Derivation ofK-indices using magnetograms constructed from digital data

Niblett, E. R.; Loomer, E I; Coles, Richard; Beek, G Jansen van

doi:10.1007/bf01465558

Cited by 7 publications

(8 citation statements)

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“…98% of these low values occurred at the K = 0, 1, 2 levels. These results concur with those already obtained by Niblett et al (1984), keeping in mind the large difference in geomagnetic activity level between the two considered datasets. Basically, the downward bias leads to an underestimation of the magnetic activity during magnetic quietness while it has very limited effect during a disturbed period.…”

Section: Resultssupporting

confidence: 92%

“…This argument concurs with that of Niblett et al (1984) who explained that "the lower K levels (...) contain much of the low energy pulsational activity with periods of 5 minutes or less". Niblett et al (1984) investigated for the OTT observatory the diurnal and seasonal distribution of the intervals for which K A and K R have different values. Their results illustrate the intervals for which K 60s   K 1s shows a local time (LT) dependency.…”

Section: Effect Of the Sampling Interval On The K Indexsupporting

confidence: 88%

“…Data Science Journal, Volume 10, 30 August 2011 Figure 7 presents the seasonal distribution of discrepant K for both observatories. To take into account the latitudinal difference between the two stations, the histograms from Niblett et al (1984) was shifted by 6 months.…”

Section: Effect Of the Sampling Interval On The K Indexmentioning

confidence: 99%

“…The bias on K index values related to the sampling interval in digital recording of magnetic variations became of concern when magnetograms plotted from digital magnetometer data were put into use replacing analog magnetometers for K indices hand-scaling. Niblett et al (1984) used data from the Ottawa geomagnetic observatory to investigate the bias introduced by deriving the traditional K index from magnetograms plotted from recorded digital data. They hand-scaled K indices on analog photographic magnetograms (K A ) and on analog magnetograms reconstructed using digital magnetic data in the form of 1-minute averaged values or spot values at selected sampling intervals of 1-second or greater (K R ).…”

Section: Introductionmentioning

confidence: 99%

“…Diurnal distribution of intervals for discrepant K as a function of LT. The dashed curves correspond to K A and K R for OTT in 1982 (fromNiblett et al, 1984; LT = UT -5h); the solid curve corresponds to K 1s and K 60s for PAF in 2008.5-2010.5 (this study; LT = UT + 5h).…”

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confidence: 99%

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On the Influence of the Data Sampling Interval on Computer-Derived K-Indices

2011

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International audienceThe K index was devised by Bartels et al. (1939) to provide an objective monitoring of irregular geomagnetic activity. The K index was then routinely used to monitor the magnetic activity at permanent magnetic observatories as well as at temporary stations. The increasing number of digital and sometimes unmanned observatories and the creation of INTERMAGNET put the question of computer production of K at the centre of the debate. Four algorithms were selected during the Vienna meeting (1991) and endorsed by IAGA for the computer production of K indices. We used one of them (FMI algorithm) to investigate the impact of the geomagnetic data sampling interval on computer produced K values through the comparison of the computer derived K values for the period 2009, January 1st to 2010, May 31st at the Port-aux-Francais magnetic observatory using magnetic data series with different sampling rates (the smaller: 1 second; the larger: 1 minute). The impact is investigated on both 3-hour range values and K indices data series, as a function of the activity level for low and moderate geomagnetic activity

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Section: Resultssupporting

confidence: 92%

Section: Effect Of the Sampling Interval On The K Indexsupporting

confidence: 88%

Section: Effect Of the Sampling Interval On The K Indexmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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