Anisotropy Constraints Research Articles

On the O-mode instability generated by dual core-halo solar wind electrons

Abstract In situ measurements reported with different spacecraft reveal the temperature anisotropy constraints of solar wind species. Micro-instabilities driven by the temperature anisotropy are investigated as key mechanism which limit an unchecked rise in the temperature anisotropy in dilute space plasmas. The present study considers the excitation of O-mode instability under the excessive electrons parallel temperature condition i.e., T ‖e > T ⊥e . Looking at the recent developments made by different satellite missions, a dual core-halo electron distribution is employed that represents a true picture of solar wind electrons. We employ Vlasov–Maxwell’s model equations and derive the dispersion relation of the O-wave whose analytical solution characterizes the growth rate of O-mode instability. We take different sets of temperature anisotropy and beta combinations associated with core-halo electron components that highlight the instability characteristics e.g. growth rate and the range of wave number of unstable mode. We note an increment in the growth rate with the increase of anisotropic ratios associated either with core electrons or halo electrons and or the combination thereof. In view of a global perspective of solar wind, it may be a favorable study with the contribution of non-thermal solar wind electrons.

Constraints on primordial magnetic fields from their impact on the ionization history with Planck 2018

ABSTRACT We update and extend our previous cosmic microwave background anisotropy constraints on primordial magnetic fields through their dissipation by ambipolar diffusion and magnetohydrodynamic decaying turbulence effects on the post-recombination ionization history. We derive the constraints using the latest Planck 2018 data release which improves on the E-mode polarization leading to overall tighter constraints with respect to Planck 2015. We also use the low-multipole E-mode polarization likelihood obtained by the SROLL2 map making algorithm and we note how it is compatible with larger magnetic field amplitudes than the Planck 2018 baseline, especially for positive spectral indices. The 95 per cent confidence level constraints on the amplitude of the magnetic fields from the combination of the effects is $\sqrt{\langle B^2 \rangle } \lt 0.69 (\lt 0.72)$ nG for Planck 2018 (SROLL2) by marginalizing on the magnetic spectral index. We also investigate the impact of a damping scale allowed to vary and the interplay between the magnetic field effects and the lensing amplitude parameter.

Spectral distortion constraints on photon injection from low-mass decaying particles

ABSTRACT Spectral distortions (SDs) of the cosmic microwave background (CMB) provide a powerful tool for studying particle physics. Here we compute the distortion signals from decaying particles that convert directly into photons at different epochs during cosmic history, focusing on injection energies $E_\mathrm{inj}\lesssim 20\, \mathrm{keV}$. We deliver a comprehensive library of SD solutions, using CosmoTherm to compute the SD signals, including effects on the ionization history and opacities of the Universe, and blackbody-induced stimulated decay. Then, we use data from COBE/FIRAS and EDGES to constrain the properties of the decaying particles. We explore scenarios where these provide a dark matter (DM) candidate or constitute only a small fraction of DM. We complement the SD constraints with CMB anisotropy constraints, highlighting new effects from injections at very-low photon energies ($h\nu \lesssim 10^{-4}\, {\rm eV}$). Our model-independent constraints exhibit rich structures in the lifetime-energy domain, covering injection energies Einj ≃ 10−10 eV − 10 keV and lifetimes $\tau _X\simeq 10^5-10^{33}\, \mathrm{s}$. We discuss the constraints on axions and axion-like particles, revising existing SD constraints in the literature. Our limits are competitive with other constraints for axion masses $m_a c^2\gtrsim 27\, {\rm eV}$ and we find that simple estimates based on the overall energetics are generally inaccurate. Future CMB spectrometers could significantly improve the obtained constraints, thus providing an important complementary probe of early-universe particle physics.

Constraints on the Upper Mantle Structure Beneath the Pacific From 3‐D Anisotropic Waveform Modeling

AbstractSeismic radial anisotropy is a crucial tool to help constrain flow in the Earth's mantle. However, Earth structure beneath the oceans imaged by current 3‐D radially anisotropic mantle models shows large discrepancies. Here, we provide constraints on the radially anisotropic upper mantle structure beneath the Pacific by waveform modeling and subsequent inversion. Specifically, we objectively evaluate three 3‐D tomography mantle models which exhibit varying distributions of radial anisotropy through comparisons of independent real data sets with synthetic seismograms computed with the spectral‐element method. The data require an asymmetry at the East Pacific Rise (EPR) with stronger positive radial anisotropy ξ = = 1.13–1.16 at ∼100 km depth to the west of the EPR than to the east (ξ = 1.11–1.13). This suggests that the anisotropy in this region is due to the lattice‐preferred orientation of anisotropic mantle minerals produced by shear‐driven asthenospheric flow beneath the South Pacific Superswell. Our new radial anisotropy constraints in the Pacific show three distinct positive linear anomalies at ∼100 km depth. These anomalies are possibly related to mantle entrainment at the Nazca‐South America subduction zone, flow at the EPR and from the South Pacific Superswell and shape‐preferred orientation (SPO) of melt beneath Hawaii. Radial anisotropy reduces with lithospheric age to ξ < 1.05 in the west at ∼100 km depth, which possibly reflects a deviation from horizontal flow as the mantle is entrained with subducting slabs, a change in temperature or water content that could alter the anisotropic olivine fabric or the SPO of melt.

Constraints on Neff of high energy non-thermal neutrino injections upto >z∼ 108 from CMB spectral distortions and abundance of light elements

High energy neutrinos and anti-neutrinos (≳ 100 GeV) can inject energetic electromagnetic particles into the baryon-photon plasma in the high redshift universe through electroweak showers from electroweak bremsstrahlung, inelastic scattering with the background electrons and nucleons, and by pair-production of standard model particles on background neutrinos and anti-neutrinos. In this paper, we evolve the particle cascades of high energy non-thermal neutrinos injections, using dark matter decay as a specific example, including relevant collision processes of these neutrinos with the background particles and taking into account the expansion of the universe. We study the effect of these non-thermal neutrino injections on the CMB spectral shape and abundance of light elements produced in the big bang nucleosynthesis. We show that CMB spectral distortions and abundance of light elements can constrain neutrino energy density at the recombination, parameterized as contribution to Neff, from high energy neutrino injection. These constraints are stronger by several orders of magnitudes compared to the CMB anisotropy constraints. We also show that CMB spectral distortions can probe neutrino injections to significantly higher redshifts (z>2× 106) as compared to pure electromagnetic energy injection.

Pleistocene ignimbrites of western Armenia - Paleomagnetic and magnetic anisotropy constraints on flow direction and stratigraphy

Voluminous early to middle Pleistocene pyroclastic flow deposits were generated from Mount Aragats (Aragats Volcanic Province, AVP), one of the largest volcanoes in the Arabia-Eurasia continental collision zone. Here we report paleomagnetic results, in combination with anisotropy of magnetic susceptibility (AMS) analysis, from 31 outcrops belonging to six ignimbrite units of the western part of the AVP (covering an area of more than 5000 km2). Paleomagnetic directional analysis of samples from 26 outcrops of the three younger ignimbrite units yields a well-defined normal polarity direction of D = 339.2°, I = 55.7°, k = 278.4 and α95 = 1.7°. The virtual coincidence of paleomagnetic directions points to an emplacement of the units within a restricted time of similar geomagnetic secular variation (i.e., few hundred years). However, new isotope 40Ar/39Ar ages of the three units suggest two separated events at ~0.65 and ~ 0.75 Ma. The possibility of similar paleomagnetic directions at 0.65 and 0.75 Ma or the occurrence of a widespread remagnetization event at 0.65 Ma cannot be fully excluded, but both scenarios are highly unlikely. In contrast to that, five sites from the three older units show reversed magnetic polarity, which implies an age of emplacement older than the last magnetic polarity reversal at ~780 ka. This agrees with recent 40Ar/39Ar ages of the three older units at ~0.93 Ma. The paleomagnetic scatter of the older units is high compared to the younger ones. Even if paleomagnetic directions and radiometric age are similar, available data cannot unequivocally indicate if the three older units were generated from the same or three different eruptions. The high quality AMS data result in three different types of fabric (lineated, foliated and undetermined) that are all commonly observed in the studied pyroclastic deposits. Accordingly, we use lineation, tilt of foliation, or both for the determination of paleoflow direction. Results reveal a radial flow pattern surrounding Mt. Aragats, which is, however, highly influenced by topographic features, such as valleys, even in proximity of the eruption center.

Coulomb Collisions as a Candidate for Temperature Anisotropy Constraints in the Solar Wind

Abstract Many solar wind observations at 1 au indicate that the proton (as well as electron) temperature anisotropy is limited. The data distribution in the (A a , β a,∥)-plane have a rhombic-shaped form around β a,∥ ∼ 1. The boundaries of the temperature anisotropy at β a,∥ > 1 can be well explained by the threshold conditions of the mirror (whistler) and oblique proton (electron) firehose instabilities in a bi-Maxwellian plasma, whereas the physical mechanism of the similar restriction at β a,∥ < 1 is still under debate. One possible option is Coulomb collisions, which we revisit in the current work. We derive the relaxation rate of the temperature anisotropy in a bi-Maxwellian plasma that we then study analytically and by observed proton data from WIND. We found that increases toward small β p,∥ < 1. We matched the data distribution in the (A p , β p,∥)-plane with the constant contour s−1, corresponding to the minimum value for collisions to play a role. This contour fits rather well the left boundary of the rhombic-shaped data distribution in the (A p , β p,∥)-plane. Thus, Coulomb collisions are an interesting candidate for explaining the limitations of the temperature anisotropy in the solar wind with small β a,∥ < 1 at 1 au.

Improved CMB anisotropy constraints on primordial magnetic fields from the post-recombination ionization history

We investigate the impact of a stochastic background of Primordial Magnetic Fields (PMF) generated before recombination on the ionization history of the Universe and on the Cosmic Microwave Background radiation (CMB). Pre-recombination PMFs are dissipated during recombination and reionization via decaying MHD turbulence and ambipolar diffusion. This modifies the local matter and electron temperatures and thus affects the ionization history and Thomson visibility function. We use this effect to constrain PMFs described by a spectrum of power-law type, extending our previous study (based on a scale-invariant spectrum) to arbitrary spectral index. We derive upper bounds on the integrated amplitude of PMFs due to the separate effect of ambipolar diffusion and MHD decaying turbulence and their combination. We show that ambipolar diffusion is relevant for $n_{\rm B}>0$ whereas for $n_{\rm B}<0$ MHD turbulence is more important. The bound marginalized over the spectral index on the integrated amplitude of PMFs with a sharp cut-off is $\sqrt{\langle B^2 \rangle}<0.83$ nG. We discuss the quantitative relevance of the assumptions on the damping mechanism and the comparison with previous bounds.

Effect of low anisotropy and supernova constraints on cosmological models

The 194 supernova Ia data and the effect of anisotropy are combined to reconstruct the dark energy equation of state parameter [Formula: see text] and the deceleration parameter [Formula: see text]. Using the supernovae type Ia data, we evaluate the anisotropy effects (although low) on dark energy parametrization [Formula: see text] and we compare the results with [Formula: see text]CDM model. Present supernova observations are analyzed using a standard [Formula: see text] method and the minimal [Formula: see text] values obtained for each model are compared. We confirm the difficulty of discriminating between these models using present SNIa data only. By means of the maximum likelihood method, we find that the best-fit dynamical [Formula: see text] and [Formula: see text] parameters [Formula: see text] are obtained from the SNIa dataset. In particular, we find the best-fit values of [Formula: see text]CDM model ([Formula: see text] = 0.013, [Formula: see text] = 197.559) for [Formula: see text] = 0.3 and ([Formula: see text] = 0.02, [Formula: see text] = 196.983) for [Formula: see text] = 0.27. Finally, we found that the presence of anisotropy is confirmed in mentioned models via SNIa dataset.

Microstructure design using graphs

Thin films with tailored microstructures are an emerging class of materials with applications such as battery electrodes, organic electronics, and biosensors. Such thin film devices typically exhibit a multi-phase microstructure that is confined, and show large anisotropy. Current approaches to microstructure design focus on optimizing bulk properties, by tuning features that are statistically averaged over a representative volume. Here, we report a tool for morphogenesis posed as a graph-based optimization problem that evolves microstructures recognizing confinement and anisotropy constraints. We illustrate the approach by designing optimized morphologies for photovoltaic applications, and evolve an initial morphology into an optimized morphology exhibiting substantially improved short circuit current (68% improvement over a conventional bulk-heterojunction morphology). We show optimized morphologies across a range of thicknesses exhibiting self-similar behavior. Results suggest that thicker films (250 nm) can be used to harvest more incident energy. Our graph based morphogenesis is broadly applicable to microstructure-sensitive design of batteries, biosensors and related applications.

Solar wind temperature anisotropy constraints from streaming instabilities

Due to the relatively low rate of particle-particle collisions in the solar wind, kinetic instabilities (e.g., the mirror and firehose) play an important role in regulating large deviations from temperature isotropy. These instabilities operate in the high β∥ &gt; 1 plasmas, and cannot explain the other limits of the temperature anisotropy reported by observations in the low beta β∥ &lt; 1 regimes. However, the instability conditions are drastically modified in the presence of streaming (or counterstreaming) components, which are ubiquitous in space plasmas. These effects have been analyzed for the solar wind conditions in a large interval of heliospheric distances, 0.3–2.5 AU. It was found that proton counter-streams are much more crucial for plasma stability than electron ones. Moreover, new instability thresholds can potentially explain all observed bounds on the temperature anisotropy, and also the level of differential streaming in the solar wind.

Elucidating ΛCDM: Impact of Baryon Acoustic Oscillation Measurements on the Hubble Constant Discrepancy

Abstract We examine the impact of baryon acoustic oscillation (BAO) scale measurements on the discrepancy between the value of the Hubble constant (H 0) inferred from the local distance ladder and that from Planck cosmic microwave background (CMB) data. While the BAO data alone cannot constrain H 0, we show that combining the latest BAO results with WMAP, Atacama Cosmology Telescope (ACT), or South Pole Telescope (SPT) CMB data produces values of H 0 that are lower than the distance ladder, independent of Planck, and that this downward pull was less apparent in some earlier analyses that used only angle-averaged BAO scale constraints rather than full anisotropic information. At the same time, the combination of BAO and CMB data also disfavors the lower values of H 0 preferred by the Planck high-multipole temperature power spectrum. Combining galaxy and Lyα forest BAO with a precise estimate of the primordial deuterium abundance produces km s−1 Mpc−1 for the flat model. This value is completely independent of CMB anisotropy constraints and is lower than the latest distance ladder constraint, although tension also exists between the galaxy BAO and Lyα BAO. These results show that it is not possible to explain the H 0 disagreement solely with a systematic error specific to the Planck data. The fact that tensions remain even after the removal of any single data set makes this intriguing puzzle all the more challenging to resolve.

Cosmological constraints on exotic injection of electromagnetic energy

We compute cosmic microwave background (CMB) anisotropy constraints on exotic forms of energy injection in electromagnetic (e.m.) channels over a large range of timescales. We show that these constraints are very powerful around or just after recombination, although CMB keeps some sensitivity e.g. to decaying species with lifetimes as long as 1025 s. These bounds are complementary to CMB spectral distortions and primordial nucleosynthesis ones, which dominate at earlier timescales, as we also review here. For the first time, we describe the effects of the e.m. energy injection on the CMB power spectra as a function of the injection epoch, using the lifetime of a decaying particle as proxy. We also identify a suitable on-the-spot approximation, that can be used to derive accurate constraints, and describe its differences with the most up-to-date treatment. Our results are of interest not only for early universe relics constituting (a fraction of) the dark matter, but also for other exotic injection of e.m. radiation. For illustration, we apply our formalism to: i) Primordial black holes of mass 1013.5 g ≲ M ≲ 1016.8 g, showing that the constraints are comparable to the ones obtained from gamma-ray background studies and even dominate below ∼ 1014 g. ii) To a peculiar mass-mixing range in the sterile neutrino parameter space, complementary to other astrophysical and laboratory probes. iii) Finally, we provide a first estimate of the room for improvement left for forthcoming 21 cm experiments, comparing it with the reach of proposed CMB spectral distortion (PiXiE) and CMB angular power spectrum (CORE) missions. We show that the best and most realistic opportunity to look for this signal (or to improve over current constraints) in the 21 cm probe is to focus on the Cosmic Dawn epoch, 15 ≲ z ≲ 30, where the qualitatively unambiguous signature of a spectrum in emission can be expected for models that evade all current constraints.

Probing early-universe phase transitions with CMB spectral distortions

Global, symmetry-breaking phase transitions in the early universe can generate scaling seed networks which lead to metric perturbations. The acoustic waves in the photon-baryon plasma sourced by these metric perturbations, when Silk damped, generate spectral distortions of the cosmic microwave background (CMB). In this work, the chemical potential distortion ($\mu$) due to scaling seed networks is computed and the accompanying Compton $y$-type distortion is estimated. The specific model of choice is the $O(N)$ nonlinear $\sigma$-model for $N\gg 1$, but the results remain the same order of magnitude for other scaling seeds. If CMB anisotropy constraints to the $O(N)$ model are saturated, the resulting chemical potential distortion $\mu \lesssim 2\times 10^{-9}$.

Structure of the membrane protein MerF, a bacterial mercury transporter, improved by the inclusion of chemical shift anisotropy constraints

MerF is a mercury transport membrane protein from the bacterial mercury detoxification system. By performing a solid-state INEPT experiment and measuring chemical shift anisotropy frequencies in aligned samples, we are able to improve on the accuracy and precision of the initial structure that we presented. MerF has four N-terminal and eleven C-terminal residues that are mobile and unstructured in phospholipid bilayers. The structure presented here has average pairwise RMSDs of 1.78 A for heavy atoms and 0.92 A for backbone atoms.

Primordial Non‐Gaussianity and Dark Energy Constraints from Cluster Surveys

Galaxy cluster surveys will be a powerful probe of dark energy. At the same time, cluster abundance is sensitive to any non-Gaussianity of the primordial density field. It is therefore possible that non-Gaussian initial conditions might be misinterpreted as a sign of dark energy or at least degrade the expected constraints on dark energy parameters. To address this issue, we perform a likelihood analysis of an ideal cluster survey similar in size and depth to the upcoming South Pole Telescope/Dark Energy Survey (SPT-DES). We analyze a model in which the strength of the non-Gaussianity is parameterized by the constant fNL; this model has been used extensively to derive Cosmic Microwave Background (CMB) anisotropy constraints on non-Gaussianity, allowing us to make contact with those works. We find that the constraining power of the cluster survey on dark energy observables is not significantly diminished by non-Gaussianity provided that cluster redshift information is included in the analysis. We also find that even an ideal cluster survey is unlikely to improve significantly current and future CMB constraints on non-Gaussianity. However, when all systematics are under control, it could constitute a valuable cross check to CMB observations.

Anisotropic resistivity tomography

Geophysical tomographic techniques have the potential to remotely detect and characterize geological features, such as fractures and spatially varying lithologies, by their response to signals passed through these features. Anisotropic behaviour in many geological materials necessitates the generalization of tomographic methods to include anisotropic material properties in order to attain high-quality images of the subsurface. In this paper, we present a finite element (FE) based direct-current electrical inversion method to reconstruct the conductivity tensor at each node point of a FE mesh from electrical resistance measurements. The inverse problem is formulated as a functional optimization and the non-uniqueness of the electrical inverse problem is overcome by adding penalty terms for structure and anisotropy. We use a modified Levenberg–Marquardt method for the functional optimization and the resulting set of linear equation is solved using pre-conditioned conjugate gradients. The method is tested using both synthetic and field experiments in cross-well geometry. The acquisition geometry for both experiments uses a cross-well experiment at a hard-rock test site in Cornwall, southwest England. Two wells, spaced at 25.7 m, were equipped with electrodes at a 1 m spacing at depths from 21–108 m and data were gathered in pole–pole geometry. The test synthetic model consists of a strongly anisotropic and conductive body underlain by an isotropic resistive formation. Beneath the resistive formation, the model comprises a moderately anisotropic and moderately conductive half-space, intersected by an isotropic conductive layer. This model geometry was derived from the interpretation of a seismic tomogram and available geological logs and the conductivity values are based on observed conductivities. We use the test model to confirm the ability of the inversion scheme to recover the (known) true model. We find that all key features of the model are recovered. However, the inversion model is smoother than the true model and the difference in absolute value of anisotropy and conductivity between features is slightly underestimated. Using an anisotropic conductivity distribution aggravates the problem of non-uniqueness of the solution of the inverse electrical problem. This problem can be overcome by applying appropriate structural and anisotropy constraints. We find that running a suite of inversions with varying constraint levels and subsequent examination of the results (including the inspection of residual maps) offers a viable method for choosing appropriate numerical values for the imposed constraints. Inversion of field data reveals a strongly anisotropic subsurface with marked spatial variations of both magnitude of anisotropy and conductivity. Average conductivities range from 0.001 S m−1 (= 1000 Ω m) to 0.003 S m−1 (= 333 Ω m) and anisotropy values range from 0 per cent to more than 300 per cent. As an independent test of the reliability of the structures revealed by anisotropic electric tomography, anisotropic seismic traveltime tomograms were calculated. We find a convincing structural agreement between the two independently derived images. Areas of high electric anisotropy coincide with seismically anisotropic areas and we observe an anticorrelation between electric conductivity and seismic velocity. Both observations are consistent with anisotropy anomalies caused by fracturing or layering.

Near‐Infrared Properties of Galaxy Clusters: Luminosity as a Binding Mass Predictor and the State of Cluster Baryons

We explore the near-infrared properties of galaxies within 27 galaxy clusters using data from the Two Micron All Sky Survey (2MASS). For a subsample of 13 clusters with available X-ray imaging data, we examine the properties of both the galaxies and the intracluster medium. We show that the K-band luminosity is correlated with cluster mass, providing a binding mass estimate accurate to 45%. The mass-to-light ratio in our ensemble increases by a factor of ~2 over the cluster mass range (1014-1015 M☉). We examine the total baryon fraction, showing that it is an increasing function of cluster mass. Using the mass-to-light ratio of massive clusters, we find that ΩM = 0.19 ± 0.03; using the total baryon fraction we find that ΩM = 0.28 ± 0.03, in good agreement with recent cosmic microwave background (CMB) anisotropy constraints. Differences between these two estimates suggest that the K-band mass-to-light ratio in massive clusters may be lower than that in the universe by as much as ~30%. We examine the stellar mass fraction, the intracluster medium (ICM) mass to stellar mass ratio, and the cluster iron mass fraction. The stellar mass fraction decreases by a factor of 1.8 from low- to high-mass clusters, and the ICM to stellar mass ratio increases from 5.9 to 10.4 over the same mass range. Together, these measurements suggest a decrease of star formation efficiency with increasing cluster mass and provide constraints on models of the thermodynamic history of the intracluster medium. The cluster iron mass to total mass ratio is constant and high, suggesting that some efficient and uniform enrichment process may have taken place before the bulk of stars in cluster galaxies formed.

Undermining thecosmological principle:almost isotropic observations in inhomogeneous cosmologies

We challenge the widely held belief that the cosmologicalprinciple is anobvious consequence of the observed isotropy of the cosmic microwavebackground radiation (CMB), combined with the Copernican principle.We performa detailed analysis of a class of inhomogeneous perfect fluidcosmologiesadmitting an isotropic radiation field, with a view to assessing theirviability as models of the real universe. These spacetimes aredistinguishedfrom FLRW universes by the presence of inhomogeneous pressure,which results in an acceleration of the fluid (fundamentalobservers). We examine their physical, geometrical andobservational characteristics for all observer positionsin the spacetimes. To this end, we derive exact,analytic expressions for the distance-redshift relations andanisotropies for any observer, and compare their predictionswith available observational constraints. As far as theauthors are aware, this work represents the first exactanalysis of the observational properties of an inhomogeneouscosmological model for all observer positions. Considerableattention is devoted to the anisotropy in the CMB. Thedifficulty of defining the surface of last scattering inexact, inhomogenous cosmological models is discussed; severalalternative practical definitions are presented, and one ofthese is used to estimate the CMB anisotropy for any model.The isotropy constraints derived from `local' observations(redshift ≲1) are also considered, qualitatively. Acrucial aspect of this work is the application of theCopernican principle: for a specific model to be acceptable wedemand that it must be consistent with current observationalconstraints (especially anisotropy constraints) for allobserver locations. The most important results of the paperare presented as exclusion plots in the two-dimensionalparameter space of the models. We show that there is a regionof parameter space not ruled out by the constraints we considerand containing models that are significantly inhomogeneous. Itfollows immediately from this that the cosmological principlecannot be assumed to hold on the basis of present observationalconstraints.

Cosmic Microwave Background Anisotropy Constraints on Open and Flat‐Λ Cold Dark Matter Cosmogonies from UCSB South Pole, ARGO, MAX, White Dish, and SuZIE Data

We use combinations of 10 small-scale cosmic microwave background anisotropy data sets from the UCSB South Pole 1994, ARGO, MAX 4 and 5, White Dish, and SuZIE experiments to constrain cosmogonies. We consider open and spatially flat-? cold dark matter cosmogonies with nonrelativistic mass density parameter ?0 in the range 0.1-1, baryonic mass density parameter ?B in the range 0.005-0.029 h-2, and age of the universe t0 in the range 10-20 Gyr. Marginalizing over all parameters but ?0, the combined data favor a ?01 (1) open (flat-?) model. Excluding the smallest angular scale SuZIE data, an ?00.3 (1) open (flat-?) model is favored. Considering only multifrequency data with error bars consistent with sample variance and noise considerations, i.e., the South Pole 1994 Ka band, the MAX 4 ? Draconis, and the MAX 5 HR5127 data, an ?00.1 (1) open (flat-?) model is favored. For both open and flat-? models and for all three combinations of data sets, after marginalizing over all other parameters, a lower ?Bh2 (~0.005) or younger (t0~10 Gyr) universe is favored. However, the data do not rule out other values of ?0 in the flat-? model and other values of ?Bh2 in both models. At 2 ? confidence, model normalizations deduced from the small-scale data are consistent with those derived from the Differential Microwave Radiometer data. We emphasize that since we consider only a small number of data sets, these results are tentative.