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Restoration of the K and F Components of the Solar Corona from LASCO-C2 Images over 24 Years [1996 - 2019]
Lamy, Philippe; Gilardy, Hugo; Llebaria, Antoine +2 more
We present a photometrically accurate restoration of the K- and F-coronae from white-light images obtained over 24 years [1996 - 2019] by the Large-Angle Spectrometric COronagraph (LASCO-C2) onboard the Solar and Heliospheric Observatory (SOHO). The procedure starts with the data set of unpolarized images of 512 × 512 pixels produced by the polari…
A Transient Coronal Sigmoid in Active Region NOAA 11909: Build-up Phase, M-class Eruptive Flare, and Associated Fast Coronal Mass Ejection
Monstein, Christian; Joshi, Bhuwan; Manoharan, P. K. +2 more
In this article, we investigate the formation and disruption of a coronal sigmoid from the active region (AR) NOAA 11909 on 07 December 2013, by analyzing multi-wavelength and multi-instrument observations. Our analysis suggests that the formation of the sigmoid initiated ≈ 1 hour before its eruption through a coupling between two twisted coronal …
Detecting and Characterising Small-Scale Brightenings in Solar Imaging Data
Morgan, Huw; Humphries, Llŷr Dafydd; Kuridze, David
Observations of small-scale brightenings in the low solar atmosphere can provide valuable constraints on possible heating and heat transport mechanisms. We present a method for the detection and analysis of brightenings, and demonstrate its application to time-series imagery of the Interface Region Imaging Spectrograph (IRIS) in the extreme ultrav…
Evaluating Pointing Strategies for Future Solar Flare Missions
Ireland, Jack; Christe, Steven D.; Inglis, Andrew R. +1 more
Solar flares are events of intense scientific interest. Although certain solar conditions are known to be associated with flare activity, the exact location and timing of an individual flare on the Sun cannot as yet be predicted with certainty. Missions whose science objectives depend on observing solar flares must often make difficult decisions o…
Segmentation of Coronal Features to Understand the Solar EUV and UV Irradiance Variability III. Inclusion and Analysis of Bright Points
Giono, Gabriel; van der Zwaard, Rens; Kariyappa, Rangaiah +3 more
The study of solar irradiance variability is of great importance in heliophysics, Earth's climate, and space weather applications. These studies require careful identifying, tracking and monitoring of features in the solar photosphere, chromosphere, and corona. Do coronal bright points contribute to the solar irradiance or its variability as input…
Divergence and Vorticity of Subsurface Flows During Solar Cycles 23 and 24
Howe, R.; Komm, R.; Hill, F.
We study the solar-cycle variation of the divergence and vorticity of subsurface horizontal flows from the surface to a depth of 16 Mm. The flows were derived with ring-diagram analysis applied to Michelson Doppler Imager (MDI) Dynamics Program, Global Oscillation Network Group (GONG), and Helioseismic and Magnetic Imager (HMI) Dopplergrams. We st…
A Comparison of Sparse and Non-sparse Techniques for Electric-Field Inversion from Normal-Component Magnetograms
Yeates, Anthony R.; Mackay, Duncan H.
An important element of 3D data-driven simulations of solar magnetic fields is the determination of the horizontal electric field at the solar photosphere. This electric field is used to drive the 3D simulations and inject energy and helicity into the solar corona. One outstanding problem is the localisation of the horizontal electric field such t…
Improved Approach in the Coupling Function Between Primary and Ground Level Cosmic Ray Particles Based on Neutron Monitor Data
Georgoulis, M. K.; Xaplanteris, L.; Livada, M. +3 more
In this work an improved approach of existing approximations on the coupling function between primary and ground-level cosmic-ray particles is presented. The proposed coupling function is analytically derived based on a formalism used in Quantum Field Theory calculations. It is upgraded compared to previous versions with the inclusion of a wider e…
A Uniform Series of Low-Latitude Coronal Holes in 1973-2018
Asikainen, T.; Mursula, K.; Hamada, A.
Coronal holes (CHs) are regions in the solar corona characterized by plasma density lower than in the surrounding quiet Sun. Therefore they appear dark in images of the solar atmosphere made, e.g., in extreme ultraviolet (EUV). Identifying CHs on solar images is difficult since CH boundaries are not sharp, but typically obscured by magnetic struct…
A Study of Variations in Correlation Between Rotation Residual and Meridional Velocity of Sunspot Groups
Javaraiah, J.
We analyzed the combined 142 years sunspot-group data from Greenwich Photoheliograpic Results (GPR) and Debrecen Photoheliographic Data (DPD) and determined the yearly mean residual rotation rate and the meridional velocity of sunspot groups in different 5∘ latitude intervals. We find that there exists a considerable latitude-time depen…