Search

It is known that δ-type sunspot groups have a high flare productivity and produce strong flares. In particular, βγδ type sunspots are the most active type of all. A βγδ active region NOAA 9957 with frequent flux cancellations but without any marked flare activity during its decay phase was studied in this work. Using SOHO/MDI Dopplergrams and magnetograms, we detected continuous prominent downflow motions of 1500 - 1700 m s for several hours on the magnetic neutral line in this region. In the downflow region, penumbral structures were observed to decay. We will interpret and discuss the phenomenon as a case of submergence of the magnetic flux. [ABSTRACT FROM AUTHOR]

Recent studies of NOAA active region 10953, by Okamoto et al. ( Astrophys. J. Lett. 673, 215, ; Astrophys. J. 697, 913, ), have interpreted photospheric observations of changing widths of the polarities and reversal of the horizontal magnetic field component as signatures of the emergence of a twisted flux tube within the active region and along its internal polarity inversion line (PIL). A filament is observed along the PIL and the active region is assumed to have an arcade structure. To investigate this scenario, MacTaggart and Hood ( Astrophys. J. Lett. 716, 219, ) constructed a dynamic flux emergence model of a twisted cylinder emerging into an overlying arcade. The photospheric signatures observed by Okamoto et al. (, ) are present in the model although their underlying physical mechanisms differ. The model also produces two additional signatures that can be verified by the observations. The first is an increase in the unsigned magnetic flux in the photosphere at either side of the PIL. The second is the behaviour of characteristic photospheric flow profiles associated with twisted flux tube emergence. We look for these two signatures in AR 10953 and find negative results for the emergence of a twisted flux tube along the PIL. Instead, we interpret the photospheric behaviour along the PIL to be indicative of photospheric magnetic cancellation driven by flows from the dominant sunspot. Although we argue against flux emergence within this particular region, the work demonstrates the important relationship between theory and observations for the successful discovery and interpretation of signatures of flux emergence. [ABSTRACT FROM AUTHOR]

A maximum a posteriori (MAP) technique is developed to identify solar features in cotemporal and cospatial images of line-of-sight magnetic flux, continuum intensity, and equivalent width observed with the NASA/National Solar Observatory (NSO) Spectromagnetograph (SPM). The technique facilitates human understanding of patterns in large data sets and enables systematic studies of feature characteristics for comparison with models and observations of long-term solar activity and variability. The method uses Bayes’ rule to compute the posterior probability of any feature segmentation of a trio of observed images from per-pixel, class-conditional probabilities derived from independently-segmented training images. Simulated annealing is used to find the most likely segmentation. New algorithms for computing class-conditional probabilities from three-dimensional Gaussian mixture models and interpolated histogram densities are described and compared. A new extension to the spatial smoothing in the Bayesian prior model is introduced, which can incorporate a spatial dependence such as center-to-limb variation. How the spatial scale of training segmentations affects the results is discussed, and a new method for statistical separation of quiet Sun and quiet network is presented. [ABSTRACT FROM AUTHOR]

Measurements of maximum magnetic flux, minimum intensity, and size are presented for 12 967 sunspot umbrae detected on the National Aeronautics and Space Administration/National Solar Observatory (NASA/NSO) spectromagnetograms between 1993 and 2004 to study umbral structure and strength during the solar cycle. The umbrae are selected using an automated thresholding technique. Measured umbral intensities are first corrected for center-to-limb intensity dependence. Log-normal fits to the observed size distribution confirm that the size-spectrum shape does not vary with time. The intensity – magnetic-flux relationship is found to be steady over the solar cycle. The dependence of umbral size on the magnetic flux and minimum intensity are also independent of the cycle phase and give linear and quadratic relations, respectively. While the large sample size does show a low-amplitude oscillation in the mean minimum intensity and maximum magnetic flux correlated with the solar cycle, this can be explained in terms of variations in the mean umbral size. These size variations, however, are small and do not substantiate a meaningful change in the size spectrum of the umbrae generated by the Sun. Thus, in contrast to previous reports, the observations suggest the equilibrium structure, as manifested by the invariant size-magnetic field relationship, as well as the mean size ( i.e., strength) of sunspot umbrae do not significantly depend on the solar-cycle phase. [ABSTRACT FROM AUTHOR]

A Neutron spin-echo (NSE) spectrometer of the next generation is under construction at the Spallation Neutron Source (SNS) in Oak Ridge, USA. A NSE spectrometer measures small velocity changes of the neutrons encoded by the neutrons spin clock at a sample while the Neutron spin precesses in large magnetic fields following Bloch's equation. This instrument will be the best of its class both with respect to resolution and dynamic range. In order to reach this ambitious goal, a large magnetic precision field integral before and after the sample is required which directly scales linearly with the resolution of the instrument. Therefore superconducting technology will be used to allow for a higher magnetic field integral. Here, we present the design, manufacturing and test performance of the solenoids which are the result of a collaboration between jülich Research Center (FZJ) and Babcock Noell GmbH (BNG). The solenoids generate an integrated magnetic flux density of 1.8 Tªm and use active shielding to reduce the fringe field. The operation temperature of about 4 K is reached by means of pulse-tube coolers in order to minimize vibrations. A special feature of this magnet system is the very accurate measurement of the cold mass-position after cool-down and during operation. The accuracy of this measurement system is in the order of micrometers. This information is required for the adjustment of so called Fresnel coils outside the cryostat. Using these correction elements, a field integral homogeneity better than 10-6 Tªm for different Neutron paths through one of the solenoids can be achieved. [ABSTRACT FROM AUTHOR]

Gas transmission pipelines in the United States are primarily inspected using the magnetic flux leakage (MFL) nondestructive evaluation (NDE) technique. However, accurate analysis of the NDE signals in terms of the underlying defects requires a thorough knowledge of various operational parameters such as B-H characteristics of the pipe wall, the velocity of the scanning tool, etc. In certain situations, information about such operational parameters is either absent or hard to obtain. Appropriate signal processing techniques can be applied to the raw MFL signals to ensure that defect characterization is possible in spite of local variations in the test situation. This paper presents two such signal processing methods—one, to compensate the MFL signal for variations in pipe-material grade, and the other to remove the effects of signal distortion that occur due to the velocity of the scanning device. [ABSTRACT FROM AUTHOR]

Each year, the annual meeting of the APS Division of Plasma Physics (DPP) brings together a broad representation of the many active subfields of plasma physics and enjoys an audience that is equally diverse. The meeting was well attended and largely went as planned despite the interventions of hurricane Sandy which caused the city of Providence to shut-down during the first day of the conference. The meeting began on Monday morning with a review of the physics of cosmic rays, 2012 being the 100th year since their discovery, which illustrated the central importance of plasma physics to astrophysical problems. Subsequent reviews covered the importance of tokamak plasma boundaries, progress towards ignition on the National Ignition Facility (NIF), and magnetized plasma turbulence. The Maxwell prize address, by Professor Liu Chen, covered the field of nonlinear Alfvén wave physics. Tutorial lectures were presented on the verification of gyrokinetics, new capabilities in laboratory astrophysics, magnetic flux compression, and tokamak plasma start-up. [ABSTRACT FROM AUTHOR]

The article offers brief information on research studies related to digital communication. One study states the researchers in China and the U.S. have proposed a wireless magnetic flux sensor-based hand tracking method which will help in interacting with portable devices. Another study states that researchers in Singapore have presented a method for unsupervised change detection in satellite imagery. Another study states that in recent decades the fibre Bragg grating strain have been developed.

The article presents a study on the presence of fluid core of the innermost core of the Earth's layer by Jean Dickey at the National Aeronautics and Space Administration's (NASA) Jet Propulsion Laboratory and Oliver de Viron at the Institute of Earth Physics in Paris. The study implies the surface magnetic measurements to determine the magnetic flux of the liquid core. Moreover, researchers have found four robust modes of angular-momentum oscillations that correspond with magnetic waves.