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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Compatibility of FeCrAlMo in Flowing Pb-Li at 600°C to 700°C

A series of monometallic thermal convection loops (TCLs) has been conducted to determine the maximum temperature where FeCrAl alloys have compatibility with eutectic lead lithium (Pb-Li) for a dual-coolant fusion blanket. Pre-oxidizing commercial alloy APMT (Fe-21Cr-5Al-3Mo) for 2 h at 1000°C to form a surface α-Al 2 O 3 layer was very effective in reducing the mass loss of specimens in the hot and cold legs of the most recent TCL that was operated for 1000 h with a peak temperature of 700°C. However, unlike previous experiments, the postexposure room temperature ductility of many of the APMT specimens was degraded to <10% total elongation, and many of the specimens at the highest temperature (>680°C) were severely damaged or were not recovered. Furthermore, wide-angle X-ray scattering found that the pre-formed α-Al 2 O 3 scale transformed to a mixture of trigonal and tetragonal LiAlO 2 . The overall results suggest that the maximum temperature for FeCrAl is limited to <700°C.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

THREE-DIMENSIONAL RECONSTRUCTION OF AN ERUPTING FILAMENT WITH SOLAR DYNAMICS OBSERVATORY AND STEREO OBSERVATIONS

On 2010 August 1, a global solar event was launched involving almost the entire Earth-facing side of the Sun. This event mainly consisted of a C3.2 flare, a polar crown filament eruption, and two Earth-directed coronal mass ejections. The observations from the Solar Dynamics Observatory (SDO) and STEREO showed that all the activities were coupled together, suggesting a global character of the magnetic eruption. We reconstruct the three-dimensional geometry of the polar crown filament using observations from three different viewpoints (STEREO A, STEREO B, and SDO) for the first time. The filament undergoes two eruption processes. First, the main body of the filament rises up, while it also moves toward the low-latitude region with a change in inclination by {approx}48{sup 0} and expands only in the altitudinal and latitudinal direction in the field of view of the Atmospheric Imaging Assembly. We investigate the true velocities and accelerations of different locations along the filament and find that the highest location always has the largest acceleration during this eruption process. During the late phase of the first eruption, part of the filament material separates from the eastern leg. This material displays a projectile motion and moves toward the west at a constant velocity of 141.8 km s{sup -1}. This may imply that the polar crown filament consists of at least two groups of magnetic systems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

THE RISE OF ACTIVE REGION FLUX TUBES IN THE TURBULENT SOLAR CONVECTIVE ENVELOPE

We use a thin flux tube model in a rotating spherical shell of turbulent convective flows to study how active region scale flux tubes rise buoyantly from the bottom of the convection zone to near the solar surface. We investigate toroidal flux tubes at the base of the convection zone with field strengths ranging from 15 kG to 100 kG at initial latitudes ranging from 1{sup 0} to 40{sup 0} with a total flux of 10{sup 22} Mx. We find that the dynamic evolution of the flux tube changes from convection dominated to magnetic buoyancy dominated as the initial field strength increases from 15 kG to 100 kG. At 100 kG, the development of {Omega}-shaped rising loops is mainly controlled by the growth of the magnetic buoyancy instability. However, at low field strengths of 15 kG, the development of rising {Omega}-shaped loops is largely controlled by convective flows, and properties of the emerging loops are significantly changed compared to previous results in the absence of convection. With convection, rise times are drastically reduced (from years to a few months), loops are able to emerge at low latitudes, and tilt angles of emerging loops are consistent with Joy's law for initial field strengths of {approx}>40 kG. We also examine other asymmetries that develop between the leading and following legs of the emerging loops. Taking all the results together, we find that mid-range field strengths of {approx}40-50 kG produce emerging loops that best match the observed properties of solar active regions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

ON A CORONAL BLOWOUT JET: THE FIRST OBSERVATION OF A SIMULTANEOUSLY PRODUCED BUBBLE-LIKE CME AND A JET-LIKE CME IN A SOLAR EVENT

The coronal blowout jet is a peculiar category among various jet phenomena, in which the sheared base arch, often carrying a small filament, experiences a miniature version of blowout eruption that produces large-scale coronal mass ejection (CME). In this paper, we report such a coronal blowout jet with high-resolution multi-wavelength and multi-angle observations taken from Solar Dynamics Observatory, Solar Terrestrial Relations Observatory, and Big Bear Solar Observatory. For the first time, we find that simultaneous bubble-like and jet-like CMEs were dynamically related to the blowout jet that showed cool and hot components next to each other. Our observational results indicate that (1) the cool component resulted from the eruption of the filament contained within the jet's base arch, and it further caused the bubble-like CME; (2) the jet-like CME was associated with the hot component, which was the outward moving heated plasma generated by the reconnection of the base arch and its ambient open field lines. On the other hand, bifurcation of the jet's cool component was also observed, which resulted from the uncoupling of the erupting filament's two legs that were highly twisted at the very beginning. Based on these results, we propose a model to interpret the coronal blowout jet, in which the external reconnection not only produces the jet-like CME, but also leads to the rising of the filament. Subsequently, internal reconnection starts underneath the rising filament and thereby causes the bubble-like CME.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

AN OVER-AND-OUT HALO CORONAL MASS EJECTION DRIVEN BY THE FULL ERUPTION OF A KINKED FILAMENT

Over-and-out coronal mass ejections (CMEs) represent a broad class of CMEs that come from flare-producing magnetic explosions of various sizes but are laterally far offset from the flare, and their productions can be depicted by the magnetic-arch-blowout scenario. In this paper, we present observations of an over-and-out halo CME from the full eruption of a small kinking filament in an emerging active region (AR). In combination with the results of a derived coronal magnetic configuration, our observations showed that the CME was associated with a coronal helmet streamer, and the filament was located in the northern outskirts of the streamer base. Formed along a neutral line where flux cancellation was forced by the emerging AR with the surrounding opposite-polarity magnetic field, the filament underwent a full, non-radial eruption along the northern leg of the streamer arcade, accompanied by a clockwise deflection of the eruption direction. As a characteristic property of kink instability, the eruption displayed a clear inverse {gamma} shape, indicative of a writhing motion of the filament apex. Coronal dimmings, including a remote one, formed in opposite-polarity footprint regions of the streamer arcade during the eruption, and the consequent CME was laterally offset from the AR. These observations suggest that the kink instability is likely to be the driver in the eruption. The event can be well explained by putting this driver into the magnetic-arch-blowout model, in which the eruption-direction deflection and the full-eruption nature of the kinking filament are caused by the guiding action of the streamer arcade and the external reconnection between them.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

USE OF INCIDENT AND REFLECTED SOLAR PARTICLE BEAMS TO TRACE THE TOPOLOGY OF MAGNETIC CLOUDS

Occasionally, large solar energetic particle (SEP) events occur inside magnetic clouds (MCs). In this work, the onset time analysis, the peak intensity analysis, and the decay phase analysis of SEPs are used to investigate two large SEP events inside MCs: the 1998 May 2 and 2002 April 21 events. The onset time analysis of non-relativistic electrons and {approx}MeV nucleon{sup -1} heavy ions shows the stability of the magnetic loop structure during a period of a few hours in the events examined. The joint analysis of pitch-angle distributions and peak intensities of electrons exhibits that, depending on the particle pitch angle observed at 1 AU, in the April event the reflection point of particles may be distributed along a wide spatial range, implying that the magnetic loop is a magnetic bottle connected to the Sun with both legs. In contrast, in the May event particle reflection occurs abruptly at the magnetic mirror formed by a compressed field enhancement behind the interplanetary shock, consistent with its open field line topology.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

MORPHOLOGICAL EVOLUTION OF A THREE-DIMENSIONAL CORONAL MASS EJECTION CLOUD RECONSTRUCTED FROM THREE VIEWPOINTS

The propagation properties of coronal mass ejections (CMEs) are crucial to predict its geomagnetic effect. A newly developed three-dimensional (3D) mask fitting reconstruction method using coronagraph images from three viewpoints has been described and applied to the CME ejected on 2010 August 7. The CME's 3D localization, real shape, and morphological evolution are presented. Due to its interaction with the ambient solar wind, the morphology of this CME changed significantly in the early phase of evolution. Two hours after its initiation, it was expanding almost self-similarly. The CME's 3D localization is quite helpful to link remote sensing observations to in situ measurements. The investigated CME was propagating to Venus with its flank just touching STEREO B. Its corresponding interplanetary CME in the interplanetary space shows a possible signature of a magnetic cloud with a preceding shock in Venus Express (VEX) observations, while from STEREO B only a shock is observed. We have calculated three principal axes for the reconstructed 3D CME cloud. The orientation of the major axis is, in general, consistent with the orientation of a filament (polarity inversion line) observed by SDO/AIA and SDO/HMI. The flux rope axis derived by the Minimal Variance Analysis from VEX indicates a radial-directed axis orientation. It might be that locally only the leg of the flux rope passed through VEX. The height and speed profiles from the Sun to Venus are obtained. We find that the CME speed possibly had been adjusted to the speed of the ambient solar wind flow after leaving the COR2 field of view and before arriving at Venus. A southward deflection of the CME from the source region is found from the trajectory of the CME geometric center. We attribute it to the influence of the coronal hole where the fast solar wind emanated from.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

LOW-ALTITUDE RECONNECTION INFLOW-OUTFLOW OBSERVATIONS DURING A 2010 NOVEMBER 3 SOLAR ERUPTION

For a solar flare occurring on 2010 November 3, we present observations using several SDO/AIA extreme-ultraviolet (EUV) passbands of an erupting flux rope followed by inflows sweeping into a current sheet region. The inflows are soon followed by outflows appearing to originate from near the termination point of the inflowing motion-an observation in line with standard magnetic reconnection models. We measure average inflow plane-of-sky speeds to range from {approx}150 to 690 km s{sup -1} with the initial, high-temperature inflows being the fastest. Using the inflow speeds and a range of Alfven speeds, we estimate the Alfvenic Mach number which appears to decrease with time. We also provide inflow and outflow times with respect to RHESSI count rates and find that the fast, high-temperature inflows occur simultaneously with a peak in the RHESSI thermal light curve. Five candidate inflow-outflow pairs are identified with no more than a minute delay between detections. The inflow speeds of these pairs are measured to be {approx}10{sup 2} km s{sup -1} with outflow speeds ranging from {approx}10{sup 2} to 10{sup 3} km s{sup -1}-indicating acceleration during the reconnection process. The fastest of these outflows are in the form of apparently traveling density enhancements along the legs of the loops rather than the loop apexes themselves. These flows could possibly either be accelerated plasma, shocks, or waves prompted by reconnection. The measurements presented here show an order of magnitude difference between the retraction speeds of the loops and the speed of the density enhancements within the loops-presumably exiting the reconnection site.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THREE-DIMENSIONAL STRUCTURE AND EVOLUTION OF EXTREME-ULTRAVIOLET BRIGHT POINTS OBSERVED BY STEREO/SECCHI/EUVI

We unveil the three-dimensional structure of quiet-Sun EUV bright points and their temporal evolution by applying a triangulation method to time series of images taken by SECCHI/EUVI on board the STEREO twin spacecraft. For this study we examine the heights and lengths as the components of the three-dimensional structure of EUV bright points and their temporal evolutions. Among them we present three bright points which show three distinct changes in the height and length: decreasing, increasing, and steady. We show that the three distinct changes are consistent with the motions (converging, diverging, and shearing, respectively) of their photospheric magnetic flux concentrations. Both growth and shrinkage of the magnetic fluxes occur during their lifetimes and they are dominant in the initial and later phases, respectively. They are all multi-temperature loop systems which have hot loops ({approx}10{sup 6.2} K) overlying cooler ones ({approx}10{sup 6.0} K) with cool legs ({approx}10{sup 4.9} K) during their whole evolutionary histories. Our results imply that the multi-thermal loop system is a general character of EUV bright points. We conclude that EUV bright points are flaring loops formed by magnetic reconnection and their geometry may represent the reconnected magnetic field lines rather than the separator field lines.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

WISE/NEOWISE PRELIMINARY ANALYSIS AND HIGHLIGHTS OF THE 67P/CHURYUMOV-GERASIMENKO NEAR NUCLEUS ENVIRONS

On 2010 January 18-19 and June 28-29, the Wide-field Infrared Survey Explorer (WISE) spacecraft imaged the Rosetta mission target, comet 67P/Churyumov-Gerasimenko. We present a preliminary analysis of the images, which provide a characterization of the dust environment at heliocentric distances similar to those planned for the initial spacecraft encounter, but on the outbound leg of its orbit rather than the inbound. Broadband photometry yields low levels of CO{sub 2} production at a comet heliocentric distance of 3.32 AU and no detectable production at 4.18 AU. We find that at these heliocentric distances, large dust grains with mean grain diameters on the order of a millimeter or greater dominate the coma and evolve to populate the tail. This is further supported by broadband photometry centered on the nucleus, which yield an estimated differential dust particle size distribution with a power-law relation that is considerably shallower than average. We set a 3{sigma} upper limit constraint on the albedo of the large-grain dust at {<=}0.12. Our best estimate of the nucleus radius (1.82 {+-} 0.20 km) and albedo (0.04 {+-} 0.01) are in agreement with measurements previously reported in the literature.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

MULTIPLE PLASMA EJECTIONS AND INTERMITTENT NATURE OF MAGNETIC RECONNECTION IN SOLAR CHROMOSPHERIC ANEMONE JETS

The recent discovery of chromospheric anemone jets with the Solar Optical Telescope (SOT) on board Hinode has shown an indirect evidence of magnetic reconnection in the solar chromosphere. However, the basic nature of magnetic reconnection in chromosphere is still unclear. We studied nine chromospheric anemone jets from SOT/Hinode using Ca II H filtergrams, and we found multiple bright, plasma ejections along the jets. In most cases, the major intensity enhancements (larger than 30% relative to the background intensity) of the loop correspond to the timing of the plasma ejections. The typical lifetime and size of the plasma ejecta are about 20-60 s and 0.3-1.5 Mm, respectively. The height-time plot of jet shows many sub-structures (or individual jets) and the typical lifetime of the individual jet is about one to five minutes. Before the onset of the jet activity, a loop appears in Ca II H and gradually increases in size, and after few minutes several jets are launched from the loop. Once the jet activity starts and several individual jets are launched, the loop starts shrinking with a speed of {approx}4 km s{sup -1}. In some events, a downward moving blob with a speed of {approx}35 km s{sup -1} was observed, associated with the upward moving plasma along one of the legs of the loop hosting the jets. The upward moving plasma gradually developed into jets. Multiple plasma ejections in chromospheric anemone jet show the strongly time-dependent as well as intermittent nature of magnetic reconnection in the solar chromosphere.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

RHESSI AND SDO/AIA OBSERVATIONS OF THE CHROMOSPHERIC AND CORONAL PLASMA PARAMETERS DURING A SOLAR FLARE

X-ray and extreme ultraviolet (EUV) observations are an important diagnostic of various plasma parameters of the solar atmosphere during solar flares. Soft X-ray and EUV observations often show coronal sources near the top of flaring loops, while hard X-ray emission is mostly observed from chromospheric footpoints. Combining RHESSI with simultaneous Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) observations, it is possible for the first time to determine the density, temperature, and emission profile of the solar atmosphere over a wide range of heights during a flare, using two independent methods. Here we analyze a near limb event during the first of three hard X-ray peaks. The emission measure, temperature, and density of the coronal source is found using soft X-ray RHESSI images while the chromospheric density is determined using RHESSI visibility analysis of the hard X-ray footpoints. A regularized inversion technique is applied to AIA images of the flare to find the differential emission measure (DEM). Using DEM maps, we determine the emission and temperature structure of the loop, as well as the density, and compare it with RHESSI results. The soft X-ray and hard X-ray sources are spatially coincident with the top and bottom of the EUV loop, but the bulk of the EUV emission originates from a region without cospatial RHESSI emission. The temperature analysis along the loop indicates that the hottest plasma is found near the coronal loop-top source. The EUV observations suggest that the density in the loop legs increases with increasing height while the temperature remains constant within uncertainties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

OBSERVATIONS AND MODELS OF SLOW SOLAR WIND WITH Mg{sup 9+} IONS IN QUIESCENT STREAMERS

Quiescent streamers are characterized by a peculiar UV signature as pointed out by the results from the observations of the Ultraviolet and Coronograph Spectrometer (UVCS) on board SOHO: the intensity of heavy-ion emission lines (such as O VI) shows dimmer core relative to the edges. Previous models show that the structure of the heavy-ion streamer emission relates to the acceleration regions of the slow solar wind at streamer legs and to gravitational settling processes in the streamer core. Observations of Mg{sup 9+} ion EUV emission in coronal streamers at solar minimum were first reported by the UVCS instrument. The Mg X 625 A emission is an order of magnitude smaller than the O VI 1032 A emission, requiring longer exposures to obtain statistically significant results. Here, Mg X coronal observations are analyzed and compared, for the first time, with the solar minimum streamer structure in hydrogen and O VI emissions. We employ the 2.5D three-fluid model, developed previously to study the properties of O{sup 5+} ions in streamers, and calculate for the first time the density, temperature, and outflow structure of Mg{sup 9+} ions in the solar minimum streamer. The Mg{sup 9+} ions are heated by an empirical radial heating function constrained by observations of the kinetic ion temperature obtained from Mg X emission line profiles. The detailed structure of Mg{sup 9+} density, temperature, and outflow speed is determined by the Coulomb momentum and energy exchange as well as electromagnetic interactions with electrons and protons in the three-fluid model of the streamer. The results of the model are in good qualitative agreement with observations, and provide insights on the possible link between the magnetic structure of the streamer, slow solar wind sources, and relative abundances of heavy ions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

PARTIAL SLINGSHOT RECONNECTION BETWEEN TWO FILAMENTS

We present a rare observation of an interaction between two filaments around AR 11358 and AR 11361 on 2011 December 3 that is strongly suggestive of the occurrence of slingshot reconnection. A small elbow-shaped active-region filament (F12) underwent a failed eruption that brought it into contact with a nearby larger, thicker filament (F34). Accompanied by the appearance of complicated internal structures below the erupting F12, its two legs separated away from each other and then connected into F34. This process led the filaments to change their connectivity to form two newly linked filaments, and one of them showed a clear inverse {gamma}-shape. However, the alteration in the filament connectivity was imperfect since F34 is discernible after the eruption. These observations can be interpreted as a partial slingshot reconnection between two filaments that had unequal axial magnetic flux.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

INJECTION OF PLASMA INTO THE NASCENT SOLAR WIND VIA RECONNECTION DRIVEN BY SUPERGRANULAR ADVECTION

To understand the origin of the solar wind is one of the key research topics in modern solar and heliospheric physics. Previous solar wind models assumed that plasma flows outward along a steady magnetic flux tube that reaches continuously from the photosphere through the chromosphere into the corona. Inspired by more recent comprehensive observations, Tu et al. suggested a new scenario for the origin of the solar wind, in which it flows out in a magnetically open coronal funnel and mass is provided to the funnel by small-scale side loops. Thus mass is supplied by means of magnetic reconnection that is driven by supergranular convection. To validate this scenario and simulate the processes involved, a 2.5 dimensional (2.5D) numerical MHD model is established in the present paper. In our simulation a closed loop moves toward an open funnel, which has opposite polarity and is located at the edge of a supergranulation cell, and magnetic reconnection is triggered and continues while gradually opening up one half of the closed loop. Its other half connects with the root of the open funnel and forms a new closed loop which is submerged by a reconnection plasma stream flowing downward. Thus we find that the outflowing plasma in the newly reconnected funnel originates not only from the upward reconnection flow but also from the high-pressure leg of the originally closed loop. This implies an efficient supply of mass from the dense loop to the dilute funnel. The mass flux of the outflow released from the funnel considered in our study is calculated to be appropriate for providing the mass flux at the coronal base of the solar wind, though additional heating and acceleration mechanisms are necessary to keep the velocity at the higher location. Our numerical model demonstrates that in the funnel the mass for the solar wind may be supplied from adjacent closed loops via magnetic reconnection as well as directly from the footpoints of open funnels.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

SDO/AIA observations of a partially erupting prominence

We report an observation of a partially erupting prominence and its associated dynamical plasma processes based on observations recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. The prominence first went through a slow rise (SR) phase followed by a fast rise (FR) phase. The SR phase began after a couple of small brightenings were seen toward the footpoints. When the prominence had transitioned from SR to FR, it had already become kinked. The prominence shows strong brightening at the central kink location during the start of FR. We interpret this as an internal magnetic reconnection occurring at a vertical current sheet forming between the two legs of the erupting prominence (flux rope). The brightening at the central kink location is seen in all EUV channels of AIA. The contributions of differential emission at higher temperatures are larger compared to that for typical coronal temperatures supporting a reconnection scenario at the central kink location. The plasma above the brightening location is ejected as a hot plasmoid-like structure embedded in a coronal mass ejection, and those below the brightening move down in the form of blobs moving toward the Sun's surface. The unique time resolution of the AIA has allowed these eruptive aspects, including SR-to-FR, kinking, central current sheet formation, plasmoid-like eruption, and filament 'splitting', to be observed in a single event, providing strong and comprehensive evidence in favor of the model of partially erupting flux ropes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Convective overstability in radially stratified accretion disks under thermal relaxation

This paper expands the stability criterion for radially stratified, vertically unstratified accretion disks incorporating thermal relaxation. We find a linear amplification of epicyclic oscillations in these disks that depends on the effective cooling time, i.e., an overstability. The growth rates of the overstability vanish for both extreme cases, e.g., infinite cooling time and instantaneous cooling, i.e., the adiabatic and fully isothermal cases. However, for thermal relaxation times τ on the order of the orbital frequency, τΩ ∼ 1, modes grow at a rate proportional to the square of the Brunt-Väisälä frequency. The overstability is based on epicyclic motions, with the thermal relaxation causing gas to heat while radially displaced inward and cool while radially displaced outward. This causes the gas to have a lower density when moving outward compared to when it moves inward, so it feels the outward-directed pressure force more strongly on that leg of the journey. We suggest the term 'convective overstability' for the phenomenon which has already been studied numerically in the nonlinear regime in the context of amplifying vortices in disks under the name 'subcritical baroclinic instability'. The aim of the present paper is to make clear that vortex formation in three-dimensional disks is not necessarily subcritical, i.e., does not need a finite perturbation, nor is it baroclinic in the sense of geophysical fluid dynamics, which requires on vertical shear. We find that convective overstability is a linear instability that will operate under a wide range of physical conditions for circumstellar disks.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

High-resolution observations of active region moss and its dynamics

The High Resolution Coronal Imager has provided the sharpest view of the EUV corona to date. In this paper, we exploit its impressive resolving power to provide the first analysis of the fine-scale structure of moss in an active region. The data reveal that the moss is made up of a collection of fine threads that have widths with a mean and standard deviation of 440 ± 190 km (FWHM). The brightest moss emission is located at the visible head of the fine-scale structure and the fine structure appears to extend into the lower solar atmosphere. The emission decreases along the features, implying that the lower sections are most likely dominated by cooler transition region plasma. These threads appear to be the cool, lower legs of the hot loops. In addition, the increased resolution allows for the first direct observation of physical displacements of the moss fine structure in a direction transverse to its central axis. Some of these transverse displacements demonstrate periodic behavior, which we interpret as a signature of kink (Alfvénic) waves. Measurements of the properties of the transverse motions are made and the wave motions have means and standard deviations of 55 ± 37 km for the transverse displacement amplitude, 77 ± 33 s for the period, and 4.7 ± 2.5 km s{sup –1} for the velocity amplitude. The presence of waves in the transition region of hot loops could have important implications for the heating of active regions.

79 ASTRONOMY AND ASTROPHYSICS↗