南研究院）；Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder（科罗拉多大学博尔德分校大气与空间物理实验室）；Lockheed Martin Advanced Technology Center（洛克希德·马丁先进技术中心）；Commonwealth Scientific and Industrial Research Organisation（联邦科学与工业研究组织）
