| 6th of September 2022 |
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| First measurement of interplanetary scintillation with ASKAP |
| by Chhetri et al. |
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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. |