A multi-wavelength study of solar coronal-hole regions showing radio enhancements

Moran, T.; Gopalswamy, Ν.; Dammasch, I. E.; Wilhelm, K.

doi:10.1051/0004-6361:20010569

Cited by 18 publications

(16 citation statements)

References 24 publications

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“…These results are based on a comparison of the profiles of WL measurements in the inner corona and path integrated density profiles from Ulysses data, but have been criticized by Pätzold (see Bird, 1998, 1999, and the answer to the criticisms by Woo and Habbal, 1998). Direct radio observations (see, e.g., Nindos et al, 1999;Pohjolainen et al, 2000;Pohjolainen, 2000;Moran et al, 2001) of coronal holes did not bring any clear evidence for plume emission, when compared with EIT maps. Hence, as of today, there is no definite conclusion on plume observability at radio wavelengths.…”

Section: Introductionmentioning

confidence: 95%

Solar Coronal Plumes

Poletto

2015

Living Rev. Sol. Phys.

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Polar plumes are thin long ray-like structures that project beyond the limb of the Sun polar regions, maintaining their identity over distances of several solar radii. Plumes have been first observed in white-light (WL) images of the Sun, but, with the advent of the space era, they have been identified also in X-ray and UV wavelengths (XUV) and, possibly, even in in situ data. This review traces the history of plumes, from the time they have been first imaged, to the complex means by which nowadays we attempt to reconstruct their 3-D structure. Spectroscopic techniques allowed us also to infer the physical parameters of plumes and estimate their electron and kinetic temperatures and their densities. However, perhaps the most interesting problem we need to solve is the role they cover in the solar wind origin and acceleration: Does the solar wind emanate from plumes or from the ambient coronal hole wherein they are embedded? Do plumes have a role in solar wind acceleration and mass loading? Answers to these questions are still somewhat ambiguous and theoretical modeling does not provide definite answers either. Recent data, with an unprecedented high spatial and temporal resolution, provide new information on the fine structure of plumes, their temporal evolution and relationship with other transient phenomena that may shed further light on these elusive features. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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Section: Introductionmentioning

confidence: 95%

Solar Coronal Plumes

Poletto

2015

Living Rev. Sol. Phys.

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“…They discuss the relation between enhanced temperatures and unipolar regions. Moran et al (2001) observed enhanced 17 GHz radio emission from magnetic field concentrations.…”

Section: Introductionmentioning

confidence: 94%

Electron cyclotron maser emission from solar coronal funnels?

Vocks

Mann

2004

A&A

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Abstract. The sun is covered by a network of supergranular cells. The convective motion of these cells leads to the formation of strong magnetic fields at the cell boundaries. At larger heights in the solar transition region and low corona, this magnetic field geometry expands rapidly within a short distance, and forms the magnetic structure of "coronal funnels". This field line geometry represents a magnetic mirror, and since the plasma density strongly increases with depth in the transition region, the electron velocity distribution function (VDF) can develop a loss cone. Within such a coronal funnel, the plasma frequency can have smaller values than the electron cyclotron frequency, ω p < Ω e . These are the necessary conditions for the generation of X-mode waves through the electron cyclotron maser mechanism. Since there is some observational evidence for radio emission from the supergranular network, it is of interest to investigate the possibility of this plasma wave generation in a quiet stellar atmosphere in detail. In this paper, a kinetic model is used to calculate the electron VDF in a coronal funnel. A method is derived to determine wave growth rates from the electron VDF. Its application on the coronal funnel VDF indeed results in X-mode wave growth. However, it is also found that wave absorption by higher-order resonances at larger heights in the atmosphere plays an important role.

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“…A study of radio on-disk CMEs has recently been presented by Ramesh et al (2003). Coronal Holes (Moran et al, 2001) are apparent on radio images as radiation enhancements. Radio imaging facilities used for monitoring include NoRH (the Nobeyama Radioheliograph, Nakajima et al, 1995) and the Siberian Solar Radio Telescope (Grechnev et al, 2003).…”

Section: Radio Measurementsmentioning

confidence: 99%

Solar weather monitoring

et al. 2005

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Abstract. Space Weather nowcasting and forecasting require solar observations because geoeffective disturbances can arise from three types of solar phenomena: coronal mass ejections (CMEs), flares and coronal holes. For each, we discuss their definition and review their precursors in terms of remote sensing and in-situ observations. The objectives of Space Weather require some specific instrumental features, which we list using the experience gained from the daily operations of the Solar Influences Data analysis Centre (SIDC) at the Royal Observatory of Belgium. Nowcasting requires real-time monitoring to assess quickly and reliably the severity of any potentially geoeffective solar event. Both research and forecasting could incorporate more observations in order to feed case studies and data assimilation respectively. Numerical models will result in better predictions of geomagnetic storms and solar energetic particle (SEP) events. We review the data types available to monitor solar activity and interplanetary conditions. They come from space missions and ground observatories and range from sequences of dopplergrams, magnetograms, white-light, chromospheric, coronal, coronagraphic and radio images, to irradiance and in-situ time-series. Their role is summarized together with indications about current and future solar monitoring instruments.

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A multi-wavelength study of solar coronal-hole regions showing radio enhancements

Cited by 18 publications

References 24 publications

Solar Coronal Plumes

Solar Coronal Plumes

Electron cyclotron maser emission from solar coronal funnels?

Solar weather monitoring

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