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Berghmans, David; Clette, F.

doi:10.1023/a:1005189508371

Cited by 295 publications

(266 citation statements)

References 17 publications

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“…TRACE 17.1 nm emission formed at ≈1 MK is cospatial with Hα at ≈1 × 10 4 K, but not with C IV at 1 × 10 5 K (De Pontieu et al 2003). In a study of quiet-Sun brightenings, Berghmans et al (1998) compared events observed with EIT in He II (30.4 nm; 80 000 K) and Fe XII (19.5 nm; 1.4 MK). Despite the large difference in the formation temperatures, the relations between the brightening parameters, size, duration, peak radiance, and radiative loss, were rather similar, possibly indicating that the same physical process was responsible for both aspects of the events.…”

Section: The Thermal Structurementioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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Section: The Thermal Structurementioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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“…Propagating extreme ultraviolet (EUV) intensity disturbances were discovered in the solar polar plumes (Deforest & Gurman 1998) and coronal loops (Berghmans & Clette 1999) with the Extreme ultraviolet Imaging Telescope (EIT) onboard SOlar and Heliospheric Observatory (SOHO). The follow-up studies (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Propagating EUV disturbances are usually quasi-monochromatic with the periods categorised into two classes: the A&A 543, A9 (2012) short period (∼3−5 min, see De Moortel et al 2000, 2002bDe Moortel 2009;King et al 2003;Marsh et al 2003;Wang et al 2009a) and long period (∼10−30 min, see Berghmans & Clette 1999;McIntosh et al 2008;Marsh et al 2009;Wang et al 2009b;Yuan et al 2011). De Moortel et al (2002b found statistically that the 3-min oscillations are more likely to be detected above sunspot regions, while the 5-min oscillations are usually found off the sunspots (e.g.…”

Section: Introductionmentioning

confidence: 99%

Measuring the apparent phase speed of propagating EUV disturbances

Yuan

Nakariakov

2012

A&A

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Context. Propagating disturbances of the EUV emission intensity are commonly observed over a variety of coronal structures. Parameters of these disturbances, particularly the observed apparent (image-plane projected) propagation speed, are important tools for MHD coronal seismology. Aims. We design and test tools to reliably measure the apparent phase speed of propagating disturbances in imaging data sets. Methods. We designed cross-fitting technique (CFT), 2D coupled fitting (DCF) and best similarity match (BSM) to measure the apparent phase speed of propagating EUV disturbances in the running differences of time-distance plots (R) and background-removed and normalised time-distance plots (D).Results. The methods were applied to the analysis of quasi-periodic EUV disturbances propagating at a coronal fan-structure of active region NOAA11330 on 27 Oct. 2011, observed with the Atmospheric Imaging Assembly (AIA) on SDO in the 171 Å bandpass. The noise propagation in the AIA image processing was estimated, resulting in the preliminary estimation of the uncertainties in the AIA image flux. This information was used in measuring the apparent phase speed of the propagating disturbances with the CFT, DCF and BSM methods, which gave consistent results. The average projected speed is measured at 47.6 ± 0.6 km s −1 and 49.0 ± 0.7 km s −1 for R and D, with the corresponding periods at 179.7 ± 0.2 s and 179.7 ± 0.3 s, respectively. We analysed the effects of the lag time and the detrending time in the running difference processing and the background-removed plot, on the measurement of the speed, and found that they are fairly weak. Conclusions. The CFT, DCF and BSM methods are found to be reliable techniques for measuring the apparent (projected) phase speed. The samples of larger effective spatial length are more suitable for these methods. Time-distance plots with background removal and normalisation allow for more robust measurements, with little effect of the choice of the detrending time. Cross-fitting technique provides reliable measurements on good samples (e.g. samples with large effective detection length and recurring features). 2D coupled-fitting is found to be sensitive to the initial guess for parameters of the 2D fitting function. Thus DCF is only optimised in measuring one of the parameters (the phase speed in our application), while the period is poorly measured. Best similarity measure is robust for all types of samples and very tolerant to image pre-processing and regularisation (smoothing).

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“…Running difference images in the "coronal" 171 and 211 Å bands do show upward-propagating disturbances most of the time, but these are typical for warm A&A 535, A46 (2011) loops (cf. SOHO/EIT, Berghmans & Clette 1999;and TRACE Schrijver et al 1999).…”

Section: Introductionmentioning

confidence: 99%

SDO AIA and Hinode EIS observations of “warm” loops

Zanna

O’Dwyer

Mason

2011

A&A

130

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We present simultaneous observations of active region "warm" (1 MK) loops using the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and Hinode EUV Imaging Spectrometer (EIS). Sample EIS spectra for a loop footpoint and a lop leg region are presented, and are used to describe the spectral lines which contribute to the six AIA EUV channels, both directly and predicted with DEM modeling. We find good overall agreement between observed and predicted count rates for the 131 Å, 193 Å, and 335 Å bands, but highlight a number of problems, partly to be ascribed to inter-calibration issues, partly due to the fact that a large number of lines remain unidentified for the 94 Å, 171 Å, and 211 Å bands. We also found that the 335 Å band is severely affected by cross-talk with the 131 Å band and by second order contributions. We extend our previous work where we highlighted the multi-thermal nature of the SDO AIA bands to show that emission from lines formed at typical transition region temperatures (log T [K] = 5.0-5.8) can be significant for all the EUV channels, and even dominant in some cases. We also assess the possibility of deriving accurate emission measures from the AIA observations. We have found that the inversion of the AIA data to obtain a description of the thermal characteristics of warm loops is unreliable. We highlight the need for further work on the relevant atomic data before the AIA data can be reliably used for plasma diagnostic purposes.

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Cited by 295 publications

References 17 publications

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Measuring the apparent phase speed of propagating EUV disturbances

SDO AIA and Hinode EIS observations of “warm” loops

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