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An assessment of Pc5 pulsations observed during the Carrington Storm

Thomson, Alan; Kelly, Gemma; Humphries, Thomas; Williamson, John. 2015 An assessment of Pc5 pulsations observed during the Carrington Storm. [Poster] In: 12th European Space Weather Week , Ostend, Belgium, 23-27 Nov 2015. (Unpublished)

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Abstract/Summary

The Greenwich observatory magnetogram for 2nd September 1859 shows prolonged periods of ULF Pc5-like pulsations, most likely global Pc5s driven by the solar wind during the recovery phase of the storm. Unlike the very rapid and presumably very high amplitude variations that are off scale during the peak of the magnetic storm on 1st September 1859, the pulsation events have been well preserved in the records of the time. (Further information on and images of the scanned Carrington magnetograms can be found at www.bgs.ac.uk/data/Magnetograms/home.html.) We therefore try to put the measured amplitude and duration of the Carrington Pc5 pulsations into some context by analysing them in relation to modern day records. For this we analyse Pc5 pulsations occurring in data from the Hartland, UK observatory, which is geographically close to Greenwich, and Wingst observatory, Germany. Wingst, in particular, has a geomagnetic latitude believed to be closer to that of Greenwich at the time of the Carrington storm (around 50 degrees north). For both observatories there are complete records from the early 1980s to the present day, providing a continuous data set, over three decades, containing many severe storms from the recent past. We use 1-minute mean horizontal component field data that are filtered in the Pc5 150-600 second pass band, and in other pass bands for comparison, by means of an 8th order Butterworth filter. By means of various measures (e.g. amplitude, duration, root-mean-square over the day, and others) we try to determine how atypical the Carrington pulsations were. We discuss issues such as how the differing magnetometer responses to high frequency magnetic variations, ‘then’ and ‘now’, may affect the interpretation of results across more than 150 years and how the results depend on time of day.

Item Type: Publication - Conference Item (Poster)
NORA Subject Terms: Earth Sciences
Space Sciences
Date made live: 15 Jul 2016 09:02 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/513957

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