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Abstract Meteor radio afterglows (MRAs) and optical persistent trains (PTs) are two types of long‐lived phenomena which are occasionally observed following the occurrence of a meteor. Both phenomena are thought to be produced by intrinsic emission mechanisms; PTs have been associated with chemiluminescent reactions between meteoric metals and atmospheric ozone whereas MRA emission arises due to radiation emitted by processes in the meteor's plasma trail. Previous research has identified an association between these phenomena, and proposed a mechanism by which the reactions responsible for PTs could also fuel MRAs. In this work, we investigate said connection using a substantially larger catalog containing hundreds of examples of each phenomenon. Using meteor data from the Global Meteor Network (GMN), we performed a directed search in all‐sky radio images obtained by the Long Wavelength Array (LWA) radio telescope to identify meteors with MRAs. The resulting catalog spanned nearly 2 years and contained a total of 2,887 meteors, with 675 MRA events and 372 PTs. Statistical analyses suggest that the connection between the two phenomena is not as strong as previously supposed. Additionally, we show that the MRA occurrence rates do not have a strong seasonal dependence, meteoroid strength dependence, or preference between meteor showers and sporadics. Interestingly, we find that a meteor's entry angle appears to play a significant role in whether an MRA is observed. 

Abstract We present a census of 100 pulsars, the largest below 100 MHz, including 94 normal pulsars and six millisecond pulsars, with the Long Wavelength Array (LWA). Pulse profiles are detected across a range of frequencies from 26–88 MHz, including new narrowband profiles facilitating profile evolution studies, and breaks in pulsar spectra at low frequencies. We report mean flux density, spectral index, curvature, and low-frequency turnover-frequency measurements for 97 pulsars, including new measurements for 61 sources. Multifrequency profile widths are presented for all pulsars, including component spacing for 27 pulsars with two components. Polarized emission is detected from 27 of the sources (the largest sample at these frequencies) in multiple frequency bands, with one new detection. We also provide new timing solutions for five recently discovered pulsars. Low-frequency observations with the LWA are especially sensitive to propagation effects arising in the interstellar medium. We have made the most sensitive measurements of pulsar dispersion measures (DMs) and rotation measures, with median uncertainties of 2.9 × 10⁻⁴pc cm⁻³and 0.01 rad m⁻², respectively, and can track their variations over almost a decade, along with other frequency-dependent effects. This allows for stringent limits on average magnetic fields, with no variations detected above ∼20 nG. Finally, the census yields some interesting phenomena in individual sources, including the detection of frequency- and time-dependent DM variations in B2217+47, and the detection of highly circularly polarized emission from J0051+0423. 

Abstract We conducted an all‐sky imaging transient search with the Owens Valley Radio Observatory Long Wavelength Array (OVRO‐LWA) data collected during the Perseid meteor shower in 2018. The data collection during the meteor shower was motivated to conduct a search for intrinsic radio emission from meteors below 60 MHz known as the meteor radio afterglows (MRAs). The data collected were calibrated and imaged using the core array to obtain lower angular resolution images of the sky. These images were input to a pre‐existing LWA transient search pipeline to search for MRAs as well as cosmic radio transients. This search detected 5 MRAs and did not find any cosmic transients. We further conducted peeling of bright sources, near‐field correction, visibility differencing and higher angular resolution imaging using the full array for these 5 MRAs. These higher angular resolution images were used to study their plasma emission structures and monitor their evolution as a function of frequency and time. With higher angular resolution imaging, we resolved the radio emission size scales to less than 1 km physical size at 100 km heights. The spectral index mapping of one of the long duration event showed signs of diffusion of plasma within the meteor trails. The unpolarized emission from the resolved radio components suggest resonant transition radiation as the possible radiation mechanism of MRAs. 

ABSTRACT Efforts are underway to use high-precision timing of pulsars in order to detect low-frequency gravitational waves. A limit to this technique is the timing noise generated by dispersion in the plasma along the line of sight to the pulsar, including the solar wind. The effects due to the solar wind vary with time, influenced by the change in solar activity on different time-scales, ranging up to ∼11 yr for a solar cycle. The solar wind contribution depends strongly on the angle between the pulsar line of sight and the solar disc, and is a dominant effect at small separations. Although solar wind models to mitigate these effects do exist, they do not account for all the effects of the solar wind and its temporal changes. Since low-frequency pulsar observations are most sensitive to these dispersive delays, they are most suited to test the efficacy of these models and identify alternative approaches. Here, we investigate the efficacy of some solar wind models commonly used in pulsar timing using long-term, high-cadence data on six pulsars taken with the Long Wavelength Array, and compare them with an operational solar wind model. Our results show that stationary models of the solar wind correction are insufficient to achieve the timing noise desired by pulsar timing experiments, and we need to use non-stationary models, which are informed by other solar wind observations, to obtain accurate timing residuals. 

ABSTRACT Using the first station of the Long Wavelength Array (LWA1), we examine polarized pulsar emission between 25 and 88 MHz. Polarized light from pulsars undergoes Faraday rotation as it passes through the magnetized interstellar medium. Observations from low-frequency telescopes are ideal for obtaining precise rotation measures (RMs) because the effect of Faraday rotation is proportional to the square of the observing wavelength. With these RMs, we obtained polarized pulse profiles to see how polarization changes in the 25–88 MHz range. The RMs were also used to derive values for the electron-density-weighted average Galactic magnetic field along the line of sight. We present RMs and polarization profiles of 15 pulsars acquired using data from LWA1. These results provide new insight into low-frequency polarization characteristics and pulsar emission heights, and complement measurements at higher frequencies. 

Abstract With the Expanded Long Wavelength Array (ELWA) and pulsar binning techniques, we searched for off-pulse emission from PSR B0950+08 at 76 MHz. Previous studies suggest that off-pulse emission can be due to pulsar wind nebulae (PWNe) in younger pulsars. Other studies, such as that done by Basu et al. (2012), propose that in older pulsars this emission extends to some radius that is on the order of the light cylinder radius, and is magnetospheric in origin. Through imaging analysis we conclude that this older pulsar with a spin-down age of 17 Myr has a surrounding PWN, which is unexpected since as a pulsar ages its PWN spectrum is thought to shift from being synchrotron to inverse-Compton-scattering dominated. At 76 MHz, the average flux density of the off-pulse emission is 0.59 ± 0.16 Jy. The off-pulse emission from B0950+08 is ∼ 110 ± 17 arcseconds (0.14 ± 0.02 pc) in size, extending well-beyond the light cylinder diameter and ruling out a magnetospheric origin. Using data from our observation and the surveys VLSSr, TGSS, NVSS, FIRST, and VLASS, we have found that the spectral index for B0950+08 is about −1.36 ± 0.20, while the PWN’s spectral index is steeper than −1.85 ± 0.45. 

Abstract We present observations of 86 meteor radio afterglows (MRAs) using the new broadband imager at the Long Wavelength Array Sevilleta (LWA‐SV) station. The MRAs were detected using the all‐sky images with a bandwidth up to 20 MHz. We fit the spectra with both a power law and a log‐normal function. When fit with a power law, the spectra varied from flat to steep and the derived spectral index distribution from the fit peaked at −1.73. When fit with a log‐normal function, the spectra exhibits turnovers at frequencies between 30 and 40 MHz, and appear to be a better functional fit to the spectra. We compared the spectral parameters from the two fitting methods with the physical properties of MRAs. We observe a weak correlation between the log‐normal turnover frequency and the altitude of MRAs. The spectral indices from the power law fit do not show any strong correlations with the physical properties of MRAs. However, the full width half maximum (FWHM) duration of MRAs is correlated with the local time, incidence angle, luminosity and optically derived kinetic energy of parent meteoroid. Also, the average luminosity of MRAs seems to be correlated with the kinetic energy of parent meteoroid and the altitude at which they occur.