EUV irradiance observations from SDO/EVE as a diagnostic of solar flares

AbstractFor the past six years, the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory has been monitoring changes in the Sun's extreme ultraviolet output over a range of timescales. Its primary function is to provide measurements of the solar spectral irradiance that is responsible for driving fluctuations in Earth's ionosphere and thermosphere. However, despite its modest spectral resolution and lack of spatial information, the EVE spectral range contains many lines and continua that have become invaluable for diagnosing the response of the lower solar atmosphere itself to an injection of energy, particularly during a flare's impulsive phase. In addition, high temperature emission lines can also be used to track changes in temperature and density of flaring plasma in the corona. The high precision of EVE observations are therefore crucial in helping us understand particle acceleration and energy transport mechanisms during solar flares, as well as the origins of the Sun's most geoeffective emission.

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Validation of computed extreme ultraviolet emission spectra during solar flares

Earth Planets and Space ◽

10.1186/s40623-021-01402-7 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Shohei Nishimoto ◽

Kyoko Watanabe ◽

Toshiki Kawai ◽

Shinsuke Imada ◽

Tomoko Kawate

Keyword(s):

Solar Flares ◽

Rise Time ◽

Extreme Ultraviolet ◽

Emission Spectra ◽

Physical Models ◽

Spectral Irradiance ◽

X Rays ◽

Solar Dynamics Observatory ◽

Ultraviolet Emission ◽

Proposed Model

AbstractX-rays and extreme ultraviolet (EUV) emissions from solar flares rapidly change the physical composition of the Earth’s thermosphere and ionosphere, thereby causing space weather phenomena such as communication failures. Numerous empirical and physical models have been developed to estimate the effects of flare emissions on the Earth’s upper atmosphere. We verified the reproduction of the flare emission spectra using a one-dimensional hydrodynamic calculation and the CHIANTI atomic database. To validate the proposed model, we used the observed EUV spectra obtained by the Extreme ultraviolet variability experiment (EVE) on board the Solar Dynamics Observatory (SDO). We examined the “EUV flare time-integrated irradiance” and “EUV flare line rise time” of the EUV emissions for 21 events by comparing the calculation results of the proposed model and observed EUV spectral data. The proposed model successfully reproduced the EUV flare time-integrated irradiance of the Fe VIII 131 Å, Fe XVIII 94 Å, and Fe XX133 Å, as well as the 55–355 Å and 55–135 Å bands. For the EUV flare line rise time, there was an acceptable correlation between the proposed model estimations and observations for all Fe flare emission lines. These results demonstrate that the proposed model can reproduce the EUV flare emission spectra from the emitting plasma with a relatively high formation temperature. This indicates that the physics-based model is effective for the accurate reproduction of the EUV spectral irradiance.

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Validation of Computed Extreme Ultraviolet Emission Spectra During Solar Flares

10.21203/rs.3.rs-52084/v2 ◽

2020 ◽

Author(s):

Shohei Nishimoto ◽

Kyoko Watanabe ◽

Toshiki Kawai ◽

Shinsuke Imada ◽

Tomoko Kawate

Keyword(s):

Solar Flares ◽

Rise Time ◽

Extreme Ultraviolet ◽

Emission Spectra ◽

Physical Models ◽

X Rays ◽

Solar Dynamics Observatory ◽

Ultraviolet Emission ◽

Proposed Model ◽

Solar Dynamics

Abstract X-rays and extreme ultraviolet (EUV) emissions from solar flares rapidly change the physical composition of the Earth’s thermosphere and ionosphere, thereby causing space weather phenomena such as communication failures. To predict the effects of flare emissions on the Earth’s upper atmosphere, numerous empirical and physical models have been developed. We verify the extent of reproducing the flare emission spectra using a one-dimensional hydrodynamic calculation and the CHIANTI atomic database. To verify the proposed model, we use the observed EUV spectra obtained by the extreme ultraviolet variability (EVE) on board the Solar Dynamics Observatory (SDO). We examined the “EUV flare time-integrated irradiance” and “EUV flare line rise time” of the EUV emissions for 21 events by comparing the calculation results of the proposed model and observed EUV spectral data. The proposed model succeeded in reproducing the EUV flare time-integrated irradiance of the Fe VIII 131 Å , Fe XVIII 94 Å, and Fe XX 133 Å, as well as the 55 to 355 Å and 55 to 135 Å bands. For the EUV flare line rise time, there was acceptable correlation between the proposed model estimations and observations for all Fe flare emission lines. These results demonstrate that the proposed model can reproduce the EUV flare emission spectra from the emitting plasma with relatively high formation temperature. This indicates that the physics-based model is effective for the accurate reproduction of EUV spectral flux.

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Diagnostics of non-thermal-distributions from solar flare EUV line spectra

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001039 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 414-417

Author(s):

Elena Dzifčáková ◽

Alena Zemanová ◽

Jaroslav Dudík ◽

Juraj Lörinčík

Keyword(s):

Electron Distribution ◽

Extreme Ultraviolet ◽

Impulsive Phase ◽

Distribution Functions ◽

Solar Dynamics Observatory ◽

Thermal Electron ◽

Line Intensities ◽

Thermal Distribution ◽

Temperature Diagnostics ◽

Solar Dynamics

AbstractSpectral line intensities observed by the Extreme Ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) during 2012 March 9 M6.3 flare were used to diagnose a presence of a non-thermal electron distribution represented by a κ-distribution. The diagnosed electron densities ($\approx 2 \times {10^{11}}{\rm{c}}{{\rm{m}}^{ - 3}}$) are affected only a little by the presence of the non-thermal distribution, and are within the uncertainties of observation. On the other hand, the temperature diagnostics based on the line ratios involving different ionization degrees is strongly affected by the type of the electron distribution. The distribution functions diagnosed from relative Fe line intensities demonstrate the presence of strongly non-thermal distributions during the impulsive phase of the flare and later their gradual thermalization.

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

Science Advances ◽

10.1126/sciadv.aaw6548 ◽

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.

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Solar extreme ultraviolet (EUV) flare observations and findings from the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE)

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000466 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 27-40

Author(s):

Thomas N. Woods ◽

Francis G. Eparvier ◽

James P. Mason

Keyword(s):

Extreme Ultraviolet ◽

Late Phase ◽

Impulsive Phase ◽

The Sun ◽

Solar Dynamics Observatory ◽

X Ray ◽

Gradual Phase ◽

Stellar Flares ◽

Solar Dynamics ◽

Coronal Dimming

AbstractNew solar soft X-ray (SXR) and extreme ultraviolet (EUV) irradiance observations from NASA Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) provide full coverage from 0.1 to 106 nm and continuously at a cadence of 10 seconds for spectra at 0.1 nm resolution. These observations during flares can usually be decomposed into four distinct characteristics: impulsive phase, gradual phase, coronal dimming, and EUV late phase. Over 6000 flares have been observed during the SDO mission; some flares show all four phases, and some only show the gradual phase. The focus is on the newer results about the EUV late phase and coronal dimming and its relationship to coronal mass ejections (CMEs). These EVE flare measurements are based on observing the sun-as-a-star, so these results could exemplify stellar flares. Of particular interest is that new coronal dimming measurements of stars could be used to estimate mass and velocity of stellar CMEs.

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Validation of Extreme Ultraviolet Emission Spectra During Solar Flares

10.21203/rs.3.rs-52084/v1 ◽

2020 ◽

Author(s):

Shohei Nishimoto ◽

Kyoko Watanabe ◽

Toshiki Kawai ◽

Shinsuke Imada ◽

Tomoko Kawate

Keyword(s):

Solar Flares ◽

Rise Time ◽

Extreme Ultraviolet ◽

Emission Spectra ◽

Physical Models ◽

X Rays ◽

Solar Dynamics Observatory ◽

Ultraviolet Emission ◽

Proposed Model ◽

Solar Dynamics

Abstract X-rays and extreme ultraviolet (EUV) emissions from solar flares rapidly change the physical composition of the Earth’s thermosphere and ionosphere, thereby causing space weather phenomena such as communication failures. To predict the effects of flare emissions on the Earth’s upper atmosphere, numerous empirical and physical models have been developed. We verify the extent of reproducing the flare emission spectra using a one-dimensional hydrodynamic calculation and the CHIANTI atomic database. To verify the proposed model, we use the observed EUV spectra obtained by the extreme ultraviolet variability (EVE) on board the Solar Dynamics Observatory (SDO). We examined the “EUV flare time-integrated irradiance” and “EUV flare line rise time” of the EUV emissions for 21 events by comparing the calculation results of the proposed model and observed EUV spectral data. The proposed model succeeded in reproducing the EUV flare time-integrated irradiance of the Fe VIII 131 Å, Fe XVIII 94 Å, and Fe XX 133 Å, as well as the 55 to 355 Å and 55 to 135 Å bands. For the EUV flare line rise time, there was acceptable correlation between the proposed model estimations and observations for all Fe flare emission lines. These results demonstrate that the proposed model can reproduce the EUV flare emission spectra from the emitting plasma with relatively high formation temperature. This indicates that the physics-based model is effective for the accurate reproduction of EUV spectral flux.

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The Solar and Heliospheric Observatory

International Astronomical Union Colloquium ◽

10.1017/s0252921100085596 ◽

1984 ◽

Vol 86 ◽

pp. 155-158 ◽

Cited By ~ 1

Author(s):

Giancarlo Noci

Keyword(s):

Solar Physics ◽

Grazing Incidence ◽

Spectral Irradiance ◽

The Sun ◽

Solar Dynamics Observatory ◽

Solar Constant ◽

Heliospheric Observatory ◽

Explorer Mission ◽

Solar Dynamics ◽

Euv Spectrum

In the past years several space missions have been proposed for the study of the Sun and of the Heliosphere. These missions were intended to clarify various different aspects of solar physics. For example, the GRIST (Grazing Incidence Solar Telescope) mission was intended as a means to improve our knowledge of the upper transition region and low corona through the detection of the solar EUV spectrum with a spatial resolution larger than in previous missions; the DISCO (Dual Spectral Irradiance and Solar Constant Orbiter) and SDO (Solar Dynamics Observatory) missions were proposed to gat observational data about the solar oscillations better than those obtained from ground based instruments; the SOHO (Solar and Heliospheric Observatory) mission was initially proposed to combine the properties of GRIST with the study of the extended corona (up to several radii of heliocentric distance) by observing the scattered Ly-alpha and OVI radiation, which was also the basis of the SCE (Solar Corona Explorer) mission proposal; the development of the interest about the variability of the Sun, both in itself and for its consequences in the history of the Earth, led to propose observations of the solar constant (included in DISCO).

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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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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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Generation of solar spicules and subsequent atmospheric heating

Science ◽

10.1126/science.aaw2796 ◽

2019 ◽

Vol 366 (6467) ◽

pp. 890-894 ◽

Cited By ~ 24

Author(s):

Tanmoy Samanta ◽

Hui Tian ◽

Vasyl Yurchyshyn ◽

Hardi Peter ◽

Wenda Cao ◽

...

Keyword(s):

Solar Atmosphere ◽

Opposite Polarity ◽

Solar Observatory ◽

Magnetized Plasma ◽

Solar Chromosphere ◽

Solar Dynamics Observatory ◽

Polarity Magnetic Field ◽

Solar Dynamics ◽

Solar Spicules ◽

Lower Solar Atmosphere

Spicules are rapidly evolving fine-scale jets of magnetized plasma in the solar chromosphere. It remains unclear how these prevalent jets originate from the solar surface and what role they play in heating the solar atmosphere. Using the Goode Solar Telescope at the Big Bear Solar Observatory, we observed spicules emerging within minutes of the appearance of opposite-polarity magnetic flux around dominant-polarity magnetic field concentrations. Data from the Solar Dynamics Observatory showed subsequent heating of the adjacent corona. The dynamic interaction of magnetic fields (likely due to magnetic reconnection) in the partially ionized lower solar atmosphere appears to generate these spicules and heat the upper solar atmosphere.

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