Sunspot Umbra Research Articles

Long-term variation of sunspot penumbra to umbra area ratio

AbstractA typical sunspot, as seen in white-light intensity images, has a two part structure: a dark umbra and a lighter penumbra. Such distinction primarily arises due to the different orientations of magnetic fields in these two regions. In this study, we use the Kodaikanal white-light digitized data archive to analyze the long-term evolution of umbral and penumbal area. We used an ‘automated algorithm’ to uniquely identify the sunspot umbra (including the calculation of penumbra to umbra ratio) from these digitized intensity images. Our analysis reveals that the ratio increases slightly with the increase of sunspot area upto 100 μHem but eventually settles down to a constant value after that. This study, not only allows us to better understand the evolution of an individual spot and its corresponding magnetic field but this is also beneficial for solar dynamo studies which aim to reproduce such structures using a MHD theory.

МАГНІТНІ ПОЛЯ СОНЯЧНИХ ПЛЯМ У 24-МУ ЦИКЛІ СОНЯЧНОЇ АКТИВНОСТІ

The data of visual measurements of the magnetic field in sunspots umbra, obtained in four observatories during 24 cycles of solar activity, are compared. Magnetic field strength modules with averaging over each observatory are analyzed. The measurements taken in the Astronomical Observatory of the University of Kyiv (KAO) were used as base, where 170 spots were measured on average 4 times each at intervals of one to two daysduring the group passing through the solar disk. Measurements of the Ural, Crimean and Mount Wilson Observatory, performed within 24 hours of observation in the KAO, are used in the study. It was found that the average value of the magnetic field per cycle, obtained from the data of three observatories UrAO, CrAO and KAO, was 26.0 ± 0.3, 25.0 ± 0.2 and 25.2 ± 0.2 cT, respectively. They differ by no more than 3 standard errors, while the Mount Wilson Observatory gives a significantly lower magnetic field – 23.8 ± 0.1 cT. This result is confirmed by the work of R. Rezaei et al., 2015, which compares the visual measurements in Mount Wilson with Tenerife Infrared Polarimeter (TIP) and Facility InfRared Spectropolarimeter (FIRS) for the 23rd and 24th cycle of solar activity. The average magnetic field value for observations of TIP and FIRS in 24 cycles is 26.0 cT, which is slightly higher than we obtained from the visual observations of three observatories, while MtW shows a few centitesla less. The mean square error of the average per cycle of the magnetic field, based on the data of TIP and FIRS is 0.2 cT, so the difference with the MtW is reliable. An understatement of the measured intensity of the magnetic field of the spots requires a revision of the measurement calibration in Mount Wilson. The data of the Crimean Astrophysical Observatory can be considered reference for subsequent comparisons with the results of observations of other observatories. For the calculation of the annual index Bsp of magnetic fields of sunspot size 22-44 Mm, the data of visual measurements of all 4 observatories are traditionally used. We have found that variations in the magnetic field of sunspots are the same as in previous cycles: the peak occurs in the second-third years after the maximum number of spots. The average for the 24 cycle Bsp index is 24.9 ± 0.3 сT, which allows us to consider this magnetic cycle as moderately strong. Reduction of the sunspots magnetic field in 2018 to 23 cT allows it to expect in 2019 the highest near-ground level of galactic cosmic rays in the last half century.

Structure of sunspot light bridges in the chromosphere and transition region

Context. Light bridges (LBs) are elongated structures with enhanced intensity embedded in sunspot umbra and pores. Aims. We studied the properties of a sample of 60 LBs observed with the Interface Region Imaging Spectrograph (IRIS). Methods. Using IRIS near- and far-ultraviolet spectra, we measured the line intensity, width, and Doppler shift; followed traces of LBs in the chromosphere and transition region (TR); and compared LB parameters with umbra and quiet Sun. Results. There is a systematic emission enhancement in LBs compared to nearby umbra from the photosphere up to the TR. Light bridges are systematically displaced toward the solar limb at higher layers: the amount of the displacement at one solar radius compares well with the typical height of the chromosphere and TR. The intensity of the LB sample compared to the umbra sample peaks at the middle/upper chromosphere where they are almost permanently bright. Spectral lines emerging from the LBs are broader than the nearby umbra. The systematic redshift of the Si iv line in the LB sample is reduced compared to the quiet Sun sample. We found a significant correlation between the line width of ions arising at temperatures from 3 × 104 to 1.5 × 105 K as there is also a strong spatial correlation among the line and continuum intensities. In addition, the intensity−line width relation holds for all spectral lines in this study. The correlations indicate that the cool and hot plasma in LBs are coupled. Conclusions. Light bridges comprise multi-temperature and multi-disciplinary structures extending up to the TR. Diverse heating sources supply the energy and momentum to different layers, resulting in distinct dynamics in the photosphere, chromosphere, and TR.

Probing the Sunspot Atmosphere with Three-Minute Oscillations

We present a seismological method to probe the solar atmosphere above sunspot umbrae with three-minute oscillations. Our technique allows us to estimate both the vertical distance between atmospheric layers and the wave-propagation speed without specifying any extra parameters, in particular, the phase speed of the wave or the emission formation heights. Our method uses the projected wave paths of slow MHD waves propagating through the atmospheric layers of different heights and guided by the magnetic field. The length of the projected wave path depends upon the distance between the layers and the inclination angle of the magnetic field with respect to the line of sight, allowing us to estimate the distance between the layers from measured projected wave paths and the local magnetic-field vector. In turn, the wave-propagation delay registered at different heights allows for the calculation of the phase speed. We estimated the vertical distance between the emission layers at the temperature minimum (1600 {\AA}) and transition region (304 {\AA}), as well as the average phase speed above the sunspot umbrae, for three active regions. We found that the distance between the 1600 {\AA} emission layer and the transition region above the sunspot umbrae lies in the range of 500 -- 800 km. The average phase speed between these layers was found to be about 30 km/s giving the sound speed of 6 km/s. The temperature between the layers has been roughly estimated as 3000 K and corresponds to the region of the temperature minimum. The results obtained are consistent with the semiempirical model of the sunspot umbrae atmosphere by Fontenla, 2009. The manuscript has been accepted for publication in Solar Physics journal.

Some Features of the Variation of the Magnetic Field Characteristics in the Umbra of Sunspots During Flares and Coronal Mass Ejections

The observed variations of the magnetic properties of sunspots during eruptive events (solar flares and coronal mass ejections (CMEs)) are discussed. Variations of the magnetic field characteristics in the umbra of the sunspots of active regions (ARs) recorded during eruptive events on August 2, 2011, March 9, 2012, April 11, 2013, January 7, 2014, and June 18, 2015, are studied. The behavior of the maximum of the total field strength Bmax, the minimum inclination angle of the field lines to the radial direction from the center of the Sun αmin (i.e., the inclination angle of the axis of the magnetic tube from the sunspot umbra), and values of these parameters Bmean and αmean mean within the umbra are analyzed. The main results of our investigation are discussed by the example of the event on August 2, 2011, but, in general, the observed features of the variation of magnetic field properties in AR sunspots are similar for all of the considered eruptive events. It is shown that, after the flare onset in six AR sunspots on August 2, 2011, the behavior of the specified magnetic field parameters changes in comparison with that observed before the flare onset.

Three-minute Sunspot Oscillations Driven by Magnetic Reconnection in a Light Bridge

Abstract We report a different type of three-minute chromospheric oscillation above a sunspot in association with a small-scale impulsive event in a light bridge (LB). During our observations, we found a transient brightening in the LB. The brightening was composed of elementary bursts that may be a manifestation of fast repetitive magnetic reconnections in the LB. Interestingly, the oscillations in the nearby sunspot umbra were impulsively excited when the intensity of the brightening reached its peak. The initial period of the oscillations was about 2.3 minutes and then gradually increased to 3.0 minutes with time. In addition, we found that the amplitude of the excited oscillations was twice the amplitude of oscillations before the brightening. Based on our results, we propose that magnetic reconnection occurring in an LB can excite oscillations in the nearby sunspot umbra.

Plasma Beta Stratification in the Solar Atmosphere: A Possible Explanation for the Penumbra Formation

Abstract Plasma beta is an important and fundamental physical quantity in order to understand plasma dynamics, particularly in the context of magnetically active stars, because it tells about the domination of magnetic versus thermodynamic processes on the plasma motion. We estimate the value ranges of plasma beta in different regions within the solar atmosphere and we describe a possible mechanism that helps forming a penumbra. For that we evaluate data from a 3D magnetohydrodynamic model of the solar corona above a magnetically active region. We compare our results with previously established data that is based on magnetic field extrapolations and that was matched for some observations. Our model data suggest that plasma beta in the photosphere should be considered to be larger than unity outside of sunspots. However, in the corona we also find that the beta value range reaches lower than previously thought, which coincides with a recent observation. We present an idea based on a gravity-driven process in a high-beta regime that might be responsible for the formation of the penumbra around sunspot umbra, where the vertical field strength reaches a given threshold. This process would also explain counter-Evershed flows. Regarding the thermal and magnetic pressure within the mixed-polarity solar atmosphere, including non-vertical magnetic field and quiet regions, plasma beta may reach unity at practically any height from the photosphere to the outer corona.

Solar ALMA Observations: Constraining the Chromosphere above Sunspots

Abstract We present the first high-resolution Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a sunspot at wavelengths of 1.3 and 3 mm, obtained during the solar ALMA Science Verification campaign in 2015, and compare them with the predictions of semi-empirical sunspot umbral/penumbral atmosphere models. For the first time, millimeter observations of sunspots have resolved umbral/penumbral brightness structure at the chromospheric heights, where the emission at these wavelengths is formed. We find that the sunspot umbra exhibits a radically different appearance at 1.3 and 3 mm, whereas the penumbral brightness structure is similar at the two wavelengths. The inner part of the umbra is ∼600 K brighter than the surrounding quiet Sun (QS) at 3 mm and is ∼700 K cooler than the QS at 1.3 mm, being the coolest part of sunspot at this wavelength. On average, the brightness of the penumbra at 3 mm is comparable to the QS brightness, while at 1.3 mm it is ∼1000 K brighter than the QS. Penumbral brightness increases toward the outer boundary in both ALMA bands. Among the tested umbral models, that of Severino et al. provides the best fit to the observational data, including both the ALMA data analyzed in this study and data from earlier works. No penumbral model among those considered here gives a satisfactory fit to the currently available measurements. ALMA observations at multiple millimeter wavelengths can be used for testing existing sunspot models, and serve as an important input to constrain new empirical models.

Detection of emission in the Si I 1082.7 nm line core in sunspot umbrae

We analyze spectropolarimetric sunspot umbra observations taken in the near-infrared Si i 1082.7 nm line taking NLTE effects into account. The data were obtained with the GRIS instrument installed at the German GREGOR telescope. A point spread function (PSF) was constructed using prior Mercury observations with GRIS and the information provided by the adaptive optics system of the GREGOR telescope. The data were then deconvolved from the PSF using a principal component analysis deconvolution method and were analyzed via the NICOLE inversion code. The Si i 1082.7 nm line seems to be in emission in the umbra of the observed sunspot after the effects of scattered light are removed. We show how the spectral line shape of umbral profiles changes dramatically with the amount of scattered light. Indeed, the continuum levels range, on average, from 44% of the quiet Sun continuum intensity to about 20%. The inferred levels are in line with current model predictions and empirical umbral models. Current umbral empirical models are not able to reproduce the emission in the deconvolved umbral Stokes profiles. The results of the NLTE inversions suggests that to obtain the emission in the Si i 1082.7 nm line, the temperature stratification should first have a hump located at about log tau -2 and start rising at lower heights when moving into the transition region. This is, to our knowledge, the first time the Si i 1082.7 nm line is seen in emission in sunspot umbrae. The results show that the temperature stratification of current umbral models may be more complex than expected with the transition region located at lower heights above sunspot umbrae. Our finding might provide insights into understanding why the sunspot umbra emission in the millimeter spectral range is less than that predicted by current empirical umbral models.

The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere

Abstract High spatial and temporal resolution images of a sunspot, obtained simultaneously in multiple optical and UV wavelengths, are employed to study the propagation and damping characteristics of slow magnetoacoustic waves up to transition region heights. Power spectra are generated from intensity oscillations in sunspot umbra, across multiple atmospheric heights, for frequencies up to a few hundred mHz. It is observed that the power spectra display a power-law dependence over the entire frequency range, with a significant enhancement around 5.5 mHz found for the chromospheric channels. The phase difference spectra reveal a cutoff frequency near 3 mHz, up to which the oscillations are evanescent, while those with higher frequencies propagate upward. The power-law index appears to increase with atmospheric height. Also, shorter damping lengths are observed for oscillations with higher frequencies suggesting frequency-dependent damping. Using the relative amplitudes of the 5.5 mHz (3 minute) oscillations, we estimate the energy flux at different heights, which seems to decay gradually from the photosphere, in agreement with recent numerical simulations. Furthermore, a comparison of power spectra across the umbral radius highlights an enhancement of high-frequency waves near the umbral center, which does not seem to be related to magnetic field inclination angle effects.

Observational Evidence of a Flux Rope within a Sunspot Umbra

Abstract We observed an elongated filamentary bright structure inside the umbra of the big sunspot in active region NOAA 12529, which differs from the light bridges usually observed in sunspots for its morphology, magnetic configuration, and velocity field. We used observations taken with the Solar Dynamic Observatory satellite to characterize this feature. Its lifetime is 5 days, during which it reaches a maximum length of about 30″. In the maps of the vertical component of the photospheric magnetic field, a portion of the feature has a polarity opposite to that of the hosting sunspot. At the same time, in the entire feature the horizontal component of the magnetic field is about 2000 G, substantially stronger than in the surrounding penumbral filaments. Doppler velocity maps reveal the presence of both upward and downward plasma motions along the structure at the photospheric level. Moreover, looking at the chromospheric level, we noted that it is located in a region corresponding to the edge of a small filament that seems rooted in the sunspot umbra. Therefore, we interpreted the bright structure as the photospheric counterpart of a flux rope touching the sunspot and giving rise to penumbral-like filaments in the umbra.

The formation of small-scale umbral brightenings in sunspot atmospheres

Sunspot atmospheres are highly inhomogeneous hosting both quasi-stable and transient features, such as `umbral micro-jets' and dark fibril-like events. We seek to understand the morphological properties and formation mechanisms of small-scale umbral brightenings (SSUBs; analogous to umbral micro-jets) and to understand whether links between these events and short dynamic fibrils, umbral flashes, and umbral dots can be established. An SST filtergram time-series sampling the Ca II H line and a CRISP full-Stokes 15-point Ca II 8542 A line scan dataset were used. The average lifetime and lengths of 54 SSUBs identified in the sunspot umbra are found to be 44.2 seconds (sigma=20 seconds) and 0.56" (sigma=0.14"). The spatial positioning and morphological evolution of these events was investigated finding no evidence of parabolic or ballistic profiles nor a preference for co-spatial formation with umbral flashes. The presence of Stokes V profile reversals provided evidence that these events could form through the development of shocks in the chromosphere. The application of the weak-field approximation indicated that changes in the line-of-sight magnetic field were not responsible for the modifications to the line profile and suggested that thermodynamic effects are the actual cause of the increased emission. Finally, a sub-set of SSUBs were observed to form at the foot-points of short dynamic fibrils. Overall, we found no correlation between the spatial locations where these events were observed and the occurrence of umbral dots and umbral flashes. SSUBs, however, have lifetimes and spectral signatures comparable to umbral flashes and are located at the footpoints of short dynamic fibrils, during or at the end of the red-shifted stage. It is possible, therefore, that these features form due to the shocking of fibrilar material in the lower atmosphere upon its return under gravity.

A Hot Downflowing Model Atmosphere for Umbral Flashes and the Physical Properties of Their Dark Fibrils

Abstract We perform non-LTE inversions in a large set of umbral flashes, including the dark fibrils visible within them, and in the quiescent umbra by using the inversion code NICOLE on a set of full Stokes high-resolution Ca ii λ8542 observations of a sunspot at disk center. We find that the dark structures have Stokes profiles that are distinct from those of the quiescent and flashed regions. They are best reproduced by atmospheres that are more similar to the flashed atmosphere in terms of velocities, even if with reduced amplitudes. We also find two sets of solutions that finely fit the flashed profiles: a set that is upflowing, featuring a transition region that is deeper than in the quiescent case and preceded by a slight dip in temperature, and a second solution with a hotter atmosphere in the chromosphere but featuring downflows close to the speed of sound at such heights. Such downflows may be related, or even dependent, on the presence of coronal loops, rooted in the umbra of sunspots, as is the case in the region analyzed. Similar loops have been recently observed to have supersonic downflows in the transition region and are consistent with the earlier “sunspot plumes,” which were invariably found to display strong downflows in sunspots. Finally, we find, on average, a magnetic field reduction in the flashed areas, suggesting that the shock pressure is moving field lines in the upper layers.

An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers

Abstract Solar chromospheric observations of sunspot umbrae offer an exceptional view of magnetohydrodynamic wave phenomena. In recent years, a wealth of wave signatures related to propagating magneto-acoustic modes have been presented, which demonstrate complex spatial and temporal structuring of the wave components. Theoretical modeling has demonstrated how these ubiquitous waves are consistent with an m = 0 slow magneto-acoustic mode, which is excited by trapped sub-photospheric acoustic (p-mode) waves. However, the spectrum of umbral waves is broad, suggesting that the observed signatures represent the superposition of numerous frequencies and/or modes. We apply Fourier filtering, in both spatial and temporal domains, to extract chromospheric umbral wave characteristics consistent with an m = 1 slow magneto-acoustic mode. This identification has not been described before. Angular frequencies of 0.037 ± 0.007 rad s − 1 ( 2.1 ± 0.4 deg s − 1 , corresponding to a period ≈170 s) for the m = 1 mode are uncovered for spatial wavenumbers in the range of 0.45 < k < 0.90 arcsec−1 (5000−9000 km). Theoretical dispersion relations are solved, with corresponding eigenfunctions computed, which allows the density perturbations to be investigated and compared with our observations. Such magnetohydrodynamic modeling confirms our interpretation that the identified wave signatures are the first direct observations of an m = 1 slow magneto-acoustic mode in the chromospheric umbra of a sunspot.

ALMA Discovery of Solar Umbral Brightness Enhancement at λ = 3 mm

Abstract We report the discovery of a brightness enhancement in the center of a large sunspot umbra at a wavelength of 3 mm using the Atacama Large Millimeter/sub-millimeter Array (ALMA). Sunspots are among the most prominent features on the solar surface, but many of their aspects are surprisingly poorly understood. We analyzed a λ = 3 mm (100 GHz) mosaic image obtained by ALMA that includes a large sunspot within the active region AR12470, on 2015 December 16. The 3 mm map has a 300″ × 300″ field of view and 4.″9 × 2.″2 spatial resolution, which is the highest spatial resolution map of an entire sunspot in this frequency range. We find a gradient of 3 mm brightness from a high value in the outer penumbra to a low value in the inner penumbra/outer umbra. Within the inner umbra, there is a marked increase in 3 mm brightness temperature, which we call an umbral brightness enhancement. This enhanced emission corresponds to a temperature excess of 800 K relative to the surrounding inner penumbral region and coincides with excess brightness in the 1330 and 1400 Å slit-jaw images of the Interface Region Imaging Spectrograph (IRIS), adjacent to a partial lightbridge. This λ = 3 mm brightness enhancement may be an intrinsic feature of the sunspot umbra at chromospheric heights, such as a manifestation of umbral flashes, or it could be related to a coronal plume, since the brightness enhancement was coincident with the footpoint of a coronal loop observed at 171 Å.

Determination of the Alfvén Speed and Plasma-beta Using the Seismology of Sunspot Umbra

Abstract For 478 centrally located sunspots observed in the optical continuum with Solar Dynamics Observatory/Helioseismic Magnetic Imager, we perform seismological diagnostics of the physical parameters of umbral photospheres. The new technique is based on the theory of slow magnetoacoustic waves in a non-isothermally stratified photosphere with a uniform vertical magnetic field. We construct a map of the weighted frequency of three-minute oscillations inside the umbra and use it for the estimation of the Alfvén speed, plasma-beta, and mass density within the umbra. We find the umbral mean Alfvén speed ranges between 10.5 and 7.5 km s−1 and is negatively correlated with magnetic field strength. The umbral mean plasma-beta is found to range approximately between 0.65 and 1.15 and does not vary significantly from pores to mature sunspots. The mean density ranges between (1–6) × 10−4 kg m−3 and shows a strong positive correlation with magnetic field strength.

Photospheric Origin of Three-minute Oscillations in a Sunspot

Abstract The origin of the three-minute oscillations of intensity and velocity observed in the chromosphere of sunspot umbrae is still unclear. We investigated the spatio-spectral properties of the 3 minute oscillations of velocity in the photosphere of a sunspot umbra as well as those in the low chromosphere using the spectral data of the Ni i λ5436, Fe i λ5435, and Na i D2 λ5890 lines taken by the Fast Imaging Solar Spectrograph of the 1.6 m New Solar Telescope at the Big Bear Solar Observatory. As a result, we found a local enhancement of the 3 minute oscillation power in the vicinities of a light bridge (LB) and numerous umbral dots (UDs) in the photosphere. These 3 minute oscillations occurred independently of the 5 minute oscillations. Through wavelet analysis, we determined the amplitudes and phases of the 3 minute oscillations at the formation heights of the spectral lines, and they were found to be consistent with the upwardly propagating slow magnetoacoustic waves in the photosphere with energy flux large enough to explain the chromospheric oscillations. Our results suggest that the 3 minute chromospheric oscillations in this sunspot may have been generated by magnetoconvection occurring in the LB and UDs.

Lambda-shaped jets from a penumbral intrusion into a sunspot umbra: a possibility for magnetic reconnection

We present the results of high resolution co-temporal and co-spatial photospheric and chromospheric observations of sunspot penumbral intrusions. The data were taken with the Swedish Solar Telescope (SST) on the Canary Islands. Time series of Ca II H images show a series of transient jets extending roughly 3000 km above a penumbral intrusion into the umbra. For most of the time series, jets were seen along the whole length of the intruding bright filament. Some of these jets develop a clear λ -shaped structure, with a small loop appearing at their footpoint and lasting for around a minute. In the framework of earlier studies, the observed transient λ shape of these jets suggests that they could be caused by magnetic reconnection between a curved arcade-like or flux rope-like field in the lower part of the penumbral intrusion and the more vertical umbral magnetic field forming a cusp-shaped structure above the penumbral intrusion.

The 26 December 2001 Solar Eruptive Event Responsible for GLE63. II. Multi-Loop Structure of Microwave Sources in a Major Long-Duration Flare

Analysis of the observations of the SOL2001-12-26 event related to ground-level-event GLE63, including microwave spectra and images from NoRH at 17 and 34 GHz, SSRT at 5.7 GHz, and TRACE in 1600 \AA\ has led to the following results. A flare ribbon overlapped with the sunspot umbra, which is typical of large particle events. Atypical were: i) long duration of the flare of more than one hour; ii) moderate intensity of a microwave burst, about $10^4$ sfu; iii) low peak frequency of the gyrosynchrotron spectrum, around 6 GHz; and its insensitivity to the flux increase by more than one order of magnitude. This was accompanied by a nearly constant ratio of the flux emitted by the volume in the high-frequency part of the spectrum to its elevated low-frequency part determined by the area of the source. With the self-similarity of the spectrum, a similarity was observed between the moving microwave sources and the brightest parts of the flare ribbons in 1600 \AA. Comparison of the 17 GHz and 1600 \AA\ images has confirmed that the microwave sources were associated with multiple flare loops, whose footpoints appeared in ultraviolet as intermittent bright kernels. To understand the properties of the event, we simulated its microwave emission using a system of several homogeneous gyrosynchrotron sources above the ribbons. The scatter between the spectra and sizes of the individual sources is determined by the inhomogeneity of the magnetic field within the ribbons. The microwave flux is mainly governed by the magnetic flux passing through the ribbons and the sources. An apparent simplicity of microwave structures is caused by a poorer spatial resolution and dynamic range of the microwave imaging. The results indicate that microwave manifestations of accelerated electrons correspond to the structures observed in thermal emissions, as well-known models predict.

Spectral manifestations of extremely strong magnetic fields in the sunspot umbra

Fine peculiarities of the Zeeman effect in two big sunspots of October 29, 2003, and October 25, 2014, are analyzed. In order to search spectral evidences of very strong spatially unresolved magnetic fields, the Stokes I±V and V profiles of the FeI 6301.5 and 6302.5Å lines are studied in detail. Confirmed are two effects discovered earlier by Lozitsky (2016): (a) non-parallelism of bisectors in the FeI 6301.5 line at a distance of about ±250mÅ from the line center and (b) the existence of weak secondary peaks in Stokes V of the FeI 6302.5 line placed at a distance of, on the average, ±375mÅ from the line center. Close correlation (r=0.77±0.06) was found between (a) and (b) effects indicating the reality of very strong (≈8kG) unresolved magnetic fields. For the first sunspot, the presence of the abovementioned 8-kG fields is traced along 12Mm of the sunspot umbra. The filling factor is 0.2–0.3 here, and the relative Doppler velocities (without Evershed’s effect) are from −1.7 to −3.1km/s (plasma lifting). Similar parameters were also obtained for the second sunspot.