Search Publications
Magnetic fluxes of solar active regions of different magneto-morphological classes - I. Cyclic variations
Abramenko, Valentina I.; Suleymanova, Regina A.; Zhukova, Anastasija V.
Data for 3046 solar active regions (ARs) observed since 1996 May 12 to 2021 December 27 were utilized to explore how the magnetic fluxes from ARs of different complexity follow the solar cycle. Magnetograms from the Michelson Doppler Imager instrument on the Solar and Heliospheric Observatory and from the Helioseismic and Magnetic Imager instrumen…
Probing the variations in the timing of the Sun's polar magnetic field reversals through observations and surface flux transport simulations
Karak, Bidya Binay; Kumar, Pawan; Golubeva, Elena M. +2 more
The polar field reversal is a crucial process in the cyclic evolution of the large-scale magnetic field of the Sun. Various important characteristics of a solar cycle, such as its duration and strength, and also the cycle predictability, are determined by the polar field reversal time. While the regular measurements of solar magnetic field have be…
A benchmark study of atomic models for the transition region against quiet Sun observations
Mason, H. E.; Del Zanna, G.; Dufresne, R. P.
The use of the coronal approximation to model line emission from the solar transition region has led to discrepancies with observations over many years, particularly for Li- and Na-like ions. Studies have shown that a number of atomic processes are required to improve the modelling for this region, including the effects of high densities, solar ra…
Prevalence of non-stationarity in quasi-periodic pulsations (QPPs) associated with M- and X-class solar flares
Hayes, L. A.; Broomhall, A. -M.; Mehta, T.
Quasi-periodic pulsations (QPPs) are frequently observed in solar and stellar flare emission, with recent studies suggesting that an increasing instantaneous period is a common characteristic of QPPs. Determining the prevalence of non-stationarity in QPPs contributes to a better understanding of which mechanism(s) is (are) responsible in QPP gener…
Hemispheric distribution of coronal mass ejections from 1996 to 2020
Li, C.; Deng, L. H.; Zhang, X. J. +3 more
Solar magnetic structures are known to be asymmetrically distributed between the two hemispheres. To date, the hemispheric variations of the coronal mass ejections (CMEs) at different latitudes, in different cycles, and for different types (regular and specific events) are still unclear. From the list of white-light CMEs in the Coordinated Data An…
Time-dependent boundary conditions for data-driven coronal global and spherical wedge-shaped models
Feng, Xueshang; Jiang, Chaowei; Xiang, Changqing +1 more
The development of an efficient and accurate method for boundary condition treatments is of fundamental importance to data-driven magnetohydrodynamic (MHD) modelling of the global solar corona and solar active region. Particularly, in a 3D spherical wedge-shaped volume, suitable to the numerical study of solar active region, the transverse terms c…
Trajectories of coronal mass ejection from solar-type stars
Kay, Christina; Valio, Adriana; Araújo, Alexandre +3 more
The Sun and other solar-type stars have magnetic fields that permeate their interior and surface, extend through the interplanetary medium, and are the main drivers of stellar activity. Stellar magnetic activity affects the physical processes and conditions of the interplanetary medium and orbiting planets. Coronal mass ejections (CMEs) are the mo…
Statistical comparison of time profiles of Forbush decreases associated with coronal mass ejections and streams from coronal holes in solar cycles 23-24
Melkumyan, A. A.; Belov, A. V.; Abunina, M. A. +4 more
In this paper, Forbush decrease (FD) profiles are compared for events associated with (i) coronal mass ejections from active regions accompanied by solar flares (AR CMEs), (ii) filament eruptions away from active regions (non-AR CMEs), and (iii) high-speed streams (HSSs) from coronal holes (CHs). FD profiles are described by time parameters that a…
Photometric variations from stellar activity as an age indicator for solar-twins
Yana Galarza, Jhon; Lorenzo-Oliveira, Diego; Valio, Adriana +2 more
Stellar ages are elusive to measure, albeit being very important for understanding stellar evolution. We investigate the impact of photospheric activity on 2-min cadence light curves from the TESS/NASA mission of a selected sample of 30 solar-twins with well-determined ages. The photometric variability, $\mathcal {A}_{ {{TESS}}}$, of the light cur…
Centre-to-limb variations in coronal hole and quiet sun regions obtained with IRIS spectroscopic observations
Young, Peter R.; Kayshap, Pradeep
The centre-to-limb variations (CLV) of Gaussian fit parameters of the transition region Si IV 1402.77 Å spectral line in quiet Sun (QS) and coronal hole (CH) regions are presented. The results are derived from a full-disc mosaic scan obtained by the Interface Region Imaging Spectrograph on 2017 September 24. The CLV for a CH transition region line…