Aa Indices.

The aa index is a simple global geomagnetic activity index, with units of 1 nT (nanotesla), which is produced from the K indices from two approximately antipodal observatories. At present these are Hartland observatory in the UK and Canberra observatory in Australia. The main advantage in using aa indices for research purposes is that the time series spans further back (to 1868) than any of the other planetary indices time series.Also, up to date values are produced and made available weekly, giving nearer to real time availability than any other planetary index. In between the weekly updates, BGS calculates estimated aa indices, providing real time "nowcasts" which are updated on an hourly basis. These estimates are clearly marked with the letters "Est". Although calculated by the same method, the aa indices available on this service are not the definitive values. These are published by the International Service for Geomagnetic Indices, CRPE/CNET - CNRS, 4 Avenue de Neptune, F-94107 Saint Maur, Cedex, France.
dataset
:http://data.bgs.ac.uk/id/dataHolding/13480365
English
Geoscientific information
GEMET - INSPIRE themes: BGS Thesaurus of Geosciences:
Geomagnetism
Free:
NERC_DDC
-180.0000, -90.0000, 180.0000, 90.0000
WORLD [id=100000]
creation: 1868
1868 -
British Geological Survey
The Lyell Centre, Research Avenue South, EDINBURGH, EH14 4AP, United Kingdom
tel: +44 131 667 1000 Ex:233
email: enquiries@bgs.ac.uk
Role: originator
British Geological Survey
The Lyell Centre, Research Avenue South, EDINBURGH, EH14 4AP, United Kingdom
tel: +44 131 667 1000 Ex:233
email: enquiries@bgs.ac.uk
Role: originator
British Geological Survey
Environmental Science Centre,Keyworth, NOTTINGHAM, NG12 5GG, United Kingdom
tel: +44 115 936 3143
email: enquiries@bgs.ac.uk
Role: distributor

Data Quality

The aa indices are derived using data from two nearly antipodal observatories, where magnetograms were available since 1868. For each three hour interval, K indices are measured at the two stations and converted back into amplitude; an individual aa index is the average of the northern and southern values, weighted to account for the small difference in latitude of the two stations, or for the slight changes in the very place of the observatory. The definitive values are published by the International Service for Geomagnetic Indices.
INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology
COMMISSION REGULATION (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services

Constraints

otherRestrictions

Metadata about metadata

9df8df51-63b9-37a8-e044-0003ba9b0d98
British Geological Survey
Clarke,Ellen
The Lyell Centre, Research Avenue South, EDINBURGH, EH14 4AP, United Kingdom
tel: +44 131 667 1000 Ex:233
email: ecla@bgs.ac.uk
Role: point of contact
2019-12-05
English

Coupled Resource