naa a22 4500 510732453 CHVBK 20180411082958.0 cr unu---uuuuu 180411e20130801xx s 000 0 eng 10.1134/S1063772913080027 doi (NATIONALLICENCE)springer-10.1134/S1063772913080027 Active regions near the recent solar-cycle minimum: Relation between plasma heating and electrical currents [Elektronische Daten] [I. Grigor'eva, M. Livshits, G. Rudenko, I. Mysh'yakov] Data on small active regions on the Sun collected over three years (2007-2009) are analyzed. Under very quiescent conditions (a low X-ray background level), the shapes of the coronal loops of some active regions correspond fairly well to the shapes of magnetic-field lines calculated in a potential approximation. This is true of several active regions (e.g., the group AR 10999 in June 2008) in which no flares more powerful than B3 were observed. The radio emission of this active region detected by the RATAN-600 telescope was very weak and virtually no polarization was detected. Subflares were observed in most groups. It is demonstrated using AR 10933 (January 2007) as an example that a growth in the soft X-ray emission by up to factors of ten simultaneous with an increase in the radio flux is characteristic for such active regions. A source with the opposite polarization developed to the Northwest of the main spot in AR 10933. A series of SOHO/MDI (and also Hinode) magnetograms shows the emergence of new magnetic flux before the development of this polarized source, which continued for several hours on January 8, 2007. The current density at surfaces located at various heights is estimated based on observations of the total vector magnetic field (Hinode data) and a non-linear, force-free magnetic-field extrapolation. The height-integrated current becomes appreciably stronger at two nodes above a field neutral line, near the location of the main emerging flux. This supports the idea that the emergence of new magnetic flux is a key factor in the evolution of active regions at all stages of their existence. The development of this picture could help in elucidating the inter-relationship between current enhancements, plasma heating, and particle acceleration, in both weak active regions and strong activity complexes. Pleiades Publishing, Ltd., 2013 Grigor'eva I. Central Astronomical Observatory, Russian Academy of Sciences, Pulkovo, St. Petersburg, Russia aut Livshits M. N.V. Pushkov Institute of Terrestrial Magnetism, the Ionosphere, and Radio-Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow, Russia aut Rudenko G. Institute of Solar-Terrestrial Physics, Siberian Division of the Russian Academy of Sciences, Irkutsk, Russia aut Mysh'yakov I. Institute of Solar-Terrestrial Physics, Siberian Division of the Russian Academy of Sciences, Irkutsk, Russia aut Astronomy Reports Springer US; http://www.springer-ny.com 57/8(2013-08-01), 611-621 1063-7729 57:8<611 2013 57 11444 https://doi.org/10.1134/S1063772913080027 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1134/S1063772913080027 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Grigor'eva I. Central Astronomical Observatory, Russian Academy of Sciences, Pulkovo, St. Petersburg, Russia aut NATIONALLICENCE 700 1- Livshits M. N.V. Pushkov Institute of Terrestrial Magnetism, the Ionosphere, and Radio-Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow, Russia aut NATIONALLICENCE 700 1- Rudenko G. Institute of Solar-Terrestrial Physics, Siberian Division of the Russian Academy of Sciences, Irkutsk, Russia aut NATIONALLICENCE 700 1- Mysh'yakov I. Institute of Solar-Terrestrial Physics, Siberian Division of the Russian Academy of Sciences, Irkutsk, Russia aut NATIONALLICENCE 773 0- Astronomy Reports Springer US; http://www.springer-ny.com 57/8(2013-08-01), 611-621 1063-7729 57:8<611 2013 57 11444 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer