Northeast Limb Research Articles

Coronagraphic Observations of Si x 1430 nm Acquired by DKIST/Cryo-NIRSP with Methods for Telluric Absorption Correction

We report commissioning observations of the Si x 1430 nm solar coronal line observed coronagraphically with the Cryogenic Near-Infrared Spectropolarimeter at the National Science Foundation’s Daniel K. Inouye Solar Telescope. These are the first known spatially resolved observations of this spectral line, which has strong potential as a coronal magnetic field diagnostic. The observations target a complex active region located on the solar northeast limb on 2022 March 4. We present a first analysis of these data that extracts the spectral line properties through a careful treatment of the variable atmospheric transmission that is known to impact this spectral window. Rastered images are created and compared with extreme-UV observations from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument. A method for estimating the electron density from the Si x observations is then demonstrated that makes use of the forbidden line density-sensitive emissivity and an emission-measure analysis of the SDO/AIA bandpass observations. In addition, we derive an effective temperature and nonthermal line width across the region. This study informs the calibration approaches required for more routine observations of this promising diagnostic line.

Detection of Structural Control on Formation Water Quality, in Hemrin Oilfield, northern Iraq, Using Lineament Analysis and Hydrochemical Data

Formation water analyses of Tertiary reservoir (Euphrates, Jeribe, and Dhiban formations) in Hemrin oilfield reflect high salinity variation between Albufudhul, Nukhaila, and Allas domes. The present study suggests that this variation resulted by two reasons, (1) percolation of surface waters (rain water) which lead to devastation of oil type, (2) interaction between water and host rocks. Satellite image and DEM were used to detect the lineaments and morphometric analyses, which interpret the structural control on salinity variation. The main direction of lineaments are NE-SW, which prevailing with subsurface vertical faults between Albufudhul and Nukhaila domes that playing with SE limb of Albufudhul dome as conduits for percolation of surface water (rainwater), that lead to dilute the salinity and change the formation water properties from Albufudhul to Nukhaila domes, while the present of vertical fault between Nukhaila and Allas dome considered as semi impermeable according to geometry of domes, so Allas dome considered as semi closed system in comparison with Albufudhul and Nukhaila domes, that lead to increase in salinity and change of formation water properties. Formation water is classified as salinity variety water from medium salinity (TDS of 7430 mg/l), to brine, (TDS of 59118 mg/l), of mixed origin from meteoric water and connate water, of variety of pH value (6.75-8.89) from weak acidic to alkaline. Its type is Na-SO4-chloride and anions are ordered as rCl > SO4 > HCO3, whereas cations ordered as rNa > Ca > Mg. This type of water is associated with open system reservoir, influenced by percolation of surface water and consider as bad zone for preservation of hydrocarbon accumulations especially in Albufudhul and north east limb of Nukhaila domes, while Allas dome considered as closed system reservoir, which is a good zone for preservation of hydrocarbon accumulations.

2D Seismic Data Analysis of Judaida Structure, Northern Iraq

This research aims to study the structural analysis of the 2D reflection seismic data for the Judaida subsurface structure located in Kirkuk province, northern Iraq. It is located 60 Km southwest of Kirkuk oil field, and 35 Km southwest of Jambur oil field, the Daquq River passes through the study area. The reflectors in the seismic section were picked and identified by using the synthetic seismograms generated from the logs data of the Jd-1 well. Three main seismic reflectors, Fatha, Jeribe, and the Euphrates were chosen. These mentioned sedimentary formations were deposited during the Middle Miocene, Lower Miocene, and Early-Mid Miocene respectively. Time and depth maps were drawn for these three reflectors by processing average data from Jd-1well. The structural interpretation results showed a structural closure on both time and depth domains in the middle of the study area. Judaida structure represented an asymmetrical longitudinal anticline fold. The Northeast limb has a dipping angle of 6-8 degrees more dip than the Southwest limb that has a dipping angle of 1-6 degrees, and the direction of the axis of the general structure is towards the Northwest-Southeast. The general dipping of the fold is toward the north east.

Fermi LAT detection of the supernova remnant SN 1006 revisited: The southwest limb

Abstract The data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have recently been updated. Thus we re-analyze the LAT data for the supernova remnant (SNR) SN 1006. Two parts of γ-ray emission from the region are clearly resolved, which correspond to the northeast (NE) and southwest (SW) limbs of the SNR. The former has been detected in the previous LAT data (Xing et al. 2016, ApJ, 823, 44), but the latter is newly detected in this work. The detections of the two limbs are at a ∼4σ significance level, and the spectral results for the NE limb are consistent with those obtained in previous detection analyses. We construct the broadband spectral energy distribution (SED) for the SW limb. Different scenarios are considered for its SED in γ-ray energies. We conclude that, very similarly in the case of the NE limb, the high-energy and very high-energy emissions from the SW limb is likely dominated by the leptonic process, in which high-energy electrons accelerated from the shell region of the SNR inverse-Compton scatter background photons to γ-rays.

Reconstruction of palaeoclimate in Shalaii Cave, SE of Sangaw, Kurdistan Province of Iraq

Shalaii Cave is a closed system cave that contains old and active speleothems. It is located on the northeast limb of the Ashdagh anticline in Sangaw district in northeastern Iraq. The study presents new data on cave monitoring and the geochemistry of stalagmite archives relevant for the palaeoclimate of Iraq. An extensive cave monitoring program was conducted from June 2014 to March 2015, which included analyses of cave air temperature, relative humidity, cave air, dripwater, and modern calcite precipitates on glass slides. Physical parameters were measured monthly and continuously using data loggers and meteorological data; rainwater and dripwater samples were acquired for stable isotope analyses and hydrochemistry analysis. Stable isotopes of oxygen and carbon and absolute dating of U/Th series dating was used to determine palaeoclimate conditions. The microclimate of Shalaii Cave during the studied period (June-2014 to March-2015), the average temperature at the entrance point and inside the monitored cave was 17.05 °C and 20.18 °C respectively. The relative humidity at the entrance point and inside the cave was 66.6% and 100% respectively. Eleven samples of dripwater and five samples of rainwater were acquired for isotope analyses and thirteen samples of dripwater for hydrochemical analysis. From the environmental isotopes analysis (2H and 18O), all water samples fall between the global meteoric water line (GMWL) and Sangaw meteoric water line (SMWL). The precipitation samples plot well above the GMWL. The mechanism of recharge is direct recharge. Two stalagmites (SHC-01 and SHC-02) were sampled from the cave. The first sample (SHC-01) is dated from 1012 ± 42 to 494 ± 29 yr B.P. and the second sample (SHC-02) dates between 8025 ± 38 to 6977 ± 219 yr B.P. Oxygen and carbon isotope results show that there are two climate conditions for palaeoclimate reconstruction in the Sangaw district. Conditions were generally wetter and colder during 8025 ± 38 to 6977 ± 219 yr B.P. than current conditions; from 1012 ± 42 to 494 ± 29 yr B.P., drier and warmer conditions prevail, more similar to today.

Spatially Resolved Broadband Synchrotron Emission from the Nonthermal Limbs of SN1006

Abstract We present ∼400 ks NuSTAR observations of the northeast (NE) and southwest (SW) nonthermal limbs of the Galactic SNR SN1006. We discovered three sources with X-ray emission detected at ≳50 keV. Two of them are identified as background active galactic nuclei. We extract the NuSTAR spectra from a few regions along the nonthermal limbs and jointly analyze them with the XMM-Newton spectra and the radio data. The broadband radio/X-ray spectra can be well described with a synchrotron emission model from a single population of CR electrons with a power-law energy distribution and an exponential cutoff. The power-law index of the electron particle distribution function (PDF) is ≈1.88–1.95 for both the NE and SW limbs, and we do not find significant evidence for a variation of this index at different energy (curvature). There are significant spatial variations of the synchrotron emission parameters. The highest energy electrons are accelerated in regions with the lowest expansion velocity, which is opposite to what has been found in Tycho’s supernova remnant. In addition to a gradual steepening of synchrotron emission from the center of the nonthermal limbs to larger azimuthal angles, we also find that both the emission spectrum and the PDF are significantly flatter in three regions in the SW limb where the shock encounters a higher density ambient medium. The NE limb also shows significantly higher cutoff energy in the PDF than the SW limb. By comparing with the roughly symmetric TeV emission and largely asymmetric GeV emission from the two nonthermal limbs, we conclude that the asymmetry in the ambient medium and magnetic fields may have largely modified the acceleration and emission of CR leptons.

TRACKING THE CME-DRIVEN SHOCK WAVE ON 2012 MARCH 5 AND RADIO TRIANGULATION OF ASSOCIATED RADIO EMISSION

We present a multiwavelength study of the 2012 March 5 solar eruptive event, with an emphasis on the radio triangulation of the associated radio bursts. The main points of the study are reconstruction of the propagation of shock waves driven by coronal mass ejections (CMEs) using radio observations and finding the relative positions of the CME, the CME-driven shock wave, and its radio signatures. For the first time, radio triangulation is applied to different types of radio bursts in the same event and performed in a detailed way using goniopolarimetric observations from STEREO/Waves and WIND/Waves spacecraft. The event on 2012 March 5 was associated with a X1.1 flare from the NOAA AR 1429 situated near the northeast limb, accompanied by a full halo CME and a radio event comprising long-lasting interplanetary type II radio bursts. The results of the three-dimensional reconstruction of the CME (using SOHO/LASCO, STEREO COR, and HI observations), and modeling with the ENLIL cone model suggest that the CME-driven shock wave arrived at 1 AU at about 12:00 UT on March 7 (as observed by SOHO/CELIAS). The results of radio triangulation show that the source of the type II radio burst was situated on the southern flankmore » of the CME. We suggest that the interaction of the shock wave and a nearby coronal streamer resulted in the interplanetary type II radio emission.« less

Structural analysis of the Azmir – Goizha anticline, north and northeast of Sulaimani city, Kurdistan Region, Northeast Iraq

The Azmir–Goizha anticline (AGA) is located directly to north and northeast boundary of
 Sulaimani city, Kurdistan Region, NE Iraq. The anticline originally consists of two main connected
 anticlines (Azmir and Goizha anticlines) with many smaller anticlines along southwest and
 northeast limbs. In the studied area, it has length and width of about (10 and 4) kms, respectively,
 with height of 1600 m (a.s.l). It extends from Weladar village, from southeast to Khamza village at
 the northwest and further extends outside of the studied area. The anticline has very complicate
 structural setting and recently few structural analyses were conducted by different workers. The
 present study is an attempt to discover the actual structural setting of the anticline and try to review
 the previous studies critically by using data collected in the field with aid of precise stratigraphic
 analysis. Structurally, the previous pigy-back thrust imbricated fan is changed to nearly isoclinal
 detachment fold, which is detached in the form of either lift-off detachment fold or multi-
 detachment fold or multi-detachment faulted fold. In the core of the anticline, the accommodation
 of the shortening is preserved as second-order folding or second-order conjugate faulting. The
 competent cover (outer layers) of the anticline consists of Kometan and upper part Balambo
 formations. Core Azmir and Qaywan anticlines are occupied plastic incompetent layers of Sarmord
 Formation and lower part of Balambo formations while that of Azmir Bichkola and Naugirdan (or
 Goizha) anticlines are occupied. These units are deformed as disharmonic buckle folds in the cores.
 The main detachment had occurred in the lower part of the Sarmord Formation (Lower
 Cretaceous) and inside Jurassic rocks. All the mapped strike-slip and reverse faults, in the previous
 studies are not recorded in the present study. Furthermore, this study recommends excluding the
 anticline from the Imbricate Zone and including it within the High Folded Zone.

U�Pb zircon SHRIMP evidence for Cambrian volcanism in the Schistose Domain within the Galicia-Tr�s-

SHRIMP U–Pb zircon analyses have shown the complexity of dating volcanic rocks due to the presence of inner cores within zircon crystals. Using the cathodoluminescence studies assisting ion microprobe analyses allow as to conclude that: the two low-grade metavolcanic samples from the Schistose Domain of the Galicia-Tras-os-Montes Zone in the northeast limb of the Verin-Braganca synform (NW Spain and NE Portugal) yield ages of 488.7 ± 3.7Ma and 499.8 ± 3.7Ma (lowermost Ordovician-Upper Cambrian). The Schistose Domain had been traditionally considered as a parautochthonous tectonic unit, i.e. as the stratigraphic continuation of the autochthonous underlying rocks, only locally or moderately detached from them as a result of strong dragging forces from large allochthonous units above it. Current interpretation of the Schistose Domain suggests that this domain formed the outboard edge of the terrane. Important Arenig, felsic magmatism with similar geochemical signature to the volcanic bodies in the Schistose Domain of the Galicia-Tras-os-Montes Zone (GTMSD) series is present also in the adjacent Ollo de Sapo Domain of the Central Zone. This contemporary nature of magmatic events provides an additional argument to support the Iberian affinity of the Schistose Domain of the Galicia-Tras-os-Montes Zone. However, the Cambro–Ordovician facies are very different in the Schistose Domain with respect to the autochthonous unit, the Central–Iberian Zone, suggesting that the Schistose Domain must be considered as a major allochthonous unit with a displacement of over several tens of kilometers.

Paleomagnetic study of Late Paleozoic rocks in the Tacheng Basin of West Junggar (NW China): Implications for the tectonic evolution of the western Altaids

To better understand the tectonic evolution of West Junggar in the western Altaids, we have conducted a combined paleomagnetic and geochronological study on Late Devonian (D3), Late Carboniferous (C2) and Early Permian (P1) successions from the Tacheng Basin, northwest of China. Both primary and secondary characteristic remanent magnetization components have been successfully isolated and yield three reliable paleomagnetic poles of C2 and Late Permian (P2) ages. The C2 and P2 poles reveal a significant clockwise rotation of 35.6°±10.4° which is comparable to the rotation deduced in the western part of the Chingiz Range during the time interval C2 to P2. Similar rotation patterns for the two units suggest that the Chingiz–West Junggar has remained as a quasi-rigid block by the P2 time and constituted the northeast limb of the Kazakhstan Orocline. The differential rotation of ca. 25° to 30° deduced between the northeast and middle limbs of the Kazakhstan Orocline further suggests that at least a part of the curvature of the Balkhash Arc was acquired during the C2 to P2 interval and was a continuation of the middle Paleozoic oroclinal bending. Moreover, the C2 poles for West Junggar and the Junggar Block are significantly different while the P2 ones almost overlap supporting the view that final closure of the Balkhash–Junggar Ocean occurred during the C2 to P2 interval. On the other hand, a large-scale counterclockwise rotation of ca. 80° to 90° is observed in West Junggar and Junggar relative to the western part of the Chingiz Range since the P2 time, and this rotation probably represents an important intra-continental deformation within the western part of the Altaids. A reconstruction of the Paleo-Asian Ocean has been proposed in which the Kazakhstan Orocline was emphasized by using the paleomagnetic results and geological evidence.

Oroclines and paleomagnetism in Borneo and South-East Asia

Oroclinal bending of Borneo is interpreted to result from indentation and collision by the continental promontory of the Miri Zone-Central Luconia Province of northern Sundaland into southern Sundaland. The collision caused strong compression and uplift of the intervening Sibu Zone Upper Cretaceous–Eocene Rajang-Embaluh Group turbidite basin that was floored by oceanic crust of the Proto South China Sea. Timing of the collision is indicated by uplift of turbidite formations to be overlain by Upper Eocene–Lower Oligocene carbonates and intrusion of tin-mineralised granites into the turbidites at the south-east maximum inflexion of the orocline, a region complicated by juxtaposition of both shallow and deep water formations. The oroclinal model, requiring clockwise rotation of the north-west limb, is given no support from the paleomagnetic data that instead demonstrate about 50° of Cenozoic anti-clockwise rotation. Unfortunately not a single outcrop of the strongly oroclinally bent Sibu Zone rocks was measured for paleomagnetism in the north-west limb. Limited support was given for the required anti-clockwise rotation in the north-east limb. Previous syntheses emphasised anti-clockwise rotation, or stable non-rotation of the greater Borneo region as a coherent entity, without any internal deformation. Such models have ignored the oroclinal shape defined by the areal geology of the island, known since early Dutch publications. The northern Thailand–Myanmar north–south-trending geology fabric results from indentation by a promontory of continental India at the Assam–Yunnan oroclinal syntaxis, resulting in paleomagnetically-determined clockwise rotation. The bend of Peninsular Malaysia and Sumatra, from north–south changing to west–east towards Borneo in the south, remains difficult to model because of widespread remagnetisation.

Another Abundance Inhomogeneity in the South East Limb of the Cygnus Loop

Abstract We observed the south east (SE) limb of the Cygnus Loop with Suzaku. Our spatially-resolved spectroscopic study shows that a one-$kT_\mathrm{e}$ non-equilibrium ionization model represents our spectra fairly well. We find that the metal abundances obtained are all depleted relative to the solar values with a positional dependence along the radial direction of the Cygnus Loop. The abundances in the very edge of the limb show about half the solar value, whereas other regions inside the Loop show about 0.2-times the solar value, which has been believed to be a typical value for the Cygnus Loop limb. The “enhanced” abundance in the very edge of the SE limb is quite similar to that found in the north-east (NE) limb of the Loop, and thus this is another evidence of an abundance inhomogeneity in the limb regions of the Loop. The radio map shows a quite different feature: the NE limb is in the radio bright region, while the SE limb shows almost no radio. Therefore, the metal abundance variation in the SE limb can not be attributed to non-thermal emission. The abundance inhomogeneity as well as the metal depletion down to 0.2 times the solar value still remain an open question.

Three-Dimensional Motion of Plasmas Associated with a Coronal Mass Ejection Observed with NOrikura Green-Line Imaging System (NOGIS)

In order to investigate the structure and the driving mechanism of Coronal Mass Ejections (CMEs), it is important to examine in detail the magnetic field structure in the low corona. NOrikura Green-line Imaging System, with its unique capability of Doppler imaging, was used to study a CME and its source region on 1999 May 7. Prior to the CME, a small loop at the north-east limb moved toward a neighboring larger loop in the plane of the sky. Then, the small loop apparently destabilized the large loop, resulting in the CME with a red-shifted motion. The CME propagated non-radially in the plane of the sky. These observations indicate that two loop systems were involved in this CME, and the direction of mass ejection was determined by the magnetic field configuration around the source region and the location of the initial energy release in the magnetic field structure. A brief discussion is given on the loop oscillation phenomenon observed during this event.

The Cinderella loop project

The solar loop that formed off the northeast limb of the Sun on 1999 November 6 (a.k.a. the Cinderella loop) is one of the few examples of a loop on the limb observed with all three of the following imaging instruments: the Transition Region and Coronal Explorer (TRACE), the SOHO Extreme-ultraviolet Imaging Telescope (EIT), and the Yohkoh Soft X-ray Telescope (SXT). In this project we investigate the temperature differences that result when examining the Cinderella loop with one instrument compared with another. For example, what temperature differences result from the increased spatial resolution between the two EUV imagers? More specifically, given that TRACE and EIT have almost identical temperature response to coronal plasma, does the different spatial resolution of TRACE (with 0.5″ pixels) and EIT (with 2.6″ pixels) produce statistically different results? We find that the answer is no, and that our results do not change after background subtraction. In addition, the spatial resolution of EIT and SXT is similar, but the temperature responses of the two instruments are quite different. The two instruments do not seem to be viewing the same loop strands, and the plasma temperature differences are significant.

Electron density along a coronal loop observed with CDS/SOHO

The analysis of a coronal loop observed by CDS and EIT on board SOHO is presented. The loop was situated above the North-East limb at a latitude of ∼48 ◦ , being clearly visible in the hottest lines of the dataset, Fe  360.76 A, i.e. greater than 2 000 000 K. The cooler lines in the sample (i.e. O  629.73 A and He  584.35 A) showed only a brightening at the footpoints location. Based on the Fe  353.84/334.17 line ratio, the electron density along the loop was determined following three different approaches for the background subtraction. No differences, within the error bars, can be found between the three methods. At the apex, the density is 0.9 × 10 9 cm −3 , while at the footpoint it is 50% greater, i.e. 1.4 × 10 9 cm −3 . The inferred filling factor values along the loop, at the formation temperature of the lines, are in the range 0.2-0.9. One dimensional hydrodynamic modelling of the loop along a given field line, gravity neglected, was performed. A minimum χ 2 analysis results in a best fit case where the total energy input is directed preferentially to the loop footpoint (the heating rate is three times larger at the base than at the apex). An isochoric solution can not be ruled out completely. The exercise illustrates the necessity of accurate spectral diagnostics in order to derive definite conclusions from theoretical models and suggests the need for simultaneous density and temperature diagnostics.

An HiRing in the Southeast Cygnus Loop

A large ring feature is identified in 21 cm neutral hydrogen (H I) line observations of the Cygnus Loop supernova remnant. The observations were made with the Dominion Radio Astrophysical Observatory's Synthesis Telescope and 26 m telescope. The eastern and western parts of the ring are bright, but the central regions are faint. On the sky, the H I ring extends from the southeast rim toward the center of the Cygnus Loop but is argued to lie on the front side, outside the shock front, except at its eastern end. The ring is found in the IRAS 60 and 100 μm maps of the region, allowing H I and dust column densities to be determined. The association of the eastern end of the ring with the optically and X-ray–identified southeast knot supports its physical association with the Cygnus Loop. The ring's mean velocity of -4 km s-1 is offset from the Cygnus Loop galactocentric velocity of ~4 km s-1. This indicates that the ring has been accelerated by ~8 km s-1 by the rocket effect, in a similar manner to that for the H I cloud at the northeast limb of the Cygnus Loop. The Cygnus Loop cavity is proposed to result from the acceleration of several similar clouds.

Separating Thermal and Nonthermal X‐Rays in Supernova Remnants. II. Spatially Resolved Fits to SN 1006 AD

We present a spatially resolved spectral analysis of full ASCA observations of the remnant of the supernova of A.D. 1006. This remnant shows both nonthermal X-ray emission from bright limbs, generally interpreted as synchrotron emission from the loss-steepened tail of the nonthermal electron population also responsible for radio emission, and thermal emission from elsewhere in the remnant. In earlier work, we showed that the spatially integrated spectrum was well described by a theoretical synchrotron model in which shock acceleration of electrons was limited by escape, in combination with thermal models indicating high levels of iron from ejecta. Here we use new spatially resolved subsets of the earlier theoretical nonthermal models for the analysis. We find that emission from the bright limbs remains well described by those models and refine the values for the characteristic break frequency. We show that differences between the northeast and southwest nonthermal limbs are small, too small to account easily for the presence of the northeast limb, but not the southwest, in TeV γ-rays. Comparison of spectra of the nonthermal limbs and other regions confirms that simple cylindrically symmetric nonthermal models cannot describe the emission, and we put limits on nonthermal contributions to emission from the center and the northwest and southeast limbs. We can rule out solar-abundance models in all regions, finding evidence for elevated abundances. However, more sophisticated models will be required to accurately characterize these abundances.

ChandraCCD Imagery of the Northeast and Northwest Limbs of SN 1006

We present deep images of the SN 1006 remnant (G327.6+14.6) with the ACIS instrument on the Chandra X-Ray Observatory. Two regions have been observed, the synchrotron-dominated northeast limb and the thermally dominated northwest limb, as well as a substantial portion of the interior of the remnant shell. The brightest features in the X-ray images correspond closely to radio features in the northeast and to Balmer-dominated filaments in the northwest. The spectra of the brighter filaments in the northeast are harder, with less prominent line emission than those in the northwest. In addition to highly elongated filaments, both images show enhanced clumps of emission well inside of the shock front that appear to be dominated by emission from oxygen. These probably arise from shock-heated ejecta, based on analysis of their X-ray spectra. We find no firm evidence for a halo of X-ray emission outside the shock to the northeast, as predicted by the Fermi shock-acceleration picture, in which relativistic electrons should be diffusing ahead of the shock. Our limits on upstream emission are less than 1.5% of the postshock levels in regions where the supernova remnant is brightest. This strongly suggests that the bright rims are flattened sheets nearly perpendicular to the plane of the sky and that the magnetic field strength jumps at the shock by a factor significantly larger than 4, as has been proposed if the shock puts significant energy into accelerating nonthermal ions. The spectra obtained of the northwest rim are all dominated by the helium-like ions of O, Ne, Mg, and Si expected from shocks with ionization (net) parameters of order 100 cm-3 yr and electron temperatures of 0.5-1 keV, far lower than the postshock ion temperature implied by estimates of the shock speed obtained from the shape of the Hα line.

Structure of the Hinear the Northeast Limb of the Cygnus Loop

Observations of the 21 cm neutral hydrogen line of the northeastern part of the Cygnus Loop have been made with the Dominion Radio Astrophysical Observatory's Synthesis Telescope and the 26 m telescope. The northeast rim has a region almost free of confusing bright structures, allowing analysis of the velocity structure of the smoothly distributed H I near the limb. Spectral line maps in 128 channels with 1.65 km s-1 velocity separation were constructed for the region. The kinematic and positional data are evidence for a cloud of atomic material in the form of an expanding partial shell adjacent to the northeast limb of the Cygnus Loop. The partial shell is of relatively high density (4 cm-3), is expanding at 6 km s-1 with a velocity dispersion of 3 km s-1, is thick (~3 pc), and has a mass of ~8 M☉. Possible origins of the shell are discussed.

Improved Estimate of the Magnetic Field in a Prominence

We present new results on the inversion of spectropolarimetric data of the He I D3 line in a prominence. These data were taken with the High Altitude Observatory Stokes II polarimeter on 1980 August 5. Full Stokes profiles in I, Q, U, and V were recorded at 13 locations of a prominence at the northeast limb. This prominence erupted 3 hr later, giving rise to the day of year 218 Solar Maximum Mission coronal transient. The data were originally analyzed in a paper by Querfeld et al. Here we analyze the data using the new inversion algorithm proposed by Lopez Ariste & Casini based on pattern recognition techniques. This method employs full Stokes profiles, and in tests on synthetic data, it proved to be much more precise than previous diagnostic procedures. When applied to the Stokes data of the prominence under study, it gives magnetic field strengths at least 2 times larger than previous estimates.