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Lozitsky, V. G.; Baranovsky, E. A.; Lozitska, N. I.; Leiko, U. M.

doi:10.1023/a:1005298827306

Cited by 30 publications

(15 citation statements)

References 9 publications

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“…In this case it would be the first time that simultaneous observations of magnetic field and activity indicators have been performed during flares in the stellar context. In the solar case, a simultaneous increase of magnetic field and Hα has been observed (Lozitsky et al 2000).…”

Section: Discrepant Points In B L and Activity Indicatorsmentioning

confidence: 93%

A dominant magnetic dipole for the evolved Ap star candidate EK Eridani

Aurière¹,

Konstantinova-Antova²,

Petit³

et al. 2011

A&A

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Context. EK Eri is one of the most slowly rotating active giants known, and has been proposed to be the descendant of a strongly magnetic Ap star. Aims. We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. Methods. We used the NARVAL spectropolarimeter at the Bernard Lyot telescope at the Pic du Midi Observatory, along with the leastsquares deconvolution method, to extract high signal-to-noise ratio Stokes V profiles from a timeseries of 28 polarisation spectra. We have derived the surface-averaged longitudinal magnetic field B . We fit the Stokes V profiles with a model of the large-scale magnetic field and obtained Zeeman Doppler images of the surface magnetic strength and geometry. We studied the classical activity indicators, the Ca ii H and K lines, the Ca ii infrared triplet, and Hα line, as well as the stellar radial velocity. Results. B variations of up to about 80 G are observed without any reversal of its sign, and which are in phase with photometric ephemeris. The activity indicators are shown to vary smoothly on a timescale compatible with the rotational period inferred from photometry (308.8 d), however large deviations can occur from one rotation to another. The surface magnetic field variations of EK Eri appear to be dominated by a strong magnetic spot (of negative polarity) which is phased with the dark (cool) photometric spot. Our modeling shows that the large-scale magnetic field of EK Eri is strongly poloidal. For a rotational axis inclination of i = 60• , we obtain a model that is almost purely dipolar. Conclusions. In the dipolar model, the strong magnetic/photometric spot corresponds to the negative pole of the dipole, which could be the remnant of that of an Ap star progenitor of EK Eri. Our observations and modeling conceptually support this hypothesis, suggesting an explanation of the outstanding magnetic properties of EK Eri as the result of interaction between deep convection and the remnant of an Ap star magnetic dipole. Nevertheless, the longitudinal magnetic field curve clearly shows changes from one rotation to the next, indicating that the surface magnetic topology is not static as in an Ap star.

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Section: Discrepant Points In B L and Activity Indicatorsmentioning

confidence: 93%

A dominant magnetic dipole for the evolved Ap star candidate EK Eridani

Aurière¹,

Konstantinova-Antova²,

Petit³

et al. 2011

A&A

View full text Add to dashboard Cite

show abstract

“…In some papers, a nonmonotonic change in the magnetic field with altitude has been obtained (see, e.g., Lozitsky et al, 2000), while in others a monotonous attenuation with altitude was obtained (see, e.g. Abramenko and Baranovsky, 2004;Baranovsky et al, 2009).…”

Section: Semi-empirical Modelsmentioning

confidence: 99%

“…We consider three methods for estimations of local magnetic fields in solar flares: (1) analysis of bisectors of I  V profiles (Lozitsky, 2015); (2) search for Zeeman-like effects in cores of spectral lines with very low Lande factors, g eff  0.01 (Lozitsky, 1993(Lozitsky, , 1998; (3) semi-empirical modeling using many spectral lines and two-component models (see, e.g., Lozitsky et al, 2000). We illustrate the application of named methods to different observational data and to different spectral lines.…”

mentioning

confidence: 99%

Estimations of Local Magnetic Fields in Solar Flares: Basic Methods and Some Results

Lozitsky¹,

Baranovsky²,

Lozitska³

et al. 2017

OAP

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ABSTRACT. We consider three methods for estimations of local magnetic fields in solar flares: (1) analysis of bisectors of I  V profiles (Lozitsky, 2015); (2) search for Zeeman-like effects in cores of spectral lines with very low Lande factors, g eff  0.01 (Lozitsky, 1993(Lozitsky, , 1998; (3) semi-empirical modeling using many spectral lines and two-component models (see, e.g., Lozitsky et al., 2000). We illustrate the application of named methods to different observational data and to different spectral lines. Our main conclusions are following: (a) upper limit of local magnetic fields in solar flares is, at least, 10 4 G, (b) such extremely strong fields can occur in very small, spatially unresolved scales, (c) lifetime of such fields is, at least, a few minutes..

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“…It becomes clear that there are two types of magnetic changes: irreversible and impulsive. The former includes flux emergence, cancellation, evolving magnetic shear and helicity Asai et al 2001;Mathew & Ambastha 2000;Kim et al 2001;Kurokawa et al 2002;Spirock et al 2002); the latter is probably caused by high-energy particles bombarding the solar surface (Lozitsky et al 2000;Kosovichev & Zharkova 2001). Falconer (2001) suggested ways of CME prediction based on the irreversible changes in the magnetic vector.…”

Section: Activity-associated Magnetic Changesmentioning

confidence: 99%