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dc.contributor.authorGarcia, Odd Erik
dc.contributor.authorTheodorsen, Audun
dc.date.accessioned2017-03-29T13:44:29Z
dc.date.available2017-03-29T13:44:29Z
dc.date.issued2017-03
dc.description.abstractThe auto-correlation function and the frequency power spectral density due to a super-position of uncorrelated exponential pulses are considered. These are shown to be independent of the degree of pulse overlap and thereby the intermittency of the stochastic process. For constant pulse duration and a one-sided exponential pulse shape, the power spectral density has a Lorentzian shape which is flat for low frequencies and a power law at high frequencies. The algebraic tail is demonstrated to result from the discontinuity in the pulse function. For a strongly asymmetric two-sided expo- nential pulse shape, the frequency spectrum is a broken power law with two scaling regions. In the case of a symmetric pulse shape, the power spectral density is the square of a Lorentzian function. The steep algebraic tail at high frequencies in these cases is demonstrated to follow from the discontinuity in the derivative of the pulse function. A random distribution of pulse durations is shown to result in apparently longer correlation times but has no influence on the asymptotic power law tail of the frequency spectrum. The effect of additional random noise is also discussed, leading to a flat spectrum for high frequencies. The probability density function for the fluctuations is shown to be independent of the distribution of pulse durations. The predictions of this model describe the variety of auto-correlation functions and power spectral densities reported from experimental measurements in the scrape-off layer of magnetically confined plasmas.en_US
dc.descriptionLink to publishers version: 10.1063/1.4978955en_US
dc.identifier.citationGarcia OE, Theodorsen A. Auto-correlation function and frequency spectrum due to a super-position of uncorrelated exponential pulses. Physics of Plasmas 2017;24;032309en_US
dc.identifier.cristinIDFRIDAID 1461850
dc.identifier.doi10.1063/1.4978955
dc.identifier.issn1070-664X
dc.identifier.issn1089-7674
dc.identifier.urihttps://hdl.handle.net/10037/10894
dc.language.isoengen_US
dc.relation.journalPhysics of Plasmas
dc.relation.projectIDNorges forskningsråd: 240510/F20en_US
dc.rights.accessRightsopenAccessen_US
dc.subjectVDP::Mathematics and natural science: 400en_US
dc.titleAuto-correlation function and frequency spectrum due to a super-position of uncorrelated exponential pulsesen_US
dc.typePeer revieweden_US


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