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6th of September 2022
First measurement of interplanetary scintillation with ASKAP
by Chhetri et al.
Chhetri et al. report on a measurement of interplanetary scintillation (IPS) using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. Although this proof-of-concept observation utilised just 3 seconds of data on a single source, this is nonetheless a significant result, since the exceptional wide field of view of ASKAP, and this validation of its ability to observe within 10 degrees of the Sun, mean that ASKAP has the potential to observe an interplanetary coronal mass ejection (CME) after it has expanded beyond the field of view of white light coronagraphs, but long before it has reached the Earth. The team demonstrates that, by adopting a "Target Of Opportunity" approach, where the telescope is triggered by the detection of a CME in white-light coronagraphs, the majority of interplanetary CMEs could be observed by ASKAP while in an elongation range < 30 degrees. It is therefore highly complementary to the colocated Murchison Widefield Array, a lower-frequency instrument which is better suited to observing at elongations > 20 degrees.

The image above is a schematic of the IPS detection in the ASKAP field of view of 36 beams, shown as overlapping circles. Only data from one beam, indicated with the dark circle, was downloaded for this analysis. The position of our target source and the second detected source are indicated with the red star and a black cross respectively. Sources that could be detectable (above a significance of 5 standard deviations) in 200 ms images, based on the Rapid ASKAP Continuum Survey (RACS), are shown with grey dots. To demonstrate the predicted density of IPS sources in a 1 minute ASKAP observation, based on counts of flat-spectrum sources, 131 RACS sources using blue stars are randomly highlighted.

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