FinCOSPAR2017 on Seili
- Using interferometric riometry imaging with KAIRA to map high-energy ionospheric electron precipitation
The Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) is a radio receiving system located at Kilpisjärvi in Northern Finland. It is based on the Low-Frequency Array (LOFAR) design and comprises two phased-arrays (low-band and high-band), with a shared digital signal-processing back-end.
The 48~low-band antennas of KAIRA are dual-polarisation inverted-V dipoles, in a quasi-random layout (~ 34m diameter). This layout suppresses sidelobes and facilitates instantaneous all-sky imaging using synthetic-aperture interferometry.
By comparing instantaneous images to established quiet-sky radio maps, the ionospheric absorption can be determined. Thus KAIRA, in addition to functioning as a radiotelescope and radar receiver, can also be used as an all-sky interferometric imaging riometer. Unlike the multibeam riometers, which form discrete beams on the sky, this interferometric technique has spatially-continuous sampling of the incoming cosmic radio noise emissions.
Because this form of riometric imaging is analogous to the `fish-eye' lens used by optical all-sky cameras, it has been possible to conduct comparative studies of scientifically-interesting electron-precipitation events. In this work we do this to examine the nature of the high-energy particles during the growth-phase preceding substorm onset and relate it to existing substorm morphology, noting cosmic noise absorption (CNA) is consistently equatorward of discrete arcs, but still contained within the region of diffuse aurora.
Here are some photographs from the trip:
|The ferry disgorges the conference-goers like a|
giant vomiting whale that has beached on the island.
|The main building on Seili. Once an asylum hospital, now it |
is a research station operated by the University of Turku.
|The main conference-room where the presentations were given.|
Notice the metal grill on the door to prevent escape.
|No, this is not the student accommodation. It is one |
of the museum-preserved asylum rooms at Seili.
|Escape! There could be nothing worse that being trapped |
interminably on an island of madness. And, as I write this,
I am now safely back on Tromsø. Er... wait a second...