Displacement Analysis of Solar Magnetic Field Images in EUV Wavelengths of Space Solar Telescope

In this paper, the combination of nonlinear gradient iteration and crossing method is presented in order to analyze high precision remote sensing images of solar magnetic field in extreme ultraviolet (EUV) wavelengths which are usually affected by solar magnetic evolution, satellite attitude changes and random satellite jitter, and to reduce structural complexity the complicated correlation tracker is normally adopted. Using crossing method which better approached the inefficiency by computing full-scale solar magnetic field images, nine point areas are uniformly selected in full-scale solar magnetic field images which solves the problem of low-computing efficiency. Meanwhile, nonlinear gradient iteration algorithm through numerical simulation experiments is adopted to analyze displacement of solar magnetic field images in EUV wavelengths, which reduces the errors due to the solar intensity changing and tiny deformation of solar magnetic field compared to traditional algorithms. The results clearly indicate that the precision of mean error field and square deviation field for deformed displacement are both less than 5% of pixel by solar magnetic field images of Solar Dynamics Observatory (SDO).

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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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Nature of the energy source powering solar coronal loops driven by nanoflares

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833404 ◽

2018 ◽

Vol 615 ◽

pp. L9 ◽

Cited By ~ 24

Author(s):

L. P. Chitta ◽

H. Peter ◽

S. K. Solanki

Keyword(s):

Magnetic Field ◽

Energy Source ◽

Extreme Ultraviolet ◽

Magnetic Energy ◽

Plasma Heating ◽

Active Regions ◽

Coronal Loops ◽

Solar Dynamics Observatory ◽

Mixed Polarity ◽

Solar Dynamics

Context. Magnetic energy is required to heat the corona, the outer atmosphere of the Sun, to millions of degrees. Aims. We study the nature of the magnetic energy source that is probably responsible for the brightening of coronal loops driven by nanoflares in the cores of solar active regions. Methods. We consider observations of two active regions (ARs), 11890 and 12234, in which nanoflares have been detected. To this end, we use ultraviolet (UV) and extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) for coronal loop diagnostics. These images are combined with the co-temporal line-of-sight magnetic field maps from the Helioseismic and Magnetic Imager (HMI) onboard SDO to investigate the connection between coronal loops and their magnetic roots in the photosphere. Results. The core of these ARs exhibit loop brightening in multiple EUV channels of AIA, particularly in its 9.4 nm filter. The HMI magnetic field maps reveal the presence of a complex mixed polarity magnetic field distribution at the base of these loops. We detect the cancellation of photospheric magnetic flux at these locations at a rate of about 1015 Mx s−1. The associated compact coronal brightenings directly above the cancelling magnetic features are indicative of plasma heating due to chromospheric magnetic reconnection. Conclusions. We suggest that the complex magnetic topology and the evolution of magnetic field, such as flux cancellation in the photosphere and the resulting chromospheric reconnection, can play an important role in energizing active region coronal loops driven by nanoflares. Our estimate of magnetic energy release during flux cancellation in the quiet Sun suggests that chromospheric reconnection can also power the quiet corona.

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Magneto-seismology: effect of inhomogeneous magnetic field on transversal coronal loop oscillations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308014774 ◽

2007 ◽

Vol 3 (S247) ◽

pp. 123-132

Author(s):

G. Verth

Keyword(s):

Magnetic Field ◽

Fine Structure ◽

Plasma Density ◽

Coronal Loop ◽

Extreme Ultraviolet ◽

Wave Theory ◽

Inhomogeneous Magnetic Field ◽

Solar Dynamics Observatory ◽

Flare Loop ◽

Solar Dynamics

AbstractThe extreme-ultraviolet (EUV) imagers onboard the planned Solar Dynamics Observatory (SDO) and Solar Orbiter (SO) will offer us the best chance yet of using observations of post-flare loop oscillations to probe the fine structure of the corona. Recently developed magnetohydrodynamic (MHD) wave theory has shown that the properties of loop oscillations depend on their plasma fine structure. Up to this point, many studies have concentrated solely on the effect of plasma density stratification on coronal loop oscillations. In this paper we develop MHD wave theory which models the effect of an inhomogeneous magnetic field on coronal loop oscillations. The results have the potential to be used in testing the efficacy of photospheric magnetic field extrapolations and have important implications regarding magneto-seismology of the corona.

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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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Improvement of the Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Inversion Code

The Astrophysical Journal ◽

10.3847/1538-4357/ac2aa8 ◽

2021 ◽

Vol 923 (1) ◽

pp. 84

Author(s):

Ana Belén Griñón-Marín ◽

Adur Pastor Yabar ◽

Yang Liu ◽

J. Todd Hoeksema ◽

Aimee Norton

Keyword(s):

Magnetic Field ◽

Field Vector ◽

Magnetic Field Vector ◽

Solar Dynamics Observatory ◽

Filling Fraction ◽

Resolution Element ◽

New Strategy ◽

Moderate Field ◽

Solar Dynamics ◽

Field Strengths

Abstract A spectral line inversion code, Very Fast Inversion of the Stokes Vector (VFISV), has been used since 2010 May to infer the solar atmospheric parameters from the spectropolarimetric observations taken by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. The magnetic filling factor, the fraction of the surface with a resolution element occupied by magnetic field, is set to have a constant value of 1 in the current version of VFISV. This report describes an improved inversion strategy for the spectropolarimetric data observed with HMI for magnetic field strengths of intermediate values in areas spatially not fully resolved. The VFISV inversion code has been modified to enable inversion of the Stokes profiles with two different components: one magnetic and one nonmagnetic. In this scheme, both components share the atmospheric components except for the magnetic field vector. In order to determine whether the new strategy is useful, we evaluate the inferred parameters inverted with one magnetic component (the original version of the HMI inversion) and with two components (the improved version) using a Bayesian analysis. In pixels with intermediate magnetic field strengths (e.g., plages), the new version provides statistically significant values of filling fraction and magnetic field vector. Not only does the fitting of the Stokes profile improve, but also the inference of the magnetic parameters and line-of-sight velocity are obtained uniquely. The new strategy is also proven to be effective for mitigating the anomalous hemispheric bias in the east–west magnetic field component in moderate field regions.

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Hot prominence spicules launched from turbulent cool solar prominences

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936027 ◽

2019 ◽

Vol 627 ◽

pp. L5 ◽

Cited By ~ 2

Author(s):

L. P. Chitta ◽

H. Peter ◽

L. Li

Keyword(s):

Transition Region ◽

Extreme Ultraviolet ◽

The Sun ◽

Solar Dynamics Observatory ◽

Solar Prominences ◽

Solar Filament ◽

Solar Dynamics ◽

Ultraviolet Observations ◽

Hot Corona ◽

Shed Light

A solar filament is a dense cool condensation that is supported and thermally insulated by magnetic fields in the rarefied hot corona. Its evolution and stability, leading to either an eruption or disappearance, depend on its coupling with the surrounding hot corona through a thin transition region, where the temperature steeply rises. However, the heating and dynamics of this transition region remain elusive. We report extreme-ultraviolet observations of quiescent filaments from the Solar Dynamics Observatory that reveal prominence spicules propagating through the transition region of the filament-corona system. These thin needle-like jet features are generated and heated to at least 0.7 MK by turbulent motions of the material in the filament. We suggest that the prominence spicules continuously channel the heated mass into the corona and aid in the filament evaporation and decay. Our results shed light on the turbulence-driven heating in magnetized condensations that are commonly observed on the Sun and in the interstellar medium.

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On the Dynamics of the Largest Active Region of the Solar Cycle 24

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317008924 ◽

2017 ◽

Vol 13 (S335) ◽

pp. 32-35

Author(s):

Ranadeep Sarkar ◽

Nandita Srivastava ◽

Sajal Kumar Dhara

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Active Region ◽

Comparative Study ◽

Lorentz Force ◽

Sunspot Group ◽

Solar Dynamics Observatory ◽

Solar Cycle 24 ◽

Solar Dynamics ◽

Cycle 24

AbstractWe have studied the dynamics of the solar active region (AR) NOAA 12192 using full-disc continuum images and the vector magnetograms observed by the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO). AR 12192 is the largest region of the solar cycle 24. It underwent a noticeable growth and produced 6 X-class, 22 M-class and 53 C-class flares during its disc passage. But the most peculiar fact of this AR is that it was associated with only one CME in spite of producing several X-class flares. In this work, we present the area evolution of this giant sunspot group during the first three rotations when it appeared as AR 12172, AR 12192 and AR 12209, respectively. We have also attempted to make a comparative study of the flare-related photospheric magnetic field and Lorentz force changes for both the eruptive and non-eruptive flares produced by AR 12192.

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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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