Radiative properties of magnetic elements

Steiner, O.; Hauschildt, P. H.; Bruls, J. H. M. J.

doi:10.1051/0004-6361:20010540

Cited by 85 publications

(89 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is a well known effect, which leads to the appearance of bright points in molecular lines at the locations of magnetic flux concentrations (Steiner et al 2001;Schüssler et al 2003) and makes molecular lines a sensitive tool for mapping photospheric temperatures and magnetic fields (Berdyugina et al 2005). However, to our knowledge, it is the first time that molecular lines are directly linked to the enhancement of the irradiance variability.…”

Section: Discussionmentioning

confidence: 99%

The role of the Fraunhofer lines in solar brightness variability

Шапиро

Solanki

Krivova

et al. 2015

A&A

View full text Add to dashboard Cite

Context. The solar brightness varies on timescales from minutes to decades. A clear identification of the physical processes behind such variations is needed for developing and improving physics-based models of solar brightness variability and reconstructing solar brightness in the past. This is, in turn, important for better understanding the solar-terrestrial and solar-stellar connections. Aims. We estimate the relative contributions of the continuum, molecular, and atomic lines to the solar brightness variations on different timescales. Methods. Our approach is based on the assumption that variability of the solar brightness on timescales greater than a day is driven by the evolution of the solar surface magnetic field. We calculated the solar brightness variations employing the solar disc area coverage of magnetic features deduced from the MDI/SOHO observations. The brightness contrasts of magnetic features relative to the quiet Sun were calculated with a non-LTE radiative transfer code as functions of disc position and wavelength. By consecutive elimination of molecular and atomic lines from the radiative transfer calculations, we assessed the role of these lines in producing solar brightness variability. Results. We show that the variations in Fraunhofer lines define the amplitude of the solar brightness variability on timescales greater than a day and even the phase of the total solar irradiance variability over the 11-year cycle. We also demonstrate that molecular lines make substantial contribution to solar brightness variability on the 11-year activity cycle and centennial timescales. In particular, our model indicates that roughly a quarter of the total solar irradiance variability over the 11-year cycle originates in molecular lines. The maximum of the absolute spectral brightness variability on timescales greater than a day is associated with the CN violet system between 380 and 390 nm.

show abstract

Section: Discussionmentioning

confidence: 99%

The role of the Fraunhofer lines in solar brightness variability

Шапиро

Solanki

Krivova

et al. 2015

A&A

View full text Add to dashboard Cite

show abstract

“…This seems perhaps unlikely here since the G-band is formed deep in the photosphere (Rutten, 1999) at 140 km above t 500 = 1 (Steiner, Hauschildt, and Bruls, 2001) or as low as 60 km (Nordlund, Stein, and Asplund, 2009). This should lie below the magnetic canopy.…”

Section: Magnetic Suppression Of Oscillatory Powermentioning

confidence: 95%

Space – Time Distribution of G-band and Ca ii H-line Intensity Oscillations in Hinode/SOT – FG Observations

Lawrence

Cadavid

2009

Sol Phys

View full text Add to dashboard Cite

Abstract.We study the space-time distributions of intensity fluctuations in 2 -3 hour sequences of multispectral, high-resolution, high-cadence, broad-band filtergram images of the Sun made by the SOT-FG system aboard the Hinode spacecraft. In the frequency range 5.5 < f < 8.0 mHz both G-band and Ca II H-line oscillations are suppressed in the presence of magnetic fields, but the suppression disappears for f > 10 mHz.By looking at G-band frequencies above 10 mHz we find that the oscillatory power, both at these frequencies and at lower frequencies too, lies in a mesh pattern with cell scale 2 -3 Mm, clearly larger than normal granulation, and with correlation times on the order of hours. The mesh pattern lies in the dark lanes between stable cells found in time-integrated G-band intensity images. It also underlies part of the bright pattern in time-integrated H-line emission. This discovery may reflect dynamical constraints on the sizes of rising granular convection cells together with the turbulence created in strong intercellular downflows.2

show abstract

“…Away from disk centre, the inclination of the partially evacuated flux tube allows the hot wall of the adjacent granule to be observed. Observations in the G-band (4305 Å) are often used as a proxy for studying BPs as they appear brighter due to the reduced abundance of the CH molecule at higher temperatures (Steiner et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Dynamic properties of bright points in an active region

Keys

Mathioudakis

Jess

et al. 2014

A&A

View full text Add to dashboard Cite

Context. Bright points (BPs) are small-scale, magnetic features ubiquitous across the solar surface. Previously, we have observed and noted their properties for quiet Sun regions. Here, we determine the dynamic properties of BPs using simultaneous quiet Sun and active region data. Aims. The aim of this paper is to compare the properties of BPs in both active and quiet Sun regions and to determine any difference in the dynamics and general properties of BPs as a result of the varying magnetic activity within these two regions. Methods. High spatial and temporal resolution G-band observations of active region AR11372 were obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope. Three subfields of varying polarity and magnetic flux density were selected with the aid of magnetograms obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. Bright points within these subfields were subsequently tracked and analysed. Results. It is found that BPs within active regions display attenuated velocity distributions with an average horizontal velocity of ∼0.6 km s −1 , compared to the quiet region which had an average velocity of 0.9 km s −1 . Active region BPs are also ∼21% larger than quiet region BPs and have longer average lifetimes (∼132 s) than their quiet region counterparts (88 s). No preferential flow directions are observed within the active region subfields. The diffusion index (γ) is estimated at ∼1.2 for the three regions. Conclusions. We confirm that the dynamic properties of BPs arise predominately from convective motions. The presence of stronger field strengths within active regions is the likely reason behind the varying properties observed. We believe that larger amounts of magnetic flux will attenuate BP velocities by a combination of restricting motion within the intergranular lanes and by increasing the number of stagnation points produced by inhibited convection. Larger BPs are found in regions of higher magnetic flux density and we believe that lifetimes increase in active regions as the magnetic flux stabilises the BPs.

show abstract

Radiative properties of magnetic elements

Cited by 85 publications

References 14 publications

The role of the Fraunhofer lines in solar brightness variability

The role of the Fraunhofer lines in solar brightness variability

Space – Time Distribution of G-band and Ca ii H-line Intensity Oscillations in Hinode/SOT – FG Observations

Dynamic properties of bright points in an active region

Contact Info

Product

Resources

About