The Generation of K Indices from Digitally Recorded Magnetic Data

Riddick, John C.; Stuart, W.F.

doi:10.1007/978-94-009-5283-6_24

Cited by 9 publications

(6 citation statements)

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“…Riddick and Stuart, 1984;Menvielle et al, 1995). To some extent, this preserved continuity with the older K-index time series, but research on K-algorithm development continues to this day.…”

Section: Hand and Computer Scalingmentioning

confidence: 97%

Long-term biases in geomagnetic K and aa indices

Love¹

2011

Ann. Geophys.

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Abstract. Analysis is made of the geomagnetic-activity aa index and its source K-index data from groups of groundbased observatories in Britain, and Australia, 1868.0-2009.0, solar cycles 11-23. The K data show persistent biases, especially for high (low) K-activity levels at British (Australian) observatories. From examination of multiple subsets of the K data we infer that the biases are not predominantly the result of changes in observatory location, localized induced magnetotelluric currents, changes in magnetometer technology, or the modernization of K-value estimation methods. Instead, the biases appear to be artifacts of the latitudedependent scaling used to assign K values to particular local levels of geomagnetic activity. The biases are not effectively removed by weighting factors used to estimate aa. We show that long-term averages of the aa index, such as annual averages, are dominated by medium-level geomagnetic activity levels having K values of 3 and 4.

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Section: Hand and Computer Scalingmentioning

confidence: 97%

Long-term biases in geomagnetic K and aa indices

Love¹

2011

Ann. Geophys.

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“…Many algorithms for the derivation of K indices from digital data have been proposed in recent years (Van Wijk & Nagtegaall977; Riddick &Stuart 1984;Hopgood 1986;Walker 1987;Wilson 1987;Jankowski et al 1988;Hattingh, Loubser & Nagtegaal 1989;Golovkov, Papitashvili & Papitashvili 1989;Pirjola, Ryno & Sucksdorff 1990). These algorithms have been tested with different data sets, and using different statistical tests.…”

Section: Introductionmentioning

confidence: 99%

Computer production of Kindices: review and comparison of methods

Menvielle

Papitashvili²,

Hakkinen

et al. 1995

Geophysical Journal International

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The K indices are to be hand-scaled from analogue magnetograms following morphological criteria expressed in the so-called Mayaud rules. All observatories used to follow these rules in the routine hand-scaling of K indices from analogue magnetograms. As a result of digitalization and automation of observatories, however, observers in charge who are experienced in K scaling from analogue magnetograms are becoming increasingly rare. Therefore the organizations running observatories were forced to find compensating machine methods for the production of K indices. The basic features of the K indices and the Mayaud rules are first reviewed, and then the methods developed for computer derivation of K indices are discussed.In order to decide which of the proposed algorithms was suitable, a comparison among them was organized by the IAGA Working Group on geomagnetic indices. The comparison was made with a common data set, using the same statistical tests. The results are summarized and discussed. Further comparisons between the K indices produced by computer with the different methods are presented in this paper. Four methods were acknowledged by the Working Group during the Vienna IUGG general Assembly in 1991. The results confirm that these methods provide acceptable results in comparison to the average quality of hand-scaled indices.A comparison between computer-produced K indices and reference K indices handscaled following the Bartels-Mayaud rules is also presented. It appears that only two acknowledged methods provide computer-produced K in good agreement with handscaled K. The best computer method (the FMI method) is found to be good enough to allow the continuation of the long tradition of producing K indices without any serious jump in the statistics.

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“…A similar disk drive on the PDP 11/70 allows for data transfer to the main computer. The A3 X-Y flat-bed plotter is used to create reduced scale magnetograms of suitable quality for the monthly preliminary data books, and standardised scale value magnetograms for K index scaling (see Riddick and Stuart, 1984).…”

Section: Data Processingmentioning

confidence: 99%

The digital recording system operated at the U.K. magnetic observatories

Forbes

Riddick

1984

Geophysical Surveys

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Abstract. A digital recording system has been operated at the U.K. observatories since 1979. The magnetic elements H, D, and Z are monitored continuously by a triaxial fluxgate magnetometer operating in the variometer mode, Ordinate values are recorded at 30-sec intervals. Total field and the temperature of the variometer chamber are measured at the start of each 10-rain data block.Fluxgate magnetometer baseline values are derived from absolute measurements made by proton vector magnetometer and Kew declinometer in the conventional manner.In this paper the data handling procedures are described and the quality of the data over a period of two years is discussed,

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The Generation of K Indices from Digitally Recorded Magnetic Data

Cited by 9 publications

References 1 publication

Long-term biases in geomagnetic <i>K</i> and <i>aa</i> indices

Long-term biases in geomagnetic <i>K</i> and <i>aa</i> indices

Computer production of Kindices: review and comparison of methods

The digital recording system operated at the U.K. magnetic observatories

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The Generation of K Indices from Digitally Recorded Magnetic Data

Cited by 9 publications

References 1 publication

Long-term biases in geomagnetic &lt;i&gt;K&lt;/i&gt; and &lt;i&gt;aa&lt;/i&gt; indices

Long-term biases in geomagnetic &lt;i&gt;K&lt;/i&gt; and &lt;i&gt;aa&lt;/i&gt; indices

Computer production of Kindices: review and comparison of methods

The digital recording system operated at the U.K. magnetic observatories

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Product

Resources

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Long-term biases in geomagnetic <i>K</i> and <i>aa</i> indices

Long-term biases in geomagnetic <i>K</i> and <i>aa</i> indices