North Lobe Research Articles

Probing the Length of the Heliospheric Tail with Energetic Neutral Atoms (ENAs) from 0.52 to 80 keV

The shape of the heliosphere is currently under active debate. Energetic neutral atoms (ENAs) offer the best method for investigating the global structure of the heliosphere. To date, the Interstellar Boundary Explorer (IBEX) and the Ion and Neutral Camera (INCA) that was on board Cassini provide the only global ENA observations of the heliosphere. While extensive modeling has been done at IBEX-Hi energies (0.52–6 keV), no global ENA modeling has been conducted for INCA energies (5.2–55 keV). Here, we use an ENA model of the heliosphere based on hybrid results that capture the heating and acceleration of pickup ions (PUIs) at the termination shock to compare modeled global ENA results with IBEX-Hi and INCA observations using both a long- and short-tail model of the heliosphere. We find that the modeled ENA results for the two heliotail configurations produce similar results from the IBEX-Hi through the INCA energies. We conclude from our modeled ENAs, which only include PUI acceleration at the termination shock, that ENA observations in currently available energy ranges are insufficient for probing the shape and length of the heliotail. However, as a prediction for the future IMAP-Ultra mission (3–300 keV) we present modeled ENA maps at 80 keV, where the cooling length (∼600 au) is greater than the distance where the long- and short-heliotail models differ (∼400 au), and find that IMAP-Ultra should be able to identify the shape of the heliotail, predicting differences in the north lobe to downwind flux ratio between the models at 48%.

A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy cluster

Abstract Clusters of varying mass ratios can merge and the process significantly disturbs the cluster environments and alters their global properties. Active radio galaxies are another phenomenon that can also affect cluster environments. Radio jets can interact with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384 (hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its morphology suggests that A2384 is a post-merger system where A2384(S) has already interacted with the A2384(N), and as a result hot gas has been stripped over a ∼1 Mpc region between the two bodies. We have obtained its 325 MHz GMRT data, and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S). One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in the opposite direction. This results in displacement in the bridge close to A2384(S). Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and entropy enhancement at the radio lobe-X-ray plasma interaction site, which further suggests that the radio lobe is changing thermal plasma properties. We have also studied the radio properties of the FR I radio galaxy, and found that the size and radio luminosity of the interacting north lobe of the FR I galaxy are lower than those of the accompanying south lobe.

Searching for intergalactic star forming regions in Stephan’s Quintet with SITELLE

Stephan’s Quintet (SQ), the prototypical compact group of galaxies in the local Universe, has been observed with the imaging Fourier transform spectrometer SITELLE, attached to the Canada-France-Hawaii-Telescope, to perform a deep search for intergalactic star-forming emission. In this paper we present the extended ionised gaseous structures detected and analyse their kinematical properties. The large field of view (11′ × 11′) and the spectral ranges of SITELLE have allowed a thorough study of the entire galaxy system, its interaction history and the main properties of the ionised gas. The observations have revealed complex three-dimensional strands in SQ seen for the first time, as well as the spatially resolved velocity field for a new SQ dwarf galaxy (M 82-like) and the detailed spectral map of NGC 7320c, confirming its AGN nature. A total of 175 SQ Hα emission regions have been found, 22 of which present line profiles with at least two kinematical components. We studied 12 zones and 28 sub-zones in the SQ system in order to define plausible physical spatial connections between its different parts in the light of the kinematical information gathered. In this respect we have found five velocity systems in SQ: (i) v = [5600−5900] km s−1 associated with the new intruder and the southern debris region; (ii) v = [5900−6100] km s−1, associated with the north starburst A and south starburst A and the strands connected to these zones; (iii) v = [6100−6600] km s−1, associated with the strands from the large-scale shock region (LSSR); (iv) v = [6600−6800] km s−1, associated with the young tidal tail, the starburst A (SQA), NGC 7319, and the NGC 7319 north lobe; and (v) v = [6800−7000] km s−1, associated with the strands seen connecting LSSR with SQA. We fail to detect ionised gas emission in the old tail, neither in the vicinity of NGC 7318A nor in NGC 7317, and the connection between NGC 7319 north lobe and SQA cannot be confirmed. Conversely, a clear gaseous bridge has been confirmed both spatially and kinematically between the LSSR zone and the NGC 7319 AGN nucleus. Finally, a larger scale, outer rim winding the NGC 7318B/A system clockwise north-west to south-east has been highlighted in continuum and in Hα. This structure may be reminiscent of a sequence of a previously proposed scenario for SQ a sequence of individual interactions.

Ion dynamics in magnetotail reconnection in the presence of density asymmetry

AbstractWe present the first dual‐spacecraft observations of antiparallel, asymmetric magnetic reconnection in the Earth's magnetotail. The measurements were made with the comprehensive instrumentation of the ARTEMIS mission at the lunar distance near the dusk flank. The north lobe had high‐density mantle and boundary layer plasma, while the south lobe had a much lower density, consistent with the prevailing solar wind conditions. The two spacecraft observed a finite width reconnection flow channel emanating from a tailward moving X line. Within the jet, the Hall magnetic field polarity corresponding to the high‐density north lobe was enhanced, and the peak flow velocity was shifted toward the low‐density south side, consistent with expectations from simulations. Two counterstreaming populations are seen in the distribution functions in most parts of the exhaust, in contrast to single‐population convective flows reported in a previous asymmetric magnetotail reconnection event. Furthermore, the density difference of the two distinct mixing populations of different density is visible in the exhaust distributions up to ∼150di downstream of the X line. We observe no signatures of Speiser‐like ion motion near the neutral plane, in agreement with theoretical expectations for asymmetric boundary conditions.

Giant lobes of Centaurus A as seen in radio andγ-ray images obtained with theFermi-LAT andPlancksatellites

The γ -ray data of Fermi -LAT on the giant lobes of Centaurus A are analysed together with the high frequency radio data obtained with the Planck satellite. The large γ -ray photon statistics, accumulated during seven years of observations, and the recently updated Fermi -LAT collaboration software tools allow substantial extension of the detected γ -ray emission towards higher energy, up to 30 GeV, and lower energy, down to 60 MeV. Moreover, the new γ -ray data allow us to explore the spatial features of γ -ray emission of the lobes. For the north lobe, we confirm, with higher statistical significance, our earlier finding on the extension of γ -ray emission beyond the radio image. Moreover, the new analysis reveals significant spatial variation of γ -ray spectra from both lobes. On the other hand, the Planck observations at microwave frequencies contain important information on spectra of synchrotron emission in the cutoff region, and thus allow model-independent derivation of the strength of the magnetic field and the distribution of relativistic electrons based on the combined γ -ray and radio data. The interpretation of multiwavelength spectral energy distributions of the lobes within a pure leptonic model requires strong enhancement of the magnetic field at the edge of the south lobe. Alternatively, a more complex, leptonic-hadronic model of the γ -ray emission, postulating a non-negligible contribution of the π 0 -decay component at highest energies, can explain the γ -ray data with a rather homogeneous distribution of the magnetic field over the giant lobes.

Fláajökull (north lobe), Iceland: active temperate piedmont lobe glacial landsystem

ABSTRACTA 1:6250 map of the foreland of Fláajökull's north lobe as it appeared in 1989, together with a 1:350 scale map of a sample area of recently exposed glacial landforms from 2014, enables an assessment of the spatial and temporal evolution of glacial landform assemblages at the margin of an active temperate piedmont lobe terminating at ice-marginal thickening till wedges. The pattern of landform development captured in these maps indicates that the glacier margin developed strong longitudinal crevassing and well-developed ice-marginal pecten (three-dimensional crenulations) during its historical recession. This is recorded by early recessional phase linear push moraines on well-drained distal slopes of the foreland and the later development of interrelated sawtooth moraines, crevasse squeeze ridges and till eskers, indicative of extending ice flow and poorly drained submarginal conditions. This landform record is a palaeoglaciological signature of a changing process–form regime inherent within the active temperate piedmont lobe landsystem model.

Simulation of interplanetary magnetic field By penetration into the magnetotail

Based on our global 3D magnetospheric MHD simulation model, we investigate the phenomena and physical mechanism of the By component of the interplanetary magnetic field (IMF) penetrating into the magnetotail. We find that the dayside reconnected magnetic field lines move to the magnetotail, get added to the lobe fields, and are dragged in the IMF direction. However, the By component in the plasma sheet mainly originates from the tilt and relative slippage of the south and north lobes caused by plasma convection, which results in the original Bz component in the plasma sheet rotating into a By component. Our research also shows that the penetration effect of plasma sheet By from the IMF By during periods of northward IMF is larger than that during periods of southward IMF.

The substorm current wedge and midnight sector partial ring current near substorm onset: A synthesis based on a magnetotail magnetic field geometry model

The Substorm Current Wedge (SCW) occurrence in the late growth and onset phases of substorms was proposed as thecurrent system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally wassuggested to be the strong westward auroral electrojet (WEJ). However, the SCW-WEJ system has no viable generator current.Similarly, the asymmetric or Partial Ring Current (PRC) increases in strength during the growth phase, and is sometimes associatedwith an enhanced Region 2 field-aligned current (FAC) closing to the ionosphere, but specifics of that closure have been lacking.Here we present a unifying picture which includes the SCW post- and pre-midnight (AM and PM, respectively) currents and agenerator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotailmagnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types ofclosed field line regions-stretched lines in the central part of the plasmasheet (SPS) and dipolar lines (DPS) between the low latitudeboundary layer (LLBL) regions and the SPS. There is also an important plasmasheet transition region (TPS) in which thedipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which themidnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which becomespart of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on thedawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the ionosphere.These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriatelocations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and thefinal upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originallyproposed SCW.

The magnetic field of the H ii region NGC 6334A from Faraday rotation

We have studied the polarization characteristics and Faraday rotation of the extragalactic radio source J17204$-$3554, that appears projected on the north lobe of the galactic H II region NGC 6334A. From observations made with the Very Large Array at 6.0 and 3.6 cm in three different epochs (1994, 1997, and 2006), we estimate a rotation measure of +5100$\pm$900 rad m$^{-2}$ for the extragalactic source. This large rotation measure implies a line-of-sight average magnetic field of $B_\parallel \simeq +36\pm6$ $\mu$G, the largest obtained by this method for an H II region. NGC 6334A is significantly denser than other H II regions studied and this larger magnetic field is expected on the grounds of magnetic flux conservation. The ratio of thermal to magnetic pressure is $\sim$5, in the range of values determined for more diffuse H II regions.

Tree-Ring Dates for the Maximum Little Ice Age Advance of Kaskawulsh Glacier, St. Elias Mountains, Canada

A dendroglaciological study at Kaskawulsh Glacier provides the first calendar dating of a Little Ice Age glacier advance in the northeast St. Elias Mountains of Yukon Territory. Ring series from white spruce trees, Picea glauca (Moench) Voss, that had been sheared, tilted, and killed by deposition of till at the glacier’s terminal moraine were cross-dated with a millennium-length ring-width chronology developed at a site near the south end of Kluane Lake, about 25 km north of the glacier forefield. Six cross-dated samples from two sites at Kaskawulsh Glacier suggest that the north lobe of the glacier reached its greatest Holocene extent in the mid-1750s. Additional limited data suggest that the east lobe may have reached its maximum extent somewhat earlier (ca. 1717). This chronology of Little Ice Age activity of Kaskawulsh Glacier is consistent with well-dated glacier chronologies from adjacent mountain ranges in coastal and interior Alaska. The results also demonstrate the potential to derive calendar dates from subfossil wood in the St. Elias Mountains that hitherto had been dated only with much lower precision, using radiocarbon techniques.

The White River Ash: largest Holocene Plinian tephra

The White River Ash is a bi-lobate tephra in eastern Alaska, Yukon Territory, and western Northwest Territories. Plinian-type eruptions produced the north lobe ∼1900 years BP and the larger east lobe ∼1250 years BP (14C years). Present evidence favors the vent for the east lobe to be beneath the Klutlan Glacier. East lobe pumice is not present atop Mt. Churchill, so the pumice there must belong to the north lobe and is also likely to have come from a vent beneath the Klutlan Glacier. Isopachs of the east lobe, now known to stretch as far east as Great Bear Lake, indicate an east lobe volume of ∼47 km3. Thickness and grain size of the east lobe decay in exponential fashion, producing straight line plots when the thickness half-distance and clast half-distance are plotted against the square root of the isopach area, the proximal slope being steeper than the distal. The east lobe eruption is indicated to have been into a wind of about 10 m/s and to have produced an eruptive cloud height of ∼45 km. The eruption rate was at least 2.8 × 108 kg/s.

Volcanology of the Aries micaceous kimberlite, central Kimberley Basin, Western Australia

The Neoproterozoic (815.4 ± 4.3 Ma) Aries kimberlite intrudes the King Leopold Sandstone and the Carson Volcanics in the central Kimberley Basin, northern Western Australia. Aries is comprised of a N–NNE-trending series of three diatremes and associated hypabyssal kimberlite dykes and plugs. The diatremes are volumetrically dominated by massive, clast-supported, accidental lithic-rich kimberlite breccias that were intruded by hypabyssal macrocrystic phlogopite kimberlite dykes and plugs with variably uniform- to globular segregationary-textured groundmasses. Lower-diatreme facies, accidental lithic-rich breccias probably formed through fall-back of debris into the vent with a major contribution from the collapse of the vent walls. These massive breccias are overlain by a sequence of bedded volcaniclastic breccias in the upper part of the north lobe diatreme. Abundant, poorly vesicular to nonvesicular, juvenile kimberlite ash and lapilli, with morphologies that are indicative of phreatomagmatic fragmentation processes, occur in a reversely graded volcaniclastic kimberlite breccia unit at the base of this sequence. This unit and overlying bedded accidental lithic-rich breccias are interpreted to be sediment gravity-flow deposits (including possible debris flows) derived from the collapse of the crater walls and/or tephra ring deposits that surrounded the crater. Diatreme-forming eruptions may have been initiated by magma–water interactions along fracture and joint-controlled aquifers within the King Leopold Sandstone. The current level of exposure of the diatremes probably extends from the lower-diatreme facies up into the base of a bedded upper-diatreme sequence.

PACERMAN -- II. Application and statistical characterization of improved RM maps

We have proposed a new method - PACERMAN - to calculate Faraday rotation measure (RM) maps from multifrequency polarization angle data in order to avoid the so-called nπ-ambiguity. Here, we apply our PACERMAN algorithm to two polarization data sets of extended radio sources in the Abell 2255 and the Hydra A cluster, and compare the RM maps obtained using PACERMAN to RM maps obtained employing already existing methods. Thereby, we provide a new high-quality RM map of the Hydra north lobe which is in good agreement with the existing one but find significant differences in the case of the south lobe of Hydra A. We demonstrate the reliability and the robustness of PACERMAN. In order to study the influence of map-making artefacts, which are imprinted by wrong solutions to the nπ-ambiguities, and of the error treatment of the data, we calculated and compared magnetic field power spectra from various RM maps. The power spectra were derived using the method recently proposed by EnBlin & Vogt. We demonstrate the sensitivity of statistical analysis to artefacts and noise in the RM maps and thus we demonstrate the importance of an unambiguous determination of RM maps and an understanding of the nature of the noise in the data. We introduce and perform statistical tests to estimate the quality of the derived RM maps, which demonstrate the quality improvements due to PACERMAN.

A BAYESIAN VIEW ON FARADAY ROTATION MAPS - SEEING THE MAGNETIC POWER SPECTRUM IN CLUSTERS OF GALAXIES

Magnetic fields are an important ingredient of galaxy clusters and are indirectly observed on cluster scales as radio haloes and radio relics. One promising method to shed light on the properties of cluster wide magnetic fields is the analysis of Faraday rotation maps of extended extragalactic radio sources. We developed a Fourier analysis for such Faraday rotation maps in order to determine the magnetic power spectra of cluster fields. In an advanced step, here we apply a Bayesian maximum likelihood method to the RM map of the north lobe of Hydra A on the basis of our Fourier analysis and derive the power spectrum of the cluster magnetic field. For Hydra A, we measure a spectral index of -5/3 over at least one order of magnitude implying Kolmogorov type turbulence. We find a dominant scale of about 3 kpc on which the magnetic power is concentrated, since the magnetic autocorrelation length is <TEX>${\lambda}_B = 3 {\pm} 0.5\;kpc$</TEX>. Furthermore, we investigate the influences of the assumption about the sampling volume (described by a window function) on the magnetic power spectrum. The central magnetic field strength was determined to be <TEX>${\~}7{\pm}2{\mu}G$</TEX> for the most likely geometries.

Is the Cepheus E Outflow Driven by a Class 0 Protostar?

New early release observations of the Cepheus E outflow and its embedded source, obtained with the Spitzer Space Telescope, are presented. We show the driving source is detected in all 4 IRAC bands, which suggests that traditional Class 0 classification, although essentially correct, needs to accommodate the new high sensitivity infrared arrays and their ability to detected deeply embedded sources. The IRAC, MIPS 24 and 70 microns new photometric points are consistent with a spectral energy distribution dominated by a cold, dense envelope surrounding the protostar. The Cep E outflow, unlike its more famous cousin the HH 46/47 outflow, displays a very similar morphology in the near and mid-infrared wavelengths, and is detected at 24 microns. The interface between the dense molecular gas (where Cep E lies) and less dense interstellar medium, is well traced by the emission at 8 and 24 microns, and is one of the most exotic features of the new IRAC and MIPS images. IRS observations of the North lobe of the flow confirm that most of the emission is due to the excitation of pure H2 rotational transitions arising from a relatively cold (Tex~700 K) and dense (N{H}~9.6E20 cm-2 molecular gas.

MERLIN observations of Stephan's Quintet

We present MERLIN L-band images of the compact galaxy group, Stephan's Quintet. The Seyfert 2 galaxy, NGC 7319, the brightest member of the compact group, is seen to have a triple radio structure typical of many extra-galactic radio sources which have a flat spectrum core and two steep spectrum lobes with hot spots. The two lobes are asymmetrically distributed on opposite sides of the core along the minor axis of the galaxy. Ultraviolet emission revealed in a high resolution HRC/ACS HST image is strongly aligned with the radio plasma and we interpret the intense star formation in the core and north lobe as an event induced by the collision of the north radio jet with over-dense ambient material. In addition, a re-mapping of archive VLA L-band observations reveals more extended emission along the major axis of the galaxy which is aligned with the optical axis. Images formed from the combined MERLIN and archive VLA data reveal more detailed structure of the two lobes and hot spots.

Imaging and Spatially Resolved Spectroscopy of AFGL 2688 in the Thermal Infrared Region

We present ground-based high-resolution (~03) imaging of AFGL 2688 at L' (3.8 μm) and M' (4.7 μm). A wealth of structure in the central region is revealed as a consequence of less extinction in the thermal infrared. A clear border in the southern lobe at L' corresponds to the edge of the heavily obscured region in visible, indicating that there is a dense material surrounding the central region. The images also show a narrow dark lane oriented to 140° east of north with the normal at 50°. The normal position angle is inconsistent with the optical polar axis (P.A. = 15°) but is aligned to the high-velocity CO components found in the radio wavelength observations. The central star remains invisible at L' and M'. Several clumpy regions in the north lobe dominate in L' and M' luminosity. In particular, a pointlike source (peak A) at 05 northeast of the center of the nebula exhibits the highest surface brightness with a very red spectral energy distribution (SED). Based on the almost identical SED at adjacent regions, we suggest that the pointlike source is not self-luminous, as was proposed, but is a dense dusty blob reflecting thermal emission from the central star. We also present spatially resolved slit spectroscopy of the bright dusty blobs. An emission feature at 3.4 μm as well as at 3.3 μm is detected everywhere within our field of view. There is no spatial variation in the infrared emission feature throughout the observed area (02-15, or 240-1800 AU from the central source). The constant flux ratio of the emission feature relative to the continuum is consistent with the view that the blobs are mostly reflecting the light from the central star in the 3 μm region.

Dual spacecraft observations of lobe magnetic field perturbations before, during and after plasmoid release

This study examines a data set returned by IMP 8 and Geotail on January 29, 1995 during a substorm which resulted in the ejection of a plasmoid. The two spacecraft (s/c) were situated in the north lobe of the tail and both observed a traveling compression region (TCR). We show that in this instance dual s/c measurements can be used to model all three dimensions of the underlying plasmoid and to estimate its rate of expansion. For this event plasmoid dimensions of ΔX ∼18, ΔY ∼30, and ΔZ ∼10 Re are determined from the IMP 8 and Geotail observations. Furthermore, a factor of ∼2 increase in the amplitude of the TCR occurred in the 1.5 min it took to move from IMP 8 to Geotail. Modeled using conservation of magnetic flux, this increase in lobe compression implies that the underlying plasmoid was expanding at a rate of ∼140 km/s. Finally, a reconfiguration of the lobe magnetic field followed plasmoid ejection which moved magnetic flux tubes into the wake behind the plasmoid where they would become available to feed the reconnection region.

Magnetic fabric constraints on the initial geometry of the Sudbury Igneous Complex: a folded sheet or a basin-shaped igneous body?

Interpreted either as a folded igneous sheet or a basin-shaped intrusion, the origin of the Palaeoproterozoic Sudbury Igneous Complex (SIC), Ontario, Canada, has been debated by geologists for over a century. Most recent proposals view the SIC to have been emplaced as a horizontal impact melt and subsequently folded after solidification. This requires the SIC to have folded from an originally horizontal sheet, to the present basinal geometry, with dips of 30° in the North Range and 70° in the East Range. The fold scenario would require the sharply curved juncture between the North and East Ranges (North Lobe) to be deformed in the solid-state due to folding. In order to test the fold model, the rock fabric was investigated in the East and North Ranges and the North Lobe of SIC at 256 sites with the aid of anisotropy of magnetic susceptibility (AMS). A sampling transect through an undeformed portion of the SIC in the western North Range reveals that the gabbro-norite exhibits SIC contact-parallel magnetic foliation and down-dip magnetic lineation, both of which, respectively, correlate to an igneous foliation and lineation. The granophyre, in contrast, features spatially consistent magnetic lineation that is oriented orthogonal to the SIC contact. This magnetic lineation can be correlated to a mineral fabric characterised by aligned acicular crystals of plagioclase, and is interpreted to be a wall-orthogonal crystallisation texture. The East and North Ranges in the eastern SIC reveal similar patterns of AMS fabrics. The magnetic lineation of the granophyre is orthogonal to the basal contact of the SIC in the East and North Ranges, and in the fold-like North Lobe between the two ranges. An axial-planar magnetic foliation is developed in the granophyre as the North Lobe is approached, but the magnetic lineation is nevertheless contact-orthogonal and well-defined. This AMS fabric is interpreted to be a combination of an original igneous contact-orthogonal lineation and a foliation resulting from tectonic overprint. The preservation of the contact-orthogonal magnetic lineation implies low levels of tectonic overprint. Conservative shortening strains estimated from AMS numerical modelling suggest <15% strain in the North Lobe, but most likely <5% strain, as judged from the paucity of microstructural evidence for solid-state deformation. Such low levels of strain are more consistent with a basin-shaped intrusive origin for the SIC, rather than folding of an initially horizontal, and consolidated igneous sheet. This rules out models of initial horizontal sheet emplacement including the recently proposed impact-melt model for the SIC.

First Results from Swan Lyman α Solar Wind Mapper on SOHO

After one year of almost flawless operation on board the SOHO spacecraft poised at L1 Lagrange point, we report the main features of SWAN observations. SWAN is mainly dedicated to the monitoring of the latitude distribution of the solar wind by the La method. Maps of sky Lα emissions were recorded througout the year. The region of maximum emission, located in the upwind hemisphere, deviates strongly from the pattern that could be expected from a solar wind constant with latitude. It is divided into two lobes by a depression aligned with the solar equatorial plane called the Lyα groove already noted in 1976 Prognoz data. The north lobe is much brighter than the south lobe. These two characteristics can be explained qualitatively by an enhanced ionization along the neutral sheet where the slow solar wind is concentrated, which results from the higher low-latitude solar wind mass flux as measured by Ulysses. The groove is the direct imprint on the sky of the enhanced carving by the slow solar wind, at this time of solar minimum, when the tilt angle of the neutral sheet is small. The question is still pending to predict what will happen with the ascending phase of the solar cycle. Observations of comets are briefly mentioned, with the ability of SWAN to monitor the H2O production of many comets. Operations of the instrument are briefly described, including some instrumental problems which could be solved by software modifications sent to the instrument.