Resolving moving heliospheric structures using interplanetary scintillation observations with the Murchison Widefield Array

Abstract

We have conducted a blind search in 49 consecutive days of interplanetary scintillation observations made by the Murchison Widefield Array from mid-2019, with overlapping daily observations approximately East and South-East of the Sun at an elongation of $\sim$30 degrees and a field of view of 30 degrees. These observations detect an unprecedented density of sources. In spite of these observations being taken at sunspot minimum, this search has revealed several interesting transitory features characterised by elevated scintillation levels. One solar wind enhancement is captured in two observations several hours apart, allowing its radial movement away from the Sun to be measured. We present here a methodology for measuring the plane-of-sky velocity for the moving heliospheric structure. The plane-of-sky velocity was inferred as $0.66\pm 0.147{}^{\text{o}}{\text{hr}}^{-1}$, or $480\pm 106\text{km}{\text{s}}^{-1}$ assuming a distance of 1AU. After cross-referencing our observed structure with multiple catalogues of heliospheric events, we propose that the likely source of our observed structure is a stream-interaction region originating from a low-latitude coronal hole. This work demonstrates the power of widefield interplanetary scintillation observations to capture detailed features in the heliosphere which are otherwise unresolvable and go undetected.

14 pages, 5 figures

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