Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals
Cosmic 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 ionisation of the atmosphere...
Published in: | Nonlinear Processes in Geophysics |
---|---|
Main Author: | |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2016
|
Subjects: | |
Online Access: | https://doi.org/10.5194/npg-23-215-2016 https://doaj.org/article/e1b0abee1b9745229ebfa1a3e51f4880 |
id |
ftdoajarticles:oai:doaj.org/article:e1b0abee1b9745229ebfa1a3e51f4880 |
---|---|
record_format |
openpolar |
spelling |
ftdoajarticles:oai:doaj.org/article:e1b0abee1b9745229ebfa1a3e51f4880 2023-05-15T17:48:28+02:00 Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals C. M. Hall 2016-08-01T00:00:00Z https://doi.org/10.5194/npg-23-215-2016 https://doaj.org/article/e1b0abee1b9745229ebfa1a3e51f4880 EN eng Copernicus Publications http://www.nonlin-processes-geophys.net/23/215/2016/npg-23-215-2016.pdf https://doaj.org/toc/1023-5809 https://doaj.org/toc/1607-7946 1023-5809 1607-7946 doi:10.5194/npg-23-215-2016 https://doaj.org/article/e1b0abee1b9745229ebfa1a3e51f4880 Nonlinear Processes in Geophysics, Vol 23, Iss 4, Pp 215-222 (2016) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2016 ftdoajarticles https://doi.org/10.5194/npg-23-215-2016 2022-12-31T09:21:35Z Cosmic 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 ionisation 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 decibels (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 characterised by generalised Hurst exponents, α . Considering all periods greater than 1 h, α ≈ 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 characterised by a generalised Hurst exponent ≈ 1.24 and thus non-persistent fractional Brownian motion, whereas generation of cosmic noise is characterised by a generalised Hurst exponent ≈ 1. The technique unfortunately did not result in clear physical understanding of the ionospheric phenomena, and thus, in this respect, the application was not successful; the analysis could, however, be used as a tool for instrument validation. Article in Journal/Newspaper Ny Ålesund Ny-Ålesund Directory of Open Access Journals: DOAJ Articles Ny-Ålesund Nonlinear Processes in Geophysics 23 4 215 222 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 C. M. Hall Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
Cosmic 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 ionisation 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 decibels (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 characterised by generalised Hurst exponents, α . Considering all periods greater than 1 h, α ≈ 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 characterised by a generalised Hurst exponent ≈ 1.24 and thus non-persistent fractional Brownian motion, whereas generation of cosmic noise is characterised by a generalised Hurst exponent ≈ 1. The technique unfortunately did not result in clear physical understanding of the ionospheric phenomena, and thus, in this respect, the application was not successful; the analysis could, however, be used as a tool for instrument validation. |
format |
Article in Journal/Newspaper |
author |
C. M. Hall |
author_facet |
C. M. Hall |
author_sort |
C. M. Hall |
title |
Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals |
title_short |
Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals |
title_full |
Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals |
title_fullStr |
Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals |
title_full_unstemmed |
Spectral characteristics of high-latitude raw 40 MHz cosmic noise signals |
title_sort |
spectral characteristics of high-latitude raw 40 mhz cosmic noise signals |
publisher |
Copernicus Publications |
publishDate |
2016 |
url |
https://doi.org/10.5194/npg-23-215-2016 https://doaj.org/article/e1b0abee1b9745229ebfa1a3e51f4880 |
geographic |
Ny-Ålesund |
geographic_facet |
Ny-Ålesund |
genre |
Ny Ålesund Ny-Ålesund |
genre_facet |
Ny Ålesund Ny-Ålesund |
op_source |
Nonlinear Processes in Geophysics, Vol 23, Iss 4, Pp 215-222 (2016) |
op_relation |
http://www.nonlin-processes-geophys.net/23/215/2016/npg-23-215-2016.pdf https://doaj.org/toc/1023-5809 https://doaj.org/toc/1607-7946 1023-5809 1607-7946 doi:10.5194/npg-23-215-2016 https://doaj.org/article/e1b0abee1b9745229ebfa1a3e51f4880 |
op_doi |
https://doi.org/10.5194/npg-23-215-2016 |
container_title |
Nonlinear Processes in Geophysics |
container_volume |
23 |
container_issue |
4 |
container_start_page |
215 |
op_container_end_page |
222 |
_version_ |
1766154549164244992 |