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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

A search for SiO, OH, CO and HCN radio emission from silicate-carbon stars

We report upper limits for radio emission of SiO at 86 and 43 GHz, of OH at 1612 and 1665/1667 MHz, of CO at 115 GHz and HCN at 88.6 GHz in the silicate-carbon stars. These upper limits of SiO imply that oxygen-rich material has not been detected within 2R(sub star) of a central star even though the detected emission from silicate dust grains, H2O and OH maser establishes the presence of oxygen-rich material from about tens to thousands of AU of a central star. The upper limit of the SiO abundance is consistent with that found in oxygen-rich envelopes. Upper limits of the mass loss rate (based on the CO data) are estimated to be between 10(exp -6) to 10(exp -7) solar mass/yr assuming a distance of 1.5 kpc for these stars. The absence of HCN microwave emission implies that no carbon-rich material can be detected at large distances (thousands of AU) from a central star. The lack of detections of SiO, CO, and HCN emission is most likely due to the large distances of these stars. A number of C stars were detected in CO and HCN, but only the M supergiant VX Sgr was detected in CO.

Little-Marenin, I. R.↗
NASA NTRS2001

Orbits of Saturn's Inner Moons and Other Observations Connected within the 1995-1996 Saturnian Ring Plane Crossing

We reduced and analyzed radio images of Saturn taken in 1990-1995 at 0.35, 2.0, 3.6 and 6.1 cm wavelength. The latitudinal brightness distribution varies substantially over time. Detailed modeling of these data shows that NH4SH condenses at the thermochemical equilibrium temperature of 235.5 K only at Northern mid-latitudes. Over most of the planet, condensation does not occur until the gas cools to 190 +/- 5 K. Supersaturation may also cause the dark equatorial region seen in 1995 at 6.1 cm. Observations of the rings show that the West (dusk) ansa is brighter than the East (dawn) ansa by factors up to 2. The magnitude of the asymmetry increases with increasing wavelength and with decreasing distance to the planet. This East-West asymmetry may be due to multiple scattering in gravitational wakes. We improved the Monte Carlo scattering code used to model the microwave emission from Saturn's rings at multiple wavelengths. The basic code outlined in Dunn, Molnar, and Fix describes the rings as a uniform, infinite layer of ice spheres with a finite vertical extent. The particle sizes follow a power law distribution and scatter light according to a linear combination of Mie and isotropic phase functions. These parameters may be adjusted to reflect the physical properties in the scattering properties of the ring particles. This is used to construct a model which can be directly compared to Very Large Array data. The code has been extended by including anisotropic particle distributions, primarily in the form of the wake structures that are likely to exist in the enhancements. The vertical extent of the wakes equals that of the ring layer. Between the wakes are regions of diminished density so that the optical depth integrated over many wakes matches that of the Voyager occultation experiments. This allows us to model the brightness temperature as a function of azimuth and look for asymmetric scattering behavior in the rings. By changing the width and relative density of the wakes, we can alter the nature of the gross scattering properties of the rings to match what is seen in our data.

Lissauer, Jack J.↗
NASA NTRS2002

Overview of the Chandra X-Ray Observatory Facility

The Chandra X-Ray Observatory (originally called the Advanced X-Ray Astrophysics Facility - AXAF) is the X-Ray component of NASA's "Great Observatory" Program. Chandra is a NASA facility that provides scientific data to the international astronomical community in response to scientific proposals for its use. The Observatory is the product of the efforts of many organizations in the United States and Europe. The Great Observatories also include the Hubble Space Telescope for space-based observations of astronomical objects primarily in the visible portion of the electromagnetic spectrum, the now defunct Compton Gamma- Ray Observatory that was designed to observe gamma-ray emission from astronomical objects, and the soon-to-be-launched Space Infrared Telescope Facility (SIRTF). The Chandra X-Ray Observatory (hereafter CXO) is sensitive to X-rays in the energy range from below 0.1 to above 10.0 keV corresponding to wavelengths from 12 to 0.12 nanometers. The relationship among the various parts of the electromagnetic spectrum, sorted by characteristic temperature and the corresponding wavelength, is illustrated. The German physicist Wilhelm Roentgen discovered what he thought was a new form of radiation in 1895. He called it X-radiation to summarize its properties. The radiation had the ability to pass through many materials that easily absorb visible light and to free electrons from atoms. We now know that X-rays are nothing more than light (electromagnetic radiation) but at high energies. Light has been given many names: radio waves, microwaves, infrared, visible, ultraviolet, X-ray and gamma radiation are all different forms. Radio waves are composed of low energy particles of light (photons). Optical photons - the only photons perceived by the human eye - are a million times more energetic than the typical radio photon, whereas the energies of X-ray photons range from hundreds to thousands of times higher than that of optical photons. Very low temperature systems (hundreds of degrees below zero Celsius) produce low energy radio and microwave photons, whereas cool bodies like our own (about 30 degrees Celsius) produce infrared radiation. Very high temperatures (millions of degrees Celsius) are one way of producing X-rays.

Weisskopf, M. C.↗
NASA NTRS1994

A multisource limb flare observed at multiple radio wavelengths

A flare with several radio sources occurred on the solar limb at 2155 UT on 1989 June 20. It was observed by the Very Large Array (VLA) and the Owens Valley Radio Observatory (OVRO). The VLA data consisted of images at 1.4 GHz, while OVRO provided spectral and spatial information over the range 1-15 GHz. We develop a new gyrosynchrotron model to analyze the sources observed at flare peak. This model differs from many previous ones in that it contains spatial variations of both the magnetic field and accelerated particle density. It uses a new gyrosynchrotron approximation which is valid at very low harmonics of the gyrofrequency. For the first time we find that the cause of the change of microwave source size with frequency in the event studied was due primarily to the spatial variation of the accelerated electron density. This is contrary to the common assumption that the variation in size is due to a nonuniform magnetic field. We also investigate a polarized source which brightened later in the flare, finding that it could have been due to plasma radiation or gyrosynchrotron emission.

Kucera, T. A.↗
DOE OSTI2024

Frontier system-on-chip (SoC) technology for microwave diagnostics (invited)

The next generation of fusion reactors, exemplified by projects such as the Demonstration Power Plant following the International Thermonuclear Experimental Reactor, faces the monumental challenge of proving the viability of generating electricity through thermonuclear fusion. This pursuit introduces heightened complexities in diagnostic methodologies, particularly in microwave-based diagnostics. The increased neutron fluence necessitates significant reductions in vessel penetrations and the elimination of internal diagnostics, posing substantial challenges. SoC technology offers a promising solution by enabling the miniaturization, modularization, integration, and enhancing the reliability of microwave systems. After seven years of research, our team successfully pioneered the V- and W-band system-on-chip approach, leading to the development of active transmitters and passive receiver modules applied in practical settings, notably within the DIII-D tokamak project. Arrays of these modules have supported microwave imaging diagnostics. New physics measurement results from the Electron Cyclotron Emission Imaging system on DIII-D provide compelling evidence of improved diagnostics following the adoption of SoC technology. Furthermore, we achieved a breakthrough in developing an F-band SoC, advancing higher frequency capabilities for fusion devices. These achievements represent a significant leap forward in fusion diagnostic technology, marking substantial progress toward establishing reliable and efficient plasma diagnostics for future fusion reactors.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2019

MeV Emission from Pulsar Wind Nebulae: Understanding Extreme Particle Acceleration in Highly Relativistic Outflows

The Earth is constantly bombarded from outer space by energetic particles. Where and how these "cosmic rays" are produced is poorly understood, with various particle types and energies likely originating from different sources. Particularly mysterious is the source of high-energy e+/- produced in our Galaxy, especially those responsible for both the high fraction of e+ in the GeV cosmic ray lepton spectrum and the e+/- and observed excess of microwaves and gamma-rays detected towards the Galactic center and bulge. While these particles could be evidence for exotic forms of dark matter, they might also be produced by "normal" astrophysical sources such as pulsars the strongly magnetized, rapidly rotating neutron stars whose rotational energy powers an ultra-relativistic outflow (commonly referred to as a "pulsar wind") whose interaction with the surrounding medium creates a pulsar wind nebula .While the detection of TeV emission from numerous PWNe strongly suggest they contain e+/- with PeV or higher energies, how and to what energies these particles are produced is unknown, let alone their dependence on the properties of the pulsar, pulsar wind, and surrounding medium. A major reason for this uncertainty is the lack of information concerning their MeV properties, since the synchrotron emission from the highest energy e+/- peaks in this waveband. Only by combining the MeV spectrum of PWNe measured by proposed missions with that obtained at lower (primarily radio and X-ray) and higher (TeV) photon energies by current and hopefully future facilities is it possible to measure the full spectrum of e+/- in these sources. The resultant insights into the underlying acceleration mechanism would significantly impact many areas of astrophysics from indirect searches for dark matter to the origin of cosmic rays to the physics of relativistic outflows observed from active galactic nuclei, gamma-ray bursts, and some gravitational wave events.

Gelfand, Joseph D.↗
NASA NTRS1992

Radio synthesis imaging during the GRO solar campaign

The Owens Valley (OVRO) Solar Array was recently expanded to 5 antennas. Using frequency synthesis, the 5-element OVRO Solar Array has up to 450 effective baselines, which can be employed as necessary to make maps at frequencies in the range 1 to 18 GHz. Fortuitously, the last of the 5 antennas was completed and brought into operation on 7 Jun., just in time for the Gamma Ray Observatory (GRO)/Max 1991 observing campaign. Many events were observed jointly with OVRO and the BATSE experiment on GRO, including the six larger events that are presented in tabular form. Unfortunately, the X flares that occurred during the campaign all occurred outside the OVRO time range. The UV coverage of the newly expanded solar array, combined with frequency synthesis, should give a more complete view of solar flares in the microwave range by providing simultaneous spatial and spectral resolution. A promising application of MEM (maximum entropy) is also being pursued that will use smoothness criteria in both the spatial and spectral domains to give brightness temperature maps at each observed frequency (up to 45 frequencies every 10 s). Such maps can be compared directly with the theory of microwave emission to yield plasma parameters in the source - notably the number and energy distribution of electrons, for comparison with the x ray and gamma ray results from GRO.

Gary, Dale E.↗
NASA NTRS2002

DSN and GAVRT observations of Jupiter at 13 GHz and the calibration of the Cassini radar instrument for passive radiometry

One objective of the Cassini-Jupiter Microwave Observing Campaign observations was to measure Jupiter's average disk temperature with high accuracy at 13.78 GHz, which is the frequency of the radar receiver on the spacecraft. Preliminary results of the ground-based observations are reported. A second objective of the Cassini-JMOC project included an educational compment that allowed middle- and high school students to participate directly in the ground-based observations and data analysis.

radio astronomy Jupiter radio emission Cassini pas↗
DOE OSTI2020

Information Carried by Electromagnetic Radiation Launched from Accelerated Polarization Currents

We show experimentally that a continuous, linear, dielectric antenna in which a superluminal polarization-current distribution accelerates can be used to transmit a broadband signal that is reproduced in a comprehensible form at a chosen target distance and angle. The requirement for this exact correspondence between broadcast and received signals is that each moving point in the polarization-current distribution approaches the target at the speed of light at all times during its transit along the antenna. This results in a one-to-one correspondence between the time at which each point on the moving polarization current enters the antenna and the time at which all of the radiation emitted by this particular point during its transit through the antenna arrives simultaneously at the target. This has the effect of reproducing the desired time dependence of the original broadcast signal. For other observer-detector positions, the time dependence of the signal is scrambled, due to the nontrivial relationship between emission (retarded) time and reception time. This technique represents a contrast to conventional radio transmission methods; in most examples of the latter, signals are broadcast with little or no directivity, selectivity of reception being achieved through the use of narrow frequency bands. In place of this, the current paper uses a spread of frequencies to transmit information to a particular location; the signal is weaker and has a scrambled time dependence elsewhere. Here, we point out the possible relevance of this mechanism to 5G neighborhood networks and pulsar astronomy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2023

Data-constrained Solar Modeling with GX Simulator

To facilitate the study of solarflares and active regions, we have created a modeling framework, the freelydistributed GX Simulator IDL package, that combines 3D magnetic and plasma structures with thermal andnonthermal models of the chromosphere, transition region, and corona. Its object-based modular architecture,which runs on Windows, Mac, and Unix/Linux platforms, offers the ability to either import 3D density andtemperature distribution models, or to assign numerically defined coronal or chromospheric temperatures anddensities, or their distributions, to each individual voxel. GX Simulator can apply parametric heating modelsinvolving average properties of the magneticfield lines crossing a given voxel, as well as compute and investigatethe spatial and spectral properties of radio,(sub)millimeter, EUV, and X-ray emissions calculated from the model,and quantitatively compare them with observations. The package includes a fully automatic model productionpipeline that, based on minimal users input, downloads the required SDO/HMI vector magneticfield data,performs potential or nonlinear force-freefield extrapolations, populates the magneticfield skeleton withparameterized heated plasma coronal models that assume either steady-state or impulsive plasma heating, andgenerates non-LTE density and temperature distribution models of the chromosphere that are constrained byphotospheric measurements. The standardized models produced by this pipeline may be further customizedthrough specialized IDL scripts, or a set of interactive tools provided by the graphical user interface. Here, wedescribe the GX Simulator framework and its applications.

Solar active regions↗
DOE OSTI2024

Importance of gas heating in capacitively coupled radiofrequency plasma-assisted synthesis of carbon nanomaterials

In pursuit of diamond nanoparticles, a capacitively-coupled radio frequency flow-through plasma reactor was operated with methane-argon gas mixtures. Signatures of the final product obtained microscopically and spectroscopically indicated that the product was an amorphous form of graphite. This result was consistent irrespective of combinations of the macroscopic reactor settings. To explain the observed synthesis output, measurements of C 2 and gas properties were carried out by laser-induced fluorescence and optical emission spectroscopy. Strikingly, the results indicated a strong gas temperature gradient of 100 K per mm from the center of the reactor to the wall. Based on additional plasma imaging, a model of hot constricted region (filamentation region) was then formulated. It illustrated that, while the hot constricted region was present, the bulk of the gas was not hot enough to facilitate diamond sp 3 formation: characterized by much lower reaction rates, when compared to sp 2 , sp 3 formation kinetics are expected to become exponentially slow. This result was further confirmed by experiments under identical conditions but with a H 2 /CH 4 mixture, where no output material was detected: if graphitic sp 2 formation was expected as the main output material from the methane feedstock, atomic hydrogen would then be expected to etch it away in situ, such that the net production of that sp 2 -hybridized solid material is nearly a zero. Finally, the crucial importance of gas heating was corroborated by replacing RF with microwave source whereby facile sp 3 production was attained with H 2 /CH 4 gas mixture.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Energetic Electrons Accelerated and Trapped in a Magnetic Bottle above a Solar Flare Arcade

Where and how flares efficiently accelerate charged particles remains an unresolved question. Recent studies revealed that a “magnetic bottle” structure, which forms near the bottom of a large-scale reconnection current sheet above the flare arcade, is an excellent candidate for confining and accelerating charged particles. However, further understanding its role requires linking the various observational signatures to the underlying coupled plasma and particle processes. Here we present the first study combining multiwavelength observations with data-informed macroscopic magnetohydrodynamics and particle modeling in a realistic eruptive flare geometry. The presence of an above-the-loop-top magnetic bottle structure is strongly supported by the observations, which feature not only a local minimum of magnetic field strength but also abruptly slowing plasma downflows. It also coincides with a compact above-the-loop-top hard X-ray source and an extended microwave source that bestrides the flare arcade. Spatially resolved spectral analysis suggests that nonthermal electrons are highly concentrated in this region. Our model returns synthetic emission signatures that are well matched to the observations. The results suggest that the energetic electrons are strongly trapped in the magnetic bottle region due to turbulence, with only a small fraction managing to escape. The electrons are primarily accelerated by plasma compression and facilitated by a fast-mode termination shock via the Fermi mechanism. Our results provide concrete support for the magnetic bottle as the primary electron acceleration site in eruptive solar flares. They also offer new insights into understanding the previously reported small population of flare-accelerated electrons entering interplanetary space.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2011

The Atacama Cosmology Telescope: High-Resolution Sunyaev-Zeldovich Array Observations of ACT SZE-Selected Clusters from the Equatorial Strip

We present follow-up observations with the Sunyaev-Zel'dovich Array (SZA) of optically-confirmed galaxy clusters found in the equatorial survey region of the Atacama Cosmology Telescope (ACT): ACT-CL J0022-0036, ACT-CL J2051+0057, and ACT-CL J2337+0016. ACT-CL J0022-0036 is a newly-discovered, massive ( approximately equals 10(exp 15) Solar M), high-redshift (z = 0.81) cluster revealed by ACT through the Sunyaev-Zeldovich effect (SZE). Deep, targeted observations with the SZA allow us to probe a broader range of cluster spatial scales, better disentangle cluster decrements from radio point source emission, and derive more robust integrated SZE flux and mass estimates than we can with ACT data alone. For the two clusters we detect with the SZA we compute integrated SZE signal and derive masses from the SZA data only. ACT-CL J2337+0016, also known as Abell 2631, has archival Chandra data that allow an additional X-ray-based mass estimate. Optical richness is also used to estimate cluster masses and shows good agreement with the SZE and X-ray-based estimates. Based on the point sources detected by the SZA in these three cluster fields and an extrapolation to ACT's frequency, we estimate that point sources could be contaminating the SZE decrement at the approx < 20% level for some fraction of clusters.

galaxies↗
DOE OSTI2025

Data-Driven Analysis of Multipactor Dynamics via Dynamic Mode Decomposition

Multipactor effect is a performance-limiting kinetic plasma effect that can occur in high-power microwave and radio frequency (RF) devices. Multipactor effect is of special concern in vacuum or near-vacuum conditions such as those in particle accelerators and spaceborne devices. In this work, we present a data-driven reduced-order model (ROM) based on dynamic mode decomposition (DMD) for modeling of multipactor effects. We study multipactor effects and the resulting nonlinear harmonic generation by processing high-fidelity data generated from electromagnetic particle-in-cell (EMPIC) simulations using the DMD algorithm. We also investigate time-delay embedding extensions of DMD with improved generalizability and accuracy for modeling the electron plasma current density behavior. Here, the results show that DMD provides valuable insights into multipactor phenomena by extracting relevant modal spatiotemporal patterns and frequencies. In addition, DMD offers the potential to time extrapolate EMPIC simulations at a minimal cost, thereby reducing overall simulation time.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

System-on-chip approach microwave imaging reflectometer on DIII-D tokamak

System-on-chip millimeter wave integrated circuit technology is used on the two-dimensional millimeter-wave imaging reflectometer (MIR) upgrade for density fluctuation imaging on the DIII-D tokamak fusion plasma. Customized CMOS chips have been successfully developed for the transmitter module and receiver module array, covering the 55–75 GHz working band. The transmitter module has the capability of simultaneously launching eight tunable probe frequencies (>0 dBm output power each). The receiver enclosure contains 12 receiver modules in two vertical lines. The quasi-optical local oscillator coupling of previous MIR systems has been replaced with an internal active frequency multiplier chain for improved local oscillator power delivery and flexible installation in a narrow space together with improved shielding against electromagnetic interference. The 55–75 GHz low noise amplifier, used between the receiver antenna and the first-stage mixer, significantly improves module sensitivity and suppresses electronics noise. The receiver module has a 20 dB gain improvement compared with the mini-lens approach and better than –75 dBm sensitivity, and its electronics noise temperature has been reduced from 55 000 K down to 11 200 K. Further, the V-band MIR system is developed for co-located multi-field investigation of MHD-scale fluctuations in the pedestal region with W-band electron cyclotron emission imaging on DIII-D tokamak.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

BeyondPlanck: I. Global Bayesian analysis of the Planck Low Frequency Instrument data

We describe the BEYONDPLANCK project in terms of our motivation, methodology, and main products, and provide a guide to a set of companion papers that describe each result in more detail. Building directly on experience from ESA’s Planck mission, we implemented a complete end-to-end Bayesian analysis framework for the Planck Low Frequency Instrument (LFI) observations. The primary product is a full joint posterior distribution P(ω | d), where ω represents the set of all free instrumental (gain, correlated noise, bandpass, etc.), astrophysical (synchrotron, free-free, thermal dust emission, etc.), and cosmological (cosmic microwave background – CMB – map, power spectrum, etc.) parameters. Some notable advantages of this approach compared to a traditional pipeline procedure are seamless end-to-end propagation of uncertainties; accurate modeling of both astrophysical and instrumental effects in the most natural basis for each uncertain quantity; optimized computational costs with little or no need for intermediate human interaction between various analysis steps; and a complete overview of the entire analysis process within one single framework. As a practical demonstration of this framework, we focus in particular on low-ℓ CMB polarization reconstruction with Planck LFI. In this process, we identify several important new effects that have not been accounted for in previous pipelines, including gain over-smoothing and time-variable and non-1/f correlated noise in the 30 and 44 GHz channels. Modeling and mitigating both previously known and newly discovered systematic effects, we find that all results are consistent with the ΛCDM model, and we constrained the reionization optical depth to τ = 0.066 ± 0.013, with a low-resolution CMB-based χ 2 probability to exceed of 32%. This uncertainty is about 30% larger than the official pipelines, arising from taking a more complete instrumental model into account. The marginal CMB solar dipole amplitude is 3362.7 ± 1.4 μK, where the error bar was derived directly from the posterior distribution without the need of any ad hoc instrumental corrections. We are currently not aware of any significant unmodeled systematic effects remaining in the Planck LFI data, and, for the first time, the 44 GHz channel is fully exploited in the current analysis. We argue that this framework can play a central role in the analysis of many current and future high-sensitivity CMB experiments, including LiteBIRD, and it will serve as the computational foundation of the emerging community-wide COSMOGLOBE effort, which aims to combine state-of-the-art radio, microwave, and submillimeter data sets into one global astrophysical model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Mapping the Universe in hydrogen deuteride

Hydrogen deuteride (HD) is prevalent in a wide variety of astrophysical environments, and measuring its large-scale distribution at different epochs can, in principle, provide information about the properties of these environments. In this paper we explore the prospects for accessing this distribution using line-intensity mapping of emission from the lowest rotational transition in HD, focusing on observations of the epoch of reionization (z~6–10) and earlier. We find the signal from the epoch of reionization to be most promising, through cross correlations within existing [CII] intensity mapping surveys. While the signal we predict is out of reach for current-generation projects, planned future improvements should be able to detect reionization-era HD without any additional observations, and would help to constrain the properties of the star-forming galaxies thought to play a key role in reionization. We also investigate several avenues for measuring HD during “cosmic dawn” (z~10–30), a period in which HD could provide one of the only complementary observables to 21 cm intensity maps. We conclude that existing and planned facilities are poorly matched to the specifications desirable for a significant detection, though such a measurement may be achievable with sustained future effort. Finally, we explain why HD intensity mapping of the intergalactic medium during the cosmic dark ages (z≳30) appears to be out of reach of any conceivable experiment.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

BeyondPlanck: XV. Limits on large-scale polarized anomalous microwave emission from Planck LFI and WMAP

We constrained the level of polarized anomalous microwave emission (AME) on large angular scales using Planck Low-Frequency Instrument (LFI) and WMAP polarization data within a Bayesian cosmic microwave background (CMB) analysis framework. We modeled synchrotron emission with a power-law spectral energy distribution, as well as the sum of AME and thermal dust emission through linear regression with the Planck High-Frequency Instrument (HFI) 353 GHz data. This template-based dust emission model allowed us to constrain the level of polarized AME while making minimal assumptions on its frequency dependence. We neglected CMB fluctuations, but show through simulations that these fluctuations have a minor impact on the results. We find that the resulting AME polarization fraction confidence limit is sensitive to the polarized synchrotron spectral index prior. In addition, for prior means β s < -3.1 we find an upper limit of p AME max ≲ 0.6% (95% confidence). In contrast, for means β s = -3.0, we find a nominal detection of p AME = 2.5 ± 1.0% (95% confidence). These data are thus not strong enough to simultaneously and robustly constrain both polarized synchrotron emission and AME, and our main result is therefore a constraint on the AME polarization fraction explicitly as a function of β s . Combining the current Planck and WMAP observations with measurements from high-sensitivity low-frequency experiments such as C-BASS and QUIJOTE will be critical to improve these limits further.

79 ASTRONOMY AND ASTROPHYSICS↗