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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Penetration of Magnetosheath Plasma into Dayside Magnetosphere: 1. Density, Velocity, and Rotation

In this study, we examine a large number of plasma structures (filaments), observed with the Cluster spacecraft during 2 years (2007-2008) in the dayside magnetosphere but consisting of magnetosheath plasma. To reduce the effects observed in the cusp regions and on magnetosphere flanks, we consider these events predominantly inside the narrow cone less than 30 about the subsolar point. Two important features of these filaments are (i) their stable antisunward (earthward) motion inside the magnetosphere, whereas the ambient magnetospheric plasma moves usually in the opposite direction (sunward), and (ii) between these filaments and the magnetopause, there is a region of magnetospheric plasma, which separates these filaments from the magnetosheath. The stable earthward motion of these magnetopause show the possible disconnection of these filaments from the magnetosheath, as suggested earlier by many researchers. The results also show that these events cannot be a result of back-and-forth motions of magnetopause position or surface waves propagating on the magnetopause. Another important feature of these filaments is their rotation about the filament axis, which might be a result of their passage through the velocity shear on magnetopause boundary. After crossing the velocity shear, the filaments get a rotational velocity, which has opposite directions in the noon-dusk and noon-dawn sectors. This rotation velocity may be an important factor, supporting the stability of these filaments and providing their motion into the magnetosphere.

Lyatsky, Wladislaw↗
DOE OSTI2013

ROTATING MOTIONS AND MODELING OF THE ERUPTING SOLAR POLAR-CROWN PROMINENCE ON 2010 DECEMBER 6

A large polar-crown prominence composed of different segments spanning nearly the entire solar disk erupted on 2010 December 6. Prior to the eruption, the filament in the active region part split into two layers: a lower layer and an elevated layer. The eruption occurs in several episodes. Around 14:12 UT, the lower layer of the active region filament breaks apart: One part ejects toward the west, while the other part ejects toward the east, which leads to the explosive eruption of the eastern quiescent filament. During the early rise phase, part of the quiescent filament sheet displays strong rolling motion (observed by STEREO-B) in the clockwise direction (viewed from east to west) around the filament axis. This rolling motion appears to start from the border of the active region, then propagates toward the east. The Atmospheric Imaging Assembly (AIA) observes another type of rotating motion: In some other parts of the erupting quiescent prominence, the vertical threads turn horizontal, then turn upside down. The elevated active region filament does not erupt until 18:00 UT, when the erupting quiescent filament has already reached a very large height. We develop two simplified three-dimensional models that qualitatively reproduce the observed rolling and rotating motions. The prominence in the models is assumed to consist of a collection of discrete blobs that are tied to particular field lines of a helical flux rope. The observed rolling motion is reproduced by continuous twist injection into the flux rope in Model 1 from the active region side. Asymmetric reconnection induced by the asymmetric distribution of the magnetic fields on the two sides of the filament may cause the observed rolling motion. The rotating motion of the prominence threads observed by AIA is consistent with the removal of the field line dips in Model 2 from the top down during the eruption.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

SOLAR H{alpha} OSCILLATIONS FROM INTENSITY AND DOPPLER OBSERVATIONS

Chromospheric wave activity around flares and filaments has been a research focus for years, and could provide indirect measurements of local conditions that are not otherwise accessible. One interesting observed phenomenon is oscillations in filaments, activated by distant flares and the large-scale waves they produce. Characteristics of these oscillations, such as periods, amplitudes, and lifetimes, can provide unique information about the filament. We measure oscillation properties in flares and filaments from H{alpha} chromospheric data using a new method that provides important spatial and frequency content of the dynamics. We apply the method to two flare events where filaments are observed to oscillate and determine their properties. We find strong oscillatory signal in flaring active regions in the chromosphere over a range of frequencies. Two filaments are found to oscillate without any detectable chromospheric wave acting as an activation mechanism. We find that filaments oscillate with periods of tens of minutes, but variations are significant at small spatial scales along the filamentary region. The results suggest that there is a frequency dependence of the oscillation amplitude, as well as a spatial dependence along single filaments that is more difficult to quantify. It also appears that the strength of the oscillations does not necessarily depend on the strength of the trigger, although there are other possible effects that make this conclusion preliminary. Applications of this technique to other events and different data sets will provide important new insights into the local energy densities and magnetic fields associated with dynamic chromospheric structures.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

IS FLUX ROPE A NECESSARY CONDITION FOR THE PROGENITOR OF CORONAL MASS EJECTIONS?

A magnetic flux rope structure is believed to exist in most coronal mass ejections (CMEs). However, it has been long debated whether the flux rope exists before eruption or if it is formed during eruption via magnetic reconnection. The controversy has continued because of our lack of routine measurements of the magnetic field in the pre-eruption structure, such as solar filaments. However, recently an indirect method was proposed to infer the magnetic field configuration based on the sign of helicity and the bearing direction of the filament barbs. In this paper, we apply this method to two erupting filament events, one on 2014 September 2 and the other on 2011 March 7, and find that the first filament is supported by a magnetic flux rope and the second filament is supported by a sheared arcade, i.e., the first one is an inverse-polarity filament and the second one is a normal-polarity filament. With the identification of the magnetic configurations in these two filaments, we stress that a flux rope is not a necessary condition for the pre-CME structure.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Localization and functional exploration of leiomodin-2’s C-terminal binding sites

Striated muscle contraction occurs through interactions between overlapping myosin-based thick and actin-based thin filaments within the sarcomere. For effective contraction to occur, the length of the thin filament must be maintained to allow for sufficient overlap with the thick filament. The proteins leiomodin and tropomodulin compete for binding at the pointed end of thin filaments to regulate their length, utilizing their homologous N-terminal actin and tropomyosin binding sites. Leiomodin also has a region called the C-terminal extension, absent in tropomodulin. In this region, the cardiac isoform (leiomodin-2) contains additional actin-binding sites that enable it to bind along the sides of thin filaments in a Ca2+-dependent manner. Here, using nuclear magnetic resonance spectroscopy, we localize the regions of the C-terminal extension that contain residues involved in thin filament side-binding. Using co-sedimentation assays, we reveal that these regions can independently bind thin filaments and discover that the poly-proline region plays a role as a linker, maintaining an adequate distance between two of the regions required for effective interaction to occur. In addition to its role in side-binding, we provide direct evidence that the poly-proline region interacts with profilin and propose a new mechanism by which leiomodin-2 may assist in the polymerization of profilin-bound actin at thin filament pointed ends.

ACTIN-BINDING PROTEINS↗
DOE OSTI2018

Histidine-Dependent Protein Methylation Is Required for Compartmentalization of CTP Synthase

CTP synthase (CTPS) forms compartmentalized filaments in response to substrate availability and environmental nutrient status. However, the physiological role of filaments and mechanisms for filament assembly are not well understood. Here in this work, we provide evidence that CTPS forms filaments in response to histidine influx during glutamine starvation. Tetramer conformation-based filament formation restricts CTPS enzymatic activity during nutrient deprivation. CTPS protein levels remain stable in the presence of histidine during nutrient deprivation, followed by rapid cell growth after stress relief. We demonstrate that filament formation is controlled by methylation and that histidine promotes re-methylation of homocysteine by donating one-carbon intermediates to the cytosolic folate cycle. Furthermore, we find that starvation stress and glutamine deficiency activate the GCN2/ATF4/MTHFD2 axis, which coordinates CTPS filament formation. Finally, CTPS filament formation induced by histidine-mediated methylation may be a strategy used by cancer cells to maintain homeostasis and ensure a growth advantage in adverse environments.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

Operation and development status of the J-PARC ion source

A cesium-free H{sup −} ion source driven with a LaB{sub 6} filament is being operated at the Japan Proton Accelerator Research Complex (J-PARC) without any serious trouble since the restoration from the March 2011 earthquake. The H{sup −} ion current from the ion source is routinely restricted approximately 19 mA for the lifetime of the filament. In order to increase the beam power at the linac beam operation (January to February 2013), the beam current from the ion source was increased to 22 mA. At this operation, the lifetime of the filament was estimated by the reduction in the filament current. According to the steep reduction in the filament current, the break of the filament was predicted. Although the filament has broken after approximately 10 h from the steep current reduction, the beam operation was restarted approximately 8 h later by the preparation for the exchange of new filament. At the study time for the 3 GeV rapid cycling synchrotron (April 2013), the ion source was operated at approximately 30 mA for 8 days. As a part of the beam current upgrade plan for the J-PARC, the front end test stand consisting of the ion source and the radio frequency quadrupole is under preparation. The RF-driven H{sup −} ion source developed for the J-PARC 2nd stage requirements will be tested at this test stand.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Evaluation of critical current density and residual resistance ratio limits in powder in tube Nb 3 Sn conductors

High critical current density (Jc) Nb 3 Sn A15 multifilamentary wires require a large volume fraction of small grain, superconducting A15 phase, as well as Cu stabilizer with high Residual Resistance Ratio (RRR) to provide electromagnetic stabilization and protection. In Powder-in-Tube (PIT) wires the unreacted Nb7.5wt.%Ta outer layer of the tubular filaments acts as a diffusion barrier and protects the interfilamentary Cu stabilizer from Sn contamination. A high RRR requirement generally imposes a restricted A15 reaction heat treatment (HT) to prevent localized full reaction of the filament that could allow Sn to reach the Cu. In this paper we investigate recent high quality PIT wires that achieve a J c (12 T, 4.2 K) up to ~2500 A/mm -2 and find that the minimum diffusion barrier thickness decreases as the filament aspect ratio increases from ~1 in the inner rings of filaments to 1.3 in the outer filament rings. We found that just 2-3 diffusion barrier breaches can degrade RRR from 300 to 150 or less. Using progressive etching of the Cu we also found that the RRR degradation is localized near the external filaments where deformation is highest. Consequently minimizing filament distortion during strand fabrication is important for reducing RRR degradation. The additional challenge of developing the highest possible J c must be addressed by forming the maximum fraction of high J c small-grain (SG) A15 and minimizing low J c large-grain (LG) A15 morphologies. Finally, in one wire we found that 15% of the filaments had a significantly enhanced SG/LG A15 ratio and no residual A15 in the core, a feature that opens a path to substantial J c improvement.

36 MATERIALS SCIENCE↗
DOE OSTI2025

A Wind-driven Origin for the Firework Morphology of the Supernova Remnant Pa 30

Pa 30—the likely remnant of the Galactic Type Iax supernova of 1181 AD—displays an unusual, firework-like morphology, consisting of radial filaments extending from a common center, where a white dwarf (WD) currently drives a very fast wind (speed ≳10 4 km s −1 ). We propose the filaments arose from the Rayleigh–Taylor-unstable nature of the interface between the circumstellar medium (CSM) and the shocked wind launched by the natal WD; the filaments then elongated intact due to the Kelvin–Helmholtz-stable nature of the large initial density contrast between the wind and CSM, supplemented by the slowly declining wind density profile (relative to homologously expanding ejecta). To support this interpretation, we present two-dimensional hydrodynamical simulations and derive the filament properties, including their speed, density, and temperature, all of which are consistent with observations. We suggest the filaments elongate until the wind and CSM densities become comparable at the contact discontinuity, which occurs within 1–10 yr, and then truncate because the Rayleigh–Taylor instability (RTI) halts. The subsequent Kelvin–Helmholtz instability growth timescale across the current width of the filaments is longer than the age of Pa 30, so they remain intact. The filament-less central region in Pa 30 is therefore more likely a consequence of the finite timescale over which the RTI operates, rather than a wind termination shock. In general, firework-like filaments may form in other systems, provided there is a sufficiently large density contrast between the ejecta and its surroundings.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

The initiation of coronal mass ejections by newly emerging magnetic flux

We present observational evidence that eruptions of quiescent filaments and associated coronal mass ejections (CMEs) occur as a consequence of the destabilization of large-scale coronal arcades due to interactions between these structures and new and growing active regions. Both statistical and case studies have been carried out. In a case study of a 'bulge' observed by the High-Altitude Observatory Solar Maximum Mission coronagraph, the high-resolution magnetograms from the Big Bear Solar Observatory show newly emerging and rapidly changing flux in the magnetic fields that apparently underlie the bugle. For other case studies and in the statistical work the eruption of major quiescent filaments was taken as a proxy for CME eruption. We have found that two thirds of the quiescent-filament-associated CMEs occurred after substantial amounts of new magnetic flux emerged in the vicinity of the filament. In addition, in a study of all major quiescent filaments and active regions appearing in a 2-month period we found that 17 of the 22 filaments that were associated with new active regions erupted and 26 of the 31 filaments that were not associated with new flux did not erupt. In all cases in which the new flux was oriented favorably for reconnection with the preexisting large-scale coronal arcades; the filament was observed to erupt. The appearance of the new flux in the form of new active regions begins a few days before the eruption and typically is still occurring at the time of the eruption. A CME initiation scenario taking account of these observational results is proposed.

Feynman, J.↗
NASA NTRS1995

Far-infrared studies of the Galactic Center Arc using the Kuiper Airborne Observatory

Two molecular clouds are clearly interacting with the Galactic Center Radio Arc. The HII regions located at both sites of interaction - the 'Arched Filaments' and G0.18-0.04 - are powerful sources of far-infrared radiation, each having a total luminosity of approx. 10(exp 7) solar luminosity. Using the University of Texas far-IR Photometer at 50 and 90 microns, we found that the emission is substantially more extended than the filamentary HII regions, and that, while the intensity peaks at the locations of the filaments, the dust temperature shows only weak variations, implying that the heating is relatively uniform. The Arched Filaments were also observed with the University of Chicago far-IR Array Polarimeter, STOKES, at 100 microns. The greater than 100 independently sampled positions cover most of the 5 ft x 7 ft area of the Arched Filaments. The polarization is relatively strong (up to 9.4%) almost everywhere in this region. Also, the slow and smooth variations of the polarization angles across the region are consistent with the large magnetic field strengths and the highly-ordered geometry deduced from radio measurements. However, it appears that the magnetic field direction inferred from far-IR polarization (parallel to the Arched Filaments and following their curvature) is very different from that implied by the nonthermal radio filaments. The magnetic field, gas motions, and gravitational potential gradient in the arched filament region are all consistent with gravitational shearing of the molecular cloud underlying the Arched Filaments.

Morris, Mark↗
NASA NTRS1998

Solar Prominence Eruption

The prominence that erupts in a prominence eruption is a magnetic structure in the chromosphere and corona. It is visible in chromospheric images by virtue of chromospheric-temperature plasma suspended in the magnetic field, and belongs to that large class of magnetic structures appropriately called filaments because of their characteristic sinewy sigmoidal form. Hence, the term "filament eruption" is used interchangeably with the term "prominence eruption". The magnetic field holding a filament is prone to undergo explosive changes in configuration. In these upheavals, because the filament material is compelled by its high conductivity to ride with the magnetic field that threads it, this material is a visible tracer of the field motion. The part of the magnetic explosion displayed by the entrained filament material is the phenomenon known as a filament eruption, the topic of this article. This article begins with a description of basic observed characteristics of filament eruptions, with attention to the magnetic fields, flares, and coronal mass ejections in which erupting filaments are embedded. The present understanding of these characteristics in terms of the form and action of the magnetic field is then laid out by means of a rudimentary three-dimensional model of the field. The article ends with basic questions that this picture leaves unresolved and with remarks on the observations needed to probe these questions.

Moore, Ronald L.↗
NASA NTRS1992

Flexible multiply towpreg

This invention relates to an improved flexible towpreg and a method of production therefor. The improved flexible towpreg comprises a plurality of towpreg plies which comprise reinforcing filaments and matrix forming material; the reinforcing filaments being substantially wetout by the matrix forming material such that the towpreg plies are substantially void-free composite articles, and the towpreg plies having an average thickness less than about 100 microns. The method of production for the improved flexible towpreg comprises the steps of spreading the reinforcing filaments to expose individually substantially all of the reinforcing filaments; coating the reinforcing filaments with the matrix forming material in a manner causing interfacial adhesion of the matrix forming material to the reinforcing filaments; forming the towpreg plies by heating the matrix forming material contacting the reinforcing filaments until the matrix forming material liquifies and coats the reinforcing filaments; and cooling the towpreg plies in a manner such that substantial cohesion between neighboring towpreg plies is prevented until the matrix forming material solidifies.

Muzzy, John D.↗
NASA NTRS1992

Flexible multiply towpreg and method of production therefor

This invention relates to an improved flexible towpreg and a method of production therefor. The improved flexible towpreg comprises a plurality of towpreg plies which comprise reinforcing filaments and matrix forming material; the reinforcing filaments being substantially wetout by the matrix forming material such that the towpreg plies are substantially void-free composite articles, and the towpreg plies having an average thickness less than about 100 microns. The method of production for the improved flexible towpreg comprises the steps of spreading the reinforcing filaments to expose individually substantially all of the reinforcing filaments; coating the reinforcing filaments with the matrix forming material in a manner causing interfacial adhesion of the matrix forming material to the reinforcing filaments; forming the towpreg plies by heating the matrix forming material contacting the reinforcing filaments until the matrix forming material liquefies and coats the reinforcing filaments; and cooling the towpreg plies in a manner such that substantial cohesion between neighboring towpreg plies is prevented until the matrix forming material solidifies.

Muzzy, John D.↗
NASA NTRS2017

The Triggering Mechanism of coronal jets and CMEs: Flux Cancelation

Recent investigations show that coronal jets are driven by the eruption of a small-scale filament (10,000 - 20,000 km long, called a minifilament) following magnetic flux cancelation at the neutral line underneath the minifilament. Minifilament eruptions appear to be analogous to larger-scale solar filament eruptions: they both reside, before the eruption, in the highly sheared field between the adjacent opposite-polarity magnetic flux patches (neutral line); jet-producing minifilament and larger-scale solar filament first show a slow-rise, followed by a fast-rise as they erupt; during the jet-producing minifilament eruption a jet bright point (JBP) appears at the location where the minifilament was rooted before the eruption, analogous to the situation with CME-producing larger-scale filament eruptions where a solar flare arcade forms during the filament eruption along the neutral line along which the filament resided prior to its eruption. In the present study we investigate the triggering mechanism of CME-producing large solar filament eruptions, and find that enduring flux cancelation at the neutral line of the filaments often triggers their eruptions. This corresponds to the finding that persistent flux cancelation at the neutral is the cause of jet-producing minifilament eruptions. Thus our observations support coronal jets being miniature version of CMEs.

Coronal Jets↗
DOE OSTI2020

Fine wire manipulator

A system for manipulating a filament can include a filament supply from which a filament can be drawn, the filament supply being positioned along an axis, a vacuum manipulator assembly positioned along the axis, wherein the vacuum manipulator assembly is configured to engage the filament when a vacuum is drawn through the vacuum manipulator assembly and draw the filament along the axis to a workpiece, and a welding tool comprising a welding head positioned along the axis between the filament supply and the vacuum manipulator assembly, the welding tool being configured to weld the filament to the workpiece.

Christensen, Kyle B.↗
DOE OSTI2021

Bioresorbable Primary Battery Anodes Built on Core–Double-Shell Zinc Microparticle Networks

Bioresorbable implantable electronics require power sources that are also bioresorbable with controllable electrical output and lifetime. In this paper, we report a bioresorbable zinc primary battery anode filament based on a zinc microparticle (MP) network coated with chitosan and Al 2 O 3 double shells. When discharged in 0.9% NaCl saline, a Zn MP filament with a 0.17 × 2 mm 2 cross-sectional area exhibited a stable voltage output of 0.55 V at a current of 0.01 mA. Covered by chitosan and Al 2 O 3 double shells, the zinc MP filament exhibited a directional dissolution behavior with a tunable lifetime approximately linear to its length. A stable 200 h discharging time was achieved with a 15 mm Zn MP filament. The maximum output power was found to be 12 μW at 0.03 mA for one filament. The linearity relationship between the current output and the filament cross-sectional area suggested a facile strategy to raise the power output at constant discharging voltage. The filaments could also be connected in series and in parallel to boost its overall voltage and current output, demonstrating their excellent integration capability. Furthermore, this work presents a promising pathway toward bioresorbable transient batteries with controllable lifetime and power output, demonstrating a great potential for powering transient implantable biomedical devices.

25 ENERGY STORAGE↗
DOE OSTI2014

A solar eruption driven by rapid sunspot rotation

We present the observation of a major solar eruption that is associated with fast sunspot rotation. The event includes a sigmoidal filament eruption, a coronal mass ejection, and a GOES X2.1 flare from NOAA active region 11283. The filament and some overlying arcades were partially rooted in a sunspot. The sunspot rotated at ∼10° hr{sup –1} during a period of 6 hr prior to the eruption. In this period, the filament was found to rise gradually along with the sunspot rotation. Based on the Helioseismic and Magnetic Imager observation, for an area along the polarity inversion line underneath the filament, we found gradual pre-eruption decreases of both the mean strength of the photospheric horizontal field (B{sub h} ) and the mean inclination angle between the vector magnetic field and the local radial (or vertical) direction. These observations are consistent with the pre-eruption gradual rising of the filament-associated magnetic structure. In addition, according to the nonlinear force-free field reconstruction of the coronal magnetic field, a pre-eruption magnetic flux rope structure is found to be in alignment with the filament, and a considerable amount of magnetic energy was transported to the corona during the period of sunspot rotation. Our study provides evidence that in this event sunspot rotation plays an important role in twisting, energizing, and destabilizing the coronal filament-flux rope system, and led to the eruption. We also propose that the pre-event evolution of B{sub h} may be used to discern the driving mechanism of eruptions.

79 ASTRONOMY AND ASTROPHYSICS↗