scholarly journals The Effect of Electron Beams on the Hydrogen Emission in Impulsive Flares on the Sun and Stars

1993 ◽  
Vol 137 ◽  
pp. 801-803
Author(s):  
V.V. Zharkova ◽  
V.A. Kobylinsky
Keyword(s):  
Physical Nature ◽  
High Temporal Resolution ◽  
The Sun ◽  
X Rays ◽  
Hydrogen Emission ◽  
Physical Conditions ◽  
Stellar Flares ◽  
Thermal Origin ◽  
Beam Parameters ◽  
Observational Techniques

Flares are very frequent phenomena on the sun and on other stars and are actively investigated with precise observational techniques. These studies are particularly stimulated by recent X-ray and UV observations on spacecraft (Skylab, SMM). From all these observations the flares on the sun and stars seem to be of the same physical nature but of different energetic power. A number of investigations devoted to comparison between the solar and stellar flares led to the conclusion that they have the similar mechanisms for the energy release and transport and for their manifestations in different ranges of electromagnetic radiation.The hydrogen emission is easy to observe in these events, and thus it is convenient for diagnostic analysis of physical conditions in the flares. However, the impulsive events were considered to be observed in X-rays so only. Zharkova & Kobylinsky (1992, 1993) have recently shown that the hydrogen continuous radiation of the solar flares is sensitive to the electron beam parameters. We also develop an approach to detection of the flares of non-thermal or thermal origin by observing the hydrogen Balmer and Pashen continuum emissions with high temporal resolution.

scholarly journals Magnetic reconnection and energy release on the Sun and solar-like stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 191-200
Author(s):  
Lidia van Driel-Gesztelyi
Keyword(s):  
Free Energy ◽  
Magnetic Reconnection ◽  
Energy Release ◽  
Energy Content ◽  
Magnetic Flux Density ◽  
The Sun ◽  
X Rays ◽  
Stellar Flares ◽  
Wide Wavelength Range ◽  
Hot Corona

AbstractMagnetic reconnection is thought to play an important role in liberating free energy stored in stressed magnetic fields. The consequences vary from undetectable nanoflares to huge flares, which have signatures over a wide wavelength range, depending on e.g. magnetic topology, free energy content, total flux, and magnetic flux density of the structures involved. Events of small energy release, which are thought to be the most numerous, are one of the key factors in the existence of a hot corona in the Sun and solar-like stars. The majority of large flares are ejective, i.e. involve the expulsion of large quantities of mass and magnetic field from the star. Since magnetic reconnection requires small length-scales, which are well below the spatial resolution limits of even the solar observations, we cannot directly observe magnetic reconnection happening. However, there is a plethora of indirect evidences from X-rays to radio observations of magnetic reconnection. I discuss key observational signatures of flares on the Sun and solar-paradigm stellar flares and describe models emphasizing synergy between observations and theory.

Waves and Quasi-Periodic-Pulsations in Weak Active Solar Emissions

2021 ◽  
Author(s):  
Divya Oberoi ◽  
Atul Mohan ◽  
Surajit Mondal
Keyword(s):  
Type I ◽  
The Sun ◽  
X Rays ◽  
Noise Storm ◽  
Physical Conditions ◽  
Spatially Resolved ◽  
Science Area ◽  
Radio Frequencies ◽  
Murchison Widefield Array ◽  
Release Processes

<p>The presence of Quasi-periodic pulsations (QPPs) is found to be a common feature of flaring energy release processes on the Sun. They are observed all across the EM range from hard X-rays to radio and provide insights into the physical conditions in the coronal plasma and the processes involved in the generation of these waves and oscillations. There have been numerous observations of spatially resolved QPPs at higher energies, though there are fewer examples at radio frequencies. Spatially resolved observations of these phenomena are particularly rare at low radio frequencies and there are none which are associated with the weaker episodes of active emissions which are much more numerous and frequent. The key reason limiting such studies has been the lack of availability of spectroscopic snapshot images of sufficient quality to detect and characterise the low level changes in the morphology of the sources of active emissions. Together, the data from the Murchison Widefield Array (MWA), a SKA precursor, and an imaging pipeline developed to meet the specific needs of solar imaging, now meet this challenge and enable us to explore this rich and interesting science area. Our work has led to the discovery of several previously unknown phenomena - second-scale QPPs in the size and orientation of a type III source, with simultaneous QPPs in intensity; 30 s QPPs in the radio light curve of a type I emission source associated with active region loop hosting a transient brightening; and intermittent presence of an anti-correlation in the size and intensity of a type I noise storm source along with QPPs. In this presentation we will briefly summarise these recent results and discuss their implications.</p>

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

The Interpretation of Solar Spectral Intensities

1988 ◽  
Vol 102 ◽  
pp. 329
Author(s):  
R.W.P. McWhirter
Keyword(s):  
Emission Measure ◽  
Physical Nature ◽  
Atomic Data ◽  
The Sun ◽  
Atomic Properties ◽  
Outer Atmosphere ◽  
Spectral Intensities ◽  
Thin Plasma ◽  
Number Of Authors

The intensity of a specrtal line from an optically thin plasma such as the outer atmosphere of the sun depends on both the atomic properties of the atomic ion responsible for the line and the physical nature of the plasma. In this paper we discuss the various ways in which the measured spectral intensities from the sun are used to discover something about the nature of the sun’s atmosphere. The technique has been referred to as the emission measure method. It has important limitations in terms of the accuracy of the specrtal data as well as the atomic data. We discuss some of these and suggest methods by which they may be assessed. The technique is illustrated by application to real observations from a number of authors.

About the concept of synthesis of high-performance detection and positioning systems in the areas of elements falling, separated from strategic and space missiles on the trajectories of their flight during tests and regular operation

2018 ◽  
pp. 10-21
Author(s):  
G. G. Vokin
Keyword(s):  
High Performance ◽  
Physical Nature ◽  
Positioning Systems ◽  
Physical Conditions ◽  
Highly Efficient

The article describes the approach and topical issues of synthesis of highly efficient transportable systems for search and determination of coordinates in the areas of elements falling, separated from the missiles, taking into account the dislocation of pre-empted areas of fall and physical conditions in their territories. The principles of these systems are based on the rational integration of traditional and non-traditional information sensors of different physical nature, which record the moments of landing of separated parts of the missiles.

scholarly journals AGN surveys to study galaxy evolution along cosmic times

2013 ◽  
Vol 9 (S304) ◽  
pp. 180-186
Author(s):  
Luigi Spinoglio
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Energy Production ◽  
X Rays ◽  
Radio Frequencies ◽  
Ir Spectroscopic ◽  
Observational Techniques ◽  
Production Mechanisms

AbstractVarious observational techniques have been used to survey galaxies and AGN, from X-rays to radio frequencies, both photometric and spectroscopic. I will review these techniques aimed at the study of galaxy evolution and of the role of AGNs and star formation as the two main energy production mechanisms. I will then present as a new observational approach the far-IR spectroscopic surveys that could be done with planned astronomical facilities of the next future, such as SPICA from the space and CCAT from the ground.

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 The Sun and stars as the primary energy input in planetary atmospheres

2009 ◽  
Vol 5 (S264) ◽  
pp. 3-18 ◽  
Author(s):  
Ignasi Ribas
Keyword(s):  
Planetary Atmospheres ◽  
Primary Energy ◽  
Stellar Atmospheres ◽  
Structure Evolution ◽  
Strong Impact ◽  
The Sun ◽  
X Rays ◽  
Low Mass Stars ◽  
Particle Emissions ◽  
Mere Existence

AbstractProper characterization of the host star to a planet is a key element to the understanding of its overall properties. The star has a direct impact through the modification of the structure and evolution of the planet atmosphere by being the overwhelmingly larger source of energy. The star plays a central role in shaping the structure, evolution, and even determining the mere existence of planetary atmospheres. The vast majority of the stellar flux is well understood thanks to the impressive progress made in the modeling of stellar atmospheres. At short wavelengths (X-rays to UV), however, the information is scarcer since the stellar emission does not originate in the photosphere but in the chromospheric and coronal regions, which are much less understood. The same can be said about particle emissions, with a strong impact on planetary atmospheres, because a detailed description of the time-evolution of stellar wind is still lacking. Here we review our current understanding of the flux and particle emissions of the Sun and low-mass stars and briefly address their impact in the context of planetary atmospheres.

First Results from Solar Orbiter’s Energetic Particle Detector

2021 ◽  
Author(s):  
Javier Rodriguez-Pacheco ◽  
Keyword(s):  
Energetic Particle ◽  
Wide Energy Range ◽  
High Temporal Resolution ◽  
The Sun ◽  
Particle Detector ◽  
First Results ◽  
Wide Energy ◽  
Spatio Temporal ◽  
Inner Heliosphere

<p>In this presentation, we will show the first measurements performed by EPD since the end of the commissioning phase until the latest results obtained. During these months EPD has been scanning the inner heliosphere at different heliocentric distances and heliolongitues allowing - together with other spacecraft - to investigate the spatio-temporal behavior of the particle populations in the inner heliosphere during solar minimum conditions. Solar Orbiter was launched from Cape Canaveral on February 10th, 2020, thus beginning the journey to its encounter with the Sun. Solar Orbiter carries ten scientific instruments, six remote sensing and four in situ, that will allow the mission main goal: how the Sun creates and controls the heliosphere. Among the in situ instruments, the Energetic Particle Detector (EPD) measures electrons, protons and heavy ions with high temporal resolution over a wide energy range, from suprathermal energies up to several hundreds of MeV/nucleon.</p>

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