Coupling from the Photosphere to the Chromosphere and the Corona

Wedemeyer, Sven; Lagg, A.; Nordlund, Åke

doi:10.1007/s11214-008-9447-8

Cited by 103 publications

(74 citation statements)

References 119 publications

(126 reference statements)

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“…Simulations of small-scale magnetoconvection by, e.g., Stein & Nordlund (2006) show examples of granular-sized magnetic loops with similar behavior. They probably build up a sub-canopy of horizontal fields over granules (Wedemeyer-Böhm et al 2009). Surface dynamo simulations by Schüssler & Vögler (2008) and Steiner et al (2008) clearly show that this new component of the internetwork is a direct consequence of magnetic flux expulsion from the granular interior, not only to the intergranular lanes, but also to the upper photosphere.…”

Section: Discussionmentioning

confidence: 99%

Magnetic loop emergence within a granule

Gömöry

Beck

Balthasar

et al. 2010

A&A

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Aims. We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center.Methods. We combined IR spectropolarimetry of high angular resolution performed in two Fe i lines at 1565 nm with specklereconstructed G-band imaging. We determined the magnetic field parameters by a LTE inversion of the full Stokes vector using the SIR code, and followed their evolution in time. To interpret the observations, we created a geometrical model of a rising loop in 3D. The relevant parameters of the loop were matched to the observations where possible. We then synthesized spectra from the 3D model for a comparison to the observations. Results. We found signatures of magnetic flux emergence within a growing granule. In the early phases, a horizontal magnetic field with a distinct linear polarization signal dominated the emerging flux. Later on, two patches of opposite circular polarization signal appeared symmetrically on either side of the linear polarization patch, indicating a small loop-like structure. The mean magnetic flux density of this loop was roughly 450 G, with a total magnetic flux of around 3 × 10 17 Mx. During the ∼12 min episode of loop occurrence, the spatial extent of the loop increased from about 1 to 2 arcsec. The middle part of the appearing feature was blueshifted during its occurrence, supporting the scenario of an emerging loop. There is also clear evidence for the interaction of one loop footpoint with a preexisting magnetic structure of opposite polarity. The temporal evolution of the observed spectra is reproduced to first order by the spectra derived from the geometrical model. During the phase of clearest visibility of the loop in the observations, the observed and synthetic spectra match quantitatively. Conclusions. The observed event can be explained as a case of flux emergence in the shape of a small-scale loop. The fast disappearance of the loop at the end could possibly be due to magnetic reconnection.

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Section: Discussionmentioning

confidence: 99%

Magnetic loop emergence within a granule

Gömöry

Beck

Balthasar

et al. 2010

A&A

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“…Importantly, it should be thought of more as a temperature rather than a static height regime, with the temperatures increasing from the temperature minimum to ≈10 4 K (Stix 2002). Sketches indicating the rich variety of phenomena in the chromosphere and its complexity have been presented in reviews by Wedemeyer-Böhm et al (2009) andRutten (2012). Just as the small-scale dynamics of the photosphere are dominated by granular convection, those of the chromosphere are dominated by waves.…”

Section: Chromospherementioning

confidence: 99%

“…Consequently, the photospheric field must spread out with increasing height in the solar atmosphere. The magnetic field expands until it either turns over and returns Wedemeyer-Böhm et al 2009) to connect back to the photosphere or it meets the expanding field of the neighboring flux tubes. It then forms a "magnetic canopy", i.e., a base almost parallel to the solar surface and overlying a nearly field-free atmosphere (see Fig.…”

Section: Magnetic Canopymentioning

confidence: 99%

“…6). For a comprehensive review of the current picture of the magnetic coupling of the photosphere, chromosphere and transition region to the corona, we refer to Wedemeyer-Böhm et al (2009) and restrict ourselves to a brief summary here. Estimates for the merging height of photospheric flux tubes range from some 100 km for active region to ≈1 Mm for quiet-Sun magnetic fields (Spruit 1981;Giovanelli and Jones 1982;Roberts 1990).…”

Section: Magnetic Canopymentioning

confidence: 99%

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The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

182

125

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This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

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“…Full Table 6 and reduced data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/560/A69 corona as loops (Fossum & Carlsson 2005;Wedemeyer-Böhm et al 2009). …”

Section: Introductionmentioning

confidence: 99%

A multi-wavelength view of AB Doradus outer atmosphere

Lalitha

Fuhrmeister

Wolter

et al. 2013

A&A

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Aims. We study the chromosphere and corona of the ultra-fast rotator AB Dor A at high temporal and spectral resolution using simultaneous observations with XMM-Newton in the X-rays, VLT/UVES in the optical, and the ATCA in the radio. Our optical spectra have a resolving power of ∼50 000 with a time cadence of ∼1 min. Our observations continuously cover more than one rotational period and include both quiescent periods and three flaring events of different strengths. Methods. From the X-ray observations we investigated the variations in coronal temperature, emission measure, densities, and abundance. We interpreted our data in terms of a loop model. From the optical data we characterised the flaring chromospheric material using numerous emission lines that appear in the course of the flares. A detailed analysis of the line shapes and line centres allowed us to infer physical characteristics of the flaring chromosphere and to coarsely localise the flare event on the star. Results. We specifically used the optical high-cadence spectra to demonstrate that both turbulent and Stark broadening are present during the first ten minutes of the first flare. Also, in the first few minutes of this flare, we find short-lived (one to several minutes) emission subcomponents in the Hα and Ca ii K lines, which we interpret as flare-connected shocks owing to their high intrinsic velocities. Combining the space-based data with the results of our optical spectroscopy, we derive flare-filling factors. Finally, comparing X-ray, optical broadband, and line emission, we find a correlation for two of the three flaring events, while there is no clear correlation for one event. Also, we do not find any correlation of the radio data to any other observed data.

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Coupling from the Photosphere to the Chromosphere and the Corona

Cited by 103 publications

References 119 publications

Magnetic loop emergence within a granule

Magnetic loop emergence within a granule

The magnetic field in the solar atmosphere

A multi-wavelength view of AB Doradus outer atmosphere

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