Search

Multispacecraft and multiwavelength observations of solar eruptions such as flares and coronal mass ejections are essential to understand the complex processes behind these events. The study of solar burst events in the radio-frequency spectrum has relied almost exclusively on data from ground-based radiotelescopes and dedicated heliophysics missions such as STEREO or Wind. Reanalysing existing data from the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) instrument, a Martian planetary radar sounder, we have detected 38 solar radio burst events with a correlated observation by at least one dedicated solar mission. The very high resolution of the instrument, both in temporal and frequency directions, its bandwidth, and its position in the solar system enable SHARAD to make significant contributions to heliophysics; it could inform on plasma processes on the site of the burst generation and also along the propagation path of associated fast electron beams. In this letter, we characterise the sensitivity of the instrument to type-III solar radio bursts through a statistical analysis of correlated observations, using STEREO and Wind as references. We establish the conditions under which SHARAD can observe solar bursts in terms of acquisition geometry, laying the foundation for its use as a solar radio-observatory. We also present the first analysis of type-III characteristic times at high resolution beyond 1 AU. The scaling laws are also comparable to results found on Earth, except for the fall time; a clearer distinction between fundamental and harmonic components of the bursts may be needed to resolve the discrepancy., Comment: 15 pages, 5 figures, 2 tables

Recent work has demonstrated a passive radio sounding approach that uses the Sun as a source for echo detection and ranging. As the Sun is a moving source with a position that is known a priori , we evaluate this technique’s capabilities to measure the echo’s phase history, map topography, and perform synthetic aperture radar (SAR) focusing. Here, we present our approach to implementing passive SAR using a compact, temporally incoherent radio-astronomical source as a signal of opportunity. We first evaluate the passive system’s capabilities to obtain an echo from a rough surface by determining the critical signal-to-noise ratio (SNR) for reliably observing the Sun’s echo reflection with our passive instrument. We then demonstrate that our technique can detect the necessary changes in range, phase, and reflectivity of an echo from the Sun. We next present the experimental results of our passive radar testing using the Sun at Dante’s View, Death Valley, to highlight this technique’s ability to perform 2-D imaging. Finally, with synthetic data, we demonstrate that we can use time-domain backprojection to focus a planar white noise signal, perform passive SAR imaging, and improve the measurement’s SNR and azimuth resolution. The results of passive SAR focusing on white noise highlight the potential for the Sun and Jupiter’s radio emissions to perform surface and subsurface imaging for planetary and terrestrial observations.

The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a planned neutrino telescope designed to detect radio emission from upgoing air showers generated by ultrahigh energy tau neutrino interactions in the Earth. This detection mechanism provides a measurement of the tau flux of cosmic neutrinos. We have installed an 8-channel prototype instrument at high elevation at Barcroft Field Station, which has been running since 2018, and consists of 4 dual-polarized antennas sensitive between 30-80 MHz, whose signals are filtered, amplified, digitized, and saved to disk using a custom data acquisition system (DAQ). The BEACON prototype is at high elevation to maximize effective volume and uses a directional beamforming trigger to improve rejection of anthropogenic background noise at the trigger level. Here we discuss the design, construction, and calibration of the BEACON prototype instrument. We also discuss the radio frequency environment observed by the instrument, and categorize the types of events seen by the instrument, including a likely cosmic ray candidate event., 21 pages, 20 figures

Over the last several decades, radio detection of air showers has been widely used to detect ultra-high-energy cosmic rays. We developed an experiment under controlled laboratory conditions at SLAC with which we measured the radio-frequency radiation from a charged particle shower produced by bunches of electrons as primaries with known energy. The shower took place in a target made of High Density Polyethylene located in a strong magnetic field. The experiment was designed so that Askaryan and magnetically-induced components of the radio emission could be measured independently. At the same time, we performed a detailed simulation of this experiment to predict the radio signal using two microscopic formalisms, endpoint and ZHS. In this paper, we present the simulation scheme and make a comparison with data characteristics such as linearity with magnetic field and amplitude. The simulations agree with the measurements within uncertainties and present a good description of the data. In particular, reflections within the target that accounted for the largest systematic uncertainties are addressed. The prediction of the amplitude of Askaryan emission agrees with measurements to within 5% for the endpoint formalism and 11% for the ZHS formalism. The amplitudes of magnetically-induced emission agree to within 5% for the endpoint formalism and less than 1% for the ZHS formalism. The agreement of the absolute scale of emission gives confidence in state-of-the-art air shower simulations which are based on the applied formalisms.

Passive radar sounding has been proposed as a low-cost, low-risk way to enrich the scientific return of planetary radar sounders, especially in the vicinity of bright radio sources such as Jupiter [Romero-Wolf et al. (2015), Icarus, 248:463-477], whose moons will be studied by radar sounders in the late 2020's and 2030's. To predict what passive radargrams may look like as a function of parameters such as the noise source spectrum and the surface/subsurface roughness, analytical and empirical models have been proposed in the literature [Schroeder et al. (2016), PSS, 134:52-60], and proof-of-concept hardware has been tested on Earth [Peters et al. (2018), TGRS, 56(12) 7338-7349]. To cement our understanding of passive sounding, we searched for traces of passively-acquired radar echoes in existing SHARAD radargrams. Such signals can be uncovered if the incoming noise was captured in one acquisition and its reflection by surface or subsurface features in the next one. Cross-correlating the two uncompressed rangelines could then reveal possible present Martian features using only the signals of opportunity. We started from the engineering parameters of SHARAD, such as its orbit, Rx window length, and PRF, to work out all the geometric configurations where Jovian emissions and their reflection from the surface could have been intercepted if such emissions were present. We made the assumption that waves must be specularly-reflected off the surface of Mars at a given angle, and looked for the angles at which the delay of the reflected noise matches the PRI of SHARAD. We have determined that, for the range of altitudes SHARAD operates at, the (Jupiter-Mars, Mars-SHARAD) angle must lie between 35° and 52°. Based on Friis-like arguments, we believe the SNR of such signals could reach 10 dB in the case of a smooth surface such as Elysium Planitia. We then cross-correlated this database of SHARAD radargrams with that of a model of Jovian noise occurrence at Mars using ExPRES [Hess et al. (2008), GRL, 35.13], and extracted a list of potential candidates. Preliminary analysis of these candidates shows that some of them may indeed contain passively-acquired signals that may be exploited scientifically. We have additionally conducted passive Stratton-Chu simulations [Gerekos et al. (2019), TGRS, 58(4) 2250-2265] of these cases to support interpretation.

We study in detail the sensitivity of the Antarctic Impulsive Transient Antenna (ANITA) to possible $\nu_\tau$ point source fluxes detected via $\tau$-lepton-induced air showers. This investigation is framed around the observation of four upward-going extensive air shower events very close to the horizon seen in ANITA-IV. We find that these four upgoing events are not observationally inconsistent with $\tau$-induced EASs from Earth-skimming $\nu_\tau$, both in their spectral properties as well as in their observed locations on the sky. These four events, as well as the overall diffuse and point source exposure to Earth-skimming $\nu_\tau$, are also compared against published ultrahigh-energy neutrino limits from the Pierre Auger Observatory. While none of these four events occurred at sky locations simultaneously visible by Auger, the implied fluence necessary for ANITA to observe these events is in strong tension with limits set by Auger across a wide range of energies and is additionally in tension with ANITA's Askaryan in-ice neutrino channel above $10^{19}$ eV. We conclude by discussing some of the technical challenges with simulating and analyzing these near horizon events and the potential for future observatories to observe similar events., Comment: 19 pages, 22 figures, will be published in Physical Review D (PRD)

The Sun Radio Interferometer Space Experiment (SunRISE) will provide an entirely new view on particle acceleration and transport in the inner heliosphere by creating the first low radio frequency interferometer in space to localize heliospheric radio emissions. By imaging and determining the location of decametric-hectometric (DH) radio bursts from 0.1 MHz-20 MHz, SunRISE will provide key information on particle acceleration mechanisms associated with coronal mass ejections (CMEs) and the magnetic field topology from active regions into interplanetary space. Six small spacecraft, of a 6U form factor, will fly in a supersynchronous geosynchronous Earth orbit (GEO) orbit within about 10 km of each other, in a passive formation, and image the Sun in a portion of the spectrum that is blocked by the ionosphere and cannot be observed from Earth. Key aspects that enable this mission are that only position knowledge of the spacecraft is required, not active control, and that the architecture involves a modest amount of on-board processing coupled with significant ground-based processing for navigation, position determination, and science operations. Mission-enabling advances in software-defined radios, GPS navigation and timing, and small spacecraft technologies, developed and flown on the DARPA High Frequency Research (DHFR), the Community Initiative for Continuing Earth Radio Occultation (CICERO), and the Mars Cube One (MarCO) missions, have made this mission affordable and low-risk. The SunRISE mission will involve utilizing commercial access to space, in which the SunRISE spacecraft will be carried to their target orbit as a secondary payload in conjunction with a larger host spacecraft intended for GEO.

We present a new technique to perform passive bistatic subsurface radar probes on airless planetary bodies. This technique uses the naturally occurring radio impulses generated when high-energy cosmic rays impact the body's surface. As in traditional radar sounding, the downward-beamed radio emission from each individual cosmic ray impact will reflect off subsurface dielectric contrasts and propagate back up to the surface to be detected. We refer to this technique as Askaryan radar after the fundamental physics process, the Askaryan effect, that produces this radio emission. This technique can be performed from an orbiting satellite, or from a surface lander, but since the radio emission is generated beneath the surface, an Askaryan radar can completely bypass the effects of surface clutter and backscatter typically associated with surface-penetrating radar. We present the background theory of Askaryan subsurface radar and show results from both finite-difference time-domain (FDTD) and Monte Carlo simulations that confirm that this technique is a promising planetary radar sounding method, producing detectable signals for realistic planetary science applications., Comment: 18 pages, 5 figures

Ultra-high-energy neutrinos serve as messengers of some of the highest energy astrophysical environments. Given that neutrinos are neutral and only interact via weak interactions, neutrinos can emerge from sources, traverse astronomical distances, and point back to their origins. Their weak interactions require large target volumes for neutrino detection. Using the Earth as a neutrino converter, terrestrial, sub-orbital, and satellite-based instruments are able to detect signals of neutrino-induced extensive air showers. In this paper, we describe the software code $\texttt{nuPyProp}$ that simulates tau neutrino and muon neutrino interactions in the Earth and predicts the spectrum of the $\tau$-lepton and muons that emerge. The $\texttt{nuPyProp}$ outputs are lookup tables of charged lepton exit probabilities and energies that can be used directly or as inputs to the $\texttt{nuSpaceSim}$ code designed to simulate optical and radio signals from extensive air showers induced by the emerging charged leptons. We describe the inputs to the code, demonstrate its flexibility and show selected results for $\tau$-lepton and muon exit probabilities and energy distributions. The $\texttt{nuPyProp}$ code is open source, available on Github., Comment: 42 pages, 21 figures, fixed typo in one of the author's name. Code available at https://github.com/NuSpaceSim/nupyprop

Ultra-high energy cosmic rays (UHECRs) are the messengers of the most extreme physics in the cosmos; however, efforts to identify their origins have thus far been thwarted by the fact that they don’t point back to their sources. Using statistical studies cross-correlating UHECR arrival directions with astrophysical catalogs, the ground-based Pierre Auger Observatory has reported hints of a correlation with nearby starburst galaxies, as well as lower-significance correlations with other classes of astrophysical sources. Space-based UHECR experiments, such as POEMMA and ZAP, will monitor large interaction volumes on the Earth or the Moon. Within a few years of mission operation time, both missions will achieve unprecedented exposures at energies above 40 EeV across the entire sky. We present studies of the cross-correlation between UHECR event arrival directions and astrophysical catalogs as motivated by expectations for the detector performance for POEMMA and ZAP. We find that both POEMMA and ZAP will achieve 5σ discovery reach for many plausible astrophysical scenarios.

Over the last several decades, radio detection of air showers has been widely used to detect ultra-high-energy cosmic rays. We developed an experiment under controlled laboratory conditions at SLAC with which we measured the radio-frequency radiation from a charged particle shower produced by bunches of electrons as primaries with known energy. The shower took place in a target made of High Density Polyethylene located in a strong magnetic field. The experiment was designed so that Askaryan and magnetically-induced components of the radio emission could be measured independently. At the same time, we performed a detailed simulation of this experiment to predict the radio signal using two microscopic formalisms, endpoint and ZHS. In this paper, we present the simulation scheme and make a comparison with data characteristics such as linearity with magnetic field and amplitude. The simulations agree with the measurements within uncertainties and present a good description of the data. In particular, reflections within the target that accounted for the largest systematic uncertainties are addressed. The prediction of the amplitude of Askaryan emission agrees with measurements to within 5% for the endpoint formalism and 11% for the ZHS formalism. The amplitudes of magnetically-induced emission agree to within 5% for the endpoint formalism and less than 1% for the ZHS formalism. The agreement of the absolute scale of emission gives confidence in state-of-the-art air shower simulations which are based on the applied formalisms.

At any epoch, particle physics must be open to completely unexpected discoveries, and that is reason enough to extend the reach of searches for ultra-high energy (UHE) photons. The observation of a population of photons with energies $E \gtrsim 100$ EeV would for example imply the existence of either a completely new physical phenomena, or particle acceleration mechanisms heretofore never seen or imagined. But as we outline in this Letter of Interest, there are also good arguments for super-heavy dark matter (SHDM) in a parameter range such that it could be discovered via its decays to, in particular, UHE photons. Only ultra-high energy cosmic ray observatories have capabilities to detect UHE photons. We first investigate how current and future observations can probe and constrain SHDM models in important directions, and then outline some of the scenarios that motivate such searches. We also discuss connections between constraints on SHDM and on the parameter values of cosmological models., SNOWMASS 2021 LoI. Accepted for publication in Astroparticle Physics

Funder: NASA Cryospheric Sciences, Ice‐penetrating radar observations are critical for projecting ice‐sheet contribution to sea‐level rise; however, these prognostic models have significant uncertainties due to an incomplete understanding of glacial subsurface processes. Existing radars that can characterize subsurface conditions are too resource‐intensive to simultaneously monitor ice sheets at both the necessary temporal—daily to multiannual—and spatial—tributary to continental—scales. Here, we investigate using an ambient radio source, instead of transmitting a signal, for glaciological monitoring. We demonstrate, for the first time, passive radio sounding using the Sun to accurately measure ice thickness on Store Glacier, Greenland. Passive radar sounding could provide low‐resource time‐series measurements of the cryosphere, enabling us to observe and understand evolving englacial and subglacial conditions across Greenland and Antarctica with unprecedented coverage and resolution.

In early T-cell development, single cells dynamically shift expression of multiple transcription factors (TFs) during transition from multipotentiality to T-lineage commitment, but the functional roles of many TFs have been obscure. Here, synchronizedin vitrodifferentiation systems, scRNA-seq with batch indexing, and controlled gene-disruption strategies have unraveled single-cell impacts of perturbing individual TFs at two stages in early T-cell development. Single-cell CRISPR perturbation revealed that early-acting TFs Bcl11a, Erg, Spi1 (PU.1), Gata3, and Tcf7 (TCF1) each play individualized roles promoting or retarding T-lineage progression and suppressing alternative trajectories, collectively determining population dynamics and path topologies. Later, during T-lineage commitment, cells prevented from expressing TF Bcl11b ‘realized’ this abnormality not with a developmental block, but by shifting into a divergent path via bZIP and Sox TF activation as well as E protein antagonism, finally exiting the T-lineage trajectory. These TFs thus exert a network of impacts to control progression kinetics, trajectories, and differentiation outcomes of early pro-T cells.

Repression of Spi1 encoding PU.1 is crucial for early T cell lineage commitment and depends on GATA3 and Runx1. Stage-specific Runx1 and GATA3 binding during commitment identifies a closed intronic site of mouse Spi1 that substantially contributes to Spi1 repression., PU.1 (encoded by Spi1), an ETS-family transcription factor with many hematopoietic roles, is highly expressed in the earliest intrathymic T cell progenitors but must be down-regulated during T lineage commitment. The transcription factors Runx1 and GATA3 have been implicated in this Spi1 repression, but the basis of the timing was unknown. We show that increasing Runx1 and/or GATA3 down-regulates Spi1 expression in pro–T cells, while deletion of these factors after Spi1 down-regulation reactivates its expression. Leveraging the stage specificities of repression and transcription factor binding revealed an unconventional but functional site in Spi1 intron 2. Acute Cas9-mediated deletion or disruption of the Runx and GATA motifs in this element reactivates silenced Spi1 expression in a pro–T cell line, substantially more than disruption of other candidate elements, and counteracts the repression of Spi1 in primary pro–T cells during commitment. Thus, Runx1 and GATA3 work stage specifically through an intronic silencing element in mouse Spi1 to control strength and maintenance of Spi1 repression during T lineage commitment., Graphical Abstract

When Earth-skimming tau neutrinos interact within the Earth, they generate upgoing tau leptons that can decay in the atmosphere, forming extensive air showers. The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a novel detector concept that utilizes a radio interferometer atop a mountain to search for the radio emission due to these extensive air showers. The prototype, located at the White Mountain Research Station in California, consists of 4 crossed-dipole antennas operating in the 30-80 MHz range and uses a directional interferometric trigger for reduced thresholds and background rejection. The prototype will first be used to detect down-going cosmic rays to validate the detector model. A Monte-Carlo simulation was developed to predict the acceptance of the prototype to cosmic rays, as well as the expected rate of detection. In this simulation, cosmic ray induced air showers with random properties are generated in an area around the prototype array. It is then determined if a given shower triggers the array using radio emission simulations from ZHAireS and antenna modelling from XFdtd. Here, we present the methodology and results of this simulation.

An accurate modeling of neutrino flux attenuation and the distribution of leptons they produce in transit through the Earth is an essential component to determine neutrino flux sensitivities of underground, sub-orbital and space-based detectors. Through neutrino oscillations over cosmic distances, astrophysical neutrino sources are expected to produce nearly equal fluxes of electron, muon and tau neutrinos. Of particular interest are tau neutrinos that interact in the Earth at modest slant depths to produce $\tau$-leptons. Some $\tau$-leptons emerge from the Earth and decay in the atmosphere to produce extensive air showers. Future balloon-borne and satellite-based optical Cherenkov neutrino telescopes will be sensitive to upward air showers from tau neutrino induced $\tau$-lepton decays. We present nuPyProp, a python code that is part of the nuSpaceSim package. nuPyProp generates look-up tables for exit probabilities and energy distributions for $\nu_\tau\to \tau$ and $\nu_\mu\to \mu$ propagation in the Earth. This flexible code runs with either stochastic or continuous electromagnetic energy losses for the lepton transit through the Earth. Current neutrino cross section models and energy loss models are included along with templates for user input of other models. Results from nuPyProp are compared with other recent simulation packages for neutrino and charged lepton propagation. Sources of modeling uncertainties are described and quantified., Comment: 9 pages, 6 figures, PoS(ICRC2021)1203; for associated code, see https://github.com/NuSpaceSim/nupyprop

We present the results of a simulation of the acceptance of the Antarctic Impulsive Transient Antenna (ANITA) to possible $\nu_\tau$ point source fluxes detected via $\tau$-lepton-induced air showers. This investigation is framed around the detection of four upward-going extensive air shower events observed very close to the horizon in ANITA-IV. These four events as well as the overall diffuse and point source exposure to Earth-skimming $\nu_\tau$ are also compared against published ultrahigh-energy neutrino limits from the Pierre Auger Observatory. We find that while these four events were detected at sky coordinates close to ANITA's maximum $\nu_\tau$ sensitivity and were not simultaneously visible by Auger, the implied fluence necessary for ANITA to observe these events is in tension with limits set by Auger across a wide range of energies and is additionally in tension with ANITA's Askaryan in-ice neutrino channel above~$10^{19}$~eV.

We present a passive radar sounding approach that performs direct signal suppression (DSS) with a single-channel receiver. The modified passive sounding signal processing algorithm leverages a blind deconvolution filter to estimate the direct path of the ambient noise source before using CLEAN processing for DSS. We then highlight the results of our single-channel DSS technique with both synthetic and experimental data, and we analyze its performance in terms of SNR improvement. We find that by combining an adaptive blind deconvolution approach with the CLEAN algorithm, we obtain an SNR improvement of over 10 dB for both synthetic and experimental data. The single-channel DSS technique is a further step towards low-resource, high SNR passive sounding with ambient radio noise, as it eliminates the requirement for long integration times and a two-channel DSS system.

Tau neutrinos interacting in the Earth can result in upgoing extensive air showers. These showers produce optical and radio emission that can be detected by orbital and suborbital platforms. We present results of radio emission simulations using ZHAireS for observation from low-Earth orbit as part of NASA's nuSpaceSim program to develop a comprehensive end-to-end simulation package to model these signals. Peculiar properties of the radio emission arise from the fact that these showers develop in extremely rarified portions of the Earth's atmosphere and, being observed from hundreds of kilometers distance, have distinct coherent emission features compared to ground observations.

The Payload for Ultrahigh Energy Observations (PUEO) is a NASA Long-Duration Balloon Mission that has been selected for concept development. PUEO has unprecedented sensitivity to ultra-high energy neutrinos above $10^{18}$ eV. PUEO will be sensitive to both Askaryan emission from neutrino-induced cascades in Antarctic ice and geomagnetic emission from upward-going air showers that are a result of tau neutrino interactions. PUEO is also especially well-suited for point source and transient searches. Compared to its predecessor ANITA, PUEO achieves better than an order-of-magnitude improvement in sensitivity and lowers the energy threshold for detection, by implementing a coherent phased array trigger, adding more channels, optimizing the detection bandwidth, and implementing real-time filtering. Here we discuss the science reach and plans for PUEO, leading up to a 2024 launch.

The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a concept for a neutrino telescope designed to measure tau lepton air showers generated from tau neutrino interactions near the horizon. This detection mechanism provides a pure measurement of the tau flavor of cosmogenic neutrinos, which could be used to set limits on the observed flavor ratios for cosmogenic neutrinos in a manner complimentary to the all-flavor neutrino flux measurements made by other experiments. BEACON is expected to also be capable of detecting cosmic rays through RF-only triggers. BEACON aims to achieve this sensitivity by using mountaintop radio arrays of dual-polarized antennas operating in the 30-80 MHz band which utilize directional interferometric triggering. BEACON stations are designed to efficiently use a small amount of instrumentation, allowing for deployment in a variety of high-elevation sites. The interferometric trigger provides a natural tool for directional-based anthropogenic RFI rejection at the trigger level, broadening the list for potential station sites. The BEACON prototype has seen continuous design advancements towards improving the mechanical durability and scientific capabilities since its initial deployment at White Mountain Research Station in 2018. Here we present the current prototype’s sensitivity to RF-triggered cosmic-ray background signals. We also present the next generation prototype, which includes scintillating cosmic ray detectors, improved antennas, and refined calibration techniques.

The Owens Valley Radio Observatory- Long Wavelength Array (OVRO-LWA) in Eastern California is currently undergoing an expansion to 352 dual-polarization antennas and new signal processing infrastructure. The upgraded array will operate a full-duty-cycle cosmic ray detector simultaneously with a variety of radio astronomy observations. Expanding the methods introduced in a previous demonstration, this detector will operate on the radio signals alone to trigger data capture, identify cosmic rays in the presence of radio-frequency interference (RFI), and reconstruct the air shower properties: energy, direction, and Xmax. When fully commissioned, the OVRO-LWA will observe thousands of cosmic rays per year at energies 10^17-10^18 eV and will constrain the cosmic ray composition across the cosmic ray spectrum's second knee with a typical Xmax precision better than 20g/cm^2 per air shower, thereby offering new composition information across the energy limits of Galactic accelerators. Commissioning for the OVRO-LWA is ongoing and is planned for completion in late 2021. I will present the trigger design, RFI flagging strategy, and a progress update from early commissioning.

Probing the ultra-high energy cosmic ray (UHECR) spectrum beyond the cutoff at ~40 EeV requires an observatory with large acceptance, which is challenging to implement with ground arrays. We present a concept for radio detection of UHECRs impacting the Moon's regolith from low-lunar orbit called the Zettavolt Askaryan Polarimeter (ZAP). ZAP would observe several thousands of events above the cutoff (~40 EeV) with a full-sky field of view to test whether UHECRs originate from Starburst Galaxies, Active Galactic Nuclei, or other sources associated with the matter distribution of the local universe at a distance $>$ 1 Mpc. The unprecedented sensitivity of ZAP to energies beyond 100 EeV would enable a test of source acceleration mechanisms. At higher energies, ZAP would produce the most stringent limits on super heavy dark matter (SHDM) via limits on neutrinos and gamma rays resulting from self-annihilation or decay.

The addition of an external starshade to the Nancy Grace Roman Space Telescope will enable the direct imaging of Earth-radius planets orbiting at ∼1 AU. Classification of any detected planets as Earth-like requires both spectroscopy to characterize their atmospheres and multi-epoch imaging to trace their orbits. We consider here the ability of the Starshade Rendezvous Probe to constrain the orbits of directly imaged Earth-like planets. The target list for this proposed mission consists of the 16 nearby stars best suited for direct imaging, around which ∼10 to 15 planets are expected to be discovered. Of these planets, ∼1 to 2 will be Earth-like in mass and temperature. The field of regard for the starshade mission is constrained by solar exclusion angles, resulting in four observing windows during a two-year mission. We find that for Earth-like planets that are detected at least three times during the four viewing opportunities, their semi-major axes are measured with a median precision of 7 mas, or a median fractional precision of 3%. Habitable-zone planets can be correctly identified as such 96.7% of the time, with a false positive rate of 2.8%. If a more conservative criteria are used for habitable-zone classification (95% probability), the false positive rate drops close to zero, but with only 81% of the truly Earth-like planets correctly classified as residing in the habitable zone.

The NASA supported High-Altitude Calibration (HiCal)-2 instrument flew as a companion balloon to the ANITA-4 experiment in December 2016. Based on a HV discharge pulser producing radio-frequency (RF) calibration pulses, HiCal-2 comprised two payloads, which flew for a combined 18 days, covering 1.5 revolutions of the Antarctic continent. ANITA-4 captured over 10,000 pulses from HiCal, both direct and reflected from the surface, at distances varying from 100-800 km, providing a large dataset for surface reflectivity measurements. Herein we present details on the design, construction and performance of HiCal-2., Comment: Published in NIM-A, final version

Ice sheet contributions to sea level rise present one of the greatest challenges that our society will face in the next century. However, models predicting sea level rise due to ice melt lack critical information regarding processes at the base of ice sheets. Although radio echo sounders are powerful tools that are currently used to constrain subglacial conditions, existing ice-penetrating radar systems are too resource-intensive in terms of cost, power, and logistics for multiyear deployment at a large scale. To address this, we present passive radio sounding as a low-resource approach for observing ice sheets across a range of spatial and temporal scales. While passive radar has been used for target tracking and military purposes, it has never been used for the sounding of ice sheets. Some recent work has proposed using passive radio sounding of Europa’s icy shell using Jupiter’s decametric radiation. We expand on this idea by evaluating and discussing challenges and opportunities for developing a passive radio sounder using the Sun as an illuminator of opportunity for echo detection. Here, our prototype instrument sits on the side of a cliff and measures the Sun’s direct and reflected path off the ocean surface. We then use an autocorrelation-based method to extract the amplitude and delay of the reflection. This serves as the first in situ demonstration of an autocorrelation-based passive sounder using a compact astronomical white noise signal.

FARSIDE (Farside Array for Radio Science Investigations of the Dark ages and Exoplanets) is a Probe-class concept to place a low radio frequency interferometric array on the farside of the Moon. A NASA-funded design study, focused on the instrument, a deployment rover, the lander and base station, delivered an architecture broadly consistent with the requirements for a Probe mission. This notional architecture consists of 128 dual polarization antennas deployed across a 10 km area by a rover, and tethered to a base station for central processing, power and data transmission to the Lunar Gateway. FARSIDE would provide the capability to image the entire sky each minute in 1400 channels spanning frequencies from 100 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, auroral kilometric radiation, and plasma noise from the solar wind. This would enable near-continuous monitoring of the nearest stellar systems in the search for the radio signatures of coronal mass ejections and energetic particle events, and would also detect the magnetospheres for the nearest candidate habitable exoplanets. Simultaneously, FARSIDE would be used to characterize similar activity in our own solar system, from the Sun to the outer planets, including the hypothetical Planet Nine. Through precision calibration via an orbiting beacon, and exquisite foreground characterization, FARSIDE would also measure the Dark Ages global 21-cm signal at redshifts z=50-100. The unique observational window offered by FARSIDE would enable an abundance of additional science ranging from sounding of the lunar subsurface to characterization of the interstellar medium in the solar system neighborhood.

An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 kmx10 km area on the lunar surface. The antenna nodes are tethered to the lander for central data processing, power, and data transmission to a relay satellite. The array, named FARSIDE, would provide the capability to image the entire sky in 1400 channels spanning frequencies from 100 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, the Earth's auroral kilometric radiation, and plasma noise from the solar wind. It is thus the only location within the inner solar system from which sky noise limited observations can be carried out at sub-MHz frequencies. Through precision calibration via an orbiting beacon and exquisite foreground characterization, the farside array would measure the Dark Ages global 21-cm signal at redshifts z~35-200. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range., 14 pages, 3 figures, 1 table, response to DOE request for information on lunar farside radio telescope to explore the early universe. arXiv admin note: substantial text overlap with arXiv:1911.08649

The Earth’s Ionosphere limits radio measurements on its surface, blocking out any radiation below 10 MHz. Valuable insight into many astrophysical processes could be gained by having a radio interferometer in space to image the low frequency window, which has never been achieved. One application for such a system is observing type II bursts that track solar energetic particle acceleration occurring at Coronal Mass Ejection (CME)-driven shocks. This is one of the primary science targets for SunRISE, a 6 CubeSat interferometer to circle the Earth in a GEO graveyard orbit. SunRISE is a NASA Heliophysics Mission of Opportunity that began Phase B (Formulation) in June 2020, and plans to launch for a 12-month mission in mid-2023. In this work we present an update to the data processing and science analysis pipeline for SunRISE and evaluate its performance in localizing type II bursts around a simulated CME.To create realistic virtual type II input data, we employ a 2-temperature MHD simulation of the May 13th 2005 CME event, and superimpose realistic radio emission models on the CME-driven shock front, and propagate the signal through the simulated array. Data cuts based on different plasma parameter thresholds (e.g. de Hoffman-Teller velocity and angle between shock normal and the upstream magnetic field) are tested to get the best match to the true recorded emission. This model type II emission is then fed to the SunRISE data processing pipeline to ensure that the array can localize the emission. We include realistic thermal noise dominated by the galactic background at these low frequencies, as well as new sources of phase noise from positional uncertainty of each spacecraft. We test simulated trajectories of SunRISE and image what the array recovers, comparing it to the virtual input, finding that SunRISE can resolve the source of type II emission to within its prescribed goal of 1/3 the CME width. This shows that SunRISE will significantly advance the scientific community’s understanding of type II burst generation, and consequently, acceleration of solar energetic particles at CMEs. This unique combination of SunRISE observations and MHD recreations of space weather events will allow an unprecedented look into the plasma parameters important for these processes.

Runt domain-related (Runx) transcription factors are essential for early T cell development in mice from uncommitted to committed stages. Single and double Runx knockouts via Cas9 show that target genes responding to Runx activity are not solely controlled by the dominant factor, Runx1. Instead, Runx1 and Runx3 are coexpressed in single cells; bind to highly overlapping genomic sites; and have redundant, collaborative functions regulating genes pivotal for T cell development. Despite stable combined expression levels across pro-T cell development, Runx1 and Runx3 preferentially activate and repress genes that change expression dynamically during lineage commitment, mostly activating T-lineage genes and repressing multipotent progenitor genes. Furthermore, most Runx target genes are sensitive to Runx perturbation only at one stage and often respond to Runx more for expression transitions than for maintenance. Contributing to this highly stage-dependent gene regulation function, Runx1 and Runx3 extensively shift their binding sites during commitment. Functionally distinct Runx occupancy sites associated with stage-specific activation or repression are also distinguished by different patterns of partner factor cobinding. Finally, Runx occupancies change coordinately at numerous clustered sites around positively or negatively regulated targets during commitment. This multisite binding behavior may contribute to a developmental “ratchet” mechanism making commitment irreversible.

Launching a starshade to rendezvous with the Nancy Grace Roman Space Telescope would provide the first opportunity to directly image the habitable zones of nearby sunlike stars in the coming decade. A report on the science and feasibility of such a mission was recently submitted to NASA as a probe study concept. The driving objective of the concept is to determine whether Earth-like exoplanets exist in the habitable zones of the nearest sunlike stars and have biosignature gases in their atmospheres. With the sensitivity provided by this telescope, it is possible to measure the brightness of zodiacal dust disks around the nearest sunlike stars and establish how their population compares to our own. In addition, known gas-giant exoplanets can be targeted to measure their atmospheric metallicity and thereby determine if the correlation with planet mass follows the trend observed in the Solar System and hinted at by exoplanet transit spectroscopy data. In this paper we provide the details of the calculations used to estimate the sensitivity of Roman with a starshade and describe the publicly available Python-based source code used to make these calculations. Given the fixed capability of Roman and the constrained observing windows inherent for the starshade, we calculate the sensitivity of the combined observatory to detect these three types of targets and we present an overall observing strategy that enables us to achieve these objectives., Accepted for publication in the Journal of Astronomical Telescopes, Instruments, and Systems (JATIS)

An accurate modeling of neutrino flux attenuation and the distribution of leptons they produce in transit through the Earth is an essential component to determine neutrino flux sensitivities of underground, sub-orbital and space-based detectors. Through neutrino oscillations over cosmic distances, astrophysical neutrino sources are expected to produce nearly equal fluxes of electron, muon and tau neutrinos. Of particular interest are tau neutrinos that interact in the Earth at modest slant depths to produce $��$-leptons. Some $��$-leptons emerge from the Earth and decay in the atmosphere to produce extensive air showers. Future balloon-borne and satellite-based optical Cherenkov neutrino telescopes will be sensitive to upward air showers from tau neutrino induced $��$-lepton decays. We present nuPyProp, a python code that is part of the nuSpaceSim package. nuPyProp generates look-up tables for exit probabilities and energy distributions for $��_��\to ��$ and $��_��\to ��$ propagation in the Earth. This flexible code runs with either stochastic or continuous electromagnetic energy losses for the lepton transit through the Earth. Current neutrino cross section models and energy loss models are included along with templates for user input of other models. Results from nuPyProp are compared with other recent simulation packages for neutrino and charged lepton propagation. Sources of modeling uncertainties are described and quantified., 9 pages, 6 figures, PoS(ICRC2021)1203; for associated code, see https://github.com/NuSpaceSim/nupyprop

Recent studies have proposed that Jovian decametric radiation (DAM) can be effectively exploited for probing the subsurface of Jupiter’s icy moons by using passive radio sounding. However, these studies were based on the assumption that Jovian noise is white and stationary. Therefore, additional investigations into the temporal stability, predictability, and spectral properties of Jovian noise are required to fully assess the potential of passive radar sounding and improve the acquisitions planning. In this article, we investigate these properties of the Jovian DAM to understand their impact on radar sounding performance. This is done by analyzing the recently available radio spectra acquired by the JUNO Waves instrument. Results are also evaluated for the specific case of the Radar for Icy Moon Exploration (RIME) and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) that have been selected for European Space Agency (ESA) and NASA missions to Ganymede and Europa. Our results show that the Jovian DAM is not perfectly white, but no severe distortions in the range response should be expected. The results on spatiotemporal occurrence show that Jupiter’s DAM has a variable probability of occurrence, which is rather sporadic for some frequency ranges. The results on RIME and REASON flybys show that the Jovian DAM occurrence probability is relatively low for selected sub-Jovian flybys at Europa. For the RIME Ganymede orbital phase, a large number of high occurrence passive acquisition opportunities are expected. The experimental results also show that a large bandwidth receiver would enhance the chance of recording Jovian noise.

High-energy astrophysical neutrinos, recently discovered by IceCube up to energies of several PeV, opened a new window to the high-energy Universe. Yet much remains to be known. IceCube has excellent muon flavor identification, but tau flavor identification is challenging. This limits its ability to probe neutrino physics and astrophysics. To address this limitation, we present a concept for a large-scale observatory of astrophysical tau neutrinos in the 1–100 PeV range, where a flux is guaranteed to exist. Its detection would allow us to characterize the neutrino sources observed by IceCube, to discover new ones, and test neutrino physics at high energies. The deep-valley air-shower array concept that we present provides highly background-suppressed neutrino detection with pointing resolution < 1°, allowing us to begin the era of high-energy tau-neutrino astronomy., Thematic Areas: astroparticle physics, neutrino physics, astronomy & astrophysics

Genetic mutations or regulatory failures underlie cellular malfunction in many diseases, including colorectal cancer and inflammatory bowel diseases. However, mutational defects alone fail to explain the complexity of such disorders. Epigenetic regulation—control of gene action through chemical and structural changes of chromatin—provides a platform to integrate multiple extracellular inputs and prepares the cellular genome for appropriate gene expression responses. Coregulation by polycomb repressive complex 2–mediated trimethylation of lysine 27 on histone 3 and DNA methylation has emerged as one of the most influential epigenetic controls in colorectal cancer and many other diseases, but molecular details remain inadequate. Here we review the molecular interplay of these epigenetic features in relation to gastrointestinal development, homeostasis, and disease biology. We discuss other epigenetic mechanisms pertinent to the balance of trimethylation of lysine 27 on histone 3 and DNA methylation and their actions in gastrointestinal cancers. We also review the current molecular understanding of chromatin control in the pathogenesis of inflammatory bowel diseases.

Tau neutrinos are expected to comprise roughly one third of both the astrophysical and cosmogenic neutrino flux, but currently the flavor ratio is poorly constrained and the expected flux at energies above $10^{17}$ eV is low. We present a detector concept aimed at measuring the diffuse flux of tau neutrinos in this energy range via a high-elevation mountaintop detector using the radio technique. The detector searches for radio signals from upgoing air showers generated by Earth-skimming tau neutrinos. Signals from several antennas in a compact array are coherently summed at the trigger level, permitting not only directional masking of anthropogenic backgrounds, but also a low trigger threshold. This design takes advantage of both the large viewing area available at high-elevation sites and the nearly full duty cycle available to radio instruments. We present trade studies that consider the station elevation, frequency band, number of antennas in the array, and the trigger threshold to develop a highly efficient station design. Such a mountaintop detector can achieve a factor of ten improvement in acceptance over existing instruments with 100 independent stations. With 1000 stations and three years of observation, it can achieve a sensitivity to an integrated $\mathcal{E}^{-2}$ flux of $, Comment: 26 pages, 11 figures

The zodiacal dust complex, a population of dust and small particles that pervades the Solar System, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. Here we present a new set of data obtained using a novel technique: direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory that operated near the first Sun-Earth Lagrange point from early 2016 through Summer of 2017. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum (related to the particle's mass and velocity), direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hours of Pathfinder data. We report a total of 54 candidates with momenta ranging from 0.2$\,\mu\textrm{Ns}$ to 230$\,\mu\textrm{Ns}$. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system including those resulting from Jupiter-family comets, Oort-cloud comets, Hailey-type comets, and Asteroids. We find that our measured population is consistent with a population dominated by Jupiter-family comets with some evidence for a smaller contribution from Hailey-type comets. This is in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder., Comment: 22 pages, 14 figures, accepted in ApJ

Air showers, produced by the interaction of energetic cosmic rays with the atmosphere, are an excellent alternative to study particle physics at energies beyond any human-made particle accelerator. For that, it is necessary to identify first the mass composition of the primary cosmic ray (and its energy). None of the existing high energy interaction models have been able to reproduce coherently all air shower observables over the entire energy and zenith angle phase space. This is despite having tried all possible combinations for the cosmic ray mass composition. This proposal outlines a self-consistent strategy to study high energy particle interactions and identify the energy spectra and mass composition of cosmic rays. This strategy involves the participation of different particle accelerators and astrophysics experiments. This is important to cover the entire cosmic ray energy range and a larger phase-space of shower observables to probe the high energy interaction models., Snowmass2021 - Letter of Interest

ANITA's fourth long-duration balloon flight in late 2016 detected 29 cosmic-ray (CR)-like events on a background of $0.37^{+0.27}_{-0.17}$ anthropogenic events. CRs are mainly seen in reflection off the Antarctic ice sheets, creating a characteristic phase-inverted waveform polarity. However, four of the below-horizon CR-like events show anomalous non-inverted polarity, a $p = 5.3 \times 10^{-4}$ chance if due to background. All anomalous events are from locations near the horizon; ANITA-IV observed no steeply-upcoming anomalous events similar to the two such events seen in prior flights., Comment: 6 pages, 4 figures, to appear in Physical Review Letters. Supplemental material (reference 17) available from corresponding author

Notch1 has an indispensable role in initiating the T lineage program from progenitors in the thymus. This study defines stage-specific regulation of Notch target genes and shows that Notch2 also amplifies inductive and lineage-restrictive Notch signals in early T cell development., Notch signaling is the dominant intercellular signaling input during the earliest stages of T cell development in the thymus. Although Notch1 is known to be indispensable, we show that it does not mediate all Notch signaling in precommitment stages: Notch2 initially works in parallel to promote early murine T cell development and antagonize other fates. Notch-regulated target genes before and after T lineage commitment change dynamically, and we show that this partially reflects shifts in genome-wide DNA binding by RBPJ, the transcription factor activated by complex formation with the Notch intracellular domain. Although Notch signaling and transcription factor PU.1 can activate some common targets in precommitment T progenitors, Notch signaling and PU.1 activity have functionally antagonistic effects on multiple targets, delineating separation of pro-T cells from alternative PU.1-dependent fates. These results define a distinct mechanism of Notch signal response that distinguishes the initial stages of murine T cell development.

We present a semi-analytical method for the calculation of coherent Askaryan radiation in showers induced by neutrinos of any flavor in ice. We compare our results with those of a full Monte Carlo simulation based on the ZHAireS code. This approach is able to reproduce the vector potential and hence electric field at any experimentally relevant observer position in the time domain. This work extends published results only valid for electron-induced showers. We establish the validity of the semi-analytical calculation of the radio signal produced by all types of neutrino-induced showers in ice. The method is computationally efficient and only requires as inputs the longitudinal charge excess profile of the showers and a parameterization of the vector potential in the far-field region of the shower at the Cherenkov angle that we also provide. Our methodology avoids tracking the contributions to the electric field from millions of particles every time the radio pulse has to be calculated at a given observer position. These results can be readily used in the interpretation of the data taken by experiments, and in the planning and design of future initiatives based on the radio technique in ice., 18 pages, 11 figures. Accepted in Phys. Rev. D

The ANITA balloon experiment was designed to detect radio signals initiated by neutrinos and cosmic ray air showers. These signals are typically discriminated by the polarization and phase inversions of the radio signal. The reflected signal from cosmic rays suffer phase inversion compared to a direct tau neutrino event. In this paper we study sub-surface reflection, which can occur without phase inversion, in the context of the two anomalous up-going events reported by ANITA. We find that subsurface layers and firn density inversions may plausibly account for the events, while ice fabric layers and wind ablation crusts could also play a role. This hypothesis can be tested with radar surveying of the Antarctic region in the vicinity of the anomalous ANITA events. Future experiments should not use phase inversion as a sole criterion to discriminate between downgoing and upgoing events, unless the subsurface reflection properties are well understood., 4+2 pages, 3 figures

The Sun Radio Interferometer Space Experiment (SunRISE) would provide an entirely new view on particle acceleration and transport in the inner heliosphere by creating the first low radio frequency interferometer in space to localize heliospheric radio emissions. By imaging and determining the location of decametric-hectometric (DH) radio bursts from 0.1 MHz–25 MHz, SunRISE would provide key information on particle acceleration mechanisms associated with coronal mass ejections (CMEs) and the magnetic field topology from active regions into interplanetary space. Six small spacecraft, of a 6U form factor, would fly in a supersynchronous geosynchronous Earth orbit (GEO) orbit within about 10 km of each other, in a passive formation, and image the Sun in a portion of the spectrum that is blocked by the ionosphere and cannot be observed from Earth. Key aspects that enable this mission concept are that only position knowledge of the spacecraft is required, not active control, and that the architecture involves a modest amount of on-board processing coupled with significant ground-based processing for navigation, position determination, and science operations. Mission-enabling advances in software-defined radios, GPS navigation and timing, and small spacecraft technologies, developed and flown over the past few years on DARPA High Frequency Research (DHFR), the Community Initiative for Continuing Earth Radio Occultation (CICERO), and the Mars Cube One (MarCO) missions, have made this concept affordable and low-risk. The SunRISE concept would involve utilizing commercial access to space, in which the SunRISE spacecraft would be carried to their target orbit as a secondary payload in conjunction with a larger host spacecraft intended for GEO.