Analysis of 2-d flare spectra: Velocity fields derived from H? line asymmetries

Ding, M. D.; Fang, Cheng; Huang, Yunhao

doi:10.1007/bf00680836

Cited by 47 publications

(32 citation statements)

References 21 publications

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“…In the present work, we investigated manifestations of the spectral line as a result of the combination of different Doppler shifts of different spectral line components caused by various motion patterns in the source region during the magnetic reconnection. We note here that, on the other hand, a lot of other things may account for such motion patterns as well (Canfield et al, 1990;Ding et al, 1995;Ding et al, 1999;Li et al, 2015). In addition, resolved and/or unresolved turbulence created by nonthermal processes (Ding & Fang, 1997) and the Stark-broadening in the spectral line wing (Canfield & Gayley, 1987) could further lead to the asymmetry and complex structure occurring in different stages of the energy release process.…”

Section: Discussionmentioning

confidence: 73%

Multiband Study of a Bidirectional Jet Occurred in the Upper Chromosphere

Cai

Shen

et al. 2019

JGR Space Physics

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We present a study of a jet observed by the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS), which provide high spatial-temporal resolution observational data of (extreme) ultraviolet images, spectra, and magnetograms. The jet was observed in multiple bands of AIA and manifested clear bidirectional flows in IRIS observations. The emission profiles of the Si IV 1402 Å line of the jet exhibited non-Gaussian features and double-peaked spectra, with the Doppler velocity and the nonthermal velocity up to 100 and 160 km s −1 , respectively. The plasma flows of the jet projected on the sky plane and in the line of sight (LOS) are the typical observational evidence of magnetic reconnection. The EM loci curves indicated that the plasma contains multi-temperature components. The result deduced from the DEM method and changes in intensity of several spectral lines imply that the temperature of the plasma in the jet is heated to at least 10 5.6 K. The electron density is about 10 11 cm −3 according to the intensity ratios of the O IV 1399.77/1401.16 Å doublet and Si IV 1402.77/O IV 1401.16 Å lines. Via different approaches, we reached the conclusion that the jet occurred in the upper chromosphere. Investigating the magnetograms in the period when the jet appeared, we suggest that the jet results from the magnetic reconnection between the moving magnetic structure and the magnetic field nearby.

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Section: Discussionmentioning

confidence: 73%

Multiband Study of a Bidirectional Jet Occurred in the Upper Chromosphere

Cai

Shen

et al. 2019

JGR Space Physics

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“…Similar blueshifts of 60-300 km s −1 have also been obtained in the hot Fe xix line (e.g., Teriaca et al 2003Teriaca et al , 2006Brosius & Phillips 2004;Del Zanna et al 2006) using the Coronal Diagnostic Spectrometer (CDS; Harrison et al 1995) on board the Solar and Heliospheric Observatory (SOHO). In the mean time, redshifts corresponding to downward velocities of tens of km s −1 have been measured in the chromospheric and transition region (TR) lines (e.g., Wülser et al 1994;Ding et al 1995;Czaykowska et al 1999;Teriaca et al 2003Teriaca et al , 2006Brosius 2003;Kamio et al 2005;Del Zanna et al 2006). Recently, both blueshifts and redshifts have been detected in different emission lines using the EUV Imaging Spectrometer (EIS; Culhane et al 2007) on board Hinode (e.g., Milligan & Dennis 2009;Chen & Ding 2010;Li & Ding 2011;Doschek et al 2013).…”

Section: Introductionmentioning

confidence: 99%

CHROMOSPHERIC EVAPORATION IN AN X1.0 FLARE ON 2014 MARCH 29 OBSERVED WITHIRISAND EIS

Ding

Qiu

et al. 2015

ApJ

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Chromospheric evaporation refers to dynamic mass motions in flare loops as a result of rapid energy deposition in the chromosphere. These have been observed as blueshifts in X-ray and extreme-ultraviolet (EUV) spectral lines corresponding to upward motions at a few tens to a few hundreds of km s −1 . Past spectroscopic observations have also revealed a dominant stationary component, in addition to the blueshifted component, in emission lines formed at high temperatures (∼10 MK). This is contradictory to evaporation models predicting predominant blueshifts in hot lines. The recently launched Interface Region Imaging Spectrograph (IRIS) provides high resolution imaging and spectroscopic observations that focus on the chromosphere and transition region in the UV passband. Using the new IRIS observations, combined with coordinated observations from the EUV Imaging Spectrometer, we study the chromospheric evaporation process from the upper chromosphere to corona during an X1.0 flare on 2014 March 29. We find evident evaporation signatures, characterized by Doppler shifts and line broadening, at two flare ribbons separating from each other, suggesting that chromospheric evaporation takes place in successively formed flaring loops throughout the flare. More importantly, we detect dominant blueshifts in the high temperature Fe xxi line (∼10 MK), in agreement with theoretical predictions. We also find that, in this flare, gentle evaporation occurs at some locations in the rise phase of the flare, while explosive evaporation is detected at some other locations near the peak of the flare. There is a conversion from gentle to explosive evaporation as the flare evolves.-2 -

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“…Ding et al, 1995) to the Ha intensity line profiles, we have obtained the line-ofsight velocity field v i . Using the CaII 8542 Å Stokes-V profiles, we got the longitudinal magnetic field B i .…”

Section: D Magnetic Field and Velocity Mapsmentioning

confidence: 99%