Substorm onsets at Churchill, Manitoba, inferred from radiowave emission data

Details Substorm onsets at Churchill, Manitoba, inferred from radiowave emission data Substorm onsets at Churchill, Manitoba, inferred from radiowave emission data

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm41b1731l&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #SM41B-1731

Physics

[2407] Ionosphere / Auroral Ionosphere, [2704] Magnetospheric Physics / Auroral Phenomena, [2790] Magnetospheric Physics / Substorms

Scientific paper

Two types of natural auroral radio emissions are detectable at ground level in association with substorm onsets: impulsive auroral hiss up to 1 MHz, and medium frequency burst (MFB) at 1.5-4.5 MHz. A thorough survey of MFB observed at Churchill, Manitoba, during 1994-2008 has produced a database of more than 600 events. Riometer and other ground-based data will be checked for a selection of these events to determine what fraction of MFB events is associated with substorm onset signatures; preliminary results indicate a high percentage of order 80-100 percent is associated with some substorm onset features such as prompt absorption in riometer data or a deep bay in magnetometer data. Furthermore, the large database of Churchill MFB events is expected to include a number of close DMSP conjunctions which will provide space-based data with even closer conjunction than previously achieved. Working from the other direction, MFB occurrences at Churchill have been cross-checked with two existing databases related to substorm onsets: the published database of substorm onsets determined from IMAGE satellite optical observations [Frey et al., 2004], restricted to those within 400 km of Churchill; and the database of dispersionless injection events inferred from riometer data from Gillam, Manitoba [Spanswick et al., 2007]. Preliminary examination of the data suggests that about 25 percent of the identified substorms have corresponding MFB events. This relatively low percentage may result because the onsets identified by the other techniques are based on a somewhat broader/different geographical areas than covered by the single MFB receiver at Churchill. Cross-comparing databases of substorm onsets assembled from different types of data will help establish the usefulness of each database. Close DMSP conjunctions will provide in situ data critical to elucidating the generation mechanism of the medium frequency burst. References: Frey H. U., S. B. Mende, V. Angelopoulos, E. F. Donovan(2004), Substorm onset observations by IMAGE-FUV, J. Geophys. Res., 109, A10304, doi:10.1029/2004JA010607; Spanswick E., E. Donovan, R. Friedel, A. Korth (2007), Ground based identification of dispersionless electron injections, Geophys. Res. Lett., 34, L03101, doi:10.1029/2006GL028329.

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