Coronal streamers

Koutchmy, S.; Livshits, M. A.

doi:10.1007/bf00222313

Cited by 70 publications

(40 citation statements)

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“…Pneuman and Kopp, 1971;Cuperman et al, 1990;Cuperman et al, 1992;Koutchmy and Livshits, 1992;Wang et al, 1993;Cuperman et al, 1995;Bavassano et al, 1997;Hundhausen, 1999). There seems to be a natural association of helmet streamers with coronal eruptions and coronal streamers are assumed to be the source region of the slow solar wind.…”

Section: Introductionmentioning

confidence: 99%

Untitled

2000

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Recent observations of the solar corona with the LASCO coronagraph on board of the SOHO spacecraft have revealed the occurrence of triple helmet streamers even during solar minimum, which occasionally go unstable and give rise to large coronal mass ejections. There are also indications that the slow solar wind is either a combination of a quasi-stationary flow and a highly fluctuating component or may even be caused completely by many small eruptions or instabilities. As a first step we recently presented an analytical method to calculate simple two-dimensional stationary models of triple helmet streamer configurations. In the present contribution we use the equations of time-dependent resistive magnetohydrodynamics to investigate the stability and the dynamical behaviour of these configurations. We particularly focus on the possible differences between the dynamics of single isolated streamers and triple streamers and on the way in which magnetic reconnection initiates both small scale and large scale dynamical behaviour of the streamers. Our results indicate that small eruptions at the helmet streamer cusp may incessantly accelerate small amounts of plasma without significant changes of the equilibrium configuration and might thus contribute to the non-stationary slow solar wind. On larger time and length scales, large coronal eruptions can occur as a consequence of large scale magnetic reconnection events inside the streamer configuration. Our results also show that triple streamers are usually more stable than a single streamer.

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Section: Introductionmentioning

confidence: 99%

Untitled

2000

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“…They are the product of the dynamic equilibrium between confining magnetic fields and expanding hot plasmas [4,5]. Previous studies indicate that streamers and nearby regions are important sources of the slow solar wind [8][9][10].…”

Section: Studies On Coronal Streamers and Associated Slow Solar Windmentioning

confidence: 99%

“…The streamer cusp is the localized region on the top of the magnetically-closed arcades, and below the bright plasma sheet structure (also called the streamer stalk). The heliospheric current sheet (HCS) is embedded within the plasma sheet [4,5]. Below the cusp, the streamer is bright due to the presence of denser-than-surrounding plasmas confined by its closed fields; while above the cusp the streamer stalk is bright because of the presence of the dense solar wind plasmas there.…”

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confidence: 99%

A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions

Chen

2013

Chin. Sci. Bull.

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In this article I present a review of recent studies on coronal dynamics, including research progresses on the physics of coronal streamers that are the largest structure in the corona, physics of coronal mass ejections (CMEs) that may cause a global disturbance to the corona, as well as physics of CME-streamer interactions. The following topics will be discussed in depth: (1) acceleration of the slow wind flowing around the streamer considering the effect of magnetic flux tube curvature; (2) physical mechanism accounting for persistent releases of streamer blobs and diagnostic results on the temporal variability of the slow wind speed with such events; (3) force balance analysis and energy release mechanism of CMEs with a flux rope magnetohydrodynamic model; (4) statistical studies on magnetic islands along the coronal-ray structure behind a CME and the first observation of magnetic island coalescence with associated electron acceleration; and (5) white light and radio manifestations of CME-streamer interactions. These studies shed new light on the physics of coronal streamers, the acceleration of the slow wind, the physics of solar eruptions, the physics of magnetic reconnection and associated electron acceleration, the large-scale coronal wave phenomenon, as well as the physics accounting for CME shock-induced type II radio bursts. solar wind, coronal streamer, coronal mass ejection, solar radio burst, magnetic reconnection Citation:Chen Y. A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions.

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“…Then the radiance calculated for a simple model of an isolated streamer with axial (cylindrical) symmetry was adjusted to the observed radiance. Figure 6 of Koutchmy & Livshits (1992) displays a range of radial density profiles that are significantly higher than the mean densities in equatorial regions (Saito et al 1972) and typically two orders of magnitude higher than the density in coronal holes. It should be noted that this approach strictly applies to the case of an isolated streamer and not to the streamer belt where los integration effects are different.…”

Section: Introductionmentioning

confidence: 95%

Three-dimensional reconstruction of the streamer belt and other large-scale structures of the solar corona

Saez

Llebaria

Lamy

et al. 2007

A&A

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Context. The high spatial resolution, white-light images obtained by the LASCO coronagraphs provide a detailed record of the solar corona over almost a full solar cycle. Their analysis and interpretation poses a formidable challenge for ultimately retrieving the 3-dimensional distribution of electrons in the corona. Aims. Our goal is to implement an efficient forward modeling method capable of generating high-resolution synthetic images of large-scale coronal structures (the streamer belt, isolated streamers, coronal mass ejections) over any time scales (as long as a solar cycle) to be directly compared, both qualitatively and quantitatively, to coronographic images of the corona. Methods. Our model assumes a 3-dimensional distribution of electrons described by analytic functions and represented using the octree compression's techniques. The radiance of the synthetic images is calculated with a ray-tracing algorithm that incorporates the Thomson scattering. A multi-octree generalization of the method allows simulation of the temporal evolution of the structures. We first concentrate on the coronal streamer belt. Starting from photospheric magnetograms, we calculate the position of the neutral line at the source surface (2.5 R sun ) using the potential field source surface model. The plasma sheet forming the belt is centered on the current sheet represented as the radial extension of the neutral line. Its electron density is represented by a parametric function of both the distances to the Sun center and to the current sheet. The parameters are optimized by adjusting the synthetic images to the observations, using either the coronal images or synoptic maps of the corona. The method is then extended to other large-scale coronal structures, polar plumes, and coronal mass ejections. Results. As examples, we present results for the streamer belt observed by LASCO-C2 during two Carrington rotations, CR 1910 and CR 1913, as well as illustrations of future coronographic observations expected from the STEREO and Solar Orbiter missions. The results suggest that our method is sufficient for qualitatively and quantitatively simulating the structures of the solar corona even if some discrepancies can be noticed. A systematic analysis of the LASCO data over almost a full solar cycle will be developed in forthcoming articles.

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Coronal streamers

Cited by 70 publications

References 0 publications

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A review of recent studies on coronal dynamics: Streamers, coronal mass ejections, and their interactions

Three-dimensional reconstruction of the streamer belt and other large-scale structures of the solar corona

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