scholarly journals Energetics of Hi-C EUV brightenings

2018 ◽  
Vol 615 ◽  
pp. A47 ◽  
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.

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

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).

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

Solar Physics ◽  
2019 ◽  
Vol 294 (10) ◽  
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.

scholarly journals A deep learning virtual instrument for monitoring extreme UV solar spectral irradiance

2019 ◽  
Vol 5 (10) ◽  
pp. eaaw6548
Author(s):  
Alexandre Szenicer ◽  
David F. Fouhey ◽  
Andres Munoz-Jaramillo ◽  
Paul J. Wright ◽  
Rajat Thomas ◽  
...  
Keyword(s):  
Virtual Instrument ◽  
Extreme Ultraviolet ◽  
Aerodynamic Drag ◽  
Emission Measure ◽  
Maximum Error ◽  
Spectral Irradiance ◽  
Solar Dynamics Observatory ◽  
Solar Spectral Irradiance ◽  
Solar Dynamics ◽  
Using Data

Measurements of the extreme ultraviolet (EUV) solar spectral irradiance (SSI) are essential for understanding drivers of space weather effects, such as radio blackouts, and aerodynamic drag on satellites during periods of enhanced solar activity. In this paper, we show how to learn a mapping from EUV narrowband images to spectral irradiance measurements using data from NASA’s Solar Dynamics Observatory obtained between 2010 to 2014. We describe a protocol and baselines for measuring the performance of models. Our best performing machine learning (ML) model based on convolutional neural networks (CNNs) outperforms other ML models, and a differential emission measure (DEM) based approach, yielding average relative errors of under 4.6% (maximum error over emission lines) and more typically 1.6% (median). We also provide evidence that the proposed method is solving this mapping in a way that makes physical sense and by paying attention to magnetic structures known to drive EUV SSI variability.

scholarly journals The EUV spectrum of the Sun: Quiet- and active-Sun irradiances and chemical composition

2019 ◽  
Vol 624 ◽  
pp. A36 ◽  
Author(s):  
G. Del Zanna
Keyword(s):  
Excellent Agreement ◽  
Extreme Ultraviolet ◽  
Emission Measure ◽  
Active Regions ◽  
Atomic Data ◽  
Solar Dynamics Observatory ◽  
Chemical Abundances ◽  
Temperature Plasma ◽  
Medium Resolution ◽  
Solar Dynamics

We benchmark new atomic data against a selection of irradiances obtained from medium-resolution quiet-Sun spectra in the extreme ultraviolet (EUV), from 60 to 1040 Å. We used as a baseline the irradiances measured during solar minimum on 2008 April 14 by the prototype (PEVE) of the Solar Dynamics Observatory Extreme ultraviolet Variability Experiment (EVE). We took into account some inconsistencies in the PEVE data, using flight EVE data and irradiances we obtained from Solar and Heliospheric Observatory (SoHO) Coronal Diagnostics Spectrometer (CDS) data. We performed a differential emission measure and find overall excellent agreement (to within the accuracy of the observations, about 20%) between predicted and measured irradiances in most cases, although we point out several problems with the currently available ion charge-state distributions. We used the photospheric chemical abundances of Asplund et al. (2009, ARA&A, 47, 481). The new atomic data are nearly complete in this spectral range for medium-resolution irradiance spectra. Finally, we used observations of the active Sun in 1969 to show that the composition of the solar corona up to 1 MK is nearly photospheric in this case as well. Variations of a factor of 2 are present for higher-temperature plasma, which is emitted within active regions. These results are in excellent agreement with our previous findings.

scholarly journals Extreme-ultraviolet bursts and nanoflares in the quiet-Sun transition region and corona

2021 ◽  
Vol 647 ◽  
pp. A159
Author(s):  
L. P. Chitta ◽  
H. Peter ◽  
P. R. Young
Keyword(s):  
High Resolution ◽  
Solar Atmosphere ◽  
Significant Role ◽  
Extreme Ultraviolet ◽  
Coronal Heating ◽  
Solar Dynamics Observatory ◽  
Quiet Sun ◽  
Solar Dynamics ◽  
Event Based ◽  
Open Question

The quiet solar corona consists of myriads of loop-like features, with magnetic fields originating from network and internetwork regions on the solar surface. The continuous interaction between these different magnetic patches leads to transient brightenings or bursts that might contribute to the heating of the solar atmosphere. The literature on a variety of such burst phenomena in the solar atmosphere is rich. However, it remains unclear whether such transients, which are mostly observed in the extreme ultraviolet (EUV), play a significant role in atmospheric heating. We revisit the open question of these bursts as a prelude to the new high-resolution EUV imagery expected from the recently launched Solar Orbiter. We use EUV image sequences recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) to investigate statistical properties of the bursts. We detect the bursts in the 171 Å filter images of AIA in an automated way through a pixel-wise analysis by imposing different intensity thresholds. By exploiting the high cadence (12 s) of the AIA observations, we find that the distribution of lifetimes of these events peaks at about 120 s. However, a significant number of events also have lifetimes shorter than 60 s. The sizes of the detected bursts are limited by the spatial resolution, which indicates that a larger number of events might be hidden in the AIA data. We estimate that about 100 new bursts appear per second on the whole Sun. The detected bursts have nanoflare-like energies of 1024 erg per event. Based on this, we estimate that at least 100 times more events of a similar nature would be required to account for the energy that is required to heat the corona. When AIA observations are considered alone, the EUV bursts discussed here therefore play no significant role in the coronal heating of the quiet Sun. If the coronal heating of the quiet Sun is mainly bursty, then the high-resolution EUV observations from Solar Orbiter may be able to reduce the deficit in the number of EUV bursts seen with SDO/AIA at least partly by detecting more such events.

scholarly journals Hot prominence spicules launched from turbulent cool solar prominences

2019 ◽  
Vol 627 ◽  
pp. L5 ◽  
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.

scholarly journals Estimate of Plasma Temperatures Across a CME-Driven Shock from a Comparison Between EUV and Radio Data

Solar Physics ◽  
2020 ◽  
Vol 295 (9) ◽  
Author(s):  
Federica Frassati ◽  
Salvatore Mancuso ◽  
Alessandro Bemporad
Keyword(s):  
Shock Wave ◽  
Compression Ratio ◽  
Emission Measure ◽  
Type Ii ◽  
Solar Dynamics Observatory ◽  
Radio Data ◽  
Shock Temperature ◽  
Post Shock ◽  
Dem Analysis ◽  
Solar Dynamics

Abstract In this work, we analyze the evolution of an EUV wave front associated with a solar eruption that occurred on 30 October 2014, with the aim of investigating, through differential emission measure (DEM) analysis, the physical properties of the plasma compressed and heated by the accompanying shock wave. The EUV wave was observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and was accompanied by the detection of a metric Type II burst observed by ground-based radio spectrographs. The EUV signature of the shock wave was also detected in two of the AIA channels centered at 193 Å and 211 Å as an EUV intensity enhancement propagating ahead of the associated CME. The density compression ratio $X$ X of the shock as inferred from the analysis of the EUV data is $X \approx 1.23$ X ≈ 1.23 , in agreement with independent estimates obtained from the analysis of the Type II band-splitting of the radio data and inferred by adopting the upstream–downstream interpretation. By applying the Rankine–Hugoniot jump conditions under the hypothesis of a perpendicular shock, we also estimate the temperature ratio as $T_{\mathrm{D}}/T_{\mathrm{U}} \approx 1.55$ T D / T U ≈ 1.55 and the post-shock temperature as $T_{\mathrm{D}}\approx 2.75$ T D ≈ 2.75 MK. The modest compression ratio and temperature jump derived from the EUV analysis at the shock passage are typical of weak coronal shocks.

scholarly journals Wave amplitude modulation in fan loops as observed by AIA/SDO

2020 ◽  
Vol 638 ◽  
pp. A6
Author(s):  
Aishawnnya Sharma ◽  
Durgesh Tripathi ◽  
Robertus Erdélyi ◽  
Girjesh R. Gupta ◽  
Gazi A. Ahmed
Keyword(s):  
Wavelet Analysis ◽  
Amplitude Modulation ◽  
Acoustic Waves ◽  
Extreme Ultraviolet ◽  
Loop System ◽  
Light Curves ◽  
Solar Dynamics Observatory ◽  
Distance Analysis ◽  
Cross Correlation Analysis ◽  
Time Distance

Aims. We perform a detailed analysis to understand the evolution and dynamics of propagating intensity disturbances observed in a fan loop system. Methods. We performed multiwavelength time-distance analysis of a fan loop system anchored in an isolated sunspot region (AR 12553). The active region was observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. We measured the phase speeds of the propagating intensity disturbances by employing cross-correlation analysis, and by obtaining the slopes in xt-plots. We obtained original and detrended light curves at different heights of the time-distance maps and characterised them by performing Fourier and wavelet analysis, respectively. Results. The time-distance maps reveal clear propagation of intensity oscillations in all the coronal extreme ultraviolet (EUV) channels except AIA 94 and 335 Å. We determine the nature of the intensity disturbances as slow magneto-acoustic waves by measuring their phase speeds. The time-distance maps, as well as the detrended light curves, show an increase and decrease in the amplitude of propagating 3 min oscillations over time. The amplitude variations appear most prominently in AIA 171 Å, though other EUV channels also show such signatures. The Fourier power spectrum yields the presence of significant powers with several nearby frequencies in the range of 2–3 min (5–8 mHz), along with many other smaller peaks between 2–4 min. Wavelet analysis shows an increase and decrease of oscillating power around 3 min simultaneous to the amplitude variations. We obtain the modulation period to be in the range of 20–30 min. Conclusions. Our results provide the viability of occurrence of phenomenon like “Beat” among the nearby frequencies giving rise to the observed amplitude modulation. However, we cannot at this stage rule out the possibility that the modulation may be driven by variability in an underlying unknown source.

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