Statistical Approach on Differential Emission Measure of Coronal Holes using the CATCH Catalog

AbstractCoronal holes are large-scale structures in the solar atmosphere that feature a reduced temperature and density in comparison to the surrounding quiet Sun and are usually associated with open magnetic fields. We perform a differential emission measure analysis on the 707 non-polar coronal holes in the Collection of Analysis Tools for Coronal Holes (CATCH) catalog to derive and statistically analyze their plasma properties (i.e. temperature, electron density, and emission measure). We use intensity filtergrams of the six coronal EUV filters from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, which cover a temperature range from $\approx10^{5.5}$ ≈ 10 5.5 to $10^{7.5}~\mbox{K}$ 10 7.5 K . Correcting the data for stray and scattered light, we find that all coronal holes have very similar plasma properties with an average temperature of $0.94 \pm0.18~\mbox{MK}$ 0.94 ± 0.18 MK , a mean electron density of $(2.4 \pm0.7) \times10^{8}~\mbox{cm}^{-3}$ ( 2.4 ± 0.7 ) × 10 8 cm − 3 , and a mean emission measure of $(2.8 \pm1.6) \times10^{26}~\mbox{cm}^{-5}$ ( 2.8 ± 1.6 ) × 10 26 cm − 5 . The temperature distribution within the coronal holes was found to be largely uniform, whereas the electron density shows a 30 to 40% linear decrease from the boundary towards the inside of the coronal hole. At distances greater than 20″ ($\approx15~\mbox{Mm}$ ≈ 15 Mm ) from the nearest coronal hole boundary, the density also becomes statistically uniform. The coronal hole temperature may show a weak solar-cycle dependency, but no statistically significant correlation of plasma properties with solar-cycle variations could be determined throughout the observed period between 2010 and 2019.

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Differential Emission Measure Plasma Diagnostics of a Long-Lived Coronal Hole

Solar Physics ◽

10.1007/s11207-019-1570-z ◽

2020 ◽

Vol 295 (1) ◽

Cited By ~ 3

Author(s):

Jonas Saqri ◽

Astrid M. Veronig ◽

Stephan G. Heinemann ◽

Stefan J. Hofmeister ◽

Manuela Temmer ◽

...

Keyword(s):

Coronal Hole ◽

Scattered Light ◽

Emission Measure ◽

Stray Light ◽

Lunar Eclipse ◽

Solar Dynamics Observatory ◽

Differential Emission Measure ◽

Plasma Properties ◽

Evolutionary Pattern ◽

Dominant Component

AbstractWe use Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) data to reconstruct the plasma properties from differential emission measure (DEM) analysis for a previously studied long-lived, low-latitude coronal hole (CH) over its lifetime of ten solar rotations. We initially obtain a non-isothermal DEM distribution with a dominant component centered around 0.9 MK and a secondary smaller component at 1.5 – 2.0 MK. We find that deconvolving the data with the instrument point spread function (PSF) to account for long-range scattered light reduces the secondary hot component. Using the 2012 Venus transit and a 2013 lunar eclipse to test the efficiency of this deconvolution, significant amounts of residual stray light are found for the occulted areas. Accounting for this stray light in the error budget of the different AIA filters further reduces the secondary hot emission, yielding CH DEM distributions that are close to isothermal with the main contribution centered around 0.9 MK. Based on these DEMs, we analyze the evolution of the emission measure (EM), density, and averaged temperature during the CH’s lifetime. We find that once the CH is clearly observed in EUV images, the bulk of the CH plasma reveals a quite constant state, i.e. temperature and density reveal no major changes, whereas the total CH area and the photospheric magnetic fine structure inside the CH show a distinct evolutionary pattern. These findings suggest that CH plasma properties are mostly “set” at the CH formation or/and that all CHs have similar plasma properties.

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SITES: Solar Iterative Temperature Emission Solver for Differential Emission Measure Inversion of EUV Observations

Solar Physics ◽

10.1007/s11207-019-1525-4 ◽

2019 ◽

Vol 294 (10) ◽

Cited By ~ 4

Author(s):

Huw Morgan ◽

James Pickering

Keyword(s):

Large Scale ◽

Extreme Ultraviolet ◽

Emission Measure ◽

Synthetic Data ◽

Temperature Response ◽

Solar Dynamics Observatory ◽

Differential Emission Measure ◽

Desktop Computer ◽

Temperature Regimes ◽

Solar Dynamics

Abstract Extreme ultraviolet (EUV) images of the optically-thin solar corona in multiple spectral channels give information on the emission as a function of temperature through differential emission measure (DEM) inversions. The aim of this paper is to describe, test, and apply a new DEM method named the Solar Iterative Temperature Emission Solver (SITES). The method creates an initial DEM estimate through a direct redistribution of observed intensities across temperatures according to the temperature response function of the measurement, and iteratively improves on this estimate through calculation of intensity residuals. It is simple in concept and implementation, is non-subjective in the sense that no prior constraints are placed on the solutions other than positivity and smoothness, and can process a thousand DEMs a second on a standard desktop computer. The resulting DEMs replicate model DEMs well in tests on Atmospheric Imaging Assembly/Solar Dynamics Observatory (AIA/SDO) synthetic data. The same tests show that SITES performs less well on very narrow DEM peaks, and should not be used for temperature diagnostics below ${\approx\,}0.5~\mbox{MK}$≈0.5MK in the case of AIA observations. The SITES accuracy of inversion compares well with two other established methods. A simple yet powerful new method to visualize DEM maps is introduced, based on a fractional emission measure (FEM). Applied to a set of AIA full-disk images, the SITES method and FEM visualization show very effectively the dominance of certain temperature regimes in different large-scale coronal structures. The method can easily be adapted for any multi-channel observations of optically-thin plasma and, given its simplicity and efficiency, will facilitate the processing of large existing and future datasets.

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Energetics of Hi-C EUV brightenings

Astronomy and Astrophysics ◽

10.1051/0004-6361/201629304 ◽

2018 ◽

Vol 615 ◽

pp. A47 ◽

Cited By ~ 2

Author(s):

Srividya Subramanian ◽

Vinay L. Kashyap ◽

Durgesh Tripathi ◽

Maria S. Madjarska ◽

John G. Doyle

Keyword(s):

High Resolution ◽

Energy Loss ◽

Extreme Ultraviolet ◽

Thermal Structure ◽

Emission Measure ◽

Light Curves ◽

Solar Dynamics Observatory ◽

Differential Emission Measure ◽

Dominant Mechanism ◽

Solar Dynamics

We study the thermal structure and energetics of the point-like extreme ultraviolet (EUV) brightenings within a system of fan loops observed in the active region AR 11520. These brightenings were simultaneously observed on 2012 July 11 by the High-resolution Coronal (Hi-C) imager and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We identified 27 brightenings by automatically determining intensity enhancements in both Hi-C and AIA 193 Å light curves. The energetics of these brightenings were studied using the Differential Emission Measure (DEM) diagnostics. The DEM weighted temperatures of these transients are in the range log T(K) = 6.2−6.6 with radiative energies ≈1024−25 ergs and densities approximately equal to a few times 109 cm−3. To the best of our knowledge, these are the smallest brightenings in EUV ever detected. We used these results to determine the mechanism of energy loss in these brightenings. Our analysis reveals that the dominant mechanism of energy loss for all the identified brightenings is conduction rather than radiation.

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Solar Mass Ejections and Coronal Holes

International Astronomical Union Colloquium ◽

10.1017/s0252921100030025 ◽

1996 ◽

Vol 154 ◽

pp. 105-112

Author(s):

Arvind Bhatnagar

Keyword(s):

Coronal Hole ◽

Large Scale ◽

Neutral Line ◽

Coronal Holes ◽

Field Configuration ◽

Solar Mass ◽

X Ray ◽

Filament Eruption ◽

Open Magnetic Field ◽

Interplanetary Scintillations

AbstractIn this paper we present observations of two types of solar mass ejections, which seem to be associated with the location of coronal holes. In the first type, a filament eruption was observed near a coronal hole, which gave rise to a strong interplanetary scintillations, as detected by IPS observations. In the second type, several large scale soft X-ray ‘blow-outs’ were observed in the YOHKOH SXT X-ray movies, in all the cases they erupted from or near the boundary of coronal holes and over the magnetic neutral line. It is proposed that the open magnetic field configuration of the coronal hole provides, the necessary field structure for reconnection to take place, which in turn is responsible for filament eruption, from relatively lower heights. While, in the case of X-ray ‘blow-outs’, the reconnection takes place at a greater height, resulting in high temperature soft X-ray emission visible as X-ray ‘blow-outs’.

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The 3D solar corona Cycle 24 rising phase from SDO/AIA tomography

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312004905 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 238-241

Author(s):

Federico A. Nuevo ◽

Alberto M. Vásquez ◽

Richard A. Frazin ◽

Zhenguang Huang ◽

Ward B. Manchester

Keyword(s):

Solar Corona ◽

Extreme Ultraviolet ◽

Emission Measure ◽

Source Surface ◽

Solar Dynamics Observatory ◽

Differential Emission Measure ◽

Height Range ◽

Field Source ◽

Solar Dynamics ◽

Cycle 24

AbstractWe recently extended the differential emission measure tomography (DEMT) technique to be applied to the six iron bands of the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory (SDO). DEMT products are the 3D reconstruction of the coronal emissivity in the instrument's bands, and the 3D distribution of the local differential emission measure, in the height range 1.0 to 1.25 R⊙. We show here derived maps of the electron density and temperature of the inner solar corona during the rising phase of solar Cycle 24. We discuss the distribution of our results in the context of open/closed magnetic regions, as derived from a global potential field source surface (PFSS) model of the same period. We also compare the results derived with SDO/AIA to those derived with the Extreme UltraViolet Imager (EUVI) instrument aboard the Solar TErrestrial RElations Observatory (STEREO).

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Automated coronal hole identification via multi-thermal intensity segmentation

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2017039 ◽

2018 ◽

Vol 8 ◽

pp. A02 ◽

Cited By ~ 14

Author(s):

Tadhg M. Garton ◽

Peter T. Gallagher ◽

Sophie A. Murray

Keyword(s):

Coronal Hole ◽

Thermal Emission ◽

Geomagnetic Storms ◽

Coronal Holes ◽

Ultra Violet ◽

Recognition Algorithm ◽

Magnetic Polarity ◽

Solar Dynamics Observatory ◽

Accurate Identification ◽

Solar Dynamics

Coronal holes (CH) are regions of open magnetic fields that appear as dark areas in the solar corona due to their low density and temperature compared to the surrounding quiet corona. To date, accurate identification and segmentation of CHs has been a difficult task due to their comparable intensity to local quiet Sun regions. Current segmentation methods typically rely on the use of single Extreme Ultra-Violet passband and magnetogram images to extract CH information. Here, the coronal hole identification via multi-thermal emission recognition algorithm (CHIMERA) is described, which analyses multi-thermal images from the atmospheric image assembly (AIA) onboard the solar dynamics observatory (SDO) to segment coronal hole boundaries by their intensity ratio across three passbands (171 Å, 193 Å, and 211 Å). The algorithm allows accurate extraction of CH boundaries and many of their properties, such as area, position, latitudinal and longitudinal width, and magnetic polarity of segmented CHs. From these properties, a clear linear relationship was identified between the duration of geomagnetic storms and coronal hole areas. CHIMERA can therefore form the basis of more accurate forecasting of the start and duration of geomagnetic storms.

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Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-Era Using CATCH

Solar Physics ◽

10.1007/s11207-019-1539-y ◽

2019 ◽

Vol 294 (10) ◽

Cited By ~ 11

Author(s):

Stephan G. Heinemann ◽

Manuela Temmer ◽

Niko Heinemann ◽

Karin Dissauer ◽

Evangelia Samara ◽

...

Keyword(s):

Magnetic Field ◽

Coronal Hole ◽

High Speed ◽

Extreme Ultraviolet ◽

Coronal Holes ◽

Central Meridian ◽

Solar Dynamics Observatory ◽

Speed Solar Wind ◽

Solar Dynamics ◽

Hole Boundary

Abstract Coronal holes are usually defined as dark structures seen in the extreme ultraviolet and X-ray spectrum which are generally associated with open magnetic fields. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints as regards high speed solar wind acceleration processes and compression regions arriving at Earth. In this study we present a new threshold-based extraction method, which incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSW-IDL GUI. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use CATCH to analyze non-polar coronal holes during the SDO-era, based on 193 Å filtergrams taken by the Atmospheric Imaging Assembly (AIA) and magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO). Between 2010 and 2019 we investigate 707 coronal holes that are located close to the central meridian. We find coronal holes distributed across latitudes of about ${\pm}\, 60^{\circ}$±60∘, for which we derive sizes between $1.6 \times 10^{9}$1.6×109 and $1.8 \times 10^{11}\mbox{ km}^{2}$1.8×1011 km2. The absolute value of the mean signed magnetic field strength tends towards an average of $2.9\pm 1.9$2.9±1.9 G. As far as the abundance and size of coronal holes is concerned, we find no distinct trend towards the northern or southern hemisphere. We find that variations in local and global conditions may significantly change the threshold needed for reliable coronal hole extraction and thus, we can highlight the importance of individually assessing and extracting coronal holes.

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Overview of XRT performance and first results

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308015044 ◽

2007 ◽

Vol 3 (S247) ◽

pp. 326-336

Author(s):

Antonia Savcheva ◽

Keyword(s):

Fine Structure ◽

Coronal Holes ◽

Emission Measure ◽

Active Regions ◽

Potential Fields ◽

Differential Emission Measure ◽

Short Introduction ◽

X Ray ◽

First Results ◽

Measure Analysis

AbstractIn this review we present a short introduction to the X-ray Telescope on Hinode. We discuss its capabilities and new features and compare it with Yohkoh SXT. We also discuss some of the first results that include observations of X-ray jets in coronal holes, shear change in flares, sigmoid eruptions and evolution, application of filter ratios and differential emission measure analysis, structure of active regions, fine structure of X-ray bright points, and modeling non-potential fields around filaments. Finally, we describe how XRT works with other ground and space-based instrumentation, in particular with TRACE, EIS, SOT, and SOLIS.

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