Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted than the actual ones. Since the scattering depends on the spectrum of density turbulence, better understanding of the radio wave propagation provides indirect information on the relative density fluctuations = δn / n at the effective turbulence scale length. Here, we have analyzed 30 type III bursts detected by Parker Solar Probe (PSP). For the first time, we have retrieved type III burst decay times τ d between 1 MHz and 10 MHz thanks to an unparalleled temporal resolution of PSP. We observed a significant deviation in a power-law slope for frequencies above 1 MHz when compared to previous measurements below 1 MHz by the twin-spacecraft Solar TErrestrial RElations Observatory (STEREO) mission. We note that altitudes of radio bursts generated at 1 MHz roughly coincide with an expected location of the Alfvén point, where the solar wind becomes super-Alfvénic. By comparing PSP observations and Monte Carlo simulations we predict relative density fluctuations at the effective turbulence scale length at radial distances between 2.5 R and 14 R to range from 0.22 and 0.09. Finally, we calculated relative density fluctuations measured in situ by PSP at a radial distance from the Sun of 35.7 R during the perihelion #1, and the perihelion #2 to be 0.07 and 0.06, respectively. It is in a very good agreement with previous STEREO predictions ( = 0.06 − 0.07) obtained by remote measurements of radio sources generated at this radial distance.

We present initial results from the Radio Frequency Spectrometer (RFS), the high frequency component of the FIELDS experiment on the Parker Solar Probe (PSP). During the first PSP solar encounter (2018 November), only a few small radio bursts were observed. During the second encounter (2019 April), copious Type III radio bursts occurred, including intervals of radio storms where bursts occurred continuously. In this paper, we present initial observations of the characteristics of Type III radio bursts in the inner heliosphere, calculating occurrence rates, amplitude distributions, and spectral properties of the observed bursts. We also report observations of several bursts during the second encounter which display circular polarization in the right hand polarized sense, with a degree of polarization of 0.15 − 0.38 in the range from 8-12 MHz. The degree of polarization can be explained either by depolarization of initially 100% polarized o-mode emission, or by direct generation of emission in the o and x-mode simultaneously. Direct in situ observations in future PSP encounters could provide data which can distinguish these mechanisms.

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We present a technique for deriving the temperature anisotropy of solar wind protons observed by the Parker Solar Probe mission in the near-Sun solar wind. The variation in the temperature of solar wind protons in the radial direction measured by the SWEAP Solar Probe Cup is compared with variation in the orientation of the local magnetic field measured by the FIELDS fluxgate magnetometer, and the components of the proton temperature parallel and perpendicular to the magnetic field are extracted. This procedure is applied to both moments of the proton velocity distribution function (VDF) and to the results of a non-linear fit of proton core and proton beam Maxwellian components of the VDF, and the results are compared and optimum timescales for data selection and trends in the uncertainty in the method are identified. We find that the moment-based proton temperature anisotropy is more

Radio astronomy observatories with high throughput back end instruments require real-time data processing. While computing hardware continues to advance rapidly, development of real-time processing pipelines remains difficult and time-consuming, which can limit scientific productivity. Motivated by this, we have developed Bifrost: an open-source software framework for rapid pipeline development 1 . Bifrost combines a high-level Python interface with highly efficient reconfigurable data transport and a library of computing blocks for CPU and GPU processing. The framework is generalizable, but initially it emphasizes the needs of high-throughput radio astronomy pipelines, such as the ability to process data buffers as if they were continuous streams, the capacity to partition processing into distinct data sequences (e.g., separate observations), and the ability to extract specific intervals from buffered data. Computing blocks in the library are designed for applications such as interferometry, pulsar dedispersion and timing, and transient search pipelines. We describe the design and implementation of the Bifrost framework and demonstrate its use as the backbone in the correlation and beamforming back end of the Long Wavelength Array station in the Sevilleta National Wildlife Refuge, NM.