Erratum: "Outflows at the Edges of Active Regions: Contribution to Solar Wind Formation?" ([URL ADDRESS="/cgi-bin/resolve?2008ApJ...676L.147H" STATUS="OKAY"]ApJ, 676, L147 [2008][/URL])

Harra, L. K.; Sakao, Taro; Mandrini, C. H.; Hara, Hirohisa; Imada, Shinsuke; Young, Peter R.; Driel-Gesztelyi, L. van; Baker, Donald M.

doi:10.1086/588288

Cited by 6 publications

(6 citation statements)

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“…The author found Doppler velocities of 5-10 km s −1 in the EIS Fe xii 195.12 Å line and 10-30 km s −1 in the Fe xv 284.16 Å line, occurring in areas of weak emission "in a sharp boundary between low-lying hot 3 MK loops Article published by EDP Sciences A38, page 1 of 11 A&A 584, A38 (2015) and higher cooler 1 MK loops". Harra et al (2008) also studied the blueshifts in the coronal lines of Fe xii and Fe xv and estimated line-of-sight (LOS) velocities of 20-50 km s −1 . No absolute calibration exists for EIS data and near absolute values can only be obtained for certain type of observations (Young et al 2012).…”

Section: Introductionmentioning

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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Section: Introductionmentioning

confidence: 99%

Active region upflows

Vanninathan

Madjarska

Galsgaard

et al. 2015

A&A

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“…These oscillations have been identified in the upflow regions by Guo et al (2010) and Ugarte-Urra & Warren (2011), who propose the underlying processes to be sporadic in both space and time. From a potential magnetic field extrapolation, Harra et al (2008) found, that reconnection on one side of the investigated active region generated long loops which connect across the region. They concluded, that the observed upflows were the result of an expansion of the newly formed loops as they move up toward a new equilibrium.…”

Section: Introductionmentioning

confidence: 96%

Active region upflows

Galsgaard

Madjarska²,

Vanninathan

et al. 2015

A&A

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Context.Observations of many active regions show a slow systematic outflow/upflow from their edges lasting from hours to days. At present no physical explanation has been proven, while several suggestions have been put forward. Aims. This paper investigates one possible method for maintaining these upflows assuming, that convective motions drive the magnetic field to initiate them through magnetic reconnection. Methods. We use Helioseismic and Magnetic Imager (HMI) data to provide an initial potential 3D magnetic field of the active region NOAA 11123 on 2010 November 13 where the characteristic upflow velocities are observed. A simple 1D hydrostatic atmospheric model covering the region from the photosphere to the corona is derived. Local correlation tracking of the magnetic features in the HMI data is used to derive a proxy for the time dependent velocity field. The time dependent evolution of the system is solved using a resistive 3D magnetohydrodynamic code. Results. The magnetic field contains several null points located well above the photosphere, with their fan planes dividing the magnetic field into independent open and closed flux domains. The stressing of the interfaces between the different flux domains is expected to provide locations where magnetic reconnection can take place and drive systematic flows. In this case, the region between the closed and open flux is identified as the region where observations find the systematic upflows. Conclusions. In the present experiment, the driving only initiates magneto-acoustic waves without driving any systematic upflows at any of the flux interfaces.

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“…This type of oscillations have been identified in the upflow regions by Guo et al (2010) and Ugarte-Urra & Warren (2011), who propose the underlying processes to be sporadic in both space and time. From a potential magnetic field extrapolation, Harra et al (2008) found that reconnection on one side of the investigated active region generated long loops which connect across the region. They concluded that the observed upflows were the result of an expansion of the newly formed loops as they move up, towards a new equilibrium.…”

Section: Introductionmentioning

confidence: 99%

Active region upflows: 2. Data driven MHD modeling

Galsgaard,

Madjarska,

Vanninathan

et al. 2015

Preprint

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Context. Observations of many active regions show a slow systematic outflow/upflow from their edges lasting from hours to days. At present no physical explanation has been proven, while several suggestions have been put forward. Aims. This paper investigates one possible method for maintaining these upflows assuming that convective motions drive the magnetic field to initiate them through magnetic reconnection. Methods. We use Helioseismic and Magnetic Imager (HMI) data to provide an initial potential three dimensional magnetic field of the active region NOAA 11123 on 2010 November 13 where the characteristic upflow velocities are observed. A simple one-dimensional hydrostatic atmospheric model covering the region from the photosphere to the corona is derived. Local Correlation Tracking of the magnetic features in the HMI data is used to derive a proxy for the time dependent velocity field. The time dependent evolution of the system is solved using a resistive three-dimensional MagnetoHydro-Dynamic code.Results. The magnetic field contains several null points located well above the photosphere, with their fan planes dividing the magnetic field into independent open and closed flux domains. The stressing of the interfaces between the different flux domains is expected to provide locations where magnetic reconnection can take place and drive systematic flows. In this case, the region between the closed and open flux is identified as the region where observations find the systematic upflows. Conclusions. In the present experiment, the driving only initiates magneto-acoustic waves, without driving any systematic upflows at any of the flux interfaces.

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Erratum: "Outflows at the Edges of Active Regions: Contribution to Solar Wind Formation?" ([URL ADDRESS="/cgi-bin/resolve?2008ApJ...676L.147H" STATUS="OKAY"]ApJ, 676, L147 [2008][/URL])

Cited by 6 publications

References 0 publications

Active region upflows

Active region upflows

Active region upflows

Active region upflows: 2. Data driven MHD modeling

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