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Southern Hemisphere Polar Infrared Radiation Experiment (SHIRE) Field Campaign Report
An extended-range atmospheric emitted radiance interferometer (AERI) instrument to be deployed to Scott Base (78 S, 166 E) in McMurdo Sound, Antarctica for the purpose of synergizing with the National Aeronautics and Space Administration (NASA) Polar Radiant Energy in the Far-InfraRed Experiment (PREFIRE) satellite mission (https://prefire.ssec.wisc.edu/), examining the closure of atmospheric thermal emission, and providing validation for PREFIRE. The PREFIRE mission is the first satellite mission to map Earth’s spectrally resolved thermal emission, from 5 to 50 microns, over seasonal to annual timescales. These new observations represent the beginning of an intensive examination of the nature of thermal emission from Earth (emission from both the surface and atmosphere). A primary requirement of the PREFIRE mission is to provide validation of the retrieved variables. Numerous field sites in the Arctic (such as the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) North Slope of Alaska observatory and Summit Station, Greenland) have existing instrumentation to facilitate validation, leaving an observational gap in Antarctica. Through SHIRE, we propose to establish a temporary, intensive measurement site in Antarctica to ensure that both poles are suitably represented, and benefit from this state-of-the art science. This will also allow Arctic and Antarctic atmospheric radiative states to be compared and contrasted. For SHIRE specifically, we also propose further objectives to examine the spectrally resolved thermal radiative closure of the polar atmosphere and the historical changes in Antarctic radiative forcing, using previous Antarctic field campaigns, such as the ARM West Antarctic Radiation Experiment (AWARE).
A Parametric Study of the Aerodynamic Characteristics of Nose-Cylinder-Flare Bodies at a Mach Number of 6.0
Force tests were conducted at a Mach number of 6.0 on nose-cylinder-flare bodies to determine the effect of nose shape, cylinder length, flare angle, and flare length on the longitudinal aerodynamic characteristics. A particular investigation was conducted to determine the effect of flare angle for constant flare length, surface area, and diameter. Results indicated that at a Reynolds number of approximately 0.92 x l0 (exp 6) (based on body diameter), the boundary-layer separation effects were significant only with respect to the slope of the normal-force and pitching-moment curve at low angles of attack. The variations of the aerodynamic characteristics with the various parameters were, in general, similar to those predicted by Newtonian theory below a flare angle of 30 degrees and a ratio of flare base diameter to cylinder diameter of less than approximately 2.2. The limiting diameter ratio is consistent with the extent of the low-constant dynamic-pressure region near the body caused by the bow-shock influences as predicted by axisymmetric characteristic theory. The effects of the various parameters for the flares that exceeded the limiting diameter ratio follow the trends predicted by the computed flow-field properties. The axial force for these flare configurations at zero angle of attack was, in general, computed within 10 percent by using these properties. For a constant flare length and surface area the flare effectiveness increased with increasing flare angle; however, for constant flare diameter only the axial-force coefficient was affected by flare angle.
Centrifugal acceleration of the polar wind
The effect of parallel ion acceleration associated with convection was first applied to energization of test particle polar ions by Cladis (1986). However, this effect is typically neglected in 'self-consistent' models of polar plasma outflow, apart from the fluid simulation by Swift (1990). Here we include approximations for this acceleration, which we broadly characterize as centrifugal in nature, in our time-dependent, semikinetic model of polar plasma outflow and describe the effects on the bulk parameter profiles and distribution functions of H+ and O+. For meridional convection across the pole the approximate parallel force along a polar magnetic field line may be written as F(sub cent, pole) = 1.5m(E(sub i))/B(sub i))squared (r(squared)/r(sup 3)(sub i)) where m is ion mass, r is geometric distance; and E(sub i), B(sub i) and r(sub i) refer to the electric and magnetic field magnitudes and geocentric distance at the ionosphere, respectively. For purely longitudinal convection along a constant L shell the parallel force is F(cent. long) = F(sub cent, pole)(1 - (r/(r(sub i)L))(sup 3/2)/(1 - 3r/(4 r(sub i)L))(sup 5/2). For high latitudes the difference between these two cases is relatively unimportant below approximately 5 R(sub E). We find that the steady state O+ bulk velocities and parallel temperatures strongly increase and decrease, respectively, with convection strength. In particular, the bulk velocities increase from near 0 km/s at 4000 km altitude to approximately 10 km/s at 5 R(sub E) geocentric distance for 50-mV/m ionospheric convection electric field. However, the centrifugal effect on the steady O+ density profiles depends on the exobase ion and electron temperatures: for low-base temperatures (T(sub i) = T(sub e) = 3000 K) the O+ density at high altitudes increases greatly with convection, while for higher base temperatures (T(sub i) = 5000 K, T(sub e) = 9000 K), the high-altitude O+ density decreases somewhat as convection is enhanced. The centrifugal force further has a pronounced effect on the escaping O+ flux, especially for cool exobase conditions; as referenced to the 4000-km altitude, the steady state O+ flux increases from 10(exp 5) ions/sq cm/s when the ionospheric convection field E(sub i) = 0 mV/m to approximately 10(exp 7) ions/sq cm/s when E(sub i) = 100 mV/m. The centrifugal effect also decreases the time scale for approach to steady-state. For example, in the plasma expansion for T(sub i) = T(sub e) = 3000 K, the O+ density at 7 R(sub E) reaches only 10(exp -7) of it final value approximately 1.5 hours after expansion onset for E(sub i) = 0. For meridional convection driven by E(sub i) = 50 mV/m, the density at the same time after initial injection is 30-50% of its asymptotic level. The centrifugal acceleration described here is a possible explanation for the large (up to approximately 10 km/s or more) o+ outflow velocities observed in the midlatitude polar magnetosphere with the Dynamics Explorer 1 and Akebono spacecraft.
Design, analysis and test verification of advanced encapsulation systems
Investigations into transparent conductive polymers were begun. Polypyrrole was electrochemically deposited, but the film characteristics were poor. A proprietary polymer material supplied by Polaroid was evaluated and showed promise as a readily processable material. A method was developed for calculating the magnitude and location of the maximum electric field for the family of solar-cell-like shapes. A method for calculating the lines of force for three dimensional electric fields was developed and applied to a geometry of interest to the photovoltaic program.
On the non-existence of stepped-pressure equilibria far from symmetry
The Stepped Pressure Equilibrium Code (SPEC) (Hudson et al 2012 Phys. Plasmas 19 112502) has been successful in the construction of equilibria in 3D configurations that contain a mixture of flux surfaces, islands and chaotic magnetic field lines. In this model, the plasma is sliced into sub-volumes separated by ideal interfaces, and in each volume the magnetic field is a Beltrami field. In the cases where the system is far from possessing a continuous symmetry, such as in stellarators, the existence of solutions to a stepped-pressure equilibrium with given constraints, such as a multi-region relaxed MHD minimum energy state, is not guaranteed but is often taken for granted. Using SPEC, we have studied two different scenarios in which a solution fails to exist in a slab with analytic boundary perturbations. Here we found that with a large boundary perturbation, a certain interface becomes fractal, corresponding to the break up of a Kolmogorov–Arnold–Moser (KAM) surface. Moreover, an interface can only support a maximum pressure jump while a solution of the magnetic field consistent with the force balance condition can be found. An interface closer to break-up can support a smaller pressure jump. We discovered that the pressure jump can push the interface closer to being non-smooth through force balance, thus significantly decreasing the maximum pressure it can support. Our work shows that a convergence study must be performed on a SPEC equilibrium with interfaces close to break-up. These results may also provide insights into the choice of interfaces and have applications in finding out the maximum pressure a machine can support.
The kinematics of buoyancy induced mixing
A model problem to study mixing driven by buoyancy flow fields due to a time dependent body force which consists of a steady and an oscillatory component is considered. Flow fields generated by a time dependent body force, which consists of a steady and an oscillatory component from vibrations or g-jitter, mix two fluids inside a cavity by stretching and folding the interface into various morphological patterns. These patterns show two basic structures depending on the dominant components of the body force. These structures are whirls and tendrils, corresponding to the dominance of either the steady or oscillatory component, respectively. A combination of these structures also occurs in the interaction region. In this region the effect of the steady component opposes the oscillatory component and the result is to smooth the interface, and prevent breakup of the interface. For the parametric range considered, two basic flow regimes occur: convective and chaotic. In the convective regime, the morphological patterns are topological. In the chaotic regime, mixing occurs by a repetitive sequence of bubble formation, necking, and breakup which spreads the concentration field throughout the cavity. The length stretch of the interface increases exponentially with time. The dynamical system characteristics show that in the convective regime, at a point in space, the flow field is oscillatory with elliptical phase space trajectories, and its power spectrum indicates that the flow field responds to the corresponding input frequency. Whereas, in the chaotic regime, the flow field is aperiodic, the phase space trajectories show irregular patterns, and the power spectrum shows a broadband distribution.
Improvements in Nonconservative Force Modelling for TOPEX/POSEIDON
It was recognized prior to the launch of TOPEX/POSEIDON, that the most important source of orbit error other than the gravity field, was due to nonconservative force modelling. Accordingly, an intensive effort was undertaken to study the nonconservative forces acting on the spacecraft using detailed finite element modelling (Antreasian, 1992; Antreasian and Rosborough, 1992). However, this detailed modelling was not suitable for orbit determination, and a simplified eight plate "box-wing" model was developed that took into account the aggregate effect of the various materials and associated thermal properties of each spacecraft surface. The a priori model was later tuned post launch with actual tracking data [Nerem et al., 1994; Marshall and Luthcke, 1994; Marshall et al., 1995]. More recently, Kubitschek (1997] developed a newer box-wing model for TOPEX/POSEIDON, which included updated material properties, accounted for a solar array deflection, and modelled solar array warping due to thermal effects. We have used this updated model as a basis to retune the macromodel for TOPEX/POSEIDON, and report on preliminary results using at least 36 cycles (one year) of SLR and DORIS data in 1993.
Coordinated Polar Spacecraft, Geosynchronous Spacecraft, and Ground-based Observations of Magnetopause Oscillations and Pc5 Waves in the Magnetosphere
In this paper, we present in situ observations of surface waves at the magnetopause and oscillatory magnetospheric field lines, and coordinated observations Pc5 waves at geosynchronous orbit by the GOES spacecraft, and on the ground by CANOPUS and 210 Degree Magnetic Meridian (210MMJ magnetometer arrays. On February 7,2002 during a highspeed solar wind stream, the Polar spacecraft was skimming the magnetopause in a post-noon meridian plane for approximately 3 hours. During this interval, it made two short excursions and a few partial crossings into the magnetosheath and observed quasi-periodic cold ion bursts in the region adjacent to the magnetopause current layer. The multiple magnetopause crossings as well as the velocity of the cold ion bursts indicate that the magnetopause was oscillating with about 6 minute period. Simultaneous observations of Pc5 waves at geosynchronous orbit by the GOES spacecraft and on the ground by the CANOPUS magnetometer array reveal that these magnetospheric pulsations were forced oscillations of magnetic field lines directly driven by the magnetopause oscillations. The magnetospheric pulsations occurred only in a limited longitudinal region in the post-noon dayside sector, and were not a global phenomenon as one would expect for global field line resonance. Thus, the magnetopause oscillations at the source were also limited to a localized region spanning about 4 hours in local time.
Interpretation of ozone temperature correlations. II - Analysis of SBUV ozone data
In an effort to understand the behavior of ozone in the transition region, the terms in the perturbation continuity equation have been evaluated from solar backscattered ultraviolet ozone data, National Meteorological Center temperature data, and geostrophic winds derived from the temperature data at 2 mbar, winter 1978-1979. A linear parameterization is used to estimate the chemical source term. The perturbation ozone field calculated by integrating the net forcing evaluated from the data compares well with the measured perturbation ozone field. There are occasions during the winter when the sum of the dynamic terms is small due to cancellation, and the ozone and temperature perturbations are anticorrelated. The -1 correlation between the ozone and temperature perturbations does not necessarily imply that chemical forcing is dominant.
Airborne Sunphotometer Studies of Aerosol Properties and Effects, Including Closure Among Satellite, Suborbital Remote, and In situ Measurements
Airborne sunphotometry has been used to measure aerosols from North America, Europe, and Africa in coordination with satellite and in situ measurements in TARFOX (1996), ACE-2 (1997), PRIDE (2000), and SAFARI 2000. Similar coordinated measurements of Asian aerosols are being conducted this spring in ACE-Asia and are planned for North American aerosols this summer in CLAMS. This paper summarizes the approaches used, key results, and implications for aerosol properties and effects, such as single scattering albedo and regional radiative forcing. The approaches exploit the three-dimensional mobility of airborne sunphotometry to access satellite scenes over diverse surfaces (including open ocean with and without sunglint) and to match exactly the atmospheric layers sampled by airborne in situ measurements and other radiometers. These measurements permit tests of the consistency, or closure, among such diverse measurements as aerosol size-resolved chemical composition; number or mass concentration; light extinction, absorption, and scattering (total, hemispheric back and 180 deg.); and radiative fluxes. In this way the airborne sunphotometer measurements provide a key link between satellite and in situ measurements that helps to understand any discrepancies that are found. These comparisons have led to several characteristic results. Typically these include: (1) Better agreement among different types of remote measurements than between remote and in situ measurements. (2) More extinction derived from transmission measurements than from in situ measurements. (3) Larger aerosol absorption inferred from flux radiometry than from in situ measurements. Aerosol intensive properties derived from these closure studies have been combined with satellite-retrieved fields of optical depth to produce fields of regional radiative forcing. We show results for the North Atlantic derived from AVHRR optical depths and aerosol intensive properties from TARFOX and ACE-2. Companion papers show analogous, preliminary results for Asian-Pacific aerosols and results of SAFARI-2000 closure studies on African aerosols.
Sharpening the Distance Conjecture in diverse dimensions
The Distance Conjecture holds that any infinite-distance limit in the scalar field moduli space of a consistent theory of quantum gravity must be accompanied by a tower of light particles whose masses scale exponentially with proper field distance ||$\phi$|| as m ~ exp(–λ||$\phi$||), where λ is order-one in Planck units. While the evidence for this conjecture is formidable, there is at present no consensus on which values of λ are allowed. In this paper, we propose a sharp lower bound for the lightest tower in a given infinite-distance limit in d dimensions: λ ≥ $1/\sqrt{d-2}$. In support of this proposal, we show that (1) it is exactly preserved under dimensional reduction, (2) it is saturated in many examples of string/M-theory compactifications, including maximal supergravity in d = 4 – 10 dimensions, and (3) it is saturated in many examples of minimal supergravity in d = 4 – 10 dimensions, assuming appropriate versions of the Weak Gravity Conjecture. We argue that towers with λ < $1/\sqrt{d-2}$ discussed previously in the literature are always accompanied by even lighter towers with λ ≥ $1/\sqrt{d-2}$, thereby satisfying our proposed bound. We discuss connections with and implications for the Emergent String Conjecture, the Scalar Weak Gravity Conjecture, the Repulsive Force Conjecture, large-field inflation, and scalar field potentials in quantum gravity. In particular, we argue that if our proposed bound applies beyond massless moduli spaces to scalar fields with potentials, then accelerated cosmological expansion cannot occur in asymptotic regimes of scalar field space in quantum gravity.
High-latitude convection on open and closed field lines for large IMF B(y)
S3-3 electric field observations for August 23, 1976, show a single convection cell engulfing the northern polar cap. The flow direction is that for a positive IMF B(y) component. The particle data indicate that nearly half the duskside sunward flow occurs on closed field lines whereas the dawnside flow is entirely on open field lines. This is interpreted in terms of an IMF B(y)-induced deformation in the polar cap boundary, where the deformation moves with the convective flow. Thus, convection streamlines cross the deformed polar cap boundary, but no flow crosses the boundary because it is carried by the flow. Since southern hemisphere convection is expected to occur with the opposite sense of rotation, closed field lines that will be forced to tilt azimuthally are predicted. On the nightside the tilt produces a y component of the magnetic field in the same direction as the IMF for either sign of IMF B(y). This interpretation is consistent with observations of a greater y component in the plasma sheet than the tail lobes, which are difficult to understand in terms of the common explanation of IMF penetration. Alternatives to this interpretation are also discussed.
Comparisons of Selected Atmospheric Escape Mechanisms on Venus, Mars and Titan
The similarities and differences of the escape mechanisms for H+ and D+ from Venus, H+ and D+ from Mars, and heavier ions (approximately 17 and approximately 28 amu) from Titan are described. The dominant escape process for hydrogen and deuterium on Venus is thought to originate in the night side ionosphere, located in the night side H and D bulge region, where the polarization electric field is the dominant force accelerating ionospheric H+ and D+ upward into the induced magnetic tail of Titan. The resulting loss rates approximately 8.6 x 10(exp26)/s and approximately 3.2 x 10(exp 23)/s for H+ and D+, respectively, are consistent with the large observed D/H ratio - 160 times that of terrestrial water and an ancient ocean more than 10 m of liquid uniformly distributed on the surface. In contrast, Jeans escape is the dominant loss mechanism for H and D on Mars, which has a D/H ratio approximately 5.3 times that of terrestrial water. The resulting loss rates for H and D of approximately 3.7 x 10(exp 26/s and approximately 10(exp 22)/s, respectively, can be related to possible ancient water reservoirs below the surface. When horizontal atmospheric winds are taken into account, the Jeans escape rates for H and D are enhanced considerably, as are the corresponding water reservoirs. On Titan, 28 amu ions were observed to escape along its induced magnetic tail by the Voyager 1 Plasma Science Instrument (PLS). In analogy with Venus, the escaping ions were thought to originate in the ionosphere. The Cassini mission permits a test of this principle due to the numerous flybys of Titan through both the ionosphere and the tail. A polarization electric field is obtained in the ionosphere of the TA flyby, yielding an upward acceleration of 17 and 28 amu ionospheric ions that is consistent with the flux of heavy ionospheric ions observed escaping along the magnetic tail by the Cassini Ion Mass Spectrometer (CAPS) during the T9 flyby.
Measurement of accreted helium ion velocity using Doppler spectroscopy in the CTIX compact-toroid plasma accelerator
A compact-toroid (CT) accelerator is a device for the production of plasma bodies which contain a relatively strong internal magnetic field, which permits the plasma body to withstand large forces of acceleration while retaining its magnetic field structure. Typically, the CT occupies an annular region between inner and outer radii, defined by coaxial inner and outer electrodes, across which a large electric potential is applied. The internal magnetic fields of the CT contain both a toroidal and poloidal component, as shown in Fig. 1(a). These fields are typically of comparable magnitude. Because of the effective rigidity provided by internal magnetic fields, the CT can be accelerated to high velocities in short distances. Since internal fields increase in proportion to accelerating magnetic field, there is no strength at which the accelerating magnetic fields overcome the internal field (blow-by). Because of this, the kinetic energy density of CTs can be made to exceed the energy density of magnetic fields typical of plasma containment devices such as tokamaks. CTs have the potential to be launched into the interior of such devices for either delivering fuel (typically deuterium or hydrogen), or to deliver particles of high atomic number (high-Z). An important application of high-Z CT injection into tokamaks is to aid in plasma quenching by radiation, to mitigate the effects of plasma disruptions and prevent damage to the plasma confinement device. In addition, high-Z CTs may be used as sources of kinetic energy density for plasma-compression experiments. In this case, the use of plasma species of high atomic number is also desirable, since kinetic energy density is proportional to atomic number for given CT velocity and electron density gas puffing.
Constraints on magnetic energy and mantle conductivity from the forced nutations of the earth
The possibility of a presence of a conducting layer at the base of the mantle, as suggested by Knittle and Jeanloz (1986, 1989), was examined using observations of the earth's nutations. Evidence favoring the presence of a conducting layer is found in the effect of ohmic dissipation, which can cause the amplitude of the earth's nutation to be out-of-phase with tidal forcings. It is shown that the earth's magnetic field can produce observable signatures in the forced nutations of the earth when a thin conducting layer is located at the base of the mantle. The present theoretical calculations are compared with VLBI determinations of forced nutations.
Observations of Confinement of a Paramagnetic Liquid in Model Propellant Tanks in Microgravity by the Kelvin Force
The magnetic Kelvin force has been proposed as an artificial gravity to control the orientation of paramagnetic liquid propellants such as liquid oxygen in a microgravity environment. This paper reports experiments performed in the NASA "Weightless Wonder" KC-135 aircraft, through the Reduced Gravity Student Flight Opportunities Program. The aircraft flies through a series of parabolic arcs providing about 25 s of microgravity in each arc. The experiment was conceived, designed, constructed, and performed by the undergraduate student team and their two faculty advisors. Two types of tanks were tested: square-base prismatic tanks 5 cm x 5 cm x 8.6 cm and circular cylinders 5 cm in diameter and 8.6 cm tall. The paramagnetic liquid was a 3.3 molar solution of MnCl2 in water. Tests were performed with each type of tank filled to depths of 1 cm and 4 cm. Each test compared a pair of tanks that were identical except that the base of one was a pole face of a 0.6 Tesla permanent magnet. The Kelvin force attracts paramagnetic materials toward regions of higher magnetic field. It was hypothesized that the Kelvin force would hold the liquid in the bottom of the tanks during the periods of microgravity. The tanks were installed in a housing that could slide on rails transverse to the flight direction. By manually shoving the housing, an identical impulse could be provided to each tank at the beginning of each period of microgravity. The resulting fluid motions were videotaped for later analysis.
Isothermal magnetostatic atmospheres. III - Similarity solutions with current proportional to the magnetic potential squared
A family of isothermal magnetostatic atmospheres with one ignorable coordinate corresponding to a uniform gravitational field in a plane geometry is considered. It is assumed that the current (J) is proportional to the square of the magnetostatic potential and falls off exponentially with distance. Results are presented for the contributions of the anisotropic J x B force (where B is the magnetic field induction), the gravitational force, and the gas pressure gradient to the force balance.