Solar Radio Astronomy
TL;DR: The Radio Emission of the Sun and Planets by V. V. Zheleznyakov and H. S. Massey as discussed by the authors was published by Pergamon Press, London and New York, February 1970.
Abstract: Radio Emission of the Sun and Planets By V. V. Zheleznyakov. Translated By H. S. H. Massey. Edited By J. S. Hey. (International Series of Monographs in Natural Philosophy, Vol. 25.). Pp. xiv + 697. (Pergamon Press: Oxford, London and New York, February 1970.) 300s; $40.
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TL;DR: In this paper, the authors present a review of the mechanisms for both steady, quiescent emission and intense, strongly varying outbursts of the sun's radiation, defined as those appearing on classical Hertzsprung-Russell diagrams.
Abstract: Radio astronomy of the sun has reached a high level of maturity, while radio astronomy of the stars is now a burgeoning new field of study. The present review is mainly concerned with radiation which is emitted by 'normal' stars, defined here to include those appearing on classical Hertzsprung-Russell diagrams. The mechanisms for both steady, quiescent emission and intense, strongly varying outbursts are discussed. Included are discussions of bremsstrahlung, gyrosynchrotron emission, electron-cyclotron masers, and plasma radiation. The manifestation of these mechanisms in various kinds of solar radiation are considered along with stellar manifestations.
971 citations
TL;DR: In the case of the most energetic events, the expanding material produces an interplanetary shock wave as discussed by the authors, which can be observed as a solar energetic particle (SEP) event at I AU.
Abstract: Attempts to clarify the nature of the terrestrial effects of solar activity and variability continue at an increasing pace. While mechanisms relating possible changes in terrestrial weather patterns to changes in solar lumin osity remain elusive, it has long been thought that intense geomagnetic storms and interplanetary disturbances can be traced directly to large solar flares. To describe the basic scenario in simple terms, a large release of energy first occurs in a region of strong magnetic field. The energy release results in a rapid heating of coronal and chromospheric material, which expands outward into the interplanetary medium. In the case of the most energetic events the expanding material produces an interplanetary shock wave. The most energetic aspect of the flare, the impulsive phase, is charac terized by the production of energetic (E > I MeV) electrons and protons, some of which can be observed as a solar energetic particle (SEP) event at I AU. Over the past half century attempts have been made to identify the solar flares and their particular properties that result in geomagnetic storms and SEP events. These extensive studies, of interest to both solar physicists and forecasters of effects on the terrestrial environment, seemed to lay a solid foundation for the idea that the flare itself was the cause of the subsequent activity observed in the interplanetary medium and at the Earth. About two decades ago large coronal eruptions, now known as coronal
451 citations
TL;DR: In this article, the equipment and procedures used to make the measurements and to calibrate them, and discusses some of the “most-asked” questions about the data.
Abstract: [1] The 10.7 cm solar radio flux, or F10.7 is, along with sunspot number, one of the most widely used indices of solar activity. This paper describes the equipment and procedures used to make the measurements and to calibrate them, and discusses some of the “most-asked” questions about the data.
436 citations
01 Jan 2008
179 citations
Cites background from "Solar Radio Astronomy"
...The three RHESSI flares with best counting statistics in the γ-ray range all show non-thermal emission from their footpoints but all also reveal coronal γ-ray sources (Krucker et al 2008)....
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TL;DR: The most important noncoronagraphic signatures of coronal mass ejection (CME) have been identified in the past several years, primarily with instruments on the Yohkoh and SOHO satellites as mentioned in this paper.
Abstract: A coronal mass ejection (CME), strictly speaking, is a phenomenon observed via a white-light coronal imager. In addition to coronagraphs, a wide variety of other instruments provide independent observations of CMEs, in regimes ranging from the chromosphere to interplanetary space. In this paper we list the most important of these noncoronagraphic signatures, many of which had been known even before CMEs were first identified in coronagraph observations about 30 years ago. We summarize the new aspects of CMEs discovered in the past several years, primarily with instruments on the Yohkoh and SOHO satellites. We emphasize the need for detailed statistically based comparisons between SOHO CMEs and their noncoronagraphic manifestations. We discuss how the various aspects of CMEs fit into the current standard model (sigmoids, flux rope, double dimming, arcade). While a class of CMEs follows this pattern, it does not appear to work for all events. In particular, some CMEs involve extended dimming regions and erupting transequatorial X-ray loops, indicating a more complex geometry than a simple bipolar magnetic configuration.
145 citations
References
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TL;DR: In this paper, the authors present a review of the mechanisms for both steady, quiescent emission and intense, strongly varying outbursts of the sun's radiation, defined as those appearing on classical Hertzsprung-Russell diagrams.
Abstract: Radio astronomy of the sun has reached a high level of maturity, while radio astronomy of the stars is now a burgeoning new field of study. The present review is mainly concerned with radiation which is emitted by 'normal' stars, defined here to include those appearing on classical Hertzsprung-Russell diagrams. The mechanisms for both steady, quiescent emission and intense, strongly varying outbursts are discussed. Included are discussions of bremsstrahlung, gyrosynchrotron emission, electron-cyclotron masers, and plasma radiation. The manifestation of these mechanisms in various kinds of solar radiation are considered along with stellar manifestations.
971 citations
TL;DR: In the case of the most energetic events, the expanding material produces an interplanetary shock wave as discussed by the authors, which can be observed as a solar energetic particle (SEP) event at I AU.
Abstract: Attempts to clarify the nature of the terrestrial effects of solar activity and variability continue at an increasing pace. While mechanisms relating possible changes in terrestrial weather patterns to changes in solar lumin osity remain elusive, it has long been thought that intense geomagnetic storms and interplanetary disturbances can be traced directly to large solar flares. To describe the basic scenario in simple terms, a large release of energy first occurs in a region of strong magnetic field. The energy release results in a rapid heating of coronal and chromospheric material, which expands outward into the interplanetary medium. In the case of the most energetic events the expanding material produces an interplanetary shock wave. The most energetic aspect of the flare, the impulsive phase, is charac terized by the production of energetic (E > I MeV) electrons and protons, some of which can be observed as a solar energetic particle (SEP) event at I AU. Over the past half century attempts have been made to identify the solar flares and their particular properties that result in geomagnetic storms and SEP events. These extensive studies, of interest to both solar physicists and forecasters of effects on the terrestrial environment, seemed to lay a solid foundation for the idea that the flare itself was the cause of the subsequent activity observed in the interplanetary medium and at the Earth. About two decades ago large coronal eruptions, now known as coronal
451 citations
TL;DR: Hard X-ray emissions of non-thermal electrons in the solar corona have been studied in this paper, showing that the most intense flare emissions are generally observed from the chromosphere at footpoints of magnetic loops.
Abstract: This review surveys hard X-ray emissions of non-thermal electrons in the solar corona. These electrons originate in flares and flare-related processes. Hard X-ray emission is the most direct diagnostic of electron presence in the corona, and such observations provide quantitative determinations of the total energy in the non-thermal electrons. The most intense flare emissions are generally observed from the chromosphere at footpoints of magnetic loops. Over the years, however, many observations of hard X-ray and even γ-ray emission directly from the corona have also been reported. These coronal sources are of particular interest as they occur closest to where the electron acceleration is thought to occur. Prior to the actual direct imaging observations, disk occultation was usually required to study coronal sources, resulting in limited physical information. Now RHESSI has given us a systematic view of coronal sources that combines high spatial and spectral resolution with broad energy coverage and high sensitivity. Despite the low density and hence low bremsstrahlung efficiency of the corona, we now detect coronal hard X-ray emissions from sources in all phases of solar flares. Because the physical conditions in such sources may differ substantially from those of the usual “footpoint” emission regions, we take the opportunity to revisit the physics of hard X-radiation and relevant theories of particle acceleration.
242 citations
TL;DR: The most important noncoronagraphic signatures of coronal mass ejection (CME) have been identified in the past several years, primarily with instruments on the Yohkoh and SOHO satellites as mentioned in this paper.
Abstract: A coronal mass ejection (CME), strictly speaking, is a phenomenon observed via a white-light coronal imager. In addition to coronagraphs, a wide variety of other instruments provide independent observations of CMEs, in regimes ranging from the chromosphere to interplanetary space. In this paper we list the most important of these noncoronagraphic signatures, many of which had been known even before CMEs were first identified in coronagraph observations about 30 years ago. We summarize the new aspects of CMEs discovered in the past several years, primarily with instruments on the Yohkoh and SOHO satellites. We emphasize the need for detailed statistically based comparisons between SOHO CMEs and their noncoronagraphic manifestations. We discuss how the various aspects of CMEs fit into the current standard model (sigmoids, flux rope, double dimming, arcade). While a class of CMEs follows this pattern, it does not appear to work for all events. In particular, some CMEs involve extended dimming regions and erupting transequatorial X-ray loops, indicating a more complex geometry than a simple bipolar magnetic configuration.
145 citations
TL;DR: The Siberian Solar Radio Telescope (SSRT) as mentioned in this paper is one of the world's largest solar radio heliographs, with a high time resolution of 56 ms and an angular resolution of 15 arc sec.
Abstract: The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in 1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec. Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive promin- ences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument. We compare SSRT observations at 5.7 GHz, including computed 'light curves', both morphologically and quantatively, with observations made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray observations, and dynamic radio spectra.
122 citations