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Study of non-linear phenomena in the polar ionosphere induced by the SPEAR heating facility

Awarded: NOK 0.72 mill.

The campaign carried out in November 2012 was very successful. One of the scientists who travelled to Svalbard with the project was a new PhD student from AARI. During the November 2012 campaign experiments were carried out utilizing the SPEAR heati ng facility in conjunction with the EISCAT Svalbard Radar (ESR), SuperDARN HF radars (located in Finland and Iceland) and SEE (Stimulated Electromagnetic Emissions) instruments (located in Barentsburg). The SPEAR facility was used to artificially modify the plasma environment of the ionosphere (the region of the Earth's atmosphere which extends from ~60-600km in altitude). The experiments aim to recreate the natural interactions observed in the ionosphere (such as those which create the aurora). By re-c reating these phenomena in a controlled manner it is possible to understand more about the complex interaction processes that take place. The different effects were then observed by the radar and SEE instruments. The experiments focused on varying th e transmission frequency of the SPEAR facility in relation to the naturally occurring particle densities observed in the ionosphere. The particular experimental modes were decided based upon the current ionospheric and solar conditions. By varying the fr equency it was possible to induce different effects such as the generation of artificial plasma striations and SEE. Observations of the plasma interactions manifest themselves in the ESR data as spectral enhancements at the SPEAR transmission frequency. The resulting striations are observed as 'targets' in the field of view of the SuperDARN HF radars. Concurrent data sets were obtained during periods when SPEAR was both actively transmitting and switched off. This allowed the artificial enhancemen ts to be separated from any naturally occurring phenomena. The experiments also focused around attempting to re-create artificial effects that have been observed in previous experiments to allow a larger dataset to be built up. The results indicated th at, under certain ionospheric conditions, spectral enhancements were observed in the ESR data. However, artificial striations were not always observed in the SuperDARN HF radar data. The reason behind this is currently unclear but could relate to excitat ion thresholds for the plasma processes themselves or ionospheric propagation conditions effecting the ability of the SuperDARN HF radars to detect the striations. The publication focuses on spectral analysis results from the ESR, and includes data fro m the SuperDARN HF radar. The different interaction processes induced in the ionosphere have different spectral signatures. By combining the datasets from the two radars it is possible to observe the temporal evolution of both the interaction processes and any resultant artificial plasma striations. A final campaign will take place in November 2013. Two project scientists will travel to Svalbard from AARI. The experiments will continue the investigations into small scale plasma structures in the ion osphere and will make use of the ESR, SuperDARN HF radars and SEE instrumentation.

This proposal seeks to build up a close collaboration in Svalbard in upper atmosphere physics between the University Centre in Svalbard (UNIS) in Longyearbyen and the Arctic and Antarctic Research Institute (AARI) from St. Petersburg, Russia. The focus of this project is to study non-linear phenomena in the upper polar atmosphere above Svalbard using available Norwegian and Russian radio instrumentation in Longyearbyen and Barentsburg. The UNIS operated SPEAR heating facility will be used for ionospheric modification experiments to generate ionospheric irregularities, and the EISCAT Svalbard Radar will be used to monitor the behaviour of plasma parameters. Russian radio equipment operated by AARI in Barentsburg will be used for studies of intensive stimul ated electromagnetic emissions (SEE) phenomenology in the HF modified polar ionosphere. Remote diagnostics will be performed with use of the long-distance diagnostics radio equipment at the AARI observatory in St. Petersburg.

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