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Above the noise : the search for periodicities in the inner heliosphere

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Threlfall_SolarPhys_s11207_017_1191_3_CC.pdf (8.340Mb)
Date
11/2017
Author
Threlfall, James William
De Moortel, Ineke
Conlon, Thomas Michael
Funder
Science & Technology Facilities Council
Science & Technology Facilities Council
European Research Council
European Commission
Grant ID
ST/K000950/1
ST/N000609/1
647214
269299
Keywords
Corona, active
Magnetic fields, corona
Oscillations, solar
Solar wind, theory
QB Astronomy
QC Physics
NDAS
Metadata
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Abstract
Remote sensing of coronal and heliospheric periodicities can provide vital insight into the local conditions and dynamics of the solar atmosphere. We seek to trace long (one hour or longer) periodic oscillatory signatures (previously identified above the limb in the corona by, e.g., Telloni et al., 2013, Astrophys. J., 767, 138) from their origin at the solar surface out into the heliosphere. To do this, we combine on-disk measurements taken by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and concurrent extreme ultra-violet (EUV) and coronagraph data from one of the Solar Terrestrial Relations Observatory (STEREO) spacecraft to study the evolution of two active regions in the vicinity of an equatorial coronal hole over several days in early 2011. Fourier and wavelet analysis of signals are performed. Applying white-noise-based confidence levels to the power spectra associated with detrended intensity time series yields detections of oscillatory signatures with periods from 6 − 13 hours in both AIA and STEREO data. As was found by Telloni et al. (2013), these signatures are aligned with local magnetic structures. However, typical spectral power densities all vary substantially as a function of period, indicating spectra dominated by red (rather than white) noise. Contrary to the white-noise-based results, applying global confidence levels based on a generic background noise model (allowing a combination of white noise, red noise, and transients following Auch`ere et al., 2016, Astrophys. J., 825, 110) without detrending the time series, uncovers only sporadic, spatially uncorrelated evidence of periodic signatures in either instrument. Automating this method to individual pixels in the STEREO/COR coronagraph field of view is non-trivial.
Citation
Threlfall , J W , De Moortel , I & Conlon , T M 2017 , ' Above the noise : the search for periodicities in the inner heliosphere ' , Solar Physics , vol. 292 , 165 . https://doi.org/10.1007/s11207-017-1191-3
Publication
Solar Physics
Status
Peer reviewed
DOI
https://doi.org/10.1007/s11207-017-1191-3
ISSN
0038-0938
Type
Journal article
Rights
© The Author(s) 2017 This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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  • University of St Andrews Research
URI
http://hdl.handle.net/10023/12054

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