Form of the latitude distribution of sunspot activity

The spatial (latitude) distribution of sunspots is studied, including its dependence on solar activity. It is shown that the latitude distributions of sunspots for a given year can be approximately described by the normal law, with its variance being a linear function of the current level of solar activity. Thus, an increase in activity is accompanied by an expansion of the zone of solar activity, in good agreement with earlier results. As the solar activity increases, the width of the zone of sunspot generation and the latitude maximum of the sunspot density grow somewhat more slowly than the number of sunspots, in agreement with observations. The results obtained can be used to reconstruct the spatial distributions of sunspots in the past, interpret the magnetic activity of stars, and address the requirements of the dynamo theory in the form of constraints imposed on models of cyclicity.     

The area and absolute magnetic flux of sunspots over the past 400 years

A new series of yearly-mean relative sunspot numbers SN ₂ that has been extrapolated into the past (to 1610) is presented. The Kislovodsk series with the scale factor b = 1.0094 ± 0.0059 represents a reasonable continuation of the mean-monthly and mean-yearly total sunspot areas of the Greenwich series after 1976. The second maximum of the 24th solar-activity cycle was not anomalously low, and was no lower than 6 of the past 13 cycles. A series A ₂ of values for the total sunspot area in 1610–2015 has been constructed, and is complementary to new versions of the series of the relative number of sunspots SN ₂ and the number of sunspot groups GN ₂. When needed, this series can be reduced to yield a quantity having a clear physical meaning—the spot absolute magnetic flux Φ _Σ(t)[Mx] = 2.16 × 10¹⁹ A(t) [mvh]. The maximum sunspot area during the Maunder minimum is much higher in the new series compared to the previous version. This at least partially supports the validity of arguments that cast doubt on the anomalously low ampltude of the solar cycles during the Maunder minimum that has been assumed by many researchers earlier.     

HeII <Emphasis Type="Italic">λ</Emphasis>304 emission above sunspot umbrae

Observations of sunspot umbrae in the HeII λ304 Å and HeI λ10830 Å lines are analyzed and compared. Spectral observations in the HeI λ10830 line obtained on the Large Non-Eclipse Solar Coronograph of the Sayan Solar Observatory are used, together with HeII λ304 data obtained with the SOHO/EIT and CORONAS-f spacecraft. The contrast in the HeII λ304 line was chosen as an indicator of the UV flux. The dependences of the contrast in the HeII λ304 line and the parameters of the HeI λ10830 IR triplet on the sunspot area are obtained. The sunspot areas were determined using white-light images. A division of the dependences of the parameters of the HeI λ10830 and HeII λ304 lines on the sunspot area into two branches can be distinguished for leading and trailing sunspots. Possible origins of this behavior of the line parameters are discussed.     

Short-period variations in the proper motions of sunspots from SOHO (MDI) observations

Short-period (1–60 min) variations in the coordinates of the centers of gravity of isolated sunspots are analyzed. The sunspot coordinated were determined using two sets of observational data—magnetograms and intensities—obtained by SOHO (MDI) on December 6, 1998, from 01:00 to 21:57 UT with temporal resolution 60 s and spatial resolution 0.6″/pixel. A slow drift in the sunspot coordinates was removed using a low-frequency filter with a 61-min integration window. The guiding errors (RMS～0.014″) were determined by analyzing correlated motions in pairs of sunspots, and were removed from the time series before determining the sunspot proper motions. Based on the calculated power spectra for the sunspot proper motions, two period intervals containing appreciable power were identified. One coincides with the well-known 5-min acoustic solar oscillations. The concentration of power in this interval is greater for the coordinate variations derived the magnetograms than those derived from the intensities; the harmonic amplitude for some peaks reaches ～±30 km. The other spectral interval corresponds to periods exceeding 30 min. Overall, the rms short-period variations in the sunspot proper motions are 9.9±2.2 and 16.7±7.6 km (0.014″±0.003″ and 0.024″±0.010″) for the magnetogram and intensity data, respectively.     

基于小波变换的郑州降雨量与太阳黑子活动关系分析

为探究太阳黑子活动与地区降雨量的关联性,采用连续小波变换方法,分析了1980年以来郑州地区(新郑站点)降雨量和太阳黑子数的数据变化,并对不同时段两者的相关性进行研究;进一步对两者进行交叉小波变换和小波相干谱分析,并根据两者关系通过太阳黑子数观测值对降雨量进行预测。结果表明：(1)不同时段降雨量和太阳黑子数的相关性存在正负差异的现象。降雨量的第一主周期尺度是21 a,在此主周期尺度下得到14 a主周期;太阳黑子数的第一主周期尺度是16 a,在此主周期尺度下得到11 a主周期(与经验值相符)。降雨量与太阳黑子数的主周期相差了3 a,因此导致两者的相关性在不同时段存在正负差异。(2)降雨量与太阳黑子数在1992—2008年的8～12 a时间尺度上关联性显著,且降雨量比太阳黑子数存在规律性的时间滞后,两者在2～4 a和7～10 a的时间尺度上关联性较好;降雨量比太阳黑子数分别在1991—2004年和2006—2013年这两个时间段上呈现规律性的滞后,两者在其他时间段的各时间尺度上关联性不明显。(3)根据延迟年数经验公式,由太阳黑子数观测值对降雨量进行预测,最近的降雨量峰年在2022年附近,与2...     

Long-period oscillations of the solar microwave emission

Modulations of the microwave emission of the Sun at 11.7 GHz have been studied using more than 40 events observed in 2001 at the Mets?hovi Radio Observatory. In nearly all the observed events, low-frequency modulations with periods of 3–90 min were detected. As a rule, simultaneous modulation of the emission at several frequencies was observed. One possible origin of such modulations with periods 5–10 min is parametric resonance arising in coronal magnetic loops as a result of interactions with the 5-min photospheric oscillations, while the long-period modulations could be a manifestation of sunspot oscillations. Torsional (ϑ-mode) and radial (r-mode) oscillations have such periods. The frequency of occurrence of oscillations with the determined periods is considered, and a lower limit for the brightness temperature of the oscillations is estimated.     

The microwave radiation of the corona above a large single sunspot in right- and left-circular polarization

Results of a study of the corona above a large sunspot in the active region NOAA 10105 with a penumbra size of ～70″ observed in September 2002 are reported. Maps of the active region and emission spectra were constructed using observational data from the NoRH, SSRT, and RATAN-600 telescopes. The sizes and brightness temperatures of the microwave emission above the sunspot are determined. SOHO/MDI and Kitt Peak magnetograms, as well as CaII K line images obtained at the Meudon Observatory, are compared. The derived characteristics are interpreted as cyclotron emission of thermal plasma, assuming a dipole structure for themagnetic field. A stable darkening at the sunspot center observed at short wavelengths and only in the ordinary emission mode was detected. A jump-like change was observed in the structure of the sunspot source in the ordinary emission mode, due to an increase in the size and spectral flux density. These results demand a fundamental correction of model concepts about cyclotron emission sources above sunspots, since they are at variance with the initial assumptions. It is suggested that, at the top of the transition region, the cyclotron emission source may be represented only by the third gyrolevel, but is observed in the extraordinary and ordinary emission modes (in contrast to the generally accepted model, which has a combination of the second and third gyrolevels). Taking into account the new observational data may allow us to refine model distributions of the main parameters of the coronal plasma above sunspots (the electron temperature and density) and information about the character of the magnetic field.     

Solar cyclicity during the Maunder minimum

A multifaceted statistical study of all available data on solar activity during the Maunder minimum (1645–1715) is presented. The data include European telescope observations, Asian sunspot observations using the unaided eye, concentrations of cosmogeneous isotopes, and catalogues of polar aurorae. Joint analyses of data on the cosmogeneous isotopes ¹⁰Be and ¹⁴C are a promising source of information on solar activity in the past. The dates of relative sunspot maxima during the Maunder minimum are consistent with the idea that there were chaotic bursts of solar activity randomly distributed in time during this interval. The available evidence that the 11-year cyclicity was preserved in 1645–1715 are worthy of attention but require additional deep study and verification. No convincing evidence for a 22-year periodicity of the occurrence of sunspots during the Maunder minimum has been found.     

Differences in the parameters of radio pulsars with short and long periods

A comparative analysis of various parameters of pulsars with short (P < 0.1 s) and long (P > 0.1 s) periods is carried out. There is no correlation between the radio and gamma-ray luminosities of the pulsars and their surfacemagnetic fields, but there is a correlation between the X-ray luminosity and the surfacemagnetic field. A dependence of the X-ray and gamma-ray luminosities on the magnetic field at the light cylinder is also found. This result provides evidence for the formation of hard, non-thermal emission at the periphery of the magnetosphere. An appreciable positive correlation between the luminosity and the rate of rotational energy loss by the neutron star is observed, supporting the idea that all radio pulsars have the same basic source of energy. The efficiency of the transformation of rotational energy into radiation is significantly higher in long-period pulsars. The dependence of the pulse width on the pulsar period is steeper for pulsars with short periods than for those with long periods. The results obtained support earlier assertions that there are differences in the processes generating the emission in pulsars with P < 0.1 s and those with P > 0.1 s.     

The space velocities of radio pulsars

Known models proposed to explain the high space velocities of pulsars based on asymmetry of the transport coefficients of different sorts of neutrinos or electromagnetic radiation can be efficient only in the presence of high magnetic fields (to 10¹⁶ G) or short rotation periods for the neutron stars (of the order of 1 ms). This current study shows that the observed velocities are not correlated with either the pulsar periods or their surface magnetic fields. The initial rotation periods are estimated in a model for the magnetedipolar deceleration of their spin, aßsuming that the pulsar ages are equal to their kinematic ages. The initial period distribution is bimodal, with peaks at 5 ms and 0.5 s, and similar to the current distribution of periods. It is shown that asymmetry of the pulsar electromagnetic radiation is insufficient to give rise to additional acceleration of pulsars during their evolution after the supernova explosion that gave birth to them. The observations testify to deceleration of the motion, most likely due to the influence of the interstellar medium and interactions with nearby objects. The time scale for the exponential decrease in the magnetic field τ_D and in the angle between the rotation axis and magnetic moment τ_ß are estimated, yielding τ_β = 1.4 million years. The derived dependence of the transverse velocity of a pulsar on the angle between the line of sight and the rotation axis of the neutron star corresponds to the expected dependence for acceleration mechanisms associated with asymmetry of the radiation emitted by the two poles of the star.     

The presence of a magnetic field on the pulsating subdwarf Balloon 090100001. Observations of 2012

New polarization observations of the subdwarf Bal 09 are analyzed. Bal 09 belongs to the group of hybrid sdB stars, which display both short- and long-period pulsations. Explaining certain properties of Bal 09 that were previously unknown in relation to subdwarfs (variations of the amplitude of the fundamental pulsation mode, rotational splitting of line multiplets and variation of this splitting) requires invoking information about the magnetic field of the star. According to estimates made in 2010, the longitudinal component of the magnetic field of Bal 09 is 34±63 G. This value is significantly lower than the fields found earlier for six other hot subdwarfs. New observational data for the longitudinal magnetic field of Bal 09 was obtained on July 27, 2012, using the main stellar spectrograph of the 6-m telescope of the Special Astrophysical Observatory (SAO). The longitudinal component of the magnetic field 〈B _z 〉 was found via a regression analysis. When applied to the star HD 210762 with a zero total magnetic field, this method yielded the value 〈B _z 〉 = ?12 ± 9 G. The observations also included measurements of 〈B _z 〉 for the well-studied magnetic star γ Equ, which is used at the SAO for calibration and testing of the polarimetric instruments. The estimate obtained for γ Equ is 〈B _z 〉 = ?546±16G, consistentwith the general variations of the longitudinal magnetic-field component of this star. This new study, based on data obtained on July 27, 2012, leads to a similar estimate of the longitudinal magnetic field, 〈B _z 〉 = ?23±53 G. This estimate of 〈B _z 〉 was obtained for the full analyzed spectral range (4400–4958 Å). The corresponding “limited” solution yielded ?32±63 G. The regression analysis for the individual spectral sub-bands and for bands containing characteristic spectral features, did not provide firm evidence of the presence of a magnetic field, with a strength exceeding the error in 〈B _z 〉. The data analysis leads to the conclusion that the errors of the measurements made in 2010 and 2012 are in good agreement. This testifies to the reliability of the method applied and of the resulting observational material. In addition, the estimates are in good agreement among themselves and with estimates obtained earlier, in 2010. The results unambiguously confirm the earlier conclusion that the subdwarf Bal 09 does not have magnetic field with a strength comparable to those detected earlier for six sdB and sdO stars. Estimates of 〈B _z 〉 for hot subdwarfs that have appeared in the literature since the 2010 study also provide trustworthy evidence for the absence of magnetic fields ～ 1 kG in these objects.     

The magnetic fields and density of relativistic electrons in the nucleus of NGC 1052

We analyze observations of the compact GHZ-peaked-spectrum radio source in the nucleus of the weakly active galaxy NGC 1052, assuming that the low-frequency turnover in its spectrum is due to synchrotron self-absorption. The analysis is based on a model for an inhomogeneous source of synchrotron radiation. It is shown that the magnetic field is not uniform, but the change in the field strength from the center to the edge of the compact radio source does not exceed an order of magnitude. The maximum magnetic-field strength in the nucleus of NGC 1052 is 20 G < H _⊥ < 200 G, and the density of relativistic electrons is 0.018 cm⁻³ < n _e < 0.18 cm⁻³ on scales of 0.1 pc; everywhere in the radio source, the energy density of the magnetic field exceeds the energy density of the relativistic electrons. The physical conditions are similar to those in the nuclei of the nearby radio galaxies 3C 111 and 3C 465, and differ strongly from those in the nucleus of the radio galaxy 0108+388, which is a compact GHz-peaked-spectrum source (these three galaxies were studied by the authors earlier using the same method).     

Dissipation of diamagnetic currents and plasma heating in coronal magnetic loops

SOHO and TRACE data have shown that the coronal plasma is heated most actively near sunspots, in magnetic loops that issue from the penumbral region. The source of heating is nonuniform in height, and its power is maximum near the footpoints of the magnetic loops. The heating process is typically accompanied by the injection of dense chromospheric plasma into the coronal parts of the magnetic loops. It is important that the radiative losses cannot be compensated for via electron thermal conduction in the loops, which have temperatures of 1.0–1.5 MK; therefore, some heating source must operate throughout the entire length of the loop, balancing radiative losses and maintaining a quasi-steady state of the loop over at least several hours. As observations show, the plasma density inside the loops exceeds the density of the ambient plasma by more than an order of magnitude. It is supposed that the enhanced plasma density inside the loops results from the development of the ballooning mode of a flute-type instability in the sunspot penumbra, where the plasma of the inner sunspot region, with β _i ? 1, comes into contact with the dense chromospheric plasma, which has β _e ? β _i (β is the gas-to-magnetic pressure ratio). As the chromospheric plasma penetrates into the potential field of the sunspot, the generated diamagnetic currents balance the excess gas pressure. These currents efficiently decay due to the Cowling conductivity. Even if neutrals are few in number in the plasma (accounting for less than 10^?5 of the total mass density), this conductivity ensures a heating rate that exceeds the rate of the normal Joule dissipation of diamagnetic currents by 7–8 orders of magnitude. Helium is an important factor in the context of plasma heating in magnetic loops. Its relatively high ionization potential, while not forbidding dielectronic recombination, ensures a sufficiently high number of neutrals in the coronal plasma and maintains a high heating rate due to the Cowling conductivity, even at coronal temperatures. The heating results from the “burning-out” of the nonpotential component of the magnetic field of the coronal magnetic loops. This mechanism provides the necessary heating rate for the plasma inside the loops if the loops are thin enough (with thickness of the order of 10⁵–10⁶ cm). This may imply that the observed (1–5) × 10⁸-cm-thick loops consist of numerous hot, thin threads. For magnetic loops in hydrostatic equilibrium, the calculated heating function exponentially decreases with height on characteristic scales a factor of 1.8 smaller than the total-pressure scale height, since the scale heights for the total pressure and for the ⁴He partial pressure are different. The heating rate is proportional to the square of the plasma pressure in the loop, in agreement with observational data.

     

The magnetic field of the pulsating subdwarf Balloon 090100001

We have analyzed polarization observations of the subdwarf Bal 09, which is one of a group of hybrid sdB stars that display simultaneously both short- and long-period pulsations. Certain properties previously unknown for subdwarfs have been established for Bal 09, such as variations of the pulsation amplitude of the main oscillation mode, rotational splitting of multiplets, and variations of this splitting. Information about the stellar magnetic field must be considered if we wish to explain these properties. New observational data enabling estimation of the longitudinal magnetic field of Bal 09 have been obtained on the main stellar spectrograph of the 6-m telescope of the Special Astrophysical Observatory. Studies of the longitudinal component of the magnetic field 〈B _z 〉 were carried out using a regression analysis. This method simultaneously yields estimates of the uncertainty in 〈B _z 〉. Test measurements of 〈B _z 〉 were carried out using the same method. For the star HD 158974, which has zero total magnetic field, the estimated longitudinal magnetic field is 〈B _z 〉 = −4 ± 5 G. The standard magnetic field for the Ap star α ²CVn was measured to be −363 ± 17 G, in very good agreement with measurements in the literature. The estimated longitudinal magnetic field for Bal 09 is 34 ± 63G—appreciably lower than values established earlier for six subdwarfs, ≈1.5 kG. The results of the regression analysis for both individual spectral subranges and for intervals containing characteristic spectral features did not indicate reliable detections of a magnetic field exceeding the uncertainties in 〈B _z 〉. The uncertainty in 〈B _z 〉, which was 60–80 G for the entire spectral range and 140–200 G for selected spectral intervals, leads to an estimated upper limit on the longitudinal magnetic field 〈B _z 〉 for Bal 09. This estimate for 〈B _z 〉 can place observational constraints on theoretical explanations for the amplitude variations of the pulsations, rotational splitting of multiplets, and possible variations of the internal structure of the star.     

Time-lag effects in Parker’s dynamo

The effects of a time lag in the magnetic quenching of the α effect is considered for an oscillating magnetic field in a Parker dynamo. The hypothesis of a parametric resonance in the system is justified, a modification of the solution is found, and the appearance of processes with periods much longer than the fundamental oscillation period is demonstrated.     

Search for and detection of pulsars inmonitoring observations at 111 MHz

In the course of monitoring interplanetary scintillations of a large number of sources using the Big Scanning Antenna of the Lebedev Physical Institute, a search for pulsars with periods ≥0.4 s at declinations ?9? < δ < 42? and right ascensions 0h < α < 24h was simultaneously carried out. The search was conducted using four years of observations carried out at 110.25MHz in six frequency channels making up a 2.5 MHz band and having a time resolution of 100 ms. The initial identification of pulsar candidates was done using Fourier power spectra averaged over the entire observational period; the pulsar candidates were then verified using observations with higher frequency and time resolution: 32 frequency channels and a time resolution of 12.5 ms. Eighteen new pulsars were discovered in the studied area, whose main characteristics are presented.     

Long-period oscillations of the line-of-sight velocities in and near sunspots at various levels in the photosphere

New observational data on long-period oscillations of the line-of-sight velocities detected via the Doppler shifts of spectral lines observed at various heights in and near sunspots are presented. The sunspots and nearby magnetic elements oscillate with periods ranging from 40 to 80 min. The oscillations in the line-of-sight velocities persist over the entire observation session (up to four hours). These results support theoretical models in which this phenomenon represents natural long-period oscillations (vertical-radial displacements) of entire magnetic elements (sunspots, pores, and magnetic knots) about some stable equilibrium positions.     

Broad-band multicolor photometry and polarimetry of spotted stars

We have confirmed the BY Dra-type variability of the active spotted stars MS Ser, LQ Hya, VY Ari, and EK Dra using simultaneous UBVRI photometric and polarimetric observations. We have also reliably detected the intrinsic linear polarization of their radiation and its rotational modulation in U due to the inhomogeneous distribution of active magnetized regions over the surfaces of the stars. Modeling of the linear polarization based on the Zeeman effect indicates that all the stars display strong local magnetic fields (about 2 kG, similar to those in sunspots), with filling factors of up to 40% of the total stellar surface. The magnetized regions coincide with cool photospheric spots detected in photoelectric observations.     

The large-scale solar magnetic field and 11-year activity cycles

Magnetic Hα synoptic maps of the Sun for 1915–1999 are analyzed and the intensities of spherical harmonics of the large-scale solar magnetic field computed. The possibility of using these Hα maps as a database for investigations of long-term variations of solar activity is demonstrated. As an example, the magnetic-field polarity distribution for the Hα maps and the analogous polarity distribution for the magnetographic maps of the Stanford observatory for 1975–1999 are compared. An activity index A(t) is introduced for the large-scale magnetic field, which is the sum of the magnetic-moment intensities for the dipole and octupole components. The 11-year cycle of the large-scale solar magnetic field leads the 11-year sunspot cycle by, on average, 5.5 years. It is concluded that the observed weak large-scale solar magnetic field is not the product of the decay of strong active-region fields. Based on the new data, the level of the current (23rd) solar-activity cycle and some aspects of solar-cycle theory are discussed.     

Parity fluctuations in stellar dynamos

Observations of the solar butterfly diagram from sunspot records suggest persistent fluctuations in parity, away from the overall, approximately dipolar pattern. A simple mean-field dynamo model is used with a solar-like rotation law and perturbed α effect. The parity of the magnetic field relative to the rotational equator can demonstrate can be described as resonance behavior, while the magnetic energy behaves in a more or less expected way. Possible applications of this effect are discussed in the context of various deviations of the solar magnetic field from dipolar symmetry, as reported from analyses of archival sunspot data. The model produces fluctuations in field parity, and hence in the butterfly diagram, that are consistent with observed fluctuaions in solar behavior.