skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI

Abstract

We present observations of transverse oscillations in slender Ca ii H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high- (spatial and temporal-) resolution seeing-free observations in a 1.1 Å wide passband covering the line core of Ca ii H 3969 Å from the second flight of the Sunrise balloon-borne solar observatory. The entire field of view, spanning the polarity inversion line of an active region close to the solar disk center, is covered with bright, thin, and very dynamic fine structures. Our analysis reveals the prevalence of transverse waves in SCFs with median amplitudes and periods on the order of 2.4 ± 0.8 km s{sup −1} and 83 ± 29 s, respectively (with standard deviations given as uncertainties). We find that the transverse waves often propagate along (parts of) the SCFs with median phase speeds of 9 ± 14 km s{sup −1}. While the propagation is only in one direction along the axis in some of the SCFs, propagating waves in both directions, as well as standing waves are also observed. The transverse oscillations are likely Alfvénic and are thought to be representative of magnetohydrodynamic kink waves. The wave propagation suggests that the rapid high-frequency transverse waves, often produced in the lower photosphere,more » can penetrate into the chromosphere with an estimated energy flux of ≈15 kW m{sup −2}. Characteristics of these waves differ from those reported for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere.« less

Authors:
 [1]; ; ; ; ; ; ; ;  [2];  [3]; ;  [4];  [5];  [6]
  1. Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway)
  2. Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)
  3. Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain)
  4. Instituto de Astrofísica de Andalucía (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain)
  5. High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)
  6. Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany)
Publication Date:
OSTI Identifier:
22661236
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 229; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; AMPLITUDES; BALLOONS; CALCIUM IONS; CHROMOSPHERE; FINE STRUCTURE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; OSCILLATIONS; PHOTOSPHERE; RESOLUTION; SPECTROSCOPY; STANDING WAVES; SUN; VELOCITY; WAVE PROPAGATION

Citation Formats

Jafarzadeh, S., Solanki, S. K., Gafeira, R., Noort, M. van, Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., Riethmüller, T. L., Rodríguez, J. Blanco, Iniesta, J. C. del Toro, Suárez, D. Orozco, Knölker, M., and Schmidt, W., E-mail: shahin.jafarzadeh@astro.uio.no. Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI. United States: N. p., 2017. Web. doi:10.3847/1538-4365/229/1/9.
Jafarzadeh, S., Solanki, S. K., Gafeira, R., Noort, M. van, Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., Riethmüller, T. L., Rodríguez, J. Blanco, Iniesta, J. C. del Toro, Suárez, D. Orozco, Knölker, M., & Schmidt, W., E-mail: shahin.jafarzadeh@astro.uio.no. Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI. United States. doi:10.3847/1538-4365/229/1/9.
Jafarzadeh, S., Solanki, S. K., Gafeira, R., Noort, M. van, Barthol, P., Gandorfer, A., Gizon, L., Hirzberger, J., Riethmüller, T. L., Rodríguez, J. Blanco, Iniesta, J. C. del Toro, Suárez, D. Orozco, Knölker, M., and Schmidt, W., E-mail: shahin.jafarzadeh@astro.uio.no. Wed . "Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI". United States. doi:10.3847/1538-4365/229/1/9.
@article{osti_22661236,
title = {Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI},
author = {Jafarzadeh, S. and Solanki, S. K. and Gafeira, R. and Noort, M. van and Barthol, P. and Gandorfer, A. and Gizon, L. and Hirzberger, J. and Riethmüller, T. L. and Rodríguez, J. Blanco and Iniesta, J. C. del Toro and Suárez, D. Orozco and Knölker, M. and Schmidt, W., E-mail: shahin.jafarzadeh@astro.uio.no},
abstractNote = {We present observations of transverse oscillations in slender Ca ii H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high- (spatial and temporal-) resolution seeing-free observations in a 1.1 Å wide passband covering the line core of Ca ii H 3969 Å from the second flight of the Sunrise balloon-borne solar observatory. The entire field of view, spanning the polarity inversion line of an active region close to the solar disk center, is covered with bright, thin, and very dynamic fine structures. Our analysis reveals the prevalence of transverse waves in SCFs with median amplitudes and periods on the order of 2.4 ± 0.8 km s{sup −1} and 83 ± 29 s, respectively (with standard deviations given as uncertainties). We find that the transverse waves often propagate along (parts of) the SCFs with median phase speeds of 9 ± 14 km s{sup −1}. While the propagation is only in one direction along the axis in some of the SCFs, propagating waves in both directions, as well as standing waves are also observed. The transverse oscillations are likely Alfvénic and are thought to be representative of magnetohydrodynamic kink waves. The wave propagation suggests that the rapid high-frequency transverse waves, often produced in the lower photosphere, can penetrate into the chromosphere with an estimated energy flux of ≈15 kW m{sup −2}. Characteristics of these waves differ from those reported for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere.},
doi = {10.3847/1538-4365/229/1/9},
journal = {Astrophysical Journal, Supplement Series},
number = 1,
volume = 229,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}
  • A dense forest of slender bright fibrils near a small solar active region is seen in high-quality narrowband Ca ii H images from the SuFI instrument onboard the Sunrise balloon-borne solar observatory. The orientation of these slender Ca ii H fibrils (SCF) overlaps with the magnetic field configuration in the low solar chromosphere derived by magnetostatic extrapolation of the photospheric field observed with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are qualitatively aligned with small-scale loops computed from a novel inversion approach based on best-fit numerical MHD simulation. Such loops are organized in canopy-like arches over quiet areas thatmore » differ in height depending on the field strength near their roots.« less
  • We present a comparison of high-resolution images of the solar surface taken in the Mg II k and Ca II H channels of the Filter Imager on the balloon-borne solar observatory SUNRISE. The Mg and Ca lines are sampled with 0.48 nm and 0.11 nm wide filters, respectively. The two channels show remarkable qualitative and quantitative similarities in the quiet Sun, in an active region plage and during a small flare. However, the Mg filtergrams display 1.4-1.7 times higher intensity contrast and appear more smeared and smoothed in the quiet Sun. In addition, the fibrils in a plage are wider.more » Although the exposure time is 100 times longer for Mg images, the evidence suggests that these differences cannot be explained only with instrumental effects or the evolution of the solar scene. The differences at least partially arise because of different line-formation heights, the stronger response of Mg k emission peaks to the higher temperatures, and the larger height range sampled by the broad Mg filter used here. This is evidently manifested during the flare when a surge in Mg evolves differently than in Ca.« less
  • Magneto-static models may overcome some of the issues facing force-free magnetic field extrapolations. So far they have seen limited use and have faced problems when applied to quiet-Sun data. Here we present a first application to an active region. We use solar vector magnetic field measurements gathered by the IMaX polarimeter during the flight of the Sunrise balloon-borne solar observatory in 2013 June as boundary conditions for a magneto-static model of the higher solar atmosphere above an active region. The IMaX data are embedded in active region vector magnetograms observed with SDO /HMI. This work continues our magneto-static extrapolation approach,more » which was applied earlier to a quiet-Sun region observed with Sunrise I. In an active region the signal-to-noise-ratio in the measured Stokes parameters is considerably higher than in the quiet-Sun and consequently the IMaX measurements of the horizontal photospheric magnetic field allow us to specify the free parameters of the model in a special class of linear magneto-static equilibria. The high spatial resolution of IMaX (110–130 km, pixel size 40 km) enables us to model the non-force-free layer between the photosphere and the mid-chromosphere vertically by about 50 grid points. In our approach we can incorporate some aspects of the mixed beta layer of photosphere and chromosphere, e.g., taking a finite Lorentz force into account, which was not possible with lower-resolution photospheric measurements in the past. The linear model does not, however, permit us to model intrinsic nonlinear structures like strongly localized electric currents.« less
  • We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations of both horizontal displacement and intensity in magnetic bright points found in the 300 nm and the Ca ii H 396.8 nm passbands of the filter imager on board the Sunrise balloon-borne solar observatory. Phase differences between the oscillations at the two atmospheric layers corresponding to the two passbands reveal upward propagating waves at high frequencies (up to 30 mHz). Weak signatures of standing as well as downward propagating waves are alsomore » obtained. Both compressible and incompressible (kink) waves are found in the small-scale magnetic features. The two types of waves have different, though overlapping, period distributions. Two independent estimates give a height difference of approximately 450 ± 100 km between the two atmospheric layers sampled by the employed spectral bands. This value, together with the determined short travel times of the transverse and longitudinal waves provide us with phase speeds of 29 ± 2 km s{sup −1} and 31 ± 2 km s{sup −1}, respectively. We speculate that these phase speeds may not reflect the true propagation speeds of the waves. Thus, effects such as the refraction of fast longitudinal waves may contribute to an overestimate of the phase speed.« less
  • We present the first observations of the transverse component of a photospheric magnetic field acquired by the imaging magnetograph SUNRISE/IMaX. Using an automated detection method, we obtain statistical properties of 4536 features with significant linear polarization signal. We obtain a rate of occurrence of 7 x 10{sup -4} s{sup -1} arcsec{sup -2}, which is 1-2 orders of magnitude larger than the values reported by previous studies. We show that these features have no characteristic size or lifetime. They appear preferentially at granule boundaries with most of them being caught in downflow lanes at some point. Only a small percentage aremore » entirely and constantly embedded in upflows (16%) or downflows (8%).« less