Authors: Aschwanden, Markus J.; Crosby, Norma B.; Dimitropoulou, Michaila; Georgoulis, Manolis K.; Hergarten, Stefan; McAteer, James; Milovanov, Alexander V.; Mineshige, Shin; Morales, Laura Fernanda; Nishizuka, Naoto; Pruessner, Gunnar; Sanchez, Raul; Sharma, A. Surja; Strugarek, Antoine; Uritsky, Vadim
Publication Date: 2016.
Shortly after the seminal paper “Self-Organized Criticality: An explanation of 1/fnoise” by Bak et al. (1987), the idea has been applied to solar physics, in “Avalanches and the Distribution of Solar Flares” by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magneto-hydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOC-like, and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme.
Author affiliation: Aschwanden, Markus J.. Lockheed Martin Corporation; Estados Unidos
Author affiliation: Crosby, Norma B.. Belgian Institute For Space Aeronomy; Bélgica
Author affiliation: Dimitropoulou, Michaila. University Of Athens; Grecia
Author affiliation: Georgoulis, Manolis K.. Academy Of Athens; Grecia
Author affiliation: Hergarten, Stefan. Universitat Freiburg Im Breisgau; Alemania
Author affiliation: McAteer, James. University Of New Mexico; Estados Unidos
Author affiliation: Milovanov, Alexander V.. Max Planck Institute For The Physics Of Complex Systems; Alemania. Russian Academy Of Sciences. Space Research Institute; Rusia. Enea Centro Ricerche Frascati; Italia
Author affiliation: Mineshige, Shin. Kyoto University; Japón
Author affiliation: Morales, Laura Fernanda. Canadian Space Agency; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Author affiliation: Nishizuka, Naoto. Japan National Institute Of Information And Communications Technology; Japón
Author affiliation: Pruessner, Gunnar. Imperial College London; Reino Unido
Author affiliation: Sanchez, Raul. Universidad Carlos Iii de Madrid. Instituto de Salud; España
Author affiliation: Sharma, A. Surja. University Of Maryland; Estados Unidos
Author affiliation: Strugarek, Antoine. University Of Montreal; Canadá
Author affiliation: Uritsky, Vadim. Nasa Goddard Space Flight Center; Estados Unidos
Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas
Publication Date: 2014.
AD Leo (GJ 388) is an active dM3 flare star that has been extensively observed both in the quiescent and flaring states. Since this active star is near the fully convective boundary, studying its long-term chromospheric activity in detail could be an appreciable contribution to dynamo theory. Here, using the Lomb-Scargle periodogram, we analyze the Ca II K line-core fluxes derived from CASLEO spectra obtained between 2001 and 2013 and the V magnitude from the ASAS database between 2004 and 2010. From both of these totally independent time series, we obtain a possible activity cycle with a period of approximately seven years and a less significant shorter cycle of approximately two years. A tentative interpretation is that a dynamo operating near the surface could be generating the longer cycle, while a second dynamo operating in the deep convection zone could be responsible for the shorter one. Based on the long duration of our observing program at CASLEO and the fact that we observe different spectral features simultaneously, we also analyze the relation between simultaneous measurements of the Na I index (), Hα, and Ca II K fluxes at different activity levels of AD Leo, including flares. © 2014. The American Astronomical Society. All rights reserved..
Author affiliation: Buccino, A.P. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Author affiliation: Petrucci, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Author affiliation: Mauas, P.J.D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Repository: Biblioteca Digital (UBA-FCEN). Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales