The solar chromosphere at high resolution with IBIS

Reardon, K.; Uitenbroek, H.; Cauzzi, G.

doi:10.1051/0004-6361/200811223

Cited by 52 publications

(45 citation statements)

References 32 publications

(28 reference statements)

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“…On the other hand, Judge et al (2001), using TRACE UV continua and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) lines, have detected a deficit of acoustic power along with lower intensity values in the 2-3 min period range around the quiet Sun NBPs. This deficit, which they termed "magnetic shadow", had already been reported in previous studies (Kneer & von Uexküll 1986;Cauzzi et al 2000), but it has been further exploited in two-dimensional power maps in the past few years (Krijger et al 2001;Muglach 2003;Muglach et al 2005;Vecchio et al 2007;Reardon et al 2009). It is now generally accepted that the interaction of acoustic oscillations with the inclined magnetic field lines together with the location of the magnetic canopy are responsible for the formation of the power halos and magnetic shadows and may reflect common physical processes (McIntosh & Judge 2001;McIntosh et al 2003;Muglagh et al 2005;Moretti et al 2007).…”

Section: Introductionmentioning

confidence: 55%

“…Most of the above cited authors note that power suppression does not seem to be related directly to the NBPs, but to the region adjacent to them. From our high resolution DOT Hα data and from the Interferometric Bidimensional Spectrometer (IBIS) data in the Ca ii 8542 Å and Ca ii K chromospheric lines (Vecchio et al 2007;Reardon et al 2009) it is obvious that there is a clear correlation of the power enhancement or suppression with the dark mottles surrounding the NBPs. Indeed, as we have shown in this work, the power suppression as well as the power enhancement are clearly related to dark mottles.…”

Section: Discussionmentioning

confidence: 93%

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Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Kontogiannis

Tsiropoula

Tziotziou

2010

A&A

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Context. We investigate the oscillatory behavior of the quiet solar chromosphere and its discrete components in terms of oscillation properties, i.e. network and internetwork. For this purpose, we use a time series of high resolution filtergrams at five wavelengths along the Hα profile, obtained by the Dutch Open Telescope. Aims. We aim to gain insight on the distribution of power in different period bands and its variation between network and internetwork. Our spectral resolution provides information on the vertical distribution of power, since the Hα line has both photospheric and chromospheric components. We investigate the effect of Hα mottles on chromospheric oscillations, since they are the most prominent feature of the Hα chromosphere and outline inclined magnetic fields. Methods. We use wavelet and phase difference analyses of Hα intensities and Doppler signals. Two-dimensional power maps in the 3, 5 and 7 min period bands as well as coherence and phase difference maps were constructed. Results. At photospheric heights, where the Hα ± 0.7 Å wing is formed, the 3 and 5 min power is enhanced around the network, and forms power halos. Higher in the chromosphere these areas are replaced by magnetic shadows, i.e. places of power suppression. Interestingly, the power maps show a filamentary structure in the network which correlates very well with mottles. These areas show positive phase differences at the 3 min period band. At the 5 min and 7 min period bands both positive and negative phase differences are obtained with an increased number of pixels with high coherence, indicating the existence of both upward and downward propagating waves. Conclusions. We attribute our findings to the interaction between acoustic oscillations and the magnetic fields that constitute the magnetic network. The network flux tubes diverge at chromospheric levels and obtain a significant horizontal component, which is betrayed by the presence of mottles. The variation of power reveals the discrete role of the magnetic field at different heights, which guides or suppresses the oscillations, depending on its inclination. Spectral resolution in Hα provides useful information on the coupling between the acoustic sub-canopy atmosphere and the magnetized chromosphere.

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Section: Introductionmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 93%

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Kontogiannis

Tsiropoula

Tziotziou

2010

A&A

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“…Therefore, the effectiveness of such a highpass filtering is not instantly clear. Reardon et al (2009) found no good resemblance between broad-band Ca imaging and the line core of Ca ii IR spectra either on a temporal average or in their temporal evolution considering frequencies up to 15 mHz.…”

Section: Summary and Discussionmentioning

confidence: 79%

“…Öhman 1938;Lyot 1944;Wang et al 1995;Skomorovsky et al 2012) that can have spectral pass-bands down to 0.01 nm (e.g. Reardon et al 2009;RE09), it is not immediately clear whether the same is true for broad-band interference filters with 0.1 to 1 nm fullwidth at half-maximum (FWHM) band passes. A&A 556, A127 (2013) The investigation of the intensity response of the Ca ii H broad-band filter of Hinode by Carlsson et al (2007) yielded a maximal response at a height of about 250 km, whereas Jafarzadeh et al (2013) reported about 450 km for the 0.18 nm filter of SuFi on-board of the Sunrise balloon mission (Barthol et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Can spicules be detected at disc centre in broad-band Ca ii H filter imaging data?

Beck

Rezaei

Puschmann

2013

A&A

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Context.Recently, a possible identification of type II spicules in broad-band (full-width at half-maximum (FWHM) of ∼0.3 nm) filter imaging data in Ca ii H on the solar disc was reported. Aims. We estimate the formation height range contributing to broad-band and narrow-band filter imaging data in Ca ii H to investigate whether spicules can be detected in such observations at the centre of the solar disc.Methods. We applied spectral filters of FWHMs from 0.03 nm to 1 nm to observed Ca ii H line profiles to simulate Ca imaging data. We used observations across the limb to estimate the relative intensity contributions of off-limb and on-disc structures. We compared the synthetic Ca filter imaging data with intensity maps of Ca spectra at different wavelengths and temperature maps at different optical depths obtained by an inversion of these spectra. In addition, we determined the intensity response function for the wavelengths covered by the filters of different FWHM. Results. In broad-band (FWHM = 0.3 nm) Ca imaging data, the intensity emitted off the solar limb is about 5% of the intensity at disc centre. For a 0.3-nm-wide filter centred at the Ca ii H line core, up to about one third of the off-limb intensity comes from emission in H . On the disc, only about 10 to 15% of the intensity transmitted through a broad-band filter comes from the linecore region between the H 1 minima (396.824 to 396.874 nm). No traces of elongated fibrillar structures are visible in the synthetic Ca broad-band imaging data at disc centre, in contrast to the line-core images of the Ca spectra. The intensity-weighted response function for a 0.3-nm-wide filter centred at the Ca ii H line core peaks at about log τ ∼ −2 (z ∼ 200 km). Relative contributions from atmospheric layers above 800 km are about 10%. The inversion results suggest that the slightly enhanced emission around the photospheric magnetic network in broad-band Ca imaging data is caused by a thermal canopy at a height of about 600 km.Conclusions. Broad-band (∼0.3 nm) Ca ii H imaging data do not trace upper chromospheric structures such as spicules in observations at the solar disc because of the too small relative contribution of the line core to the total wavelength-integrated filter intensity. The faint haze around network elements in broad-band Ca imaging observations at disc centre presumably traces thermal canopies in the vicinity of magnetic flux concentrations instead.

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“…A similar approach was adopted by Finsterle et al (2004) that mapped the canopy height using wave travel times, derived by the MOTH experiment and MDI magnetograms. More recently, filtergrams of the chromosphere taken at the infrared Ca ii line (Vecchio et al 2007;Reardon et al 2009) showed magnetic shadows in network areas.…”

Section: Introductionmentioning

confidence: 99%

Oscillations in a network region observed in the Hαline and their relation to the magnetic field

Kontogiannis

Tsiropoula

Tziotziou

et al. 2010

A&A

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Aims. Our aim is to gain a better understanding of the interaction between acoustic oscillations and the small-scale magnetic fields of the Sun. To this end, we examine the oscillatory properties of a network region and their relation to the magnetic configuration of the chromosphere. We link the oscillatory properties of a network region and their spatial variation with the variation of the parameters of the magnetic field. We investigate the effect of the magnetic canopy and the diverging flux tubes of the chromospheric network on the distribution of oscillatory power over the network and internetwork. Methods. We use a time series of high resolution filtergrams at five wavelengths along the Hα profile observed with the Dutch Open Telescope, as well as high resolution magnetograms taken by the SOT/SP onboard HINODE. Using wavelet analysis, we construct power maps of the 3, 5 and 7 min oscillations of the Doppler signals calculated at ±0.35 Å and ±0.7 Å from the Hα line center. These represent velocities at chromospheric and photospheric levels respectively. Through a current-free (potential) field extrapolation we calculate the chromospheric magnetic field and compare its morphology with the Hα filtergrams. We calculate the plasma β and the magnetic field inclination angle and compare their distribution with the oscillatory power at the 3, 5 and 7 min period bands. Results. Chromospheric mottles seem to outline the magnetic field lines. The Hα ± 0.35 Å Doppler signals are formed above the canopy, while the Hα ± 0.7 Å corresponding ones below it. The 3 min power is suppressed at the chromosphere around the network, where the canopy height is lower than 1600 km, while at the photosphere it is enhanced due to reflection. 3, 5 and 7 min oscillatory power is increased around the network at the photosphere due to reflection of waves on the overlying canopy, while increased 5 and 7 min power at the chromosphere is attributed mainly to wave refraction on the canopy. At these high periods, power is also increased due to p-mode leakage because of the high inclinations of the magnetic field. Conclusions. Our high resolution Hα observations and photospheric magnetograms provide the opportunity to highlight the details of the interaction between acoustic oscillations and the magnetic field of a network region. We conclude that several mechanisms that have been proposed such as p-mode leakage, mode conversion, reflection and refraction of waves on the magnetic canopy may act together and result to the observed properties of network oscillations.

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The solar chromosphere at high resolution with IBIS

Cited by 52 publications

References 32 publications

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Power halo and magnetic shadow in a solar quiet region observed in the Hαline

Can spicules be detected at disc centre in broad-band Ca ii H filter imaging data?

Oscillations in a network region observed in the Hαline and their relation to the magnetic field

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