Equatorial Distribution Research Articles

Energetic Ions Downtail of the Reconnection Site

AbstractUsing combined MHD/test particle simulations, we explore characteristics of ion (proton) acceleration tailward of a near‐Earth reconnection site. We present spatial distributions and explore acceleration mechanisms and sources of accelerated ions. Acceleration is due primarily due simple crossings of the enhanced electric field near the x‐line or in the departing plasmoid. The energetic particle distributions show the expected energy dispersed tailward streaming at the plasma sheet boundary, while equatorial distributions are more complicated, resulting from different acceleration sites within the moving plasmoid. Sources are mostly inside the central plasma sheet dawnward of the plasmoid.

Why cicadas (Hemiptera: Cicadidae) develop so slowly

Abstract Cicadas have amongst the longest development times and are also amongst the largest insects. Cicadas feed exclusively on xylem fluid, which is nutritionally dilute and difficult to obtain. One possible explanation for their slow development is that poor nutrition limits their growth rate. An analysis of 30 cicada species with known development times is consistent with this hypothesis as species with more equatorial distributions grew more rapidly than those at higher latitudes. A second possible explanation is that prolonged development maximizes net reproductive rate because there is little risk of mortality once early instar cicada nymphs establish feeding sites. Extended development probably allows nymphs to store resources and produce more offspring. Spittlebugs also feed obligately on xylem fluid and grow at similarly slow rates although they attain small adult sizes. Unlike cicadas, spittlebugs do not have steep survivorship curves and have shorter development times. The life histories of cicadas and spittlebugs are therefore consistent with both hypotheses. Cicada development times may be limited if (1) the risk of nymphal mortality equals increased fecundity associated with prolonging development, (2) fluctuating conditions sometimes favour rapid development times, or (3) host plant quality changes over time and penalizes nymphs that cannot relocate feeding sites.

Study of clinical indication, difficulties and complications of DJ stenting in urological procedure at a tertiary hospital

Background: Urolithiasis is one of the major causes of morbidity in our society as our country is located near to equatorial distribution of stone disease Indwelling ureteral stents provide free drainage from the kidney to the bladder, reduce or eliminate urinary leakage and provide ureteral stenting. The present study was designed to observe indications, difficulties and complications of indwelling double J ureteral stenting. Material and Methods: Present study was single-center, prospective, observational study, conducted in patients undergoing DJ stenting URS/ESWL (stone size > 2cm), willing to participate in study. The data collected was entered into Microsoft excel and analyzed. Statistical analysis was done using descriptive statistics. Results: In the present study, we assessed prospectively the effectiveness of DJ stent insertion for treatment of ureteral stones in 100.patients. Gender distribution in the current study was 65% male and 35 % female. 65 % patients were between the age 10 to 40 years; 20 patients have lower ureteric calculi, 37 patient having mid ureteric calculi and 8 patients having upper ureteric calculi. In current study out of 100 patients 32 patients have stone between the range of 6-10 mm, 42 patients have stone size range between 11-16 mm and only 26 patient have stone size more than 16 mm. 32 patients having mid ureteric calculi in which 30 patients DJ stent procedure successfully completed, remaining 2 patients had ureteric stricture treated with URSL. 27 patients having lower ureteric calculi in which 25 patients DJ stent procedure successfully completed, remaining 2 patient had ureteric stricture treated with ESWL followed by cystoscopy removal. 8 patients having bilateral ureteric calculi in which 6 patients DJ stent procedure successfully completed, remaining 2 patient have impacted stone treated with URSL with PCNL. 100% success rate in DJ stent insertion in patients with stone size 11-16mm followed by in 93% with stone size 6-10mm and in 76% with stone size >16mm. Conclusion: Most of the ureteral DJ stent related complications can be managed by surgical procedures hence they should be removed as soon as their purpose solves. The proper follow up from patients can help to early identification of post insertion complications of DJ stent and timely management of them.

A new monosulcate pollen from the Early Cretaceous of central-western Argentina

A new monosulcate species, Shanbeipollenites lagarcitensis sp. nov. is described from the Lower Cretaceous Lagarcito Formation, Sierras de Guayaguas (north-western San Luis Basin), Argentina. Shanbeipollenites lagarcitensis shares with other species of this genus a broadly ellipsoidal outline and a diagonally disposed distal sulcus. However, the new species differs from the psilate type species Shanbeipollenites quadrangulatus and from S. quadratus by the presence of sculptural elements distributed at the equatorial region, close to the opposite ends of the sulcus. The thicker wall, exine separation, much more strongly diagonal offset of the sulcus and the rugulate-verrucate sculpture with an equatorial distribution close to the opposite ends of the sulcus, distinguish this new species and expands the concept of the genus Shanbeipollenites. The presence of two separate exine layers supports its gymnosperm affinity. Furthermore, the occurrence of Shanbeipollenites lagarcitensis in the Albian Lagarcito Formation from mid–latitudes, central–western Argentina constitutes the youngest record of the genus worldwide. This new record expands the biostratigraphical range of the taxon into the Albian.

Energetic Ion Moments and Polytropic Index in Saturn's Magnetosphere using Cassini/MIMI Measurements: A Simple Model Based on κ‐Distribution Functions

AbstractMoments of the charged particle distribution function provide a compact way of studying the transport, acceleration, and interactions of plasma and energetic particles in the magnetosphere. We employ κ‐distributions to describe the energy spectra of H+ and O+, based on >20 keV measurements by the three detectors of Cassini's Magnetospheric Imaging Instrument, covering the time period from DOY 183/2004 to 016/2016, 5 < L < 20. From the analytical spectra we calculate the equatorial distributions of energetic ion moments inside Saturn's magnetosphere and then focus on the distributions of the characteristic energy (Ec=IE/In), temperature, and κ‐index of these ions. A semiempirical model is utilized to simulate the equatorial ion moments in both local time and L‐shell, allowing the derivation of the polytropic index (Γ) for both H+ and O+. Primary results are as follows: (a) The ∼9 < L < 20 region corresponds to a local equatorial acceleration region, where subadiabatic transport of H+ (Γ∼1.25) and quasi‐isothermal behavior of O+ (Γ∼0.95) dominate the ion energetics; (b) energetic ions are heavily depleted in the inner magnetospheric regions, and their behavior appears to be quasi‐isothermal (Γ<1); (c) the (quasi‐) periodic energetic ion injections in the outer parts of Saturn's magnetosphere (especially beyond 17–18 RS) produce durable signatures in the energetic ion moments; (d) the plasma sheet does not seem to have a ground thermodynamic state, but the extended neutral gas distribution at Saturn provides an effective cooling mechanism that does not allow the plasma sheet to behave adiabatically.

A near-infrared, optical, and ultraviolet polarimetric and timing investigation of complex equatorial dusty structures

Context. From stars to active galactic nuclei, many astrophysical systems are surrounded by an equatorial distribution of dusty material that is, in a number of cases, spatially unresolved even with cutting edge facilities. Aims. In this paper, we investigate if and how one can determine the unresolved and heterogeneous morphology of dust distribution around a central bright source using time-resolved polarimetric observations. Methods. We used polarized radiative transfer simulations to study a sample of circumnuclear dusty morphologies. We explored a grid of geometrically variable models that are uniform, fragmented, and density stratified in the near-infrared, optical, and ultraviolet bands, and we present their distinctive time-dependent polarimetric signatures. Results. As expected, varying the structure of the obscuring equatorial disk has a deep impact on the inclination-dependent flux, polarization degree and angle, and time lags we observe. We find that stratified media are distinguishable by time-resolved polarimetric observations, and that the expected polarization is much higher in the infrared band than in the ultraviolet. However, because of the physical scales imposed by dust sublimation, the average time lags of months to years between the total and polarized fluxes are important; these time lags lengthens the observational campaigns necessary to break more sophisticated, and therefore also more degenerated, models. In the ultraviolet band, time lags are slightly shorter than in the infrared or optical bands, and, coupled to lower diluting starlight fluxes, time-resolved polarimetry in the UV appears more promising for future campaigns. Conclusions. Equatorial dusty disks differ in terms of inclination-dependent photometric, polarimetric, and timing observables, but only the coupling of these different markers can lead to inclination-independent constraints on the unresolved structures. Even though it is complex and time consuming, polarized reverberation mapping in the ultraviolet-blue band is probably the best technique to rely on in this field.

Palynofloral evolution on the northern margin of the Indian Plate, southern Xizang, China during the Cretaceous Period and its phytogeographic significance

During the Cretaceous Period, the Indian Plate separated from Gondwana and drifted northwards, eventually colliding with Eurasia at the end of the period or in the early Cenozoic. This led to major changes in the composition of the flora and fauna of the region. Palynomorph assemblages from Cretaceous deposits in Gamba County, southern Xizang (Tibet), China, are analyzed herein in an attempt to determine how the vegetation of the northern margin of the Indian Plate changed. The Gamba assemblages were initially similar in composition to those from Australia but by the Santonian Stage they were more similar to those of North Africa. Differences from the former are increasingly apparent through the Albian–Cenomanian transition. The rate of evolution of the Gamba flora was about the same as that of the Australian flora prior to the Albian, somewhat slower during this stage, but faster from the Cenomanian onwards, implying that this was, to a large extent, a result of the separation of the Indian Plate from Gondwana and its northward drift during the Cretaceous Period. During the Albian, the Australian block drifted eastwards whereas the Indian Plate remained relatively static. This resulted in few changes in the Gamba palynoflora but many in palynofloras from Australia. However, the northward movement of the Indian Plate in the Late Cretaceous led to pronounced changes, with numerous inceptions of genera and species in the Gamba succession. Of these, many have an African or equatorial distribution and none has connections with Australia, indicating that the climate at this time was similar to that of North Africa and that separation from Australia was complete. The arrival of the Indian Plate in equatorial regions allowed floral exchange between its northern part and North Africa during the Santonian.

ASPHERICITY, INTERACTION, AND DUST IN THE TYPE II-P/II-L SUPERNOVA 2013EJ IN MESSIER 74

ABSTRACT SN 2013ej is a well-studied core-collapse supernova (SN) that stemmed from a directly identified red supergiant (RSG) progenitor in galaxy M74. The source exhibits signs of substantial geometric asphericity, X-rays from persistent interaction with circumstellar material (CSM), thermal emission from warm dust, and a light curve that appears intermediate between supernovae of Types II-P and II-L. The proximity of this source motivates a close inspection of these physical characteristics and their potential interconnection. We present multiepoch spectropolarimetry of SN 2013ej during the first 107 days and deep optical spectroscopy and ultraviolet through infrared photometry past ∼800 days. SN 2013ej exhibits the strongest and most persistent continuum and line polarization ever observed for a SN of its class during the recombination phase. Modeling indicates that the data are consistent with an oblate ellipsoidal photosphere, viewed nearly edge-on and probably augmented by optical scattering from circumstellar dust. We suggest that interaction with an equatorial distribution of CSM, perhaps the result of binary evolution, is responsible for generating the photospheric asphericity. Relatedly, our late-time optical imaging and spectroscopy show that asymmetric CSM interaction is ongoing, and the morphology of broad Hα emission from shock-excited ejecta provides additional evidence that the geometry of the interaction region is ellipsoidal. Alternatively, a prolate ellipsoidal geometry from an intrinsically bipolar explosion is also a plausible interpretation of the data but would probably require a ballistic jet of radioactive material capable of penetrating the hydrogen envelope early in the recombination phase. Finally, our latest space-based optical imaging confirms that the late interaction-powered light curve dropped below the stellar progenitor level, confirming the RSG star’s association with the explosion.

Solar wind‐driven variations of electron plasma sheet densities and temperatures beyond geostationary orbit during storm times

AbstractThe empirical models of the plasma sheet electron temperature and density on the nightside at distances between 6 and 11 RE are constructed based on Time History of Events and Macroscale Interactions During Substorms (THEMIS) particle measurements. The data set comprises ∼400 h of observations in the plasma sheet during geomagnetic storm periods. The equatorial distribution of the electron density reveals a strong earthward gradient and a moderate variation with magnetic local time symmetric with respect to the midnight meridian. The electron density dependence on the external driving is parameterized by the solar wind proton density averaged over 4 h and the southward component of interplanetary magnetic field (IMF BS) averaged over 6 h. The interval of the IMF integration is much longer than a typical substorm growth phase, and it rather corresponds to the geomagnetic storm main phase duration. The solar wind proton density is the main controlling parameter, but the IMF BS becomes of almost the same importance in the near‐Earth region. The root‐mean‐square deviation between the observed and predicted plasma sheet density values is 0.23 cm−3, and the correlation coefficient is 0.82. The equatorial distribution of the electron temperature has a maximum in the postmidnight to morning MLT sector, and it is highly asymmetric with respect to the local midnight. The electron temperature model is parameterized by solar wind velocity (averaged over 4 h), IMF BS (averaged over 45 min), and IMF BN (northward component of IMF, averaged over 2 h). The solar wind velocity is a major controlling parameter, and IMF BS and BN are comparable in importance. In contrast to the density model, the electron temperature shows higher correlation with the IMF BS averaged over ∼45 min (substorm growth phase time scale). The effect of BN manifests mostly in the outer part of the modeled region (r > 8RE). The influence of the IMF BS is maximal in the midnight to postmidnight MLT sector. The correlation coefficient between the observed and predicted plasma sheet electron temperature values is 0.76, and the root‐mean‐square deviation is 2.6 keV. Both models reveal better performance in the dawn MLT sector.

Variability of helium, neon, and argon in the lunar exosphere as observed by the LADEE NMS instrument

AbstractThe Neutral Mass Spectrometer (NMS) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) provided the first global characterization of He and Ar along with the discovery of Ne in the lunar exosphere. The mapping of the equatorial distribution of these noble gases revealed new selenographic and temporal variations. Helium was found to be controlled by the supply of solar wind alpha particles and by the presence of an endogenous source that supplies the exosphere at a rate of 1.9 × 1023 atoms s−1. Neon was detected over the nightside at levels comparable to He and was found to exhibit the spatial distribution of a surface accommodated noncondensable gas. The global measurements of NMS revealed the presence of a localized Ar enhancement that has never been identified before at the western maria. The variability resulting from this local enhancement is coupled to a more global but transient source.

Modeling of the structure of quiescent areas of the solar atmosphere emitting at 1–100 cm

A model for quiescent areas of the solar atmosphere corresponding to radiation at wavelengths from 1 cm to 1 m is presented. The model includes a collection of loops of various sizes, spicules, and free (inter-loop) matter. The parameters for the free matter are approximated using the input height dependences of the temperature and electron density in the atmosphere, based on known models for quiescent regions at the center of the solar disk. The model contains 10 loops of the same type with radii Rloop from 3100 to 210 000 km, with their occurrence frequency and the electron densities at their apices being the mean values for loops of a specified cluster of sizes. The loop density factor, defined as the number of loops of a given size in a 2R{ogloop} × 2Rloop area, lies in the range from six to nine. The height of the beginning of the coronal parts of the loops h0 is 2275 km. The height profile of the temperature of the coronal part of a loop is given by \(T_{l_p } (h) = T_{\min } + \left( {T_{\max loop} - T_{\min } } \right)\left\{ {\sin \left[ {\frac{\pi } {2}\left( {h - h_0 } \right)/\left( {R_{loop} - h_0 } \right)} \right]} \right\}^{0.25}\), where Tmin is the temperature of the initial model at height h0 and Tmax loop is the temperature of the loop apex. Height profiles for the initial model taking into account (for the density) the pressure at height h0 were used in the vicinity of the loop feet. The brightness was calculated by summing the brightnesses of individual layers of atmospheric components using a simple logical scheme, taking into account their probabilities and the overall transmission coefficient. The probability characteristics of the atmospheric components were found iteratively, by comparing the computed equatorial brightness distribution with the observational data. Good agreement between the theoretical brightness distributions and observational data obtained on the RATAN-600 telescope, the Nobeyama Radio Heliograph, and the Siberian Solar Radio Telescope has been obtained over a wide range of wavelengths for the first time.

Block distributions on Itokawa

Asteroid 25143 Itokawa is a small elongated asteroid with two distinct parts. The evolution of this two-part body has been the source of speculation. The scenarios for the formation of this asteroid include: two-body capture, catastrophic disruption and rapid reaccretion, YORP spin-up and mass shedding, and disruption (or partial disruption) with two-body reaccretion. In this paper we use the global and regional analyses of block populations and size–frequency distributions as evidence of the probable evolutionary history of Itokawa. The block sample used in this study is believed to be complete for blocks of size >6m and consists of a sample more than twice as large as previous known studies.Although block size-frequency distributions hint at different evolutionary paths for the head and the body, their differences are not statistically significant. The distribution of blocks across each body provides clues as to the histories of each body. The head is populated in a spherically symmetric fashion while the body has a distinct equatorial peak. When considering that the head and the body may have been separate entities for a period of time and estimating a rotational axis using minimum rotational energy considerations, the preferential equatorial distribution becomes even more pronounced. We interpret this as excellent evidence for the partial disruption of a proto-Itokawa, subsequent planarization of a debris field and reaccretion of the head and the body into its present configuration.

Two short mass-loss events that unveil the binary heart of Minkowski’s Butterfly Nebula

Studying the appearance and properties of bipolar winds is critical to understand the stellar evolution from the AGB to the planetary nebula (PN) phase. Many uncertainties exist regarding the presence and role of binary stellar systems, mainly due to the deficit of conclusive observational evidences. We investigate the extended equatorial distribution around the early bipolar planetary nebula M 2-9 ("Minkowski's Butterfly Nebula") to gather new information on the mechanism of the axial ejections. Interferometric millimeter observations of molecular emission provide the most comprehensive view of the equatorial mass distribution and kinematics in early PNe. Here we present subarcsecond angular-resolution observations of the 12CO J=2-1 line and continuum emission with the Plateau de Bure interferometer. The data reveal two ring-shaped and eccentric structures at the equatorial basis of the two coaxial optical lobes. The two rings were formed during short mass-loss episodes (~ 40 yr), separated by ~ 500 yr. Their positional and dynamical imprints provide evidence of the presence of a binary stellar system at the center, which yields critical information on its orbital characteristics, including a mass estimate for the secondary of ~< 0.2 \ms. The presence of a stellar system with a modest-mass companion at the center of such an elongated bipolar PN strongly supports the binary-based models, because these are more easily able to explain the frequent axisymmetric ejections in PNe.

A megalichthyid sarcopterygian fish from the Lower Permian (Autunian) of the Saar-Nahe Basin, Germany

A nearly complete specimen of a sarcopterygian fish from the Lower Permian (Autunian) of the Saar-Nahe Basin, southwest Germany, is described as a new genus and species of megalichthyids, Palatinichthys laticeps. It is characterized by the following unique list of characters: (1) lacrimal forms lateral margin of external naris, (2) postparietal short with respect to parietal, (3) tabular broad and shorter than supratemporal, (4) anterior margin of median extrascapular very narrow, (5) supraorbitals short, thus parietal and intertemporal participating in formation of orbital margin, (6) distance between external naris and orbit very short, and (7) squamosal abbreviated and deep. A phylogenetic analysis finds a monophyletic Megalichthyidae consisting of two clades, (Palatinichthys nov. gen.+Ectosteorhachis) and [(Megalichthys+Sengoerichthys)+Cladarosymblema)]. The sister taxa Palatinichthys nov. gen. and Ectosteorhachis share a short posterior skull table as a derived character, whereas Megalichthys, Sengoerichthys and Cladarosymblema retain an elongate postorbital region of the skull, regarded as plesiomorphic for “osteolepiforms”. After their nearly worldwide distribution in the Late Devonian and Carboniferous, megalichthyids had become rare in the Permian and have so far been reported only from North America (Ectosteorhachis) and Norway (?Megalichthys). Palatinichthys nov. gen. is a further representative within the European-North American equatorial distribution of megalichthyids during the Permian. It was probably not a common inhabitant of the large Saar-Nahe lakes. Rather, it might have lived in a different habitat within the same general area, such as deltaic streams or rivers.

On the role of ecological adaptation and geographic distribution in the response of trees to climate change

Predicting how increases in surface temperature will modulate the response of plants to rising atmospheric CO2 concentrations is an increasingly urgent aspect of climate change research. Plant responses to elevated CO2 have been well documented over the last 40 years, and the mechanisms underlying these responses are well understood. Elevated CO2 affects plants mainly by increasing photosynthesis and decreasing stomatal conductance (Ainsworth and Rogers 2007). However, the scaling up of these primary, leaf-level CO2 responses to the whole plant and canopy levels is moderated by the plant’s growth characteristics (e.g., sink strength, biomass partitioning), and the availability of soil water and nutrients (Long et al. 2004). Unlike elevated CO2, temperature has effects that extend beyond direct leaf-level responses. Temperature affects plant growth through a number of processes at varying scales, including photosynthesis, respiration, meristem initiation, cell division, water transport and phenology (Berry and Bjorkman 1980, Atkin and Tjoelker 2003, Thomas et al. 2007, Way 2011). Importantly, the response of biological activity to temperature is not linear, and it has long been known that photosynthetic thermal responses depend on the plant’s ecological adaptation (Pearcy and Harrison 1974). Consequently, the response of plant growth to increasing temperature alone (not to mention its interaction with elevated CO2) is complicated by ecological adaptation of the species or genotype examined. This, in turn, will determine the thermal optima of temperaturesensitive processes and their potential for acclimation. Nevertheless, a survey of the literature indicates that growth in most tree species responds positively to warmer growth temperature, with deciduous species showing a greater positive response than evergreen trees (Way and Oren 2010). However, this generalization does not always hold; for example, Ghannoum et al. (2010) found that evergreen eucalypts (Eucalyptus saligna and Eucalyptus sideroxylon) had a strong positive growth response to higher temperatures. In this issue, Wertin et al. (2011) demonstrate that the deciduous, temperate species Quercus rubra (northern red oak) showed a negative growth response to elevated temperature, which was strong enough to negate growth enhancements of high CO2. While elevated CO2 alone increased total biomass by 38% relative to the ambient CO2 and ambient temperature (control) treatment, plants grown at elevated CO2 and a 3°C warming had similar biomass to their control counterparts, and plants exposed to elevated CO2 and a 6°C warming had 12% less biomass than control plants (Wertin et al. 2011). Declines in growth were associated with reduced net photosynthetic rates and photosynthetic capacity at higher temperatures, as well as higher dark respiration rates (Wertin et al. 2011). Since respiration usually acclimates to temperature more strongly and quickly than photosynthesis (Gunderson et al. 2000, Campbell et al. 2007, Ow et al. 2008, Way and Sage 2008a, 2008b, Way and Oren 2010), this result is surprising. These recent warming studies highlight the gaps in our understanding and the need to synthesize alternative hypotheses that can form the basis of future experiments in this field. One potential explanation for the diversity in results from warming experiments is presented by Wertin et al. (2011): populations from the equatorial distribution limit of a species may be more prone to warming-related growth declines than populations from the poleward distribution limit. While poleward range limits have received more research attention, equatorial range limits are where negative impacts of climate Commentary

The kinematics and magnetic fields in water-fountain sources based on OH maser observations

Context. water-fountain sources are a class of post-AGB objects that exhibit bipolar jet-like structures traced by H2 O maser emission. The circumstellar envelopes of these objects show deviations from spherical symmetry. While the H2 O masers originate in a collimated outflow in the polar region, the OH masers may be distributed in the equatorial region or a biconical outflow in the circumstellar shell. Magnetic fields could play an important role in collimating the jet and shaping the circumstellar envelope of these objects.Aims. The aim of this project is to understand the morphology of the OH masers in three water-fountain sources, for which we obtained high-resolution interferometric data. We compare the observational parameters of the spectral profile and spatial distribution with our models in order to constrain the morphology and velocity fields of the OH maser shell. We would also like to understand the role of the magnetic field in shaping the circumstellar envelope of these stars. Methods. We observed the OH masers of three water-fountain sources (OH 12.8-0.9, OH 37.1-0.8, and W43A) in full polarization spectral line mode using the UK Multi-Element Radio Linked Interferometer Network. Additionally, we performed reconstruction models of OH maser shells distributed uniformly in equatorial or biconical outflows and compared them with the OH maser observations.Results. The OH masers of W43A seem to be located in the equatorial region of the circumstellar shell, while for OH 12.8-0.9 the masers are likely distributed in a biconical outflow. We measured magnetic fields of ~360 μ G and ~29 μ G on average for OH 37.1-0.8 and OH 12.8-0.9, respectively. The measured field strengths show that a large-scale magnetic field is present in the circumstellar environment of these stars. Conclusions. Our observations show that the OH maser region of the three water-fountain sources studied in this work show signs of aspherical expansion. Reconstruction of the OH maser distribution of these objects show both biconical and equatorial distributions. Magnetic fields likely play an important role in shaping the OH maser region of water-fountain sources.

The first report of a Himalayan bradoriid arthropod and the paleogeographic significance of this form

Two arthropod specimens assigned toAnabarochilina australis(Hinz-Schallreuter, 1993) from the late middle Cambrian (Guzhangian Stage,Lejopyge acanthaBiozone) Karsha Formation, Zanskar Valley, northern India comprise the first record of the Bradoriida from the Himalaya. These Indian specimens cannot be distinguished statistically from otherA. australismaterial based on valve length and height ratios, and differ only slightly in other characters. These observations justify the synonymy of a number of similar forms worldwide that previously have been only questionably attributed toA. australis.The occurrence of the species in Australia, India, Laurentia, and Kazakhstan encompassed an equatorial distribution from approximately 20° north to 20° south during late middle Cambrian time and indicates thatA. australishad the ability to disperse across deep ocean basins. Such a distribution is consistent with a planktonic lifestyle. In contrast, other congeneric species ofAnabarochilinaapparently had more localized occurrence or, in the case ofA. primordialis, were distributed across several paleocontinents and climatic zones.

Stormtime dynamics of the global thermosphere and equatorial ionosphere

Abstract. During magnetic storms the development of equatorial plasma bubbles (EPBs) and distributions of thermospheric densities are strongly influenced by the histories of imposed magnetospheric electric (εM) fields. Periods of intense EPB activity driven by penetration εM fields in the main phase are followed by their worldwide absence during recovery. A new method is applied to estimate global thermospheric energy (Eth) budgets from orbit-averaged densities measured by accelerometers on polar-orbiting satellites. During the main phase of storms Eth increases as long as the stormtime εM operates, then exponentially decays toward quiet-time values during early recovery. Some fraction of the energy deposited at high magnetic latitudes during the main phase propagates into the subauroral ionosphere-thermosphere where it affects chemical and azimuthal-wind dynamics well into recovery. We suggest a scenario wherein fossils of main phase activity inhibit full restoration of quiet-time dayside dynamos and pre-reversal enhancements of upward plasma drifts near dusk denying bottomside irregularities sufficient time to grow into EPBs.

Plasma sheet P5/3 and n and associated plasma and energy transport for different convection strengths and AE levels

To understand the large‐scale plasma sheet thermodynamics, we have used Geotail data and a formula for estimating flux tube volume to investigate statistically the equatorial distributions of P5/3 and n for slow flowing plasma in the nightside plasma sheet and compare them with the physical bases of ideal MHD and the Rice Convection Model (RCM). We have examined the distributions under three conditions: (1) weak convection and low AE, (2) enhanced convection and low AE, and (3) enhanced convection and high AE. The overall n decreases significantly with increasing convection or AE, while the overall P5/3 remains similar. We found that P5/3 drops significantly earthward along the estimated electric drift paths near midnight, inconsistent with ideal MHD. Examination of Pk5/3 and the electric and magnetic drift paths of different energy invariants, where Pk is the partial pressure of a specific energy invariant, shows that the strong duskward drift of the above thermal‐energy particles due to magnetic drift, together with there being significantly fewer higher‐energy particles from the dawn flank than from the tail, results in the strong earthward decrease of P5/3. We also found that d(Pk5/3)/dt = 0 and d(nk)/dt = 0 along the electric and magnetic drift paths used in the RCM are good approximations for slow flowing pressure‐bearing plasma sheet ions. The distributions of n indicate that low‐energy plasma becomes dominant when convection and AE are low, and their transport from the flanks may be affected by nonadiabatic processes not included in ideal MHD or the RCM.

The global distribution of sulfur dioxide ice on Io, observed with OSIRIS on the W.M. Keck telescope

We present ground based observations of Io taken with a high spatial resolution imaging spectrometer on 1 and 2 June 2006. We mapped the 1.98 and 2.12 μm absorptions of SO 2 frost, across Io's surface. We analyze these data with surface reflectance modeling using the Hapke method to determine the general frost distribution. This analysis also determined a lower limit of 700 μm on the grain size for the areas of strongest absorption. We incorporate our findings of a predominantly equatorial distribution of SO 2 frost, with the maps of Carlson et al. [Carlson, R.W., Smythe, W.D., Lopes-Gautier, R.M.C., Davies, A.G., Kamp, L.W., Mosher, J.A., Soderblom, L.A., Leader, F.E., Mehlman, R., Clark, R.N., Fanale, F.P., 1997. Geophys. Res. Lett. 24, 2479–2482], McEwen [McEwen, A.S., 1988. Icarus 73, 385–426] and Douté et al. [Douté, S., Schmitt, B., Lopes-Gautier, R., Carlson, R., Soderblom, L., Shirley, J., and The Galileo NIMS Team, 2001. Icarus 149, 107–132] to produce a self consistent explanation of the global distribution of SO 2. We propose that the differences between the above maps is attributable, in part, to the different bands that were studied by the investigators.