Spatial and Temporal Noise in Solar EUV Observations |
| |
Authors: | V Delouille P Chainais J-F Hochedez |
| |
Institution: | (1) SIDC – Royal Observatory of Belgium, Brussels, Belgium;(2) Université Blaise Pascal Clermont II, Clermont-Ferrand, France |
| |
Abstract: | Solar telescopes will never be able to resolve the smallest events at their intrinsic physical scales. Pixel signals recorded
by SOHO/(CDS, EIT, SUMER), STEREO/SECCHI/ EUVI, TRACE, SDO/AIA, and even by the future Solar Orbiter EUI/HRI contain an inherent “spatial noise” since they represent an average of the solar signal present at subpixel scales.
In this paper, we aim at investigating this spatial noise, and hopefully at extracting information from subpixel scales. Two
paths are explored. We first combine a regularity analysis of a sequence of EIT images with an estimation of the relationship
between mean and standard deviation, and we formulate a scenario for the evolution of the local signal-to-noise ratio (SNR)
as the pixel size becomes smaller. Second, we use an elementary forward modeling to examine the relationship between nanoflare
characteristics (such as area, duration, and intensity) and the global mean and standard deviation. We use theoretical distributions
of nanoflare parameters as input to the forward model. A fine-grid image is generated as a random superposition of those pseudo-nanoflares.
Coarser resolution images (simulating images acquired by a telescope) are obtained by rebinning and are used to compute the
mean and standard deviation to be analyzed. Our results show that the local SNR decays more slowly in regions exhibiting irregularities
than in smooth regions. |
| |
Keywords: | Solar corona Signal-to-noise ratio Subpixel scale Aliasing |
本文献已被 SpringerLink 等数据库收录! |
|