Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite
We present a new composite of geomagnetic activity which is designed to be as homogeneous in its construction as possible. This is done by only combining data that, by virtue of the locations of the source observatories used, have similar responses to solar wind and IMF (interplanetary magnetic...
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doaj-e5b249f8458d43d08aa2dede52de9d182020-11-24T22:59:59ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762013-11-01311957197710.5194/angeo-31-1957-2013Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data compositeM. Lockwood0L. Barnard1H. Nevanlinna2M. J. Owens3R. G. Harrison4A. P. Rouillard5C. J. Davis6Meteorology Department, University of Reading, Reading, Berkshire, UKMeteorology Department, University of Reading, Reading, Berkshire, UKFinnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, FinlandMeteorology Department, University of Reading, Reading, Berkshire, UKMeteorology Department, University of Reading, Reading, Berkshire, UKInstitut de Recherché en Astrophysique et Planétologie, 9 Ave. du Colonel Roche, BP 44 346, 31028 Toulouse Cedex 4, FranceMeteorology Department, University of Reading, Reading, Berkshire, UKWe present a new composite of geomagnetic activity which is designed to be as homogeneous in its construction as possible. This is done by only combining data that, by virtue of the locations of the source observatories used, have similar responses to solar wind and IMF (interplanetary magnetic field) variations. This will enable us (in Part 2, Lockwood et al., 2013a) to use the new index to reconstruct the interplanetary magnetic field, <i>B</i>, back to 1846 with a full analysis of errors. Allowance is made for the effects of secular change in the geomagnetic field. The composite uses interdiurnal variation data from Helsinki for 1845–1890 (inclusive) and 1893–1896 and from Eskdalemuir from 1911 to the present. The gaps are filled using data from the Potsdam (1891–1892 and 1897–1907) and the nearby Seddin observatories (1908–1910) and intercalibration achieved using the Potsdam–Seddin sequence. The new index is termed IDV(1d) because it employs many of the principles of the IDV index derived by Svalgaard and Cliver (2010), inspired by the <i>u</i> index of Bartels (1932); however, we revert to using one-day (1d) means, as employed by Bartels, because the use of near-midnight values in IDV introduces contamination by the substorm current wedge auroral electrojet, giving noise and a dependence on solar wind speed that varies with latitude. The composite is compared with independent, early data from European-sector stations, Greenwich, St Petersburg, Parc St Maur, and Ekaterinburg, as well as the composite <i>u</i> index, compiled from 2–6 stations by Bartels, and the IDV index of Svalgaard and Cliver. Agreement is found to be extremely good in all cases, except two. Firstly, the Greenwich data are shown to have gradually degraded in quality until new instrumentation was installed in 1915. Secondly, we infer that the Bartels <i>u</i> index is increasingly unreliable before about 1886 and overestimates the solar cycle amplitude between 1872 and 1883 and this is amplified in the proxy data used before 1872. This is therefore also true of the IDV index which makes direct use of the <i>u</i> index values.https://www.ann-geophys.net/31/1957/2013/angeo-31-1957-2013.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
M. Lockwood L. Barnard H. Nevanlinna M. J. Owens R. G. Harrison A. P. Rouillard C. J. Davis |
spellingShingle |
M. Lockwood L. Barnard H. Nevanlinna M. J. Owens R. G. Harrison A. P. Rouillard C. J. Davis Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite Annales Geophysicae |
author_facet |
M. Lockwood L. Barnard H. Nevanlinna M. J. Owens R. G. Harrison A. P. Rouillard C. J. Davis |
author_sort |
M. Lockwood |
title |
Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite |
title_short |
Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite |
title_full |
Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite |
title_fullStr |
Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite |
title_full_unstemmed |
Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 1: A new geomagnetic data composite |
title_sort |
reconstruction of geomagnetic activity and near-earth interplanetary conditions over the past 167 yr – part 1: a new geomagnetic data composite |
publisher |
Copernicus Publications |
series |
Annales Geophysicae |
issn |
0992-7689 1432-0576 |
publishDate |
2013-11-01 |
description |
We present a new composite of geomagnetic activity which is designed to be
as homogeneous in its construction as possible. This is done by only combining
data that, by virtue of the locations of the source observatories used, have
similar responses to solar wind and IMF (interplanetary magnetic field) variations. This will enable us (in
Part 2, Lockwood et al., 2013a) to use the new index to reconstruct the interplanetary
magnetic field, <i>B</i>, back to 1846 with a full analysis of errors. Allowance is
made for the effects of secular change in the geomagnetic field. The
composite uses interdiurnal variation data from Helsinki for 1845–1890
(inclusive) and 1893–1896 and from Eskdalemuir from 1911 to the present. The
gaps are filled using data from the Potsdam (1891–1892 and 1897–1907) and
the nearby Seddin observatories (1908–1910) and intercalibration achieved
using the Potsdam–Seddin sequence. The new index is termed IDV(1d) because it
employs many of the principles of the IDV index derived by Svalgaard and Cliver (2010), inspired by
the <i>u</i> index of Bartels (1932); however, we revert to using one-day (1d) means, as
employed by Bartels, because the use of near-midnight values in IDV introduces
contamination by the substorm current wedge auroral electrojet, giving noise and a
dependence on solar wind speed that varies with latitude. The composite is
compared with independent, early data from European-sector stations,
Greenwich, St Petersburg, Parc St Maur, and Ekaterinburg, as well as the
composite <i>u</i> index, compiled from 2–6 stations by Bartels, and the IDV index of
Svalgaard and Cliver. Agreement is found to be extremely good in all cases,
except two. Firstly, the Greenwich data are shown to have gradually degraded
in quality until new instrumentation was installed in 1915. Secondly, we
infer that the Bartels <i>u</i> index is increasingly unreliable before about 1886
and overestimates the solar cycle amplitude between 1872 and 1883 and this
is amplified in the proxy data used before 1872. This is therefore also true
of the IDV index which makes direct use of the <i>u</i> index values. |
url |
https://www.ann-geophys.net/31/1957/2013/angeo-31-1957-2013.pdf |
work_keys_str_mv |
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