Monitoring the Long Wavelength Transient Sky with the LWA1 Telescope

Radio transient astronomy has received a vastly increasing amount of interest within the last few decades. In this time, several new sources have been discovered and many more have been predicted. These sources are spread throughout the radio spectrum, and many emit strongly within the low frequency (10 - 100 MHz) regime. The first station of the Long Wavelength Array (LWA1) is a compact array of 260 dual polarization dipole antennas operating between 10 and 88 MHz. With good sensitivity, high time and frequency resolution, and an instantaneous field of view up to ~ 20,000 deg2, the LWA1 an ideal instrument for searching for transient phenom- ena. This dissertation presents transient work done with the LWA1, which includes a search for prompt emission from gamma ray bursts as well as a blind search for un- specific transients. These searches resulted in new limits on astronomical transients and the discovery of radio emission from large meteors (fireballs). This dissertation also presents a highly sensitive followup study on the fireball emission, which has yielded new insight into the origin of the emission, suggesting that it is emission of plasma waves within the plasma trail

Multi-messenger astronomy of gravitational-wave sources with flexible wide-area radio transient surveys

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of gravitational waves and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, LOFAR and MWA. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a \usim 30 second time window and \usim 200 \mendash 500 \punits{deg}^{2} sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a \emph{prompt} radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of \usim 2. For some models, we also map the parameter space that may be constrained by non-detections.Comment: 31 pages, 4 figure

The Case for Combining a Large Low‐Band Very High Frequency Transmitter With Multiple Receiving Arrays for Geospace Research: A Geospace Radar

We argue that combining a high‐power, large‐aperture radar transmitter with several large‐aperture receiving arrays to make a geospace radar—a radar capable of probing near‐Earth space from the upper troposphere through to the solar corona—would transform geospace research. We review the emergence of incoherent scatter radar in the 1960s as an agent that unified early, pioneering research in geospace in a common theoretical, experimental, and instrumental framework, and we suggest that a geospace radar would have a similar effect on future developments in space weather research. We then discuss recent developments in radio‐array technology that could be exploited in the development of a geospace radar with new or substantially improved capabilities compared to the radars in use presently. A number of applications for a geospace radar with the new and improved capabilities are reviewed including studies of meteor echoes, mesospheric and stratospheric turbulence, ionospheric flows, plasmaspheric and ionospheric irregularities, and reflection from the solar corona and coronal mass ejections. We conclude with a summary of technical requirements