Photosphere
Presiding: T Berger, Lockheed Martin Solar and Astrophysics Laboratory; M Lopez-Fuentes, Naval Research Lab
SP31A-01 08:30h
Do Dark Faculae Exist?
High-resolution images in visible light and the near infrared (NIR) continuum around 1560~nm were obtained in solar active region NOAA~10707 with the Dunn Solar Telescope (DST) at the National Solar Observatory/Sacramento Peak (NSO/SP) on 2004 December~2 and 7. A spatial resolution close to the diffraction limit of the 76~cm DST was achieved with high-order adaptive optics system. The observation were made with a near infrared tunable Lyot filter system newly developed by Big Bear Solar Observatory (BBSO). The filter has a bandpass of 2.5~Å. This allows us to observe the pure NIR continuum that represents the opacity minimum. Our data show that the contrast of faculae has the same sign in the visible and the NIR continua. There is no evidence for the existence of so-called "dark faculae", faculae that have negative contrasts in the NIR and positive contrasts in visible light. We conclude that the previously observed "dark faculae" are unresolved pores. This work is supported by NSF under grants ATM-0313591, ATM-0236945, ATM-0233931 and AST-0307676, by NASA under grants NAG5-10910, NAG5-10212 and NAG5-12733, and by Air Force under grant F49620-02-1-0265 and by NSFC-10103004.
SP31A-02 08:45h
High resolution magnetogram measurements of solar faculae
We present new images of magnetic elements near the solar limb ("faculae") along with magnetogram measurements and contrast profiles. Imaging magnetogram observations were made of AR 10377 at Μ = cosθ = 0.6 on 06-June-2003 using the Swedish 1-m Solar Telescope; the data are the highest spatial resolution magnetogram measurements of faculae to date. Contrary to previous lower resolution measurements, we find no correlation between facular contrast and magnetic flux density at a given disk position. Increasing magnetic flux density in a region implies an increasing prevalence of micropores. Previous observations which lacked sufficient spatial resolution to discern dark micropore "floors" from bright facular walls find a strong non-linear dependence of facular contrast on magnetic flux density, with decreasing contrast beyond a certain flux density. We show instead that the observed contrast of bright facular walls is independent of magnetic flux density when properly segmented from dark micropores. The observations are useful for examining the detailed structure of faculae including the dark lanes found on the disk-center side of many faculae (explained by several recent 3D MHD numerical simulations). The average radial profile for 678 faculae segmented from the dataset is very nearly gaussian with a FWHM radial extent of 265 km and an extended tail on the limbward side, as predicted by current MHD simulations.
SP31A-03 09:00h
Narrow-band Near Infrared Filtergram Observation of Light Bridges and Umbral Dots
We are presenting the observations of the active region NOAA 10709 on December, 2004 using 0.12Å~narrow band filter centered around 1.56Μm. The observation run was carried out using Dunn Tower Telescope of NSO (SacPeak) with high-order AO system. The averaged angular resolution of this observation is 0.5" or better. These high resolution data in near infrared offer a new view on the photospheric structures of sunspot near opacity minimum. By using the tunable near infrared narrow band filtergram, we are able to construct magnetic field strength map of sunspot. In particular, we will show the magnetic structure of light bridges and umbral dots.
SP31A-04 09:15h
Unified Mechanism for the Formation of Moving Magnetic Features
In the highly dynamic environment around sunspots there are small scale magnetic features, MMF's, that show clear regularities and may be thus categorized according their observed properties. For now there are at least 4 types of "MMF's" (Moving Magnetic Features). Type I MMF's are compact pairs of opposite polarity elements that may emerge anywhere in penumbra or moat region and move radially outward gradually separating; their velocities exceed the velocities of ambient flows, and their inner " foot" shares the sunspot's polarity. Type II MMF's are seen as unipolar features of the same polarity as the sunspot, moving outward from the sunspot with higher velocities than type I. Type III MMF's are also seen as unipolar features but have the polarity opposite to the sunspot's and travel with higher velocities than the other two types of MMF's. Recently the "type IV" features were observed in a sunspot formation region, that appear as compact bipoles flowing into sunspots and with an inner foot of a polarity opposite to the sunspot's. These were dubbed the MDF's (Moving Dipolar Features). The observed properties of all types of MMF's clearly violate the energy and momentum conservation laws, and thus require the application of physical mechanisms adequate for energetically open systems. Such mechanisms have been applied to type I and type II MMF's (Ryutova, Shine, Title, and Sakai, 1998, ApJ, 492, 402) with a good agreement between the theory and observations. Here we show that the same approach not only explains the origin, structure and dynamics of MDF's and type III MMF's, but consolidates all types of MMF's into one scheme. Theoretical results are compared with the observed properties of MMF's using time series of several data sets.
SP31A-05 09:30h
The Accurate and Precise Estimation of Velocities and Associated Uncertainties From Magnetograms
A statistically robust technique for determining motion perpendicular to the line of sight from a sequence of solar magnetograms is required for understanding the physics of active regions and related phenomena. However, Local Correlation Tracking (LCT), the de-facto standard for estimating motion in solar image sequences, is inconsistent with the magnetic induction equation and mathematically inappropriate for tracking magnetic elements. A new technique is presented that incorporates the magnetic induction equation directly into the analysis. This method represents a generalization of established wavelet interferometric techniques, developed for the analysis of turbulence in space-craft data, to the multi-point data represented by magnetograms. Work Supported by ONR.
SP31A-06 09:45h
Automated Detection and Identification of Solar Filaments and Sunspots
We developed a procedure for the automatic detection and identification of filaments and their disappearance. Full-disk Hα images from the Big Bear Solar Observatory (BBSO) in California are used as the data set for our procedure. Solar images are randomly selected starting from January 1, 1999 to September 1, 2004. We present an automatic solar filament detection procedure using advanced image enhancement, segmentation, pattern recognition and mathematical morphology. This procedure not only provides the detection results of filaments, but also identifies the spines, footpoints and disappearances of filaments. Low contrast filaments are emphasize and sharpen by the stabilized inverse diffusion equation (SIDE) which was introduced by Pollak et al. (2000). Adaptive image segmentation techniques are used for selecting the threshold based on the edge and local information. To distinguish sunspot from filaments, an efficient feature-based classifier, the Support Vector Machine (SVM), is utilized. Detail filament identification is achieved by morphological thinning, pruning and adaptive edge linking methods. Finally, the filament disappearances are detected by comparing the spine and footpoints of the filaments on two consecutive days. Comparing to Gao et al. (2002) and Shih and Kowalski (2003), our procedure utilizes the image enhancement techniques to enhance the low contrast filaments, and apply advanced pattern recognition and morphology techniques to identify filament and sunspots. Our work has shown the better and more complete results than other work on the automatic filament detection.