Changed Relation between Solar 10.7-cm Radio Flux and some Activity Indices which describe the Radiation at Different Altitudes of Atmosphere during Cycles 21–23

Бруевич, Е. А.; Bruevich, V. V.; Yakunina, G. V.

doi:10.1007/s12036-014-9258-0

Cited by 45 publications

(24 citation statements)

References 19 publications

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“…However, F 10.7 is considered to be a good generalized solar proxy for EUV irradiances which ionizes it. Bruevich et al [2014] stated that it is originated in the cool corona, a solar region that is closely coupled with magnetic structures responsible for creating the XUV-EUV irradiances. Also, F 10.7 depends on few processes.…”

Section: Resultsmentioning

confidence: 99%

E region electric field dependence of the solar activity

et al. 2015

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We have being studying the zonal and vertical E region electric field components inferred from the Doppler shifts of type 2 echoes (gradient drift irregularities) detected with the 50 MHz backscatter coherent radar set at São Luis, Brazil (SLZ, 2.3°S, 44.2°W) during the solar cycle 24. In this report we present the dependence of the vertical and zonal components of this electric field with the solar activity, based on the solar flux F10.7. For this study we consider the geomagnetically quiet days only (Kp ≤ 3+). A magnetic field‐aligned‐integrated conductivity model was developed for proving the conductivities, using the IRI‐2007, the MISIS‐2000, and the IGRF‐11 models as input parameters for ionosphere, neutral atmosphere, and Earth magnetic field, respectively. The ion‐neutron collision frequencies of all the species are combined through the momentum transfer collision frequency equation. The mean zonal component of the electric field, which normally ranged from 0.19 to 0.35 mV/m between the 8 and 18 h (LT) in the Brazilian sector, show a small dependency with the solar activity. Whereas the mean vertical component of the electric field, which normally ranges from 4.65 to 10.12 mV/m, highlights the more pronounced dependency of the solar flux.

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Section: Resultsmentioning

confidence: 99%

E region electric field dependence of the solar activity

et al. 2015

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“…The amplitude of rotational modulation is a widely used activity index and can be regarded as a robust proxy of the surface magnetic activity. García et al (2013) demonstrated that the variance of the Total Solar Irradiance, computed on a 60-d sliding window, closely mimics the variations of the 10.7 cm radio flux that in turn is a good indicator of the solar magnetic activity (see Bruevich et al 2014, for details). We computed the Spearman coefficient between <IQR> and different stellar parameters in order to investigate how the mean level of the stellar surface magnetic activity is linked to the stellar properties.…”

Section: Relationship Between and Global Stellar Parametersmentioning

confidence: 92%

Activity cycles in members of young loose stellar associations

Distefano

Lanzafame

Lanza

et al. 2017

A&A

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Context. Magnetic cycles analogous to the solar one have been detected in tens of solar-like stars by analyzing long-term time-series of different magnetic activity indexes. The relationship between the cycle properties and global stellar parameters is not fully understood yet. One reason for this is the sparseness of the data. Aims. In the present paper we searched for activity cycles in a sample of 90 young solar-like stars with ages between 4 and 95 Myr with the aim to investigate the properties of activity cycles in this age range. Methods. We measured the length P cyc of a given cycle by analyzing the long-term time-series of three different activity indexes: the period of rotational modulation, the amplitude of the rotational modulation and the median magnitude in the V band. For each star, we computed also the global magnetic activity index that is proportional to the amplitude of the rotational modulation and can be regarded as a proxy of the mean level of the surface magnetic activity. Results. We detected activity cycles in 67 stars. Secondary cycles were also detected in 32 stars of the sample. The lack of correlation between P cyc and P rot and the position of our targets in the P cyc /P rot − Ro −1 diagram suggest that these stars belong to the so-called Transitional Branch and that the dynamo acting in these stars is different from the solar one and from that acting in the older Mt. Wilson stars. This statement is also supported by the analysis of the butterfly diagrams whose patterns are very different from those seen in the solar case. We computed the Spearman correlation coefficient r S between P cyc , and different stellar parameters. We found that P cyc in our sample is uncorrelated with all the investigated parameters. The index is positively correlated with the convective turn-over time-scale, the magnetic diffusivity time-scale τ diff , and the dynamo number D N , whereas it is anti-correlated with the effective temperature T eff , the photometric shear ∆Ω phot and the radius R C at which the convective zone is located. We investigated how P cyc and evolve with the stellar age. We found that P cyc is about constant and that decreases with the stellare age in the range 4-95 Myr. Finally we investigated the magnetic activity of the star AB Dor A by merging ASAS time-series with previous long-term photometric data. We estimated the length of the AB Dor A primary cycle as P cyc = 16.78 ± 2yr and we found also shorter secondary cycles with lengths of 400 d, 190 d and 90 d respectively.

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“…A general index of stellar photometric variability, S ph , was defined from the standard deviation of the whole light curve. In the case of the Sun, the comparison of S ph with a well-established magnetic activity proxy, the 10.7 cm radio flux (which is a useful proxy for the combination of chromospheric, transition region, and coronal solar EUV emissions modulated by bright solar active regions (see for further details Bruevich et al 2014)), demonstrated that S ph is a good indicator of the surface magnetic activity of the Sun (García et al 2013b) and is well correlated with the chromospheric activity. Basri et al (2011) also defined a photometric variability index, called the range, R var (t len ), to characterize the variability of the Kepler targets at different time scales.…”

Section: Extracting the Photometric Magnetic Activity Levelmentioning

confidence: 99%

Rotation and magnetism ofKeplerpulsating solar-like stars

García

Ceillier

Salabert

et al. 2014

A&A

270

344

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Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the mainsequence and the subgiant branch for which stellar pulsations have been measured. The rotation period was determined by comparing the results from two different analysis methods: i) the projection onto the frequency domain of the time-period analysis, and ii) the autocorrelation function of the light curves. Reliable surface rotation rates were then extracted by comparing the results from two different sets of calibrated data and from the two complementary analyses. General photometric levels of magnetic activity in this sample of stars were also extracted by using a photometric activity index, which takes into account the rotation period of the stars. We report rotation periods for 310 out of 540 targets (excluding known binaries and candidate planet-host stars); our measurements span a range of 1 to 100 days. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature.

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Changed Relation between Solar 10.7-cm Radio Flux and some Activity Indices which describe the Radiation at Different Altitudes of Atmosphere during Cycles 21–23

Cited by 45 publications

References 19 publications

E region electric field dependence of the solar activity

E region electric field dependence of the solar activity

Activity cycles in members of young loose stellar associations

Rotation and magnetism ofKeplerpulsating solar-like stars

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