Solar Activity Observed in X-Rays and the EUV from OSO 7

Although worldwide cooperation in surveying activity has had a long history, the continuation of international programs in this area is compromised by several factors, in particular by an overall decrease of financial support which has led to concentration of our limited resources and efforts on the large research instruments. In such a situation we believe it important not to lose sight of the fact that systematic data on the ‘full disk’ state of solar activity is still, and will remain, of great significance to students both of the Sun and of the Earth and its environment. As examples, we note that the large quantity of space data (e.g., on X-rays, EUV particles, and fields) cannot be fully studied without the supporting data obtained in classical ground-based optical and radio surveys; the same applies to magnetospheric observations.Nor can we always know what critical future needs will be satisfied by our systematic daily surveys. An obvious example is the daily measure of sunspot area, others are provided by the Cartes de la Chromosphère and the Mount Wilson magnetograms which for years at a time have attracted little interest and quite suddenly have emerged as source data of inestimable value in quite unanticipated studies.

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Electrons and X-Ray Emission of Solar Flares

Symposium - International Astronomical Union ◽

10.1017/s007418090008832x ◽

1990 ◽

Vol 142 ◽

pp. 409-413

Author(s):

V. G. Kurt

Keyword(s):

Solar Activity ◽

Statistical Analysis ◽

Solar Flare ◽

Frequency Dependence ◽

Power Law ◽

Solar Flares ◽

X Rays ◽

Fast Electrons ◽

X Ray ◽

Flare Frequency

A statistical analysis of solar flare X-rays and interplanetary particle fluxes, measured onboard VENERA-13, 14 Spacecraft, was performed. The correlation of fluences for different manifestations of solar flares is strong, especially for fast electrons and hard and soft X-ray emissions. Frequency dependence on fluence value ϵi for practically all Kinds of solar flare emission can be described by power law ν (ϵ > ϵO) ∼ ϵ−0.45±0.15 which does not change significantly with solar activity. For different Hα flare importances the values of ϵi were obtained. It is proposed that appearance of certain energy flare frequency is strongly dependent on some scale factor.

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Soft solar X-rays and solar activity

Solar Physics ◽

10.1007/bf00155785 ◽

1971 ◽

Vol 21 (1) ◽

pp. 146-156 ◽

Cited By ~ 11

Author(s):

Richard G. Teske

Keyword(s):

Solar Activity ◽

X Rays

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Explosion of sungrazing comets in the solar atmosphere and solar flares

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309029524 ◽

2008 ◽

Vol 4 (S257) ◽

pp. 341-343 ◽

Cited By ~ 3

Author(s):

S. Ibadov ◽

F. S. Ibodov ◽

S. S. Grigorian

Keyword(s):

Solar Activity ◽

Solar Atmosphere ◽

Solar Flares ◽

Solar Surface ◽

The Body ◽

High Time Resolution ◽

Solar Chromosphere ◽

X Rays ◽

Frontal Surface ◽

Sungrazing Comets

AbstractExplosive evolution of nuclei of sungrazing comets near the solar surface, which occurs at conditions of intense interaction between the solar atmosphere and falling high-velocity comet nuclei as well as the relation of the phenomenon to the character of solar activity are analytically considered. It is found that, due to aerodynamic fragmentation of the falling body in the solar chromosphere and transversal expansion of the fragmented mass under the action of pressure gradient on the frontal surface, thermalization of the kinetic energy of the body occurs by sharp stopping of the disklike hypervelocity fragmented mass near the solar surface within a relatively very thin subphotospheric layer and has, therefore, an essentially impulsive and strongly explosive character. The specific energy release in the explosion region, erg/g, considerably exceeds the evaporation/sublimation heat of the body so that the process is accompanied by production of a high-temperature plasma. The energetics of such an explosive process corresponds to that of very large solar flares for falling bodies having masses equal to the mass of the nucleus of Comet Halley. Spectral observations of sungrazing comets by SOHO-like telescopes in a wide spectral range, including X rays, with a high time resolution, of the order of 0.1–10 s, are important for revealing solar activity in the form of an impact-generated photospheric flare.

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Soft solar X-rays and solar activity

Solar Physics ◽

10.1007/bf00146064 ◽

1971 ◽

Vol 19 (2) ◽

pp. 356-378 ◽

Cited By ~ 7

Author(s):

Richard G. Teske

Keyword(s):

Solar Activity ◽

X Rays

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Some fresh indications of the solar origin of 4-6-year oscillation of the Earth’s rotation parameters

Serbian Astronomical Journal ◽

10.2298/saj9959001d ◽

1999 ◽

pp. 1-10

Author(s):

D. Djurovic ◽

P. Pâquet

Keyword(s):

Solar Activity ◽

Power Spectrum ◽

Solar Irradiance ◽

Spectral Structure ◽

X Rays ◽

Frequency Range ◽

Solar Origin ◽

The Earth ◽

Rotation Parameters ◽

Uv Range

The variations of universal times difference UT1-TAI and Earth?s rotation instantaneous p?le coordinates (X,Y) are studied in the frequency range of 3 - 8 yr?1 as a function of the solar activity. It is found that power spectrum concentrations C1 and C2 are common to solar activity indicators and Earth?s rotation parameters (ERP). The linear correlation between them is also not a fortuitous one. Accordingly, by the results of this study the hypothesis of Djurovic and P?quet (1996; 1999) that the primary cause of 4-6 year oscillation lies in solar irradiance is confirmed. Between several mechanisms responsible for the ERP variations as the most probable are considered the variations of solar irradiance spectral structure (especially large in its UV range) and variations of intensity of cosmic X-rays reaching the Earth?s surface.

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Solar soft X-rays and solar activity

Solar Physics ◽

10.1007/bf00155382 ◽

1969 ◽

Vol 8 (2) ◽

pp. 348-368 ◽

Cited By ~ 21

Author(s):

Richard G. Teske ◽

Roger J. Thomas

Keyword(s):

Solar Activity ◽

X Rays

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Suzaku observation of Jupiter’s X-rays around solar maximum

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psz077 ◽

2019 ◽

Vol 71 (5) ◽

Author(s):

Masaki Numazawa ◽

Yuichiro Ezoe ◽

Kumi Ishikawa ◽

Takaya Ohashi ◽

Yoshizumi Miyoshi ◽

...

Keyword(s):

Solar Activity ◽

Compton Scattering ◽

High Energy ◽

Spectral Studies ◽

Relativistic Electrons ◽

X Rays ◽

Diffuse Emission ◽

X Ray ◽

Inverse Compton Scattering ◽

Inverse Compton

Abstract We report on results of imaging and spectral studies of X-ray emission from Jupiter observed by Suzaku. In 2006, Suzaku found diffuse X-ray emission in 1–5 keV associated with Jovian inner radiation belts. It has been suggested that the emission is caused by the inverse-Compton scattering by ultra-relativistic electrons (∼50 MeV) in Jupiter’s magnetosphere. To confirm the existence of this emission and to understand its relation to the solar activity, we conducted an additional Suzaku observation in 2014 around the maximum of the 24th solar cycle. As a result, we successfully found the diffuse emission around Jupiter in 1–5 keV again, and also found point-like emission in 0.4–1 keV. The luminosity of the point-like emission, which was probably composed of solar X-ray scattering, charge exchange, or auroral bremsstrahlung emission, increased by a factor of ∼5 with respect to the findings from 2006, most likely due to an increase of the solar activity. The diffuse emission spectrum in the 1–5 keV band was well-fitted with a flat power-law function (Γ = 1.4 ± 0.1) as in the past observation, which supported the inverse-Compton scattering hypothesis. However, its spatial distribution changed from ∼12 × 4 Jovian radius (Rj) to ∼20 × 7 Rj. The luminosity of the diffuse emission increased by the smaller factor of ∼3. This indicates that the diffuse emission is not simply responding to the solar activity, which is also known to cause little effect on the distribution of high-energy electrons around Jupiter. Further sensitive study of the spatial and spectral distributions of the diffuse hard X-ray emission is important to understand how high-energy particles are accelerated in Jupiter’s magnetosphere.

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