Hana Druckmüllerová

THERMODYNAMICS OF THE SOLAR CORONA AND EVOLUTION OF THE SOLAR MAGNETIC FIELD AS INFERRED FROM THE TOTAL SOLAR ECLIPSE OBSERVATIONS OF 2010 JULY 11

We report on the first multi-wavelength coronal observations, taken simultaneously in white light, Hα 656.3 nm, Feix 435.9 nm, Fex 637.4 nm, Fexi 789.2 nm, Fexiii 1074.7 nm, Fexiv 530.3 nm, and Nixv 670.2 nm, during the total solar eclipse of 2010 July 11 from the atoll of Tatakoto in French Polynesia. The data enabled temperature differentiations as low as 0.2 × 10 6 K. The first-ever images of the corona in Feix and Nixv showed that there was very little plasma below 5 × 10 5 K and above 2.5 × 10 6 K. The suite of multi-wavelength observations also showed that open field lines have an electron temperature near 1×10 6 K, while the hottest, 2×10 6 K, plasma resides in intricate loops forming the bulges of streamers, also known as cavities, as discovered in our previous eclipse observations. The eclipse images also revealed unusual coronal structures, in the form of ripples and streaks, produced by the passage of coronal mass ejections and eruptive prominences prior to totality, which could be identified with distinct temperatures for the first time. These trails were most prominent at 10 6 K. Simultaneous Fex 17.4 nm observations from Proba2/SWAP provided the first opportunity to compare Fex emission at 637.4 nm with its extreme-ultraviolet (EUV) counterpart. This comparison demonstrated the unique diagnostic capabilities of the coronal forbidden lines for exploring the evolution of the coronal magnetic field and the thermodynamics of the coronal plasma, in comparison with their EUV counterparts in the distance range of 1–3 R� . These diagnostics are currently missing from present space-borne and ground-based observatories.

Polar Plume Brightening During the 2006 March 29 Total Eclipse

We discuss a remarkable brightening in a polar plume, as inferred from unique coordinated observations of the white-light corona during the total eclipse of the Sun of 2006 March 29. The polar plume (also known as a polar ray, with distinctions that we discuss) was observed at the positional angle of 9°; the velocity at which the brightening propagated was about 65 km s−1, which is close to the values derived by modeling of mass/energy transfer in polar plumes/rays as well as to those acquired from images from the Extreme-ultraviolet Imaging Telescope on the European Space Agency/NASA Solar and Heliospheric Observatory (SOHO/EIT). Comparing our data with those from the SOHO/LASCO C2 coronagraph, we estimate the lifetime of the polar ray to be less than 24 hr.

STRUCTURE AND DYNAMICS OF THE 2010 JULY 11 ECLIPSE WHITE-LIGHT CORONA

The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moons shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83?minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loops and radial-oriented thin streamers, a coronal mass ejection, and a puzzling curtain-like object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASAs Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASAs Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESAs PRoject for Onboard Autonomy, and the Naval Research Laboratorys Large Angle and Spectrometric Coronagraph on ESAs Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 R ?, for this rising phase of the solar-activity cycle.

Automatic identification and validation of planar collagen organization in the aorta wall with application to abdominal aortic aneurysm.

Arterial physiology relies on a delicate three-dimensional (3D) organization of cells and extracellular matrix, which is remarkably altered by vascular diseases like abdominal aortic aneurysms (AAA). The ability to explore the micro-histology of the aorta wall is important in the study of vascular pathologies and in the development of vascular constitutive models, i.e., mathematical descriptions of biomechanical properties of the wall. The present study reports and validates a fast image processing sequence capable of quantifying collagen fiber organization from histological stains. Powering and re-normalizing the histogram of the classical fast Fourier transformation (FFT) is a key step in the proposed analysis sequence. This modification introduces a powering parameter w, which was calibrated to best fit the reference data obtained using classical FFT and polarized light microscopy (PLM) of stained histological slices of AAA wall samples. The values of w = 3 and 7 give the best correlation (Pearsons correlation coefficient larger than 0.7, R 2 about 0.7) with the classical FFT approach and PLM measurements. A fast and operator independent method to identify collagen organization in the arterial wall was developed and validated. This overcomes severe limitations of currently applied methods like PLM to identify collagen organization in the arterial wall.

STRUCTURE AND DYNAMICS OF THE 2009 JULY 22 ECLIPSE WHITE-LIGHT CORONA

The white-light corona (WLC) during the total solar eclipse of 2009 July 22 was observed by several teams in the Moons shadow stretching from India and China across the Pacific Ocean with its many isolated islands. We present a comparison of the WLC as observed by eclipse teams located in China (Shanghai region) and on the Enewetak Atoll in the Marshall Islands, with observations taken 112 minutes apart, combined with near-simultaneous space observations. The eclipse was observed at the beginning of solar cycle 24, during a deep solar minimum (officially estimated as 2008 December according to the smoothed sunspot number, but very extended). The solar corona shows several different types of features (coronal holes, polar rays, helmet streamers, faint loops, voids, etc.), though it was extremely sparse in streamers as shown from Large-Angle Spectroscopic Coronagraph data. No large-scale dynamical phenomena were seen when comparing the observations from the two sites, confirming that the corona was quiescent. We measure a Ludendorff flattening coefficient of 0.238, typical of solar minimum.

ENHANCING CORONAL STRUCTURES WITH THE FOURIER NORMALIZING-RADIAL-GRADED FILTER

Images of the corona have a high dynamic range which is excellent for quantitative photometric analysis. To understand the processes governing the solar corona, it is essential to have information about the absolute brightness as well as the underlying structure. However, due to the steep radial gradient of brightness in the images, and to the fact that structures closer to the solar disk have higher contrast than structures further from the disk, human vision cannot view the intricate structure of the corona in such images. The recently developed normalizing-radial-graded filter (NRGF) is an effective way for revealing the coronal structure. In this work, we present a more adaptive filter inspired by the NRGF, which we call the Fourier normalizing-radial-graded filter (FNRGF). It approximates the local average and the local standard deviation by a finite Fourier series. This method enables the enhancement of finer details, especially in regions of lower contrast. We also show how the influence of additive noise is reduced by a modification to the FNRGF. To illustrate the power of the method, the FNRGF is applied to images of emission from coronal forbidden lines observed during the 2010 July 11 total solar eclipse. It is also successfully applied to space-based observations of the low corona in the extreme ultraviolet and to white light coronagraph observations, thus demonstrating the validity of the FNRGF as a new tool that will help the interpretation of the information embedded in most types of coronal images.

Registration of Partially Focused Images for 2D and 3D Reconstruction of Oversized Samples

Methods of fracture surface 3D reconstruction from a series of partially focused images acquired in a small field of view (e.g., by confocal microscope or CCD camera) are well known. In this case, projection rays can be considered parallel and recorded images do not differ in any geometrical transformation from each other. In the case of larger samples (oversized for microscope or CCD camera), it is necessary to use a wider viewing field (e.g., standard cameras); taken images primarily differ in scaling but may also differ in shifting and rotation. These images cannot be used for reconstruction directly; they must be registered; that is, we must determine all transformations in which the images differ and eliminate their effects. There are several ways to do this. This paper deals with the registration based on phase correlation.

Application of image analysis method to detection and counting of glass fibers from filter samples

ABSTRACT Man-made vitreous fibers (MMVFs) are noncrystalline substances made of glass, rock or slag and are widely used as thermal or acoustic insulation materials. There is continued concern about their potential health impacts and thus, their dosimetry and behavior in the environment still require study using filters to collect fiber samples. After deposition or exposure measurements of MMVFs it is often necessary to analyze the filters with deposited fibers. This task is tedious, time-consuming, and requires skill. Therefore, many researchers have tried to simplify or automatize fiber detection and quantification. This article describes features of our in-house software, which automatically detects and counts fibers in images of filter samples. The image analysis is based on the use of a histogram equalization and an adaptive radial convolution filter that enhances fiber contrast and thus, improves the fiber identification. The accuracy of the software analysis was verified by comparison with manual counting using ordinary phase-contrast microscopy method. The correlation between the methods was very high (coefficient of determination was 0.977). However, there were some discrepancies caused by false identifications, which led to implementation of manual corrective functions. Copyright

SOLAR ECLIPSE IMAGES AND THE SOLAR WIND

Over the past decade, diverse observations of the Sun, corona, and heliosphere during solar minimum have repeatedly shown that the solar wind expands radially from the entire Sun. These results are, however, at odds with the conventional view of superradial expansion from polar coronal holes. The purpose of this Letter is to reconcile this conflict by taking a closer look at solar eclipse pictures on which the conventional view is based. The latter are referred to as processed solar eclipse pictures because they are obtained with a radially graded density filter or by the merging of images taken at different exposures and subsequent numerical image processing. We illustrate the importance of quantitative studies in understanding imaging by comparing numerically processed images and isophotes from the 2006 solar eclipse. Familiar large-scale structures traditionally interpreted in terms of density as diverging polar coronal holes and converging coronal streamers are in fact features of differenced density. This mistaking of differenced density for density when interpreting processed pictures misguided our notions of solar wind expansion, and hindered progress in connecting observations between the Sun and solar wind for three decades.

A Numerical Method for the Visualization of the Fe XIV Emission in the Solar Corona Using Broadband Filters

The goal of this article is to demonstrate how the emission from the Fe XIV?530.3?nm coronal emission line, also known as the green line, can be extracted from images taken during total solar eclipses with commercially available color cameras. This concept is technically feasible because Fe XIV is the brightest optical emission line in the inner corona, and because the sensors of these cameras are retrofitted with a standard Bayer mask, namely, a square grid of spectrally broad (about 100?nm) green, blue, and red filters in the ratio of 2:1:1. The technique presented here, and developed for this purpose, yields qualitatively accurate Fe XIV images, as tested by comparing with Fe XIV eclipse images taken with a 0.15?nm narrow-bandpass filter. While this approach cannot replace narrow-bandpass Fe XIV images for quantitative studies of the corona, it provides a simple and affordable tool for studying the morphology of coronal structures emitting preferentially at the peak ionization temperature of Fe XIV, namely, 1.8 ? 106?K.