Working Group on Geomagnetic Data and Indices
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Status of Deriviation of the Equatorial Dst Index and AE Index

We derived the Equatorial Dst index (Dst index) and the Auroral Electrojet Index (AE index) in two steps. One is the final index and the other is the provisional index.

Because of growing demands for quicker availability of Dst index and AE index we started derivation of near realtime indices (this is called also Quick Look Index or QL index). The QL Dst index was made available in October 1996 and the QL AE index was made available in January 1997 through WWW service of the WDC-C2 Geomagnetism. The Final Index is derived and distributed on an annual or bi-annual basis with enough quality suitable for any scientific analysis and made public by ISGI publication and by data book series of the WDC-C2 for Geomagnetism, Kyoto. The Provisional Index is derived as soon as the necessary (provisional) data are received from the contributing observatories and which is disseminated by post or by other means on a monthly basis. We added one more step for quick look monitoring. Quick Look index, which is derived very quick without waiting for enough number of stations and derived on a daily basis. There is only a set of values for the Final Index and another set of values for the Provisional Index but QL values are updated daily or more frequently if necessary (Users should be careful that there can be many versions of QL index). We receive requests to provide the values of QL indices for prediction purposes. We are in consideration of how we can provide the values as a input of the prediction users without confusions. To make the QL Dst and QL AE index more reliable, we need to consider the use data from more stations and we need to improve reliability of each station.

Dst index:

We derived the final Dst index through December 1996, with a delay of 6 months after the end of the year and the provisional Dst index was done through May 1997 with a delay of two months after the end of the month. We added Alibag in derivation of the provisional Dst index since January 1997. We found it to be more suitable when using additional stations due to the fact that we are suffering from variations caused by missing data in some observatories. QL Dst index is derived and distributed since October 1996 using regular 4 observatories (Kakioka, Honolulu, San Juan and Hermanus). Alibag is not used for QL index as e-mail data transmission is not stable from the station. The WWW has plots of all three levels (final, provisional and QL). When provisional index is derived QL index is deleted from the WWW and when the final index is derived, provisional and QL index is deleted for the period.

AE index:

We apolgize for the slow progress in the final AE index. The derived final AE index is through June 1988 and we will be putting more effort into catching up the provisional AE index. The derived provisional AE index is for 1990, 1993 and 1994. We hope that 1991 and 1992 will be drived by September 1997 and 1995 will be derived by the end of 1997. QL AE index has been derived since January 1997 and is plotted with colors which show the number of stations at each minute to give the reliability of the data.

The problem of derivation of the final AE index is mainly in quality of data. The problem of provisional (and QL) AE index is difficulty in obtaining data from stations especially the Russian observatories. To reduce the problems, we started cooperative work with Russian Institutions such as AARI, IZMIRAN, WDC-B and IKFIA for digitization and transmission of data throughj STEP, WDC Panel and INTERMAGNET project.

Of the 12 AE stations we are now able to receive data almost in realtime (every hour) from one station (Abisko), daily from 7 stations (College, Tixi, Yellowknife, Fort Churchill, Poste-de-la-Bleine and Narsarsuaq). There are still heavy problems in obtaining data from Russian stations but we have some good indications of possibly collecting data from Dikson. So we hope we can increase the number of stations for QL AE index. Cape Wellen was closed in October 1996 because of power failure and we expected it to be reopened in the summer of 1997 but it turned out that it will not be fixed for a few more years. This will affect not only QL index but also provisional and final AE index.


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