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Ground-based observations of an onset of localized field-aligned currents during auroral breakup around magnetic midnight


Title (Dublin Core)

en-US Ground-based observations of an onset of localized field-aligned currents during auroral breakup around magnetic midnight

Description (Dublin Core)

en-US The substorm on 2 March 1978 was selected for study as a relatively weak substorm, starting at about local magnetic midnight, that could be observed with instruments in Northern Scandinavia. The analysis is based on a comparative study of data from the IMS magnetometer network, all-sky cameras, pulsation magnetometers, and riometers in the Scandinavian area. In addition other data are used to support the results, e.g., a photograph from the DMSP-F2 satellite, showing the auroral situation over Scandinavia, and further west, immediately after the substorm onset. The substorm was preceded by a weak activation of aurora and magnetic disturbance about 3 min before the onset. After a fading that lasted for 20 s and could be observed only in optical aurora, the substorm onset led to a strong brightening of the aurora, an enhancement of the westward electrojet, a sudden rise in the ionospheric D-layer absorption, and Pi B type pulsations. Immediately after the onset, the ground magnetic data suggest the appearence of a pair of oppositely directed, localized, field-aligned currents (FACs). The main development of the signatures of the downward FAC was clearly delayed by about 3 min. There were significant correlations between the magnetic signatures of the two FACs and different features and spectra of the optical aurora, both in time and location. The observed Pi B type pulsations lasted as long as a growth in the local onset-connected FACs could be inferred. Within the first three minutes the localized three dimensional current system developed into a more sheet-like configuration. An expansion to the west, possibly accompanied by a westward travelling surge, was traced with riometers and magnetometers on Iceland and Greenland.

Creator (Dublin Core)

Opgenoorth, H.J.
Pellinen, R.J.
Maurer, H.
Kuppers, F.
Heikkila, W.J.
Kaila, K.U.
Tanskanen, P.

Subject (Dublin Core)

en-US Auroral substorm
en-US Magnetic substorm
en-US Substorm onset
en-US Field-aligned currents
en-US Auroral electrojet
en-US Atmosphere

Publisher (Dublin Core)

en-US Journal of Geophysics

Date (Dublin Core)


Type (Dublin Core)

en-US Peer-reviewed Article

Format (Dublin Core)


Identifier (Dublin Core)

Source (Dublin Core)

en-US Journal of Geophysics; Vol 48 No 1 (1980): Journal of Geophysics; 101-115

Language (Dublin Core)


Relation (Dublin Core)