| The Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA; www.sgo.fi/kaira) uses LOFAR technology to form an independent radio telescope situated in Finnish Lapland (69°4'15''N 20°45'43''E). This week we successfully implemented the KAIRA pulsar mode and ran a joint experiment with the EISCAT UHF incoherent scatter radar (www.eiscat.rl.ac.uk/radars/uhf/), based near Tromsø (Norway). EISCAT's UHF radar allows us to measure the total electron content in the ionosphere in any given direction. Variation in the total electron content in the ionosphere causes changes to the observed dispersion and rotation measures of pulsars. By simultaneously monitoring a sample of pulsars using the KAIRA HBA and EISCAT UHF, these observations can be used to study the temporal and spatial variations in the ionosphere.
This method of observing the ionosphere complements observations of the absorption of cosmic radio background due to the ionosphere, made using KAIRA as a riometer (Relative Ionospheric Opacity Meter). Riometry is a well-established technique for observing the D region of the ionosphere and using the broad bandwidth of the KAIRA LBA, local height profiles of the electron density can also be recovered from multi-frequency observations.
Observing conditions at KAIRA are somewhat different to the rest of the LOFAR telescope. It is cold. Very cold. In March the average temperature is -10°C, with lows of less than -30°C, and the average snow cover is 100cm. For the KAIRA HBA on its raised platforms, snow needs only to be swept off periodically; for the LBA, some digging is required to prevent the bandpass response being compromised. There is no high-speed ethernet connection to the KAIRA station and observers generally need to work on site in order to collect their data (and dig for their bandpass). But visitors are not completely isolated, as basic facilities are available a short walk down the road at the customs station on the Finnish-Norweigan border.