scholarly journals QUASI-PERIODIC PULSATIONS IN SOLAR AND STELLAR FLARES. REVIEW

2020 ◽  
Vol 6 (1) ◽  
pp. 3-23 ◽  
Author(s):  
Elena Kupriyanova ◽  
Dmitrii Kolotkov ◽  
Valery Nakariakov ◽  
Anastasiia Kaufman
Keyword(s):  
Spectral Resolution ◽  
State Of The Art ◽  
Electromagnetic Spectrum ◽  
The Sun ◽  
Periodic Modulation ◽  
Stellar Flares ◽  
Open Questions ◽  
Similarities And Differences ◽  
Accelerated Particles ◽  
Oscillatory Processes

This paper provides an overview of the state-of-the-art studies of oscillatory processes in solar and stellar flares, based on modern observational data from ground-based and space-borne instruments with high temporal, spatial, and spectral resolution in different bands of the electromagnetic spectrum. We examine the mecha-nisms that generate flare emission and its quasi-periodic modulation. We discuss similarities and differences be-tween solar and stellar flares, and address associated problems of superflares on the Sun and space weather. Quasi-periodic pulsations (QPPs) of flare emission are shown to be an effective tool for diagnosing both the flare processes themselves and the parameters of flaring plasmas and accelerated particles. We consider types of QPPs, their statistical properties, and methods of analysis, taking into account the non-stationarity of the QPPs’ parameters. We review the proposed mechanisms of QPPs and summarize open questions.

scholarly journals QUASI-PERIODIC PULSATIONS IN SOLAR AND STELLAR FLARES. REVIEW

2020 ◽  
Vol 6 (1) ◽  
pp. 3-29
Author(s):  
Elena Kupriyanova ◽  
Dmitrii Kolotkov ◽  
Valery Nakariakov ◽  
Anastasiia Kaufman
Keyword(s):  
State Of The Art ◽  
The Sun ◽  
Periodic Modulation ◽  
Stellar Flares ◽  
Open Questions ◽  
Magnetic Spectrum ◽  
Similarities And Differences ◽  
Electro Magnetic ◽  
Accelerated Particles ◽  
Oscillatory Processes

This paper provides an overview of the state-of-the-art studies of oscillatory processes in solar and stellar flares, based on modern observational data from ground-based and space-borne instruments with high temporal, spatial, and spectral resolution in different electro-magnetic spectrum ranges. We examine the mechanisms that generate flare emission and its quasi-periodic modulation. We discuss similarities and differences between solar and stellar flares, and address associated problems of superflares on the Sun and space weather problems. Quasi-periodic pulsations (QPPs) of flare radiation are shown to be an effective tool for diagnosing both the flare processes themselves and the parameters of flare plasma and accelerated particles. We consider types of QPPs, their statistical properties, and methods of analysis, taking into account the non-stationarity of the QPPs’ parameters. We review the proposed mechanisms of QPPs and address open questions.

scholarly journals Synergy between solar and stellar flares: challenges and perspectives

2015 ◽  
Vol 11 (S320) ◽  
pp. 419-426
Author(s):  
Suzanne L. Hawley
Keyword(s):  
Solar Flares ◽  
Additional Data ◽  
Current Status ◽  
The Sun ◽  
Stellar Flare ◽  
Stellar Flares ◽  
Similarities And Differences

AbstractI will review the current status of stellar flare observations and models, highlight similarities and differences with solar flares, and plead for additional data and insight from the “Sun as a Star”.

Revisiting the High-Pressure Properties of the Metal-Organic Frameworks ZIF-8 and ZIF-67

2020 ◽  
Author(s):  
Pia Vervoorts ◽  
Stefan Burger ◽  
Karina Hemmer ◽  
Gregor Kieslich
Keyword(s):  
High Pressure ◽  
State Of The Art ◽  
Energy Landscape ◽  
Structural Flexibility ◽  
Zeolitic Imidazolate Frameworks ◽  
Stimuli Responsive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Open Questions ◽  
Metal Organic

The zeolitic imidazolate frameworks ZIF-8 and ZIF-67 harbour a series of fascinating stimuli responsive properties. Looking at their responsitivity to hydrostatic pressure as stimulus, open questions exist regarding the isotropic compression with non-penetrating pressure transmitting media. By applying a state-of-the-art high-pressure powder X-ray diffraction setup, we revisit the high-pressure behaviour of ZIF-8 and ZIF-67 up to <i>p</i> = 0.4 GPa in small pressure increments. We observe a drastic, reversible change of high-pressure powder X-ray diffraction data at <i>p</i> = 0.3 GPa, discovering large volume structural flexibility in ZIF-8 and ZIF-67. Our results imply a shallow underlying energy landscape in ZIF-8 and ZIF-67, an observation that might point at rich polymorphism of ZIF-8 and ZIF-67, similar to ZIF-4(Zn).<br>

Revisiting the High-Pressure Properties of the Metal-Organic Frameworks ZIF-8 and ZIF-67

2020 ◽  
Author(s):  
Pia Vervoorts ◽  
Stefan Burger ◽  
Karina Hemmer ◽  
Gregor Kieslich
Keyword(s):  
High Pressure ◽  
State Of The Art ◽  
Energy Landscape ◽  
Structural Flexibility ◽  
Zeolitic Imidazolate Frameworks ◽  
Stimuli Responsive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Open Questions ◽  
Metal Organic

The zeolitic imidazolate frameworks ZIF-8 and ZIF-67 harbour a series of fascinating stimuli responsive properties. Looking at their responsitivity to hydrostatic pressure as stimulus, open questions exist regarding the isotropic compression with non-penetrating pressure transmitting media. By applying a state-of-the-art high-pressure powder X-ray diffraction setup, we revisit the high-pressure behaviour of ZIF-8 and ZIF-67 up to <i>p</i> = 0.4 GPa in small pressure increments. We observe a drastic, reversible change of high-pressure powder X-ray diffraction data at <i>p</i> = 0.3 GPa, discovering large volume structural flexibility in ZIF-8 and ZIF-67. Our results imply a shallow underlying energy landscape in ZIF-8 and ZIF-67, an observation that might point at rich polymorphism of ZIF-8 and ZIF-67, similar to ZIF-4(Zn).<br>

scholarly journals Five-Card AND Computations in Committed Format Using Only Uniform Cyclic Shuffles

2021 ◽  
Author(s):  
Yuta Abe ◽  
Yu-ichi Hayashi ◽  
Takaaki Mizuki ◽  
Hideaki Sone
Keyword(s):  
State Of The Art ◽  
Research Topic ◽  
The State ◽  
Major Research ◽  
Open Questions

AbstractIn card-based cryptography, designing AND protocols in committed format is a major research topic. The state-of-the-art AND protocol proposed by Koch, Walzer, and Härtel in ASIACRYPT 2015 uses only four cards, which is the minimum permissible number. The minimality of their protocol relies on somewhat complicated shuffles having non-uniform probabilities of possible outcomes. Restricting the allowed shuffles to uniform closed ones entails that, to the best of our knowledge, six cards are sufficient: the six-card AND protocol proposed by Mizuki and Sone in 2009 utilizes the random bisection cut, which is a uniform and cyclic (and hence, closed) shuffle. Thus, a question has arisen: “Can we improve upon this six-card protocol using only uniform closed shuffles?” In other words, the existence or otherwise of a five-card AND protocol in committed format using only uniform closed shuffles has been one of the most important open questions in this field. In this paper, we answer the question affirmatively by designing five-card committed-format AND protocols using only uniform cyclic shuffles. The shuffles that our protocols use are the random cut and random bisection cut, both of which are uniform cyclic shuffles and can be easily implemented by humans.

scholarly journals Improving Langley calibrations by reducing diurnal variations of aerosol Ångström parameters

2012 ◽  
Vol 5 (5) ◽  
pp. 6479-6492
Author(s):  
A. Kreuter ◽  
S. Wuttke ◽  
M. Blumthaler
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Aerosol Optical Depth ◽  
State Of The Art ◽  
Diurnal Variations ◽  
The Sun ◽  
Calibration Constant ◽  
Solar Noon ◽  
Sun Photometer ◽  
Photometer Calibration

Abstract. Errors in the sun photometer calibration constant lead to artificial diurnal variations, symmetric around solar noon, of the retrieved Aerosol Optical Depth (AOD) and the associated Ångström exponent α and its curvature γ. We show in simulations that within the uncertainty of state-of-the-art Langley calibrations, these diurnal variations of α and γ can be significant in low AOD conditions, while those of AOD are negligible. We implement a weighted Monte-Carlo method of finding an improved calibration constant by minimizing the diurnal variations in α and γ and apply the method to sun photometer data of a clear day in Innsbruck, Austria. The results show that our method can be used to improve the calibrations in two of the four wavelength channels by up to a factor of 3.6.

scholarly journals Parallel Crossed Chaotic Encryption for Hyperspectral Images

2018 ◽  
Vol 8 (7) ◽  
pp. 1183 ◽  
Author(s):  
Carlos Villaseñor ◽  
Eric Gutierrez-Frias ◽  
Nancy Arana-Daniel ◽  
Alma Alanis ◽  
Carlos Lopez-Franco
Keyword(s):  
Chaotic Systems ◽  
Ad Hoc ◽  
State Of The Art ◽  
Hyperspectral Images ◽  
Encryption Algorithm ◽  
Electromagnetic Spectrum ◽  
Chaotic Encryption ◽  
Raw Data ◽  
Essential Tool ◽  
Encryption Schemes

Hyperspectral images (HI) collect information from across the electromagnetic spectrum, and they are an essential tool for identifying materials, recognizing processes and finding objects. However, the information on an HI could be sensitive and must to be protected. Although there are many encryption schemes for images and raw data, there are not specific schemes for HI. In this paper, we introduce the idea of crossed chaotic systems and we present an ad hoc parallel crossed chaotic encryption algorithm for HI, in which we take advantage of the multidimensionality nature of the HI. Consequently, we obtain a faster encryption algorithm and with a higher entropy result than others state of the art chaotic schemes.

scholarly journals Hydrodynamic Models of Solar and Stellar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 289-298
Author(s):  
Giovanni Peres
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Light Curves ◽  
Physical Parameters ◽  
The Sun ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Stellar Flares

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.

scholarly journals ‘Sumer’ – Solar Ultraviolet Measurements of Emitted Radiation

1994 ◽  
Vol 144 ◽  
pp. 619-624 ◽  
Author(s):  
K. Wilhelm ◽  
W. Curdt ◽  
A. H. Gabriel ◽  
M. Grewing ◽  
M. C. E. Huber ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Extreme Ultraviolet ◽  
Flow Characteristics ◽  
Magnetic Activity ◽  
High Accuracy ◽  
The Sun ◽  
Lower Corona ◽  
Doppler Shifts ◽  
Solar Magnetic Activity ◽  
Solar Ultraviolet

AbstractThe experiment Solar Ultraviolet Measurements of Emitted Radiation (SUMER) is designed for the investigations of plasma flow characteristics, turbulence and wave motions, plasma densities and temperatures, structures and events associated with solar magnetic activity in the chromosphere, the transition zone and the corona. Specifically, SUMER will measure profiles and intensities of extreme ultraviolet (EUV) lines emitted in the solar atmosphere ranging from the upper chromosphere to the lower corona; determine line broadenings, spectral positions and Doppler shifts with high accuracy; provide stigmatic images of selected areas of the Sun in the EUV with high spatial, temporal and spectral resolution and obtain full images of the Sun and the inner corona in selectable EUV lines, corresponding to a temperature range from 104to more than 1.8 x 106K. The spatial and spectral resolution capabilities of the instrument will be considered in this contribution in some detail, and a new detector concept will be introduced.

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