Three‐dimensional Structure of the 2002 April 21 Coronal Mass Ejection

Lee, Jin Yi; Raymond, J. C.; Ko, Yuan‐Kuen; Kim, Kyoung-Sook

doi:10.1086/506981

Cited by 18 publications

(26 citation statements)

References 30 publications

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“…UVCS has observed this line typically at heliocentric distances ranging between $1.5 and 1.7 R , and it is not always easy to understand from observations in different events if the altitude of the UVCS projected field of view was either below the cusp of closed loops, or above it in the DR, or maybe even above the DR. In any case, there is a general consensus that [ Fe xviii] emission originates above the cusp of post-CME loops probably in the DR, as indirectly concluded by previous authors from considerations on many observational parameters such as elemental abundances and emission measure , plasma cooling rate and post-CME loops rising speed (Bemporad et al 2006), 3D reconstruction of CME material expansion (Lee et al 2006), and outflowing mass flux conservation (Ciaravella & Raymond 2008).…”

Section: Introductionmentioning

confidence: 76%

“…As mentioned above, observations of the [Fe xviii] line in post-CME CSs reported so far (Ciaravella et al 2002;Ko et al 2003;Raymond et al 2003;Bemporad et al 2006;Lee et al 2006;Ciaravella & Raymond 2008) show a strong line emission, but observational periods typically do not exceed a few hours, making it difficult to perform a complete study on the evolution of the line profile from each single data set. The only UVCS data set published so far in which the [ Fe xviii] line has been observed continuously for days after the CME is the one we reported in Paper I; these unique observations covered a period of $2.3 days (starting $1.5 hr after the CME) and were characterized by a strong [Fe xviii] emission detected during the whole time interval over a broad spatial region covering approximately $7 0 along the spectrometer slit (see Paper I, Figs.…”

Section: Fe XVIII Kinetic Temperatures In Cssmentioning

confidence: 99%

“…Post-CME CSs, usually identified in white-light images acquired by the Large Angle and Spectrometric Coronagraph (LASCO; Brueckner et al1995) as radial structures aligned with the CME latitude (see, e.g., Webb et al 2003), are characterized in UVCS spectra by the presence of an unusual high-temperature emission in the [ Fe xviii] k974.8 spectral line; the very high temperature of maximum formation T max ' 5 ; 10 6 K of this line makes it usually unobservable in the $10 6 K solar corona. In some works this emission has been observed only in the first few minutes ; Lee et al 2006) or hours (Ciaravella et al 2002) after the eruption, but other observations demonstrated that [Fe xviii] emission may last for even more than 2 days after the CME Bemporad et al 2006). More recently, Ciaravella & Raymond (2008) reported on the first CS that was observed in UV from its onset whose spectra show a [Fe xviii] emission lasting for %7 hr after the CME.…”

Section: Introductionmentioning

confidence: 99%

“…This work concentrates on this subject; information on plasma turbulence in post-CME CSs is derived here by studying the evolution of the [ Fe xviii] line profiles in UVCS data sets already studied by Ciaravella et al (2002), Ko et al (2003), Raymond et al (2003), Bemporad et al (2006), Lee et al (2006), and Ciaravella & Raymond (2008). In these works the authors focus on the CS plasma temperatures, densities, and elemental abundances, but there is little information on the [ Fe xviii] line profiles.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Detection of Turbulence in Post‐CME Current Sheets

Бемпорад

2008

Astrophysical Journal

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Plasma in post-CME current sheets (CSs) is expected to be highly turbulent because of the tearing and coalescence instability and/or local microscopic instabilities. For this reason, in the last decade the inconsistency between the observed ($10 4 Y10 5 km) and the expected ($1Y10 m) CS thickness has been tentatively explained in many MHD models as a consequence of plasma turbulence that should be able to significantly broaden the CS. However, from the observational point of view, little is known about this subject. A few post-CME CSs have been observed in UVCS spectra as a strong emission in the high-temperature [ Fe xviii] line, usually unobservable in the solar corona. In this work, published data on post-CME CSs observed by UVCS are reanalyzed, concentrating for the first time on the evolution of turbulence derived from the nonthermal broadening of the [Fe xviii] line profiles. Derived turbulent speeds are on the order of $60 km s À1 a few hours after the CME and slowly decay down to $30 km s À1 in the following 2 days. From this evolution the anomalous diffusivity due to microinstabilities has been estimated, and the scenario of multiple small-scale reconnections is tested. Results show that the existence of many ($10 À11 to 10 À17 CS m À3 ) microscopic CSs (CSs) of small sizes ($10Y10 4 m) could explain not only the high CS temperatures but also the much larger observed thickness of macroscopic CSs, thanks to turbulent broadening.

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Section: Introductionmentioning

confidence: 76%

Section: Fe XVIII Kinetic Temperatures In Cssmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Detection of Turbulence in Post‐CME Current Sheets

Бемпорад

2008

Astrophysical Journal

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“…However, the temperature and density range of XPE plasmas can be sampled by other spectroscopic instrumentation which allow broader diagnostic possibilities, although detection and identification of such plasmas are difficult with a spectrometer alone. Lee et al (2006) identified a localized region of hot plasma seen in the Fe xviii forbidden line at 974 Å with UVCS during a CME on 2002 April 21. It appeared to trail the CME core, and the Fe xviii line indicated a temperature of around 6 × 10 6 K. Lee et al (2006) found that the plasma was probably situated near the top of the current sheet, but they could not determine whether it was heated by reconnection or by a shock where the reconnection exhaust encountered the CME core.…”

Section: Introductionmentioning

confidence: 93%

Hot Plasma Associated With a Coronal Mass Ejection

Landi

Miralles

Raymond

et al. 2013

ApJ

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We analyze coordinated observations from the EUV Imaging Spectrometer (EIS) and X-Ray Telescope (XRT) on board Hinode of an X-ray Plasma Ejection (XPE) that occurred during the coronal mass ejection (CME) event of 2008 April 9. The XPE was trailing the CME core from behind, following the same trajectory, and could be identified both in EIS and XRT observations. Using the EIS spectrometer, we have determined the XPE plasma parameters, measuring the electron density, thermal distribution, and elemental composition. We have found that the XPE composition and electron density were very similar to those of the pre-event active region plasma. The XPE temperature was higher, and its thermal distribution peaked at around 3 MK; also, typical flare lines were absent from EIS spectra, indicating that any XPE component with temperatures in excess of 5 MK was likely either faint or absent. We used XRT data to investigate the presence of hotter plasma components in the XPE that could have gone undetected by EIS and found that-if at all present-these components have small emission measure values and their temperature is in the 8-12.5 MK range. The very hot plasma found in earlier XPE observations obtained by Yohkoh seems to be largely absent in this CME, although plasma ionization timescales may lead to non-equilibrium ionization effects that could make bright lines from ions formed in a 10 MK plasma not detectable by EIS. Our results supersede the XPE findings of Landi et al., who studied the same event with older response functions for the XRT Al-poly filter; the differences in the results stress the importance of using accurate filter response functions.

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UVCS/SOHO catalog of coronal mass ejections from 1996 to 2005: Spectroscopic proprieties

et al. 2013

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[1] Ultraviolet spectra of the extended solar corona have been routinely obtained by SOHO/UltraViolet Coronagraph Spectrometer (UVCS) since 1996. Sudden variations of spectral parameters are mainly due to the detection of coronal mass ejections (CMEs) crossing the instrumental slit. We present a catalog of CME ultraviolet spectra based upon a systematic search of events in the Large Angle and Spectrometric Coronagraph (LASCO) CME catalog, and we discuss their statistical properties. Our catalog includes 1059 events through the end of 2005, covering nearly a full solar cycle. It is available online at the URL http://solarweb.oato.inaf.it/UVCS_CME and embedded in the online LASCO CME catalog (http://cdaw.gsfc.nasa.gov/CME_list). The emission lines observed provide diagnostics of CME plasma parameters, such as the light-of-sight velocity, density, and temperature and allow to link the CME onset data to the extended corona white-light images. The catalog indicates whether there are clear signatures of features such as shock waves, current sheets, O VI flares, helical motions, and which part of the CME structures (front, cavity, or prominence material) are detected. The most common detected structure is the cool prominence material (in about 70% of the events). For each event, the catalog also contains movies, images, plots, and information relevant to address detailed scientific investigations. The number of events detected in UV is about one tenth of the LASCO CMEs and about one fourth of the halo events. We find that UVCS tends to detect faster, more massive, and energetic CME than LASCO, and for about 40% of the events, it has been possible to determine the plasma light-of-sight velocity.

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Three‐dimensional Structure of the 2002 April 21 Coronal Mass Ejection

Cited by 18 publications

References 30 publications

Spectroscopic Detection of Turbulence in Post‐CME Current Sheets

Spectroscopic Detection of Turbulence in Post‐CME Current Sheets

Hot Plasma Associated With a Coronal Mass Ejection

UVCS/SOHO catalog of coronal mass ejections from 1996 to 2005: Spectroscopic proprieties

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