Ann. Geophys., 34, 437–449, 2016 www.ann-geophys.net/34/437/2016/ doi:10.5194/angeo-34-437-2016 © Author(s) 2016. CC Attribution 3.0 License. Effect of data gaps: comparison of different spectral analysis methods Costel Munteanu1,2,3, Catalin Negrea1,4,5, Marius Echim1,6, and Kalevi Mursula2 1Institute of Space Science, Magurele, Romania 2Astronomy and Space Physics Research Unit, University of Oulu, Oulu, Finland 3Department of Physics, University of Bucharest, Magurele, Romania 4Cooperative Institute for Research in Environmental Sciences, Univ. of Colorado, Boulder, Colorado, USA 5Space Weather Prediction Center, NOAA, Boulder, Colorado, USA 6Belgian Institute of Space Aeronomy, Brussels, Belgium Correspondence to: Costel Munteanu (
[email protected]) Received: 31 August 2015 – Revised: 14 March 2016 – Accepted: 28 March 2016 – Published: 19 April 2016 Abstract. In this paper we investigate quantitatively the ef- 1 Introduction fect of data gaps for four methods of estimating the ampli- tude spectrum of a time series: fast Fourier transform (FFT), Spectral analysis is a widely used tool in data analysis and discrete Fourier transform (DFT), Z transform (ZTR) and processing in most fields of science. The technique became the Lomb–Scargle algorithm (LST). We devise two tests: the very popular with the introduction of the fast Fourier trans- single-large-gap test, which can probe the effect of a sin- form algorithm which allowed for an extremely rapid com- gle data gap of varying size and the multiple-small-gaps test, putation of the Fourier Transform. In the absence of modern used to study the effect of numerous small gaps of variable supercomputers, this was not just useful, but also the only size distributed within the time series.