Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer

Raymond, J. C.; Kohl, J. L.; Noci, G.; Antonucci, E.; Tondello, G.; Huber, M. C. E.; Gardner, L. D.; Nicolosi, P.; Fineschi, Silvano; Romoli, M.; Spadaro, D.; Siegmund, O. H. W.; Benna, C.; Ciaravella, A.; Cranmer, Steven R.; Giordano, S.; Karovska, M.; Martin, R.; Michels, J.; Modigliani, A.; Naletto, G.; Panasyuk, A. V.; Pernechele, C.; Poletto, G.; Smith, P. L.; Suleiman, R. M.; Strachan, L.

doi:10.1007/978-94-011-5236-5_35

Cited by 40 publications

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“…The oxygen abundance is derived from the spectroscopic observations of the outer corona performed during 1996 with the Ultraviolet Coronagraph Spectrometer (SOHO) in the ultraviolet region. This study shows that the depletion of oxygen, by almost one order of magnitude with respect to the photospheric values, found in the inner part of streamers by Raymond et al (1997a) is a common feature of the solar minimum streamer belt, which exhibits an abundance structure with the following characteristics. In the core of streamers the oxygen abundance is 1.3×10 −4 at 1.5 R , then it drops to 0.8×10 −4 at 1.7 R , value which remains almost constant out to 2.2 R .…”

mentioning

confidence: 68%

“…Also in the streamer branches the oxygen is depleted although to a lesser extent. The relative depletion of oxygen across the streamer is by a factor of 4 (Raymond et al, 1997a). Feldman et al (1998) and Feldman (1998) found that close to the limb, at 1.03 R , the streamer oxygen abundance is close to the photospheric value.…”

Section: Introductionmentioning

confidence: 90%

“…The most likely interpretation of the dimming of the O VI emission in the center of streamers is in terms of a local depletion of the oxygen ions Raymond et al, 1997a). Raymond et al have measured the oxygen abundance in a quiescent streamer observed in the outer corona on 23-24 July 1996.…”

Section: Introductionmentioning

confidence: 99%

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Oxygen abundance in coronal streamers during solar minimum

2001

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Abstract. We present a study of the oxygen abundance relative to hydrogen in the equatorial streamer belt of the solar corona during the recent period of activity minimum. The oxygen abundance is derived from the spectroscopic observations of the outer corona performed during 1996 with the Ultraviolet Coronagraph Spectrometer (SOHO) in the ultraviolet region. This study shows that the depletion of oxygen, by almost one order of magnitude with respect to the photospheric values, found in the inner part of streamers by Raymond et al. (1997a) is a common feature of the solar minimum streamer belt, which exhibits an abundance structure with the following characteristics. In the core of streamers the oxygen abundance is 1.3×10 −4 at 1.5 R , then it drops to 0.8×10 −4 at 1.7 R , value which remains almost constant out to 2.2 R . In the lateral bright structures that are observed to surround the core of streamers in the oxygen emission, the oxygen abundance drops monotonically with heliodistance, from 3.5×10 −4 at 1.5 R to 2.2×10 −4 at 2.2 R . The oxygen abundance structure found in the streamer belt is consistent with the model of magnetic topology of streamers proposed by Noci et al. (1997). The composition of the plasma contained in streamers is not the same as observed in the slow solar wind. Even in the lateral branches, richer in oxygen, at 2.2 R the abundance drops by a factor 2 with respect to the slow wind plasma observed with Ulysses during the declining phase of the solar cycle. Hence the slow wind does not appear to originate primarily from streamers, with the exception perhaps of the plasma flowing along the heliospheric current sheet.

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confidence: 68%

Section: Introductionmentioning

confidence: 90%

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Oxygen abundance in coronal streamers during solar minimum

2001

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“…Morphological studies on streamers using the UVCS OVI 1032Å spectral data reveal a surprising fork-like structure with the core of the streamer darker than its surroundings, while in the Ly-alpha line the streamer presents a typical helmet morphology [46]. It is further found that the OVI fork-like feature is common to many quiescent streamers at solar minimum [47].…”

Section: Morphological Studies On Coronal Streamers In the White-lighmentioning

confidence: 87%

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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“…Assuming the pre-CME plasma to be stationary, its electron density n e can be derived from the ratio of the collisional to the radiative line components. For a coronal electron temperature T e =10 6.3 K (as estimated from the ratio of the O VI λ1031.9 collisional component to the Si XII λ520.6 line intensity) and by assuming an exciting disk intensity I disk =1.94×10 13 phot cm −2 s −1 sr −1 (as measured by UVCS in 1996 at about the same phase of the solar cycle; see Raymond et al, 1997) we infer an electron density of the pre-CME corona n e =7×10 6 cm −3 . The same technique applied to the post-CME corona gives approximately the same temperature, while the coronal density decreases by about 15%; this can be expected if the passage of the CME partially evacuated the corona.…”

Section: Soho/uvcs Observationsmentioning

confidence: 99%

Multispacecraft observations of a prominence eruption

et al. 2009

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Abstract. On 9 May 2007 a prominence eruption occurred at the West limb. Remarkably, the event was observed by the STEREO/EUVI telescopes and by the HINODE/EIS and SOHO/UVCS spectrometers. We present results from all these instruments. High-cadence (∼37 s) data from STEREO/EUVI A and B in the He II λ304 line were used to study the 3-D shape and expansion of the prominence. The high spatial resolution EUVI images (∼1.5 /pixel) have been used to infer via triangulation the 3-D shape and orientation of the prominence 12 min after the eruption onset. At this time the prominence has mainly the shape of a "hook" highly inclined southward, has an average thickness of 0.068 R , a length of 0.43 R and lies, in first approximation, on a plane. Hence, the prominence is mainly a 2-D structure and there is no evidence for a twisted flux rope configuration. HIN-ODE/EIS was scanning with the 2 slit the region where the filament erupted. The EIS spectra show during the eruption remarkable non-thermal broadening (up to ∼100 km s −1 ) in the region crossed by the filament in spectral lines emitted at different temperatures, possibly with differences among lines from higher Fe ionization stages. The CME was also observed by the SOHO/UVCS instrument: the spectrograph slit was centered at 1.7 R , at a latitude of 5 • SW and recorded a sudden increase in the O VI λλ1032-1037 and Si XII λ520 spectral line intensities, representative of the CME front transit.

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Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer

Cited by 40 publications

References 45 publications

Oxygen abundance in coronal streamers during solar minimum

Oxygen abundance in coronal streamers during solar minimum

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

Multispacecraft observations of a prominence eruption

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