Identification

Title

Aa Indices.

Abstract

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.

Resource type

dataset

Resource locator

Unique resource identifier

code

13480365

codeSpace

http://data.bgs.ac.uk/id/dataHolding

Dataset language

eng

Spatial reference system

authority code

OGP

code identifying the spatial reference system

urn:ogc:def:crs:EPSG::4326

Additional information source

Complete time Series. Global: Derived from 2 Antipodal Locations.

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

originating controlled vocabulary

title

GEMET - INSPIRE themes

reference date

date type

publication

effective date

2008-06-01

Keyword set

keyword value

Geomagnetism

originating controlled vocabulary

title

BGS Thesaurus of Geosciences

reference date

date type

revision

effective date

2011

Keyword set

keyword value

NERC_DDC

Geographic location

Geographic bounding box

West bounding longitude

-180.0000

East bounding longitude

180.0000

North bounding latitude

90.0000

South bounding latitude

-90.0000

Temporal reference

Temporal extent

Begin position

1868

End position

Dataset reference date

date type

publication

effective date

1868-01-01

Frequency of update

weekly

Quality and validity

Lineage

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.

Conformity

Conformity report

specification

title

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

reference date

date type

publication

effective date

2011

degree

false

explanation

See the referenced specification

Data formats

Data format

name of format

DELIMITED ASCII - ASCII Year Files or user defined.

version of format

Not entered

Constraints related to access and use

Constraint set

Use constraints

Either: (i) the dataset is made freely available, e.g. via the Internet, for a restricted category of use (e.g. educational use only); or (ii) the dataset has not been formally approved by BGS for access and use by external clients under licence, but its use may be permitted under alternative formal arrangements; or (iii) the dataset contains 3rd party data or information obtained by BGS under terms and conditions that must be consulted in order to determine the permitted usage of the dataset. Refer to the BGS staff member responsible for the creation of the dataset if further advice is required. He / she should be familiar with the composition of the dataset, particularly with regard to 3rd party IPR contained in it, and any resultant use restrictions. This staff member should revert to the IPR Section (ipr@bgs.ac.uk) for advice, should the position not be clear.

Limitations on public access

In its role as World Data Centre for Geomagnetism (Edinburgh) we make available the data for scientific research. If the data are used in publications and presentations, the data suppliers and this WDC should be acknowledged. For commercial applications of these data, please contact the relevant institute directly.

Responsible organisations

Responsible party

organisation name

British Geological Survey

full postal address

Murchison House, West Mains Road, Edinburgh, Lothian, United Kingdom, EH9 3LA

EDINBURGH

EH9 3LA

United Kingdom

telephone number

+44 131 667 1000 Ex:233

email address

enquiries@bgs.ac.uk

responsible party role

distributor

Metadata on metadata

Metadata point of contact

organisation name

British Geological Survey

full postal address

Murchison House, West Mains Road, Edinburgh, Lothian, United Kingdom, EH9 3LA

EDINBURGH

EH9 3LA

United Kingdom

telephone number

+44 131 667 1000 Ex:233

email address

enquiries@bgs.ac.uk

responsible party role

pointOfContact

Metadata date

2012-03-26

Metadata language

eng