White-light Observations Research Articles

Prominence Activity during the 2006 Total Solar Eclipse

During total solar eclipses, we can observe the outer atmospheric layers of the sun (chromosphere and corona). The solar corona extends to several solar radii depending on the sunspot cycle. Basic coronal structures such as polar streamers, helmet type structures were observed during the 2006 total solar eclipse. Our total solar eclipse 2006 observations through both White light corona and H-Alpha filter allowed us to describe coronal structures and Prominence Activity. We found that the solar corona is extended to 4 times of solar radii, the existence different zones of white light corona were shown, moreover, we compared the defined features of solar corona at different observing locations along the track of total solar eclipse 2006. The solar limb activity was studied during both of partial and total eclipse phases by using H-Alpha and white light observations from Salloum, Egypt. We got same prominence activity during partial and total phases of the solar eclipse and recorded three prominences on solar limb. Finally, our processed image in a good agreement with the published processed images was observed from different locations along the track of total eclipse, added, similar magnetic field structure shown in our processed image and published one.

A Sun-to-Earth Analysis of Magnetic Helicity of the 2013 March 17–18 Interplanetary Coronal Mass Ejection

Abstract We compare the magnetic helicity in the 2013 March 17–18 interplanetary coronal mass ejection (ICME) flux rope at 1 au and in its solar counterpart. The progenitor coronal mass ejection (CME) erupted on 2013 March 15 from NOAA active region 11692 and is associated with an M1.1 flare. We derive the source region reconnection flux using the post-eruption arcade (PEA) method that uses the photospheric magnetogram and the area under the PEA. The geometrical properties of the near-Sun flux rope is obtained by forward-modeling of white-light CME observations. Combining the geometrical properties and the reconnection flux, we extract the magnetic properties of the CME flux rope. We derive the magnetic helicity of the flux rope using its magnetic and geometric properties obtained near the Sun and at 1 au. We use a constant-α force-free cylindrical flux rope model fit to the in situ observations in order to derive the magnetic and geometric information of the 1 au ICME. We find a good correspondence in both amplitude and sign of the helicity between the ICME and the CME, assuming a semi-circular (half torus) ICME flux rope with a length of π au. We find that about 83% of the total flux rope helicity at 1 au is injected by the magnetic reconnection in the low corona. We discuss the effect of assuming flux rope length in the derived value of the magnetic helicity. This study connecting the helicity of magnetic flux ropes through the Sun–Earth system has important implications for the origin of helicity in the interplanetary medium and the topology of ICME flux ropes at 1 au and hence their space weather consequences.

Tethered Prominence-CME Systems Captured during the 2012 November 13 and 2013 November 3 Total Solar Eclipses

Abstract We report on white light observations of high latitude tethered prominences acquired during the total solar eclipses of 2012 November 13 and 2013 November 3, at solar maximum, with a field of view spanning several solar radii. Distinguished by their pinkish hue, characteristic of emission from neutral hydrogen and helium, the four tethered prominences were akin to twisted flux ropes, stretching out to the limit of the field of view, while remaining anchored at the Sun. Cotemporal observations in the extreme ultraviolet from the Solar Dynamics Observatory (SDO/AIA) clearly showed that the pinkish emission from the cool ( K) filamentary prominences was cospatial with the 30.4 nm He II emission, and was directly linked to filamentary structures emitting at coronal temperatures K in 17.1 and 19.3 nm. The tethered prominences evolved from typical tornado types. Each one formed the core of different types of coronal mass ejections (CMEs), as inferred from coordinated LASCO C2, C3, and STEREO A and B coronagraph observations. Two of them evolved into a series of faint, unstructured puffs. One was a normal CME. The most striking one was a “light-bulb” type CME, whose three-dimensional structure was confirmed from all four coronagraphs. These first uninterrupted detections of prominence-CME systems anchored at the Sun, and stretching out to at least the edge of the field of view of LASCO C3, provide the first observational confirmation for the source of counter-streaming electron fluxes measured in interplanetary CMEs, or ICMEs.

Two Practical Methods for Coronal Intensity Determination

Determining the relative brightness of the solar corona is one of the most critical stages in solar eclipse studies. For this purpose, images taken with different exposures and polarization angles in white-light observations are used. The composite image of each polarization angle is produced by combining the images of different exposures. With the help of the intensity calibration function of these images, the relative intensity of the corona can be calculated. The total brightness of the solar corona is calculated using Stokes parameters obtained from intensity values of three polarization angles. In this study, two methods are presented: the first is used to obtain the intensity calibration function of the photographic material using calibration images, and the second is used to calculate the combined intensity values of images taken with different polarization angles.

Addendum to: Strength of the Solar Coronal Magnetic Field – A Comparison of Independent Estimates Using Contemporaneous Radio and White-Light Observations

Addendum to: Strength of the Solar Coronal Magnetic Field – A Comparison of Independent Estimates Using Contemporaneous Radio and White-Light Observations

Strength of the Solar Coronal Magnetic Field – A Comparison of Independent Estimates Using Contemporaneous Radio and White-Light Observations

We estimated the coronal magnetic field strength ($B$) during the 23 July 2016 coronal mass ejection (CME) event using i) the flux rope structure of the CME in the whitelight coronagraph images and ii) the band splitting in the associated type {\sc II} burst. No models were assumed for the coronal electron density ($N(r)$) used in the estimation.The results obtained using the above two independent methods correspond to different heliocentric distances ($r$) in the range $\approx$\,2.5\,--\,4.5$\rm R_{\odot}$, but they show excellent consistency and could be fitted with a single power-law distribution of the type $B(r)=5.7r^{-2.6}$ \textrm{G}, which is applicable in the aforementioned distance range. The power law index i.e. $-2.6$) is in good agreement with the results obtained in previous studies by different methods.

On the Link between the Release of Solar Energetic Particles Measured at Widespread Heliolongitudes and the Properties of the Associated Coronal Shocks

Abstract Under the paradigm that the main agents in the acceleration of solar energetic particles (SEPs) are shocks initially driven by coronal mass ejections, we analyze whether the properties of the shocks in the corona inferred from combining extreme-ultraviolet (EUV) and white-light (WL) observations from multiple vantage points together with magnetohydrodynamic (MHD) simulations of the corona can be used to determine the release of SEPs into different regions of the heliosphere and hence determine the longitudinal extent of the SEP events. We analyze the SEP events observed on 2011 November 3, 2013 April 11, and 2014 February 25 over a wide range of heliolongitudes. MHD simulations provide the characteristics of the background medium where shocks propagate, in particular the Alfvén and sound speed profiles that allow us to determine both the extent of the EUV waves in the low corona and the fast magnetosonic Mach number (M FM) of the shocks. The extent of the EUV waves in the low corona is controlled by this background medium and does not coincide with the extent of the SEP events in the heliosphere. Within the uncertainties of (i) the extent and speed of the shock inferred from EUV and WL images and (ii) the assumptions made in the MHD models, we follow the evolution of M FM at the region of the shock magnetically connected to each spacecraft. The estimated release times of the first SEPs measured by each spacecraft does not coincide with the time when the M FM at this region exceeds a given threshold.

Near-infrared cholecystocholangiography with direct intragallbladder indocyanine green injection: preliminary clinical results.

Near-infrared (NIR) fluorescence cholangiography by systemic administration of indocyanine green (ICG) enhances the visualization of the biliary tree anatomy. However, the simultaneous enhancement of liver parenchyma can disturb the visualization of critical details. We herein proposed a new technique of NIR cholecystocholangiography by intragallbladder ICG injection to increase the safety during laparoscopic cholecystectomy. A total of 46 patients scheduled for laparoscopic cholecystectomy for symptomatic lithiasis (n=21) or cholecystitis (n=25) were enrolled. A fluorescence cholangiography by direct gallbladder injection of ICG was performed in all cases. Of them, the ICG was injected through a previously placed percutaneous transhepatic gallbladder drainage catheter (n=18) or by intraoperative, percutaneous needle puncture of the gallbladder (n=28). Visualization of biliary structures, including the cystic duct (CD), the common bile and hepatic ducts (CBD and CHD), the gallbladder neck, and the Hartmann's pouch (HP), was performed using White Light (served as control modality) and by NIR enhancement. Cholecystocholangiography provided a significantly higher rate of visualization of the CD in case of cholecystitis with mild adhesions, and an improved visualization of the HP, CBD, and CHD in case of severe inflammation, when compared to White Light observation. There were no benefits of NIR in case of non-inflamed lithiasis. Clinical translation of NIR cholecystocholangiography has been successful with a noise-free visualization of biliary anatomy. It can be considered in difficult cases to increase the safety of laparoscopic cholecystectomy.

Variation in Coronal Activity from Solar Cycle 24 Minimum to Maximum Using Three-Dimensional Reconstructions of the Coronal Electron Density from STEREO/COR1

Three dimensional electron density distributions in the solar corona are reconstructed for 100 Carrington Rotations (CR 2054$-$2153) during 2007/03$-$2014/08 using the spherically symmetric method from polarized white-light observations with the STEREO/COR1. These three-dimensional electron density distributions are validated by comparison with similar density models derived using other methods such as tomography and a MHD model as well as using data from SOHO/LASCO-C2. Uncertainties in the estimated total mass of the global corona are analyzed based on differences between the density distributions for COR1-A and -B. Long-term variations of coronal activity in terms of the global and hemispheric average electron densities (equivalent to the total coronal mass) reveal a hemispheric asymmetry during the rising phase of Solar Cycle 24, with the northern hemisphere leading the southern hemisphere by a phase shift of 7$-$9 months. Using 14-CR (~13-month) running averages, the amplitudes of the variation in average electron density between Cycle 24 maximum and Cycle 23/24 minimum (called the modulation factors) are found to be in the range of 1.6$-$4.3. These modulation factors are latitudinally dependent, being largest in polar regions and smallest in the equatorial region. These modulation factors also show a hemispheric asymmetry, being somewhat larger in the southern hemisphere. The wavelet analysis shows that the short-term quasi-periodic oscillations during the rising and maximum phases of Cycle 24 have a dominant period of 7$-$8 months. In addition, it is found that the radial distribution of mean electron density for streamers at Cycle 24 maximum is only slightly larger (by ~30%) than at cycle minimum.

Spatial Inhomogeneity in Solar Faculae

AbstractIn this paper, we investigate the inhomogeneous spatial distribution of solar faculae. The focus is on the latitudinal and longitudinal distributions of these highly localised features covering ubiquitously the solar surface. The statistical analysis is based on white light observations of the Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) between 1996 and 2014. We found that the fine structure of the latitudinal distribution of faculae displays a quasi-biennial oscillatory pattern. Furthermore, the longitudinal distribution of photospheric solar faculae does not show homogeneous behaviour either. In particular, the non-axisymmetric behaviour of these events show similar properties as that of the active longitude (AL) found in the distribution of sunspots. Our results, preliminary though, may provide a valuable observational constrain for developing the next-generation solar dynamo model.

Development and application of the near-infrared and white-light thoracoscope system for minimally invasive lung cancer surgery.

In minimally invasive surgery, the white-light thoracoscope as a standard imaging tool is facing challenges of the low contrast between important anatomical or pathological regions and surrounding tissues. Recently, the near-infrared (NIR) fluorescence imaging shows superior advantages over the conventional white-light observation, which inspires researchers to develop imaging systems to improve overall outcomes of endoscopic imaging. We developed an NIR and white-light dual-channel thoracoscope system, which achieved high-fluorescent signal acquisition efficiency and the simultaneously optimal visualization of the NIR and color dual-channel signals. The system was designed to have fast and accurate image registration and high signal-to-background ratio by optimizing both software algorithms and optical hardware components for better performance in the NIR spectrum band. The system evaluation demonstrated that the minimally detectable concentration of indocyanine green (ICG) was 0.01 ?? ? M , and the spatial resolution was 35 ?? ? m . The in vivo feasibility of our system was verified by the preclinical experiments using six porcine models with the intravenous injection of ICG. Furthermore, the system was successfully applied for guiding the minimally invasive segmentectomy in three lung cancer patients, which revealed that our system held great promise for the clinical translation in lung cancer surgeries.

VLA Measurements of Faraday Rotation through Coronal Mass Ejections

Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun that play an important role in space weather. Faraday rotation (FR) is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. FR observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made sensitive Very Large Array (VLA) full-polarization observations using 1 - 2 GHz frequencies of a "constellation" of radio sources through the solar corona at heliocentric distances that ranged from 6 - 15 solar radii. Of the nine sources observed, three were occulted by CMEs: two sources (0842+1835 and 0900+1832) were occulted by a single CME and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday rotation since Bird et al. (1985) and the first active hunt using the VLA, we obtained white-light coronagraph images from the LASCO/C3 instrument to determine the Thomson scattering brightness, BT, providing a means to independently estimate the plasma density and determine its contribution to the observed Faraday rotation. A constant density force-free flux rope embedded in the background corona was used to model the effects of the CMEs on BT and FR. We demonstrate this model's ability to successfully reproduce both BT and FR profiles. The plasma densities (6 - 22 x 10$^3$ cm$^{-3}$) and axial magnetic field strengths (2 - 12 mG) inferred from our models are consistent with the modeling work of Liu et al. (2007) and Jensen & Russell (2008), as well as previous CME FR observations by Bird et al. (1985).

Measure the Propagation of a Halo CME and Its Driven Shock with the Observations from a Single Perspective at Earth

Abstract We present a detailed study of an Earth-directed coronal mass ejection (full-halo CME) event that happened on 2011 February 15, making use of white-light observations by three coronagraphs and radio observations by Wind/WAVES. We applied three different methods to reconstruct the propagation direction and traveling distance of the CME and its driven shock. We measured the kinematics of the CME leading edge from white-light images observed by Solar Terrestrial Relations Observatory (STEREO) Aand B, tracked the CME-driven shock using the frequency drift observed by Wind/WAVES together with an interplanetary density model, and obtained the equivalent scattering centers of the CME by the polarization ratio (PR) method. For the first time, we applied the PR method to different features distinguished from LASCO/C2 polarimetric observations and calculated their projections onto white-light images observed by STEREO-A and STEREO-B. By combining the graduated cylindrical shell (GCS) forward modeling with the PR method, we proposed a new GCS-PR method to derive 3D parameters of a CME observed from a single perspective at Earth. Comparisons between different methods show a good degree of consistence in the derived 3D results.

LASCO White-Light Observations of Eruptive Current Sheets Trailing CMEs

Many models of eruptive flares or coronal mass ejections (CMEs) involve formation of a current sheet connecting the ejecting CME flux rope with a magnetic loop arcade. However, there is very limited observational information on the properties and evolution of these structures, hindering progress in understanding eruptive activity from the Sun. In white-light images, narrow coaxial rays trailing the outward-moving CME have been interpreted as current sheets. Here, we undertake the most comprehensive statistical study of CME-rays to date. We use SOHO/LASCO data, which have a higher cadence, larger field of view, and better sensitivity than any previous coronagraph. We compare our results to a previous study of Solar Maximum Mission (SMM) CMEs, in 1984 – 1989, having candidate magnetic disconnection features at the CME base, about half of which were followed by coaxial bright rays. We examine all LASCO CMEs during two periods of minimum and maximum activity in Solar Cycle 23, resulting in many more events, \(\sim130\) CME-rays, than during SMM. Important results include: The occurrence rate of the rays is \(\sim11~\%\) of all CMEs during solar minimum, but decreases to \(\sim7~\%\) at solar maximum; this is most likely related to the more complex coronal background. The rays appear on average 3 – 4 hours after the CME core, and are typically visible for three-fourths of a day. The mean observed current sheet length over the ray lifetime is \(\sim12~R_{\odot}\), with the longest current sheet of \(18.5~R_{\odot}\). The mean CS growth rates are \(188~\mbox{km}\,\mathrm{s}^{-1}\) at minimum and \(324~\mbox{km}\,\mathrm{s}^{-1}\) at maximum. Outward-moving blobs within several rays, which are indicative of reconnection outflows, have average velocities of \(\sim350~\mbox{km}\,\mathrm{s}^{-1}\) with small positive accelerations. A pre-existing streamer is blown out in most of the CME-ray events, but half of these are observed to reform within \(\sim1\) day. The long lifetime and long lengths of the CME-rays challenge our current understanding of the evolution of the magnetic field in the aftermath of CMEs.

SOURCE REGIONS OF THE TYPE II RADIO BURST OBSERVED DURING A CME–CME INTERACTION ON 2013 MAY 22

ABSTRACT We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction-finding analysis of the Wind/WAVES and STEREO/WAVES (SWAVES) radio observations at decameter–hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radio source, indicating that the spatial location of the dominant source of the type II emission varies during the CME–CME interaction. The WAVES source directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME–CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.

ON THE ABSENCE OF EUV EMISSION FROM COMET C/2012 S1 (ISON)

ABSTRACT When the sungrazing comet C/2012 S1 (ISON) made its perihelion passage within two solar radii of the Sun’s surface, it was expected to be a bright emitter at extreme ultraviolet (EUV) wavelengths. However, despite solar EUV telescopes repointing to track the orbit of the comet, no emission was detected. This “null result” is interesting in its own right, offering the possibility of placing limits on the size and composition of the nucleus. We explain the lack of detection by considering the properties of the comet and the solar atmosphere that determine the intensity of EUV emission from sungrazing comets. By comparing these properties with those of sungrazing comet C/2011 W3 (Lovejoy), which did emit in the EUV, we conclude that the primary factor resulting in non-detectable EUV emission from C/2012 S1 (ISON) was an insufficiently large nucleus. We conclude that the radius of C/2012 S1 (ISON) was at least a factor of four less than that of C/2011 W3 (Lovejoy). This is consistent with white-light observations in the days before perihelion that suggested the comet was dramatically reducing in size on approach.

Probabilistic Absolute Position Sensor Based on Objective Laser Speckles

This paper presents a vision-based probabilistic absolute position sensor, which is able to operate on spacious technical surfaces without the modification of the surface. Instead of using artificial surface markings, the surface structure itself is used to generate objective laser speckle patterns (OLSPs), which are observable on most technical surfaces. This allows the extraction of features on surfaces, which might be too smooth for image processing under white light observation. In addition, the uniqueness of the individually observed laser speckle patterns enables a determination of the absolute position even after a sudden power loss of the sensor system. Experiments confirm the applicability of such OLSPs within a feature-based probabilistic framework on a smooth stainless steel rod and compare the results to images taken under white light illumination. The proposed sensor system successfully recovers from unknown initial states and measures the position with a peak-to-peak error of 22.1 $\mu \text{m}$ and an rms error of 5.6 $\mu \text{m}$ over a measurement range of 100 mm.

Usefulness of diagnostic laparoscopy with 5-aminolevulinic acid (ALA)-mediated photodynamic diagnosis for the detection of peritoneal micrometastasis in advanced gastric cancer after chemotherapy.

Successful cases have shown that conversion surgery after chemotherapy improves the prognosis of advanced gastric cancer. However, it is necessary to carefully select patients who have no unresectable factors prior to surgery. We recently reported that diagnostic laparoscopy with photodynamic diagnosis using oral 5-aminolevulinic acid (ALA-PDD) is a promising tool for diagnosing early peritoneal metastasis in gastric cancer. We herein evaluated the usefulness of this technique for detecting peritoneal metastases of advanced gastric cancer after chemotherapy. Diagnostic laparoscopy using sequential white light (WL) and ALA-PDD observations was performed in 38 patients with advanced gastric cancer after chemotherapy. The sensitivity of ALA-PDD for detecting peritoneal disease was compared with that of WL. The relationship between the state of peritoneal metastasis assessed by ALA-PDD and a cytological examination of the peritoneal fluid was evaluated. Twelve of the 38 patients (32%) were diagnosed with peritoneal metastases by conventional laparoscopy. However, laparoscopy with ALA-PDD detected peritoneal metastases in 4 (11%) of the 26 remaining patients. Three of these 4 patients had negative cytological results from the evaluation of the peritoneal fluid. Diagnostic laparoscopy using ALA-PDD is a useful technique for detecting metastases and determining treatment strategies to select patients with advanced gastric cancer who have received chemotherapy.

Recent advances in photodynamic diagnosis of gastric cancer using 5-aminolevulinic acid.

Photodynamic diagnosis based on 5-aminolevulinic acid-induced protoporphyrin IX has been clinically applied in many fields based upon its evidenced efficacy and adequate safety. In order to establish a personalized medicine approach for treating gastric cancer patients, rapid intraoperative detection of malignant lesions has become important. Feasibility of photodynamic diagnosis using 5-aminolevulinic acid for gastric cancer patients has been investigated, especially for the detection of peritoneal dissemination and lymph node metastasis. This method enables intraoperative real-time fluorescence detection of peritoneal dissemination, exhibiting higher sensitivity than white light observation without histopathological examination. The method also enables detection of metastatic foci within excised lymph nodes, exhibiting a diagnostic accuracy comparable to that of a current molecular diagnostics technique. Although several complicating issues still need to be resolved, such as the effect of tissue autofluorescence and the insufficient depth penetration of excitation light, this simple and rapid method has the potential to become a useful diagnostic tool for gastric cancer, as well as urinary bladder cancer and glioma.

Electron density and temperature in the solar corona from multifrequency radio imaging

Context. The 2D images obtained through rotational aperture synthesis with the Nancay Radioheliograph are suitable for quantitative exploitation. First results are presented.Aims. We study the variations of the quiet corona in brightness and size during an 8-year period and derive electron density and temperature in the corona.Methods. Images at 6 frequencies between 150 and 450 MHz for 183 quiet days between 2004 and 2011 were used. Measurements of the brightness temperature T b beyond the limb allowed coronal density models to be derived in both EW and NS radial directions, with a weak dependence on the electron temperature. The total ranges in the heliocentric distance r are 1.15–1.60 R ⊙ (EW) and 1.0–1.4 R ⊙ (NS). The agreement between results from different frequencies, in the ranges of r where there is overlapping shows the robustness of the method. The electron temperature, in turn, can be derived from the comparison of the observed mean spectra on the disk with those predicted through transfer calculations from the density models derived from limb observations. Results. The widths of the brightness profiles that were averaged yearly have minima at cycle minimum (2008–2009). These minima are more pronounced for EW profiles than for NS ones. The derived yearly-averaged density models along equatorial and polar diameters are consistent with isothermal and hydrostatic models. They are characterized by their density value n 0 extrapolated down to the base of the corona and their scale-height temperature T H . Changes in n 0 and T H with solar cycle are given for equatorial and polar regions. The kinetic temperature T e of electrons in the corona (~0.62 MK) is found to be significantly less than T H (~1.5 MK). This implies an ion temperature T i ~ 2.2 MK.Conclusions. The yearly-averaged variations of these models are less than the dispersion between models derived from other techniques, such as white light and EUV observations, partly because these two techniques are not time-averaged, and they refer to particular days. The radio models are generally less dense, which is compatible with isothermal hydrostatic equilibrium in their range of heliocentric distances, and they show different behaviors with the solar cycle in the equatorial or polar radial directions. The electron kinetic temperature T e is substantially less than T H .