Separating Nightside Interplanetary and Ionospheric Scintillation with LOFAR

Abstract

Observation of interplanetary scintillation (IPS) beyond Earth-orbit can be challenging due to the necessity to use low radio frequencies at which scintillation due to the ionosphere could confuse the interplanetary contribution. A recent paper by Kaplan {\it et al} (2015) presenting observations using the Murchison Widefield Array (MWA) reports evidence of night-side IPS on two radio sources within their field of view. However, the low time cadence of 2\,s used might be expected to average out the IPS signal, resulting in the reasonable assumption that the scintillation is more likely to be ionospheric in origin. To verify or otherwise this assumption, this letter uses observations of IPS taken at a high time cadence using the Low Frequency Array (LOFAR). Averaging these to the same as the MWA observations, we demonstrate that the MWA result is consistent with IPS, although some contribution from the ionosphere cannot be ruled out. These LOFAR observations represent the first of night-side IPS using LOFAR, with solar wind speeds consistent with a slow solar wind stream in one observation and a CME expecting to be observed in another.

Accepted for publication in Astrophysical Journal Letters

References in corpus (7)

• LOFAR: The LOw-Frequency ARray
• The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
• The Murchison Widefield Array: Design Overview
• Observing pulsars and fast transients with LOFAR
• Broadband Meter-Wavelength Observations of Ionospheric Scintillation
• The Dynamic Spectrum of Interplanetary Scintillation: First Solar Wind Observations on LOFAR
• Murchison Widefield Array Observations of Anomalous Variability: A Serendipitous Night-time Detection of Interplanetary Scintillation

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• Dual-frequency single-pulse study of PSR B0950+08
• Interplanetary Scintillation with the Murchison Widefield Array V: An All-sky Survey of Compact Sources using a Modern Low-frequency Radio Telescope
• Optimization and Commissioning of the EPIC Commensal Radio Transient Imager for the Long Wavelength Array
• The Scintillating Tail of Comet C/2020 F3 (Neowise)