Characterization of Fabry-Perot interferometers and multi-etalon transmission profiles

Reardon, K.; Cavallini, F.

doi:10.1051/0004-6361:20078473

Cited by 115 publications

(118 citation statements)

References 24 publications

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“…The IBIS instrument (Cavallini 2006;Reardon & Cavallini 2008) recorded images in the Hα 6562.8 Å line starting at 14:05 UT. However, we did not use the first two hours of data because the seeing was variable.…”

Section: Ground Observationsmentioning

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: Ground Observationsmentioning

confidence: 99%

Active region upflows

Vanninathan

Madjarska

Galsgaard

et al. 2015

A&A

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“…IBIS uses a pair of Fabry-Perot interferometers to record very narrow-band filtergrams in the spectral range 5800-8600 Å (Cavallini 2006;Reardon & Cavallini 2008). It has a 95 diameter circle field of view and a pixel size of about 0.1 .…”

Section: Ibismentioning

confidence: 99%

Hαspectroscopy and multiwavelength imaging of a solar flare caused by filament eruption

Huang

Madjarska²,

Koleva

et al. 2014

A&A

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Context. We study a sequence of eruptive events including filament eruption, a GOES C4.3 flare, and a coronal mass ejection. Aims. We aim to identify the possible trigger(s) and precursor(s) of the filament destabilisation, investigate flare kernel characteristics, flare ribbons/kernels formation and evolution, study the interrelation of the filament-eruption/flare/coronal-mass-ejection phenomena as part of the integral active-region magnetic field configuration, and determine Hα line profile evolution during the eruptive phenomena. Methods. Multi-instrument observations are analysed including Hα line profiles, speckle images at Hα -0.8 Å and Hα + 0.8 Å from IBIS at DST/NSO, EUV images and magnetograms from the SDO, coronagraph images from STEREO, and the X-ray flux observations from Fermi and GOES. Results. We establish that the filament destabilisation and eruption are the main triggers for the flaring activity. A surge-like event with a circular ribbon in one of the filament footpoints is determined as the possible trigger of the filament destabilisation. Plasma draining in this footpoint is identified as the precursor for the filament eruption. A magnetic flux emergence prior to the filament destabilisation followed by a high rate of flux cancellation of 1.34 × 10 16 Mx s −1 is found during the flare activity. The flare X-ray lightcurves reveal three phases that are found to be associated with three different ribbons occurring consecutively. A kernel from each ribbon is selected and analysed. The kernel lightcurves and Hα line profiles reveal that the emission increase in the line centre is stronger than that in the line wings. A delay of around 5-6 min is found between the increase in the line centre and the occurrence of red asymmetry. Only red asymmetry is observed in the ribbons during the impulsive phases. Blue asymmetry is only associated with the dynamic filament.

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“…A total of 175 scans of the spectral line were obtained for a total duration of 55 min. The instrumental spectral profile of IBIS is described in Reardon & Cavallini (2008) and at this wavelength has an FWHM of 4.4 pm, with spectrally scattered light less than 1.5% of the total transmission.…”

Section: Observationsmentioning

confidence: 99%

The solar chromosphere at high resolution with IBIS

Reardon

Uitenbroek

Cauzzi

2009

A&A

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Aims. Filtergrams obtained in Ca II H, Ca II K, and Hα are often employed as diagnostics of the solar chromosphere. The vastly disparate appearance between the typical filtergrams in these different lines calls into question the nature of what is actually being observed. We investigate the lack of obvious structures of magnetic origin such as fibrils and mottles in on-disk Ca II H and K images. Methods. We directly compare a temporal sequence of classical Ca II K filtergrams with a co-spatial and co-temporal sequence of spectrally resolved Ca II 854.2 images obtained with the Interferometric Bidimensional Spectrometer (IBIS), considering the effect of both the spectral and spatial smearing. We analyze the temporal behavior of the two series by means of Fourier analysis.Results. The lack of fine magnetic structuring in Ca II K filtergrams, even with the narrowest available filters, is due to observational effects, primarily contributions from the bright, photospheric wings of the line that swamp the small and dark chromospheric structures. Signatures of fibrils remain, however, in the temporal evolution of the filtergrams, in particular with the evidence of magnetic shadows around the network elements. The Ca II K filtergrams do not appear, however, to properly reflect the high-frequency behavior of the chromosphere. Using the same analysis, we find no significant chromospheric signature in the Hinode/SOT Ca II H quiet-Sun filtergrams.Conclusions. The picture provided by Hα and Ca II 854.2, which show significant portions of the chromosphere dominated by magnetic structuring, appears to reflect the true and essential nature of the solar chromosphere. Data that do not resolve this aspect, whether spatially or spectrally, may misrepresent the behavior the chromosphere.

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Characterization of Fabry-Perot interferometers and multi-etalon transmission profiles

Cited by 115 publications

References 24 publications

Active region upflows

Active region upflows

Hαspectroscopy and multiwavelength imaging of a solar flare caused by filament eruption

The solar chromosphere at high resolution with IBIS

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