Synergy between solar and stellar flares: challenges and perspectives

AbstractRecent observations of the Sun revealed that the solar atmosphere is full of flares and flare-like phenomena, which affect terrestrial environment and our civilization. It has been established that flares are caused by the release of magnetic energy through magnetic reconnection. Many stars show flares similar to solar flares, and such stellar flares especially in stars with fast rotation are much more energetic than solar flares. These are called superflares. The total energy of a solar flare is 1029 − 1032 erg, while that of a superflare is 1033 − 1038 erg. Recently, it was found that superflares (with 1034 − 1035 erg) occur on Sun-like stars with slow rotation with frequency once in 800 - 5000 years. This suggests the possibility of superflares on the Sun. We review recent development of solar and stellar flare research, and briefly discuss possible impacts of superflares on the Earth and exoplanets.

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Hydrodynamic Models of Solar and Stellar Flares

International Astronomical Union Colloquium ◽

10.1017/s0252921100031948 ◽

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.

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Radio imaging-spectroscopy observations of the Sun in decimetric and centimetric wavelengths

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313003001 ◽

2012 ◽

Vol 8 (S294) ◽

pp. 489-494 ◽

Cited By ~ 9

Author(s):

Yihua Yan ◽

Wei Wang ◽

Fei Liu ◽

Lihong Geng ◽

Zhijun Chen ◽

...

Keyword(s):

Radio Emission ◽

Solar Flares ◽

Inner Mongolia ◽

Imaging Spectroscopy ◽

Current Status ◽

The Sun ◽

Radio Imaging ◽

Time Space ◽

Decimetric Wave ◽

Wave Range

AbstractTo address fundamental processes in the solar eruptive phenomena it is important to have imaging-spectroscopy over centimetric-decimetric wave range. The Chinese Spectral Radioheliograph (CSRH) in 0.4-15 GHz range with high time, space and frequency resolutions is being constructed to achieve this goal. The perspectives to open new observational windows on solar flares and CMEs will be achieved by mapping the radio emission from unstable electron populations during the basic processes of energy release. CSRH is located in a radio quiet region in Inner Mongolia of China. The array of CSRH-I in 0.4-2.0 GHz with 40 4.5m antennas has been established and starts test observations. The 60 2m antennas for array of CSRH-II in 2-15 GHz have been mounted and assembled. The progress and current status of CSRH are introduced.

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QUASI-PERIODIC PULSATIONS IN SOLAR AND STELLAR FLARES. REVIEW

Solnechno-Zemnaya Fizika ◽

10.12737/szf-61202001 ◽

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.

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Balmer and soft X-ray emission from solar and stellar flares

Symposium - International Astronomical Union ◽

10.1017/s0074180900187637 ◽

1990 ◽

Vol 137 ◽

pp. 153-157

Author(s):

C. J. Butler

Keyword(s):

Solar Flares ◽

The Sun ◽

X Ray ◽

Stellar Flares ◽

Basic Similarity ◽

Good Agreement

Integrated soft X-ray (8-12A) fluxes for solar flares have been scaled to the equivalent EXOSAT fluxes using spectra obtained from a variety of rocket-based experiments. The data show good agreement with the soft X-ray - Hγ correlation established by Butler et al. (1988) for stellar flares and confirm the basic similarity, in this respect, of flares on the Sun to those on dMe stars.

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Sunquakes and starquakes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313014579 ◽

2013 ◽

Vol 9 (S301) ◽

pp. 349-352 ◽

Cited By ~ 1

Author(s):

Alexander G. Kosovichev

Keyword(s):

Solar Flares ◽

High Frequency ◽

Turbulent Convection ◽

The Sun ◽

Stellar Oscillations ◽

Impulsive Excitation ◽

Physical Mechanisms ◽

Stellar Flares ◽

Low Degree ◽

High Degree

AbstractIn addition to well-known mechanisms of excitation of solar and stellar oscillations by turbulent convection and instabilities, the oscillations can be excited by an impulsive localized force caused by the energy release in solar and stellar flares. Such oscillations have been observed on the Sun (‘sunquakes’), and created a lot of interesting discussions about physical mechanisms of the impulsive excitation and their relationship to the flare physics. The observation and theory have shown that most of a sunquake's energy is released in high-degree, high-frequency p modes. In addition, there have been reports on helioseismic observations of low-degree modes excited by strong solar flares. Much more powerful flares observed on other stars can cause ‘starquakes’ of substantially higher amplitude. Observations of such oscillations can provide new asteroseismic information and also constraints on mechanisms of stellar flares. I discuss the basic properties of sunquakes, and initial attempts to detect flare-excited oscillations in Kepler short-cadence data.

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The Ultraviolet Continuum in Solar and Stellar Flares

International Astronomical Union Colloquium ◽

10.1017/s0252921100153771 ◽

1989 ◽

Vol 104 (2) ◽

pp. 45-48

Author(s):

K. J. H. Phillips

Keyword(s):

Solar Flares ◽

Ultraviolet Continuum ◽

Stellar Flare ◽

Stellar Flares

SummaryUltraviolet continua observed in IUE spectra of dMc stars in a flaring state are compared with those in solar Hares. There is evidence that, as may be the case with solar flares, stellar-flare continua in particularly the λ < 1683 Å region are due to free-bound transitions in neutral silicon excited by ultraviolet lino emission.

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QUASI-PERIODIC PULSATIONS IN SOLAR AND STELLAR FLARES. REVIEW

Solar-Terrestrial Physics ◽

10.12737/stp-61202001 ◽

2020 ◽

Vol 6 (1) ◽

pp. 3-23 ◽

Cited By ~ 3

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.

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REVIEW OF DESIGN HEURISTICS AND DESIGN PRINCIPLES IN DESIGN FOR ADDITIVE MANUFACTURING

Proceedings of the Design Society ◽

10.1017/pds.2021.518 ◽

2021 ◽

Vol 1 ◽

pp. 2571-2580

Author(s):

Filip Valjak ◽

Angelica Lindwall

Keyword(s):

Additive Manufacturing ◽

Design Process ◽

Research Question ◽

Design Principles ◽

Current Status ◽

Design For Additive Manufacturing ◽

Design Heuristics ◽

Similarities And Differences ◽

Definition Of ◽

Support Methods

AbstractThe advent of additive manufacturing (AM) in recent years have had a significant impact on the design process. Because of new manufacturing technology, a new area of research emerged – Design for Additive Manufacturing (DfAM) with newly developed design support methods and tools. This paper looks into the current status of the field regarding the conceptual design of AM products, with the focus on how literature sources treat design heuristics and design principles in the context of DfAM. To answer the research question, a systematic literature review was conducted. The results are analysed, compared and discussed on three main points: the definition of the design heuristics and the design principles, level of support they provide, as well as where and how they are used inside the design process. The paper highlights the similarities and differences between design heuristics and design principles in the context of DfAM.

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Galactic tide and local stellar perturbations on the Oort cloud: creation of interstellar comets

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935330 ◽

2019 ◽

Vol 629 ◽

pp. A139 ◽

Cited By ~ 9

Author(s):

S. Torres ◽

M. X. Cai ◽

A. G. A. Brown ◽

S. P. Zwart

Keyword(s):

Dynamical Evolution ◽

Cumulative Effect ◽

Oort Cloud ◽

Radial Velocities ◽

Current Status ◽

Interstellar Space ◽

The Sun ◽

Semi Major Axis ◽

Software Environment ◽

External Perturbations

Comets in the Oort cloud evolve under the influence of internal and external perturbations, such as giant planets, stellar passages, and the Galactic gravitational tidal field. We aim to study the dynamical evolution of the comets in the Oort cloud, accounting for the perturbation of the Galactic tidal field and passing stars. We base our study on three main approaches; analytic, observational, and numerical. We first construct an analytical model of stellar encounters. We find that individual perturbations do not modify the dynamics of the comets in the cloud unless very close (<0.5 pc) encounters occur. Using proper motions, parallaxes, and radial velocities from Gaia DR2 and combining them with the radial velocities from other surveys, we then construct an astrometric catalogue of the 14 659 stars that are within 50 pc of the Sun. For all these stars we calculate the time and distance of closest approach to the Sun. We find that the cumulative effect of relatively distant (≤1 pc) passing stars can perturb the comets in the Oort cloud. Finally, we study the dynamical evolution of the comets in the Oort cloud under the influence of multiple stellar encounters from stars that pass within 2.5 pc of the Sun and the Galactic tidal field over ±10 Myr. We use the Astrophysical Multipurpose Software Environment (AMUSE), and the GPU-accelerated direct N-body code ABIE. We considered two models for the Oort cloud, compact (a ≤ 0.25 pc) and extended (a ≤ 0.5 pc). We find that the cumulative effect of stellar encounters is the major perturber of the Oort cloud for a compact configuration while for the extended configuration the Galactic tidal field is the major perturber. In both cases the cumulative effect of distant stellar encounters together with the Galactic tidal field raises the semi-major axis of ~1.1% of the comets at the edge of the Oort cloud up to interstellar regions (a > 0.5 pc) over the 20 Myr period considered. This leads to the creation of transitional interstellar comets (TICs), which might become interstellar objects due to external perturbations. This raises the question of the formation, evolution, and current status of the Oort cloud as well as the existence of a “cloud” of objects in the interstellar space that might overlap with our Oort cloud, when considering that other planetary systems should undergo similar processes leading to the ejection of comets.

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