scholarly journals A potential lag between the open solar magnetic source flux and solar EUV and X-ray emissions as measured by the Earth's ionosphere during total solar eclipses

2009 ◽  
Vol 27 (6) ◽  
pp. 2449-2456 ◽  
Author(s):  
C. J. Davis ◽  
S. A. Bell ◽  
R. Stamper ◽  
A. W. V. Poole ◽  
L. A. McKinnell ◽  
...  
Keyword(s):  
Solar Corona ◽  
Relative Size ◽  
Unexpected Result ◽  
X Rays ◽  
X Ray ◽  
Magnetic Source ◽  
Flux Measurements ◽  
E Region ◽  
Solar Eclipses ◽  
Data Gap

Abstract. Measurements of the ionospheric E-region during total solar eclipses have been used to provide information about the evolution of the solar magnetic field and EUV and X-ray emissions from the solar corona and chromosphere. By measuring levels of ionisation during an eclipse and comparing these measurements with an estimate of the unperturbed ionisation levels (such as those made during a control day, where available) it is possible to estimate the percentage of ionising radiation being emitted by the solar corona and chromosphere. Previously unpublished data from the two eclipses presented here are particularly valuable as they provide information that supplements the data published to date. The eclipse of 23 October 1976 over Australia provides information in a data gap that would otherwise have spanned the years 1966 to 1991. The eclipse of 4 December 2002 over Southern Africa is important as it extends the published sequence of measurements. Comparing measurements from eclipses between 1932 and 2002 with the solar magnetic source flux reveals that changes in the solar EUV and X-ray flux lag the open source flux measurements by approximately 1.5 years. We suggest that this unexpected result comes about from changes to the relative size of the limb corona between eclipses, with the lag representing the time taken to populate the coronal field with plasma hot enough to emit the EUV and X-rays ionising our atmosphere.

scholarly journals Projection effects in galaxy cluster samples: insights from X-ray redshifts

2019 ◽  
Vol 626 ◽  
pp. A48 ◽  
Author(s):  
M. E. Ramos-Ceja ◽  
F. Pacaud ◽  
T. H. Reiprich ◽  
K. Migkas ◽  
L. Lovisari ◽  
...  
Keyword(s):  
Spatial Information ◽  
Galaxy Cluster ◽  
X Rays ◽  
X Ray ◽  
Cluster Sample ◽  
Global Cluster ◽  
Sky Survey ◽  
The Galaxy ◽  
Flux Measurements ◽  
Cluster Properties

Presently, the largest sample of galaxy clusters selected in X-rays comes from the ROSAT All-Sky Survey (RASS). Although there have been many interesting clusters discovered with the RASS data, the broad point spread function of the ROSAT satellite limits the attainable amount of spatial information for the detected objects. This leads to the discovery of new cluster features when a re-observation is performed with higher-resolution X-ray satellites. Here we present the results from XMM-Newton observations of three clusters: RXC J2306.6−1319, ZwCl 1665, and RXC J0034.6−0208, for which the observations reveal a double or triple system of extended components. These clusters belong to the extremely expanded HIghest X-ray FLUx Galaxy Cluster Sample (eeHIFLUGCS), which is a flux-limited cluster sample (fX, 500 ≥ 5 × 10−12 erg s−1 cm−2 in the 0.1−2.4 keV energy band). For each structure in each cluster, we determine the redshift with the X-ray spectrum and find that the components are not part of the same cluster. This is confirmed by an optical spectroscopic analysis of the galaxy members. Therefore, the total number of clusters is actually seven, rather than three. We derive global cluster properties of each extended component. We compare the measured properties to lower-redshift group samples, and find a good agreement. Our flux measurements reveal that only one component of the ZwCl 1665 cluster has a flux above the eeHIFLUGCS limit, while the other clusters will no longer be part of the sample. These examples demonstrate that cluster–cluster projections can bias X-ray cluster catalogues and that with high-resolution X-ray follow-up this bias can be corrected.

scholarly journals Supersoft X-ray nebulae in the Large Magellanic Cloud

2020 ◽  
Vol 497 (3) ◽  
pp. 3234-3250 ◽  
Author(s):  
Diego A Farias ◽  
Alejandro Clocchiatti ◽  
Tyrone E Woods ◽  
Armin Rest
Keyword(s):  
Interstellar Medium ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
The Other ◽  
X Rays ◽  
X Ray ◽  
Upper Limits ◽  
Type Ia ◽  
Source Models ◽  
Flux Measurements

ABSTRACT Supersoft X-rays sources (SSSs) have been proposed as potential Type Ia supernova (SN Ia) progenitors. If such objects are indeed persistently X-ray luminous and embedded in sufficiently dense interstellar medium (ISM), they will be surrounded by extended nebular emission. These nebulae should persist even long after an SN Ia explosion, due to the long recombination and cooling times involved. With this in mind, we searched for nebular [O iii] emission around four SSSs and three SNRs in the Large Magellanic Cloud, using the 6.5-m Baade telescope at Las Campanas Observatory and the imacs camera. We confirm that, out of the four SSS candidates, only CAL 83 can be associated with an [O iii] nebula. The [O iii] luminosity for the other objects is constrained to ≲17 per cent of that of CAL 83 at 6.8 pc from the central source. Models computed with the photoionization code cloudy indicate that either the ISM densities in the environments of CAL 87, RX J0550.0-7151, and RX J0513.9-6951 must be significantly lower than surrounding CAL 83 or the average X-ray luminosities of these sources over the last ≲10  000 yr must be significantly lower than presently observed, in order to be consistent with the observed luminosity upper limits. For the three SNRs we consider (all with ages <1000 yr), our [O iii] flux measurements together with the known surrounding ISM densities strongly constrain the ionizing luminosity of their progenitors in the last several thousand years, independent of the progenitor channel.

scholarly journals Long term changes in EUV and X-ray emissions from the solar corona and chromosphere as measured by the response of the Earth’s ionosphere during total solar eclipses from 1932 to 1999

2001 ◽  
Vol 19 (3) ◽  
pp. 263-273 ◽  
Author(s):  
C. J. Davis ◽  
E. M. Clarke ◽  
R. A. Bamford ◽  
M. Lockwood ◽  
S. A. Bell
Keyword(s):  
Solar Physics ◽  
Ultra Violet ◽  
Cosmic Ray ◽  
Solar Cycle Variation ◽  
X Ray ◽  
Negligible Probability ◽  
E Region ◽  
Solar Eclipses ◽  
Ray Effects

Abstract. Measurements of the ionospheric E region during total solar eclipses in the period 1932–1999 have been used to investigate the fraction of Extreme Ultra Violet and soft X-ray radiation, 8, that is emitted from the limb corona and chromosphere. The relative apparent sizes of the Moon and the Sun are different for each eclipse, and techniques are presented which correct the measurements and, therefore, allow direct comparisons between different eclipses. The results show that the fraction of ionising radiation emitted by the limb corona has a clear solar cycle variation and that the underlying trend shows this fraction has been increasing since 1932. Data from the SOHO spacecraft are used to study the effects of short-term variability and it is shown that the observed long-term rise in 8 has a negligible probability of being a chance occurrence.Key words. Ionosphere (solar radiation and cosmic ray effects) – Solar physics, astrophysics, and astronomy (corona and transition region)

scholarly journals Diffusive transport of energetic electrons in the solar corona: X-ray and radio diagnostics

2018 ◽  
Vol 610 ◽  
pp. A6 ◽  
Author(s):  
S. Musset ◽  
E. P. Kontar ◽  
N. Vilmer
Keyword(s):  
Solar Corona ◽  
Free Path ◽  
Electron Distribution ◽  
Transport Model ◽  
Imaging Spectroscopy ◽  
Mean Free Path ◽  
Diffusive Transport ◽  
X Rays ◽  
Energetic Electrons ◽  
X Ray

Context. Imaging spectroscopy in X-rays with RHESSI provides the possibility to investigate the spatial evolution of X-ray emitting electron distribution and therefore, to study transport effects on energetic electrons during solar flares. Aims. We study the energy dependence of the scattering mean free path of energetic electrons in the solar corona. Methods. We used imaging spectroscopy with RHESSI to study the evolution of energetic electrons distribution in various parts of the magnetic loop during the 2004 May 21 flare. We compared these observations with the radio observations of the gyrosynchrotron radiation of the same flare and with the predictions of a diffusive transport model. Results. X-ray analysis shows a trapping of energetic electrons in the corona and a spectral hardening of the energetic electron distribution between the top of the loop and the footpoints. Coronal trapping of electrons is stronger for radio-emitting electrons than for X-ray-emitting electrons. These observations can be explained by a diffusive transport model. Conclusions. We show that the combination of X-ray and radio diagnostics is a powerful tool to study electron transport in the solar corona in different energy domains. We show that the diffusive transport model can explain our observations, and in the range 25–500 keV, the scattering mean free path of electrons decreases with electron energy. We can estimate for the first time the scattering mean free path dependence on energy in the corona.

scholarly journals MASSIVE PHOTON PAIRS AND FEATURES OF CHANGES IN THE X-RAY BACKGROUND OF THE SOLAR CROWN AND EARTH'S MAGNETOSPHERE

2020 ◽  
Vol 2 (7(76)) ◽  
pp. 42-46
Author(s):  
I.K. Mirzoeva
Keyword(s):  
Magnetic Field ◽  
Solar Corona ◽  
X Rays ◽  
Earth’S Magnetosphere ◽  
X Ray ◽  
Massive Photon ◽  
Photon Pairs ◽  
Earth's Magnetosphere ◽  
X Ray Background ◽  
The Magnetic Field

The analysis of the x-ray background of the solar corona in the range of 2-25 Kev for three months of 2003 was carried out.the integrated energy spectrum was obtained according to the RHESSI project. Comparison with the data of the x-ray background of The earth's magnetosphere according to the XMM-Newton project in the soft range of x-rays allowed us to draw a conclusion about the common nature of the features of seasonal variations of the x-ray background of The earth's magnetosphere and the thermal x-ray background of the solar corona. The main reason for these changes is the splitting of massive photon pairs born from vacuum in the magnetic field of the solar corona and in the magnetic field of the Earth. According to the RHESSI, XMM-Newton, and Plank projects, theoretical and experimental evidence for the existence of massive photon pairs (ultralight scalar bosons) is provided.

scholarly journals Quiescent Coronae of Active Chromosphere Stars

1983 ◽  
Vol 71 ◽  
pp. 83-108 ◽  
Author(s):  
Leon Golub
Keyword(s):  
Solar Corona ◽  
High Sensitivity ◽  
Model Atmosphere ◽  
Loop Model ◽  
X Rays ◽  
M Dwarfs ◽  
Coronal Emission ◽  
Dwarf Stars ◽  
X Ray ◽  
First Time

ABSTRACTThe EINSTEIN Observatory has for the first time provided high sensitivity X-ray measurements of quiescent coronal emission from a large sample of dwarf stars. We now have observed a sufficient number of the nearby M-dwarfs to determine an X-ray luminosity function and we have explored the activity and variability of these stars to the extent of observing, for the first time, X-ray flares with simultaneous groundbased optical and IUE ultraviolet coverage.The M dwarfs are found to have a much higher degree of variability in X-rays than does the Sun; however, in most cases a quiescent level is definable. We will discuss the quiescent emission from these stars and the changes in quiescent level on time scales from hours to ~ 1 year. We have determined coronal temperatures for many of these stars; they are generally hotter than the Solar corona and some of the more active dM stars have Tcor ~ 107 K.Arguments are presented in support of the hypothesis that M-dwarf coronae are magnetically dominated, as is the Solar corona. We then examine the usefulness of loop model atmosphere calculations in elucidating the coronal heating mechanism and the ways in which observations may be used to test competing theories. The X-ray measurements can be used to predict magnetic field strengths on these stars, with testable implications.

scholarly journals Recent solar X-ray studies in the United Kingdom

1965 ◽  
Vol 23 ◽  
pp. 61-73 ◽  
Author(s):  
K. A. Pounds
Keyword(s):  
United Kingdom ◽  
Solar Flare ◽  
X Rays ◽  
X Ray ◽  
The Past ◽  
The United Kingdom ◽  
Flux Measurements

Solar X-ray data obtained over the past year by scientists in the United Kingdom are reviewed. These include several new X-ray events reduced from the Ariel satellite results, soft X-ray flux measurements from NRL satellite 1963–21 C and notes on recent rocket studies in this field. A brief discussion is added on the nature of solar flare X-rays and their measurement.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

Some Problems in Understanding the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 1-9
Author(s):  
A. H. Gabriel
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Theoretical Modelling ◽  
Total System ◽  
Major Advance ◽  
X Ray ◽  
Proper Perspective ◽  
Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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