SDO AIA and Hinode EIS observations of “warm” loops

Zanna, G. Del; O’Dwyer, B.; Mason, H. E.

doi:10.1051/0004-6361/201117470

Cited by 131 publications

(114 citation statements)

References 24 publications

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“…These SDO/AIA observations provide unprecedented coverage in terms of spatial and temporal resolutions, and can provide new diagnostic applications, once the atomic data are well understood. As shown in O'Dwyer et al (2010) andDel Zanna et al (2011), these bands are dominated by Fe x and Fe viii in normal quiet Sun conditions. However, several unidentified spectral lines have been observed in the AIA passbands with high-resolution grazing incidence solar spectrometers (cf.…”

Section: Introductionmentioning

confidence: 82%

Atomic data for astrophysics: Fe x soft X-ray lines

Zanna¹,

Storey

Badnell

et al. 2012

A&A

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New atomic calculations for Fe x are presented. They focus on the need to model the soft X-ray spectrum and in particular the line at 94.0 Å which is the dominant contribution to the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 94 Å band in quiet Sun conditions. This line, and others in the band, are due to strong decays from n = 4 levels. We present new large-scale R-matrix (up to n = 4) and distorted-wave (DW, up to n = 6) scattering calculations for electron collisional excitation and compare them to earlier work. We find significant discrepancies with previous calculations. We show that resonances significantly increase the cross-sections for excitations from the ground state to some n = 4 levels, in particular to those in the 3s 2 3p 4 4s configuration. Cascading from higher levels is also important. We suggest a new identification for the 3s 3p 6 2 S 1/2 -3s 3p 5 4s 2 P 3/2 transition, that has a predicted intensity larger than the decays from the 3s 2 3p 4 4s levels which were identified by Edlén in 1936. The results presented here are relevant to our understanding of transitions from n = 4 levels in a wide range of other ions.

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Section: Introductionmentioning

confidence: 82%

Atomic data for astrophysics: Fe x soft X-ray lines

Zanna¹,

Storey

Badnell

et al. 2012

A&A

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“…Several authors Young et al 2012;Del Zanna et al 2011) have raised the question of which coronal imaging channel best represents the coronal structures that display plasma upflows in the EIS Fe xii lines. The reason for this is the contribution of a wide range of spectral lines to the wavelength range covered by the AIA 171 Å and 193 Å, and TRACE 171 Å channels.…”

Section: Aiamentioning

confidence: 99%

“…The channel also has a contribution from Fe x. The AIA 193 Å channel is dominated by three Fe xii lines, but it also has a significant contribution from the transition region from unidentified lines (Del Zanna et al 2011).…”

Section: Aiamentioning

confidence: 99%

Active region upflows

Vanninathan

Madjarska

Galsgaard

et al. 2015

A&A

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Context. We study upflows at the edges of active regions, called AR outflows, using multi-instrument observations. Aims. This study intends to provide the first direct observational evidence of whether chromospheric jets play an important role in furnishing mass that could sustain coronal upflows. The evolution of the photospheric magnetic field, associated with the footpoints of the upflow region and the plasma properties of active region upflows is investigated with the aim of providing information for benchmarking data-driven modelling of this solar feature. Methods. We spatially and temporally combine multi-instrument observations obtained with the Extreme-ultraviolet Imaging Spectrometer on board the Hinode, the Atmospheric Imaging Assembly and the Helioseismic Magnetic Imager instruments on board the Solar Dynamics Observatory and the Interferometric BI-dimensional Spectro-polarimeter installed at the National Solar Observatory, Sac Peak, to study the plasma parameters of the upflows and the impact of the chromosphere on active region upflows. Results. Our analysis shows that the studied active region upflow presents similarly to those studied previously, i.e. it displays blueshifted emission of 5-20 km s −1 in Fe xii and Fe xiii and its average electron density is 1.8 × 10 9 cm −3 at 1 MK. The time variation of the density is obtained showing no significant change (in a 3σ error). The plasma density along a single loop is calculated revealing a drop of 50% over a distance of ∼20 000 km along the loop. We find a second velocity component in the blue wing of the Fe xii and Fe xiii lines at 105 km s −1 reported only once before. For the first time we study the time evolution of this component at high cadence and find that it is persistent during the whole observing period of 3.5 h with variations of only ±15 km s −1 . We also, for the first time, study the evolution of the photospheric magnetic field at high cadence and find that magnetic flux diffusion is responsible for the formation of the upflow region. High cadence Hα observations are used to study the chromosphere at the footpoints of the upflow region. We find no significant jet-like (spicule/rapid blue excursion) activity to account for several hours/days of plasma upflow. The jet-like activity in this region is not continuous and blueward asymmetries are a bare minimum. Using an image enhancement technique for imaging and spectral data, we show that the coronal structures seen in the AIA 193 Å channel are comparable to the EIS Fe xii images, while images in the AIA 171 Å channel reveal additional loops that are a result of contribution from cooler emission to this channel. Conclusions. Our results suggest that at chromospheric heights there are no signatures that support the possible contribution of spicules to active region upflows. We suggest that magnetic flux diffusion is responsible for the formation of the coronal upflows. The existence of two velocity components possibly indicates the presence of two different flows, which are produce...

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“…3 above, emission from transition region plasma will dominate in all of AIA's EUV channels during a flare's precursors and early impulsive rise, while emission from plasma at temperatures around 10 MK will dominate later during the event. In an even more recent comparison of AIA images of a non-flaring loop footpoint and leg with coordinated EUV spectra from Hinode's Extreme-ultraviolet Imaging Spectrometer (EIS, Culhane et al 2007), Del Zanna et al (2011) showed that emission from lines formed at transition region temperatures can be significant for all of AIA's EUV channels, and dominant in some cases. Their observation of numerous unidentified lines in the EIS spectra underscored the need for further work on the relevant atomic data before AIA images can be reliably used for plasma diagnostic purposes.…”

Section: Based On Aia and Cdsmentioning

confidence: 99%

Using SDO’s AIA to investigate energy transport from a flare’s energy release site to the chromosphere

Brosius

Holman

2012

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Context. Coordinated observations of a GOES B4.8 microflare with SDO's Atmospheric Imaging Assembly (AIA) and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on 2010 July 31 show that emission in all seven of AIA's EUV channels brightened simultaneously nearly 6 min before RHESSI or GOES detected emission from plasma at temperatures around 10 MK. Aims. To help interpret these and AIA flare observations in general, we characterized the expected temporal responses of AIA 's 94, 131, 171, 193, 211, and 335 Å channels to solar flare brightenings by combining (1) AIA's nominal temperature response functions available through SSWIDL with (2) EUV spectral line data observed in a flare loop footpoint on 2001 April 24 with the Coronal Diagnostic Spectrometer (CDS) on timescales comparable to AIA's image cadence. Methods. The nine emission lines observed by CDS cover a wide range of formation temperature from about 0.05 to 8 MK. Line brightenings observed early during the CDS flare occurred at temperatures less than about 0.7 MK, with the largest values around 0.1 MK. These brightenings were consistent with the flare's energy transport being dominated by nonthermal particle beams. Because all of AIA's EUV channels are sensitive to emission from plasma in the 0.1 to 0.7 MK temperature range, we show that all of AIA's EUV channels will brighten simultaneously during flares like this, in which energy transport is dominated by nonthermal particle beams. Results. The 2010 July 31 flare observed by AIA and RHESSI displays this behavior, so we conclude that such beams likely dominated the flare's energy transport early during the event. When thermal conduction from a reconnection-heated, hot (∼10 MK) plasma dominates the energy transport, the AIA channels that are sensitive to emission from such temperatures (particularly the 94 and 131 Å channels) will brighten earlier than the channels that are not sensitive to such temperatures (171 and 211 Å). Conclusions. Thus, based on the differences expected between AIA's response to flares whose energy transport is dominated by nonthermal particle beams from those whose energy transport is dominated by thermal conduction, AIA can be used to determine the dominant energy transport mechanism for any given event.

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SDO AIA and Hinode EIS observations of “warm” loops

Cited by 131 publications

References 24 publications

Atomic data for astrophysics: Fe x soft X-ray lines

Atomic data for astrophysics: Fe x soft X-ray lines

Active region upflows

Using SDO’s AIA to investigate energy transport from a flare’s energy release site to the chromosphere

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