scholarly journals HIGH-RESOLUTION LABORATORY SPECTRA OF THE λ193 CHANNEL OF THE ATMOSPHERIC IMAGING ASSEMBLY INSTRUMENT ON BOARD SOLAR DYNAMICS OBSERVATORY

2014 ◽  
Vol 215 (1) ◽  
pp. 6 ◽  
Author(s):  
Elmar Träbert ◽  
Peter Beiersdorfer ◽  
Nancy S. Brickhouse ◽  
Leon Golub
Keyword(s):  
High Resolution ◽  
Solar Dynamics Observatory ◽  
Solar Dynamics

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 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.

Observations for the Role of Flux rope Eruption in a Geoeffective Solar Flare

2014 ◽  
Vol 4 (2) ◽  
pp. 555-564
Author(s):  
A.M Aslam
Keyword(s):  
Solar Flare ◽  
Flux Rope ◽  
Magnetic Configuration ◽  
Solar Dynamics Observatory ◽  
Multi Wavelength ◽  
Solar Dynamics ◽  
Halo Coronal Mass Ejection ◽  
Mass Ejection ◽  
The Waves

On September 24, 2011 a solar flare of M 7.1 class was released from the Sun. The flare was observed by most of the space and ground based observatories in various wavebands. We have carried out a study of this flare to understand its causes on Sun and impact on earth. The flare was released from NOAA active region AR 11302 at 12:33 UT. Although the region had already produced many M class flares and one X- class flare before this flare, the magnetic configuration was not relaxed and still continued to evolve as seen from HMI observations. From the Solar Dynamics Observatory (SDO) multi-wavelength (131 Ã…, 171 Ã…, 304 Ã… and 1600Ã…) observations we identified that a rapidly rising flux rope triggered the flare although HMI observations revealed that magnetic configuration did not undergo a much pronounced change. The flare was associated with a halo Coronal Mass Ejection (CME) as recorded by LASCO/SOHO Observations. The flare associated CME was effective in causing an intense geomagnetic storm with minimum Dst index -103 nT. A radio burst of type II was also recorded by the WAVES/WIND. In the present study attempt is made to study the nature of coupling between solar transients and geospace.

scholarly journals The Solar and Heliospheric Observatory

1984 ◽  
Vol 86 ◽  
pp. 155-158 ◽  
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).

scholarly journals Multi-Stranded Coronal Loops: Quantifying Strand Number and Heating Frequency from Simulated Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) Observations

Solar Physics ◽  
2021 ◽  
Vol 296 (6) ◽  
Author(s):  
Thomas Williams ◽  
Robert W. Walsh ◽  
Stephane Regnier ◽  
Craig D. Johnston
Keyword(s):  
Energy Content ◽  
Time Lag ◽  
Low Frequency ◽  
Building Blocks ◽  
Coronal Loops ◽  
Loop Model ◽  
Solar Dynamics Observatory ◽  
Heat Deposition ◽  
Total Energy Content ◽  
Solar Dynamics

AbstractCoronal loops form the basic building blocks of the magnetically closed solar corona yet much is still to be determined concerning their possible fine-scale structuring and the rate of heat deposition within them. Using an improved multi-stranded loop model to better approximate the numerically challenging transition region, this article examines synthetic NASA Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA) emission simulated in response to a series of prescribed spatially and temporally random, impulsive and localised heating events across numerous sub-loop elements with a strong weighting towards the base of the structure: the nanoflare heating scenario. The total number of strands and nanoflare repetition times is varied systematically in such a way that the total energy content remains approximately constant across all the cases analysed. Repeated time-lag detection during an emission time series provides a good approximation for the nanoflare repetition time for low-frequency heating. Furthermore, using a combination of AIA 171/193 and 193/211 channel ratios in combination with spectroscopic determination of the standard deviation of the loop-apex temperature over several hours alongside simulations from the outlined multi-stranded loop model, it is demonstrated that both the imposed heating rate and number of strands can be realised.

scholarly journals Электрические токи в униполярных областях с разной скоростью затухания магнитного потока в пятне

2021 ◽  
Vol 117 (1) ◽  
pp. 29-37
Author(s):  
Юрий Фурсяк ◽  
Андрей Плотников ◽  
Валентина Абраменко
Keyword(s):  
Solar Dynamics Observatory ◽  
Solar Dynamics

Используя магнитографические данные прибора Helioseismic and Magnetic Imager (HMI) на борту космического аппарата Solar Dynamics Observatory (SDO), мы вычислили параметры магнитного поля и электрических токов для униполярных активных областей (АО) с низкой (≤ 2.1 × 1019 Мкс ч−1, всего исследовано 11 АО) и высокой (≥ 7.0 × 1019 Мкс ч−1, проанализиро-вано 5 АО) скоростью затухания магнитного потока в пятне. Получены следующие результаты: 1) чем сильнее локальные (мелкомасштабные) электрические токи в окрестности униполярного пятна, тем быстрее оно затухает; 2) распределенный (глобальный, крупномасштабный) электрический ток вокруг быстро затухающих пятен практически нулевой, и от него не приходится ожидать стабилизирующего воздействия на процесс распада пятна; 3) для четырех случаев медленно затухающих пятен выявлен ненулевой распределенный электрический ток величиной до 5.0 × 1012 А. Такой ток может оказывать стабилизирующее  действие на распад пятна. Таким образом, полученные нами результаты указывают на то, что электрические токи малых масштабов оказывают скорее деструктивное воздействие на пятно, а присутствие крупномасштабных токов может стабилизировать пятно. Однако данный механизм, по-видимому, не является единственным и доминирующим в процессах стабилизации пятен.

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

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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