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Morgan H.,Sefydliad Mathemateg a Ffiseg | Druckmuller M.,Brno University of Technology
Solar Physics | Year: 2014

Extreme ultra-violet images of the corona contain information over a wide range of spatial scales, and different structures such as active regions, quiet Sun, and filament channels contain information at very different brightness regimes. Processing of these images is important to reveal information, often hidden within the data, without introducing artefacts or bias. It is also important that any process be computationally efficient, particularly given the fine spatial and temporal resolution of Atmospheric Imaging Assembly on the Solar Dynamics Observatory (AIA/SDO), and consideration of future higher resolution observations. A very efficient process is described here, which is based on localised normalising of the data at many different spatial scales. The method reveals information at the finest scales whilst maintaining enough of the larger-scale information to provide context. It also intrinsically flattens noisy regions and can reveal structure in off-limb regions out to the edge of the field of view. We also applied the method successfully to a white-light coronagraph observation. © 2014 The Author(s).

Morgan H.,Sefydliad Mathemateg a Ffiseg | Morgan H.,University of Hawaii at Manoa | Jeska L.,Sefydliad Mathemateg a Ffiseg | Leonard D.,Sefydliad Mathemateg a Ffiseg
Astrophysical Journal, Supplement Series | Year: 2013

Advanced image processing of Large Angle and Spectrometric Coronagraph Experiment (LASCO) C2 observations reveals the expansion of the active region closed field into the extended corona. The nested closed-loop systems are large, with an apparent latitudinal extent of 50°, and expanding to heights of at least 12 Ṙ. The expansion speeds are ∼10 km s-1 in the AIA/SDO field of view, below ∼20 km s-1 at 2.3 Ṙ, and accelerate linearly to ∼60 km s-1 at 5 Ṙ. They appear with a frequency of one every ∼3 hr over a time period of around three days. They are not coronal mass ejections (CMEs) since their gradual expansion is continuous and steady. They are also faint, with an upper limit of 3% of the brightness of background streamers. Extreme ultraviolet images reveal continuous birth and expansion of hot, bright loops from a new active region at the base of the system. The LASCO images show that the loops span a radial fan-like system of streamers, suggesting that they are not propagating within the main coronal streamer structure. The expanding loops brighten at low heights a few hours prior to a CME eruption, and the expansion process is temporarily halted as the closed field system is swept away. Closed magnetic structures from some active regions are not isolated from the extended corona and solar wind, but can expand to large heights in the form of quiescent expanding loops. © 2013. The American Astronomical Society. All rights reserved.

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