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Paper: Local and Global Magnetic Fields of Late-Type Dwarfs OT Ser and YZ CMi
Volume: 494, Physics and Evolution of Magnetic and Related Stars
Page: 120
Authors: Bychkov, V. D.; Bychkova, L. V.; Madej, J.; Panferov, A. A.
Abstract: Differential rotation is the primary energy source for generation of local magnetic fields in the atmospheres of late-type stars (Moss et al. 1995). Moreover, the colder a star, the greater the effect, which was confirmed by observations. For instance, Saar (1988) measured the surface magnetic fields of late-type stars using the integral method Robinson (1980) and drew attention to the fact that the average magnetic field in the spots reaches the values of 1500 G for the G-type dwarfs, 2500 G for the K dwarfs, and 3500 G for the M-dwarf stars. The fraction of the surface of a star covered by spots also increases towards the latest spectral types. These well-known observational facts were explained by theoretical models, such as the α2 mechanism, for instance (Moss et al. 1995). Late-type dwarfs exhibit periodic eruptions resulting from the field line reconnection of newly generated local magnetic fields. This feature is observed in G, K, and M dwarfs, constituting 95%of all the stars in our Galaxy. The most prominent are the field reconnections in the so-called flare stars, which are the M dwarfs. This is understandable, since the peak flux of M dwarfs is placed in the red and infrared regions of the spectrum, whereas a flash has the maximum emission in the violet spectral region. Analysis of long-term photometric observations revealed that, on the average, energy of flares was found constant over a long time period for each flare star. That is to say, this conclusion implies that the power of the local magnetic field generator remains constant at this stage of evolution of stars.
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