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dc.contributor.authorHall, Chris
dc.date.accessioned2015-08-25T12:59:31Z
dc.date.available2015-08-25T12:59:31Z
dc.date.issued2015-07-07
dc.description.abstractCosmic noise at 40 MHz is measured at Ny-Ålesund (79◦ N, 12◦ E) using a relative ionospheric opacity meter (“riometer”). A riometer is normally used to determine the degree to which cosmic noise is absorbed by the intervening ionosphere, giving an indication of ionization of the atmosphere at altitudes lower than generally monitored by other instruments. The usual course is to determine a “quiet-day” variation, this representing the galactic noise signal itself in the absence of absorption; the current signal is then subtracted from this to arrive at absorption expressed in dB. By a variety of means and assumptions, it is thereafter possible to estimate electron density profiles in the very lowest reaches of the ionosphere. Here however, the entire signal, i.e. including the cosmic noise itself will be examined and spectral characteristics identified. It will be seen that distinct spectral subranges are evident which can, in turn be identified with non-Gaussian processes characterized by generalized Hurst exponents, α. Considering all periods greater than 1 h, α ≈ 1.24 – an indication of fractional Brownian motion, whereas for periods greater than 1 day α ≈ 0.9 – approximately pink noise and just in the domain of fractional Gaussian noise. The results are compared with other physical processes suggesting that absorption of cosmic noise is characterized by a generalized Hurst exponent ≈ 1.24 and thus non-persistent fractional Brownian motion, whereas generation of cosmic noise is characterized by a generalized Hurst exponent ≈ 1.en_US
dc.identifier.citationNonlinear Processes in Geophysics Discussions 2(2015) s. 969-987en_US
dc.identifier.cristinIDFRIDAID 1252874
dc.identifier.doidoi:10.5194/npgd-2-969-2015
dc.identifier.issn2198-5634
dc.identifier.urihttps://hdl.handle.net/10037/7973
dc.identifier.urnURN:NBN:no-uit_munin_7543
dc.language.isoengen_US
dc.publisherCopernicus Publicationsen_US
dc.rights.accessRightsopenAccess
dc.subjectVDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Astrofysikk, astronomi: 438en_US
dc.subjectVDP::Mathematics and natural science: 400::Physics: 430::Astrophysics, astronomy: 438en_US
dc.titleSpectral characteristics of high latitude raw 40MHz cosmic noise signalsen_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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