Improvement of the inversion accuracy of the Ca II line profiles using response functions

The line profile inversion is as a rule used to model the atmosphere. The algorithm for determining the temperature and electron density in the middle chromosphere has been developed based on inversion of the profiles of five Ca II chromospheric lines. Necessary information is contained in the function called by us the population function. This function is used to calculate the frequency-dependent source functions in lines and, consequently, the rates of radiative transitions. However, the accuracy of population function reconstruction in the inversion procedure is insufficient for the goal to be achieved. The accuracy is increased by using the intensity response function conception. The response functions of five Ca II lines to the population function disturbances have been calculated. The accuracy to be achieved has been estimated using one of the semiempirical models of the sunspot umbra as an example.     

Relationship of the Magnetic-Field Strength and the Brightness of the Sunspot Umbra and the Center of a Facular Knot

Geomagnetism and Aeronomy - Two main features define a sunspot as an object: a strong magnetic field and a low umbra temperature. The same can be said about a facular knot, in the center of which...     

On the modeling of visible sunspot layers

One option for a stationary model of the asymmetric sunspot previously presented by the authors is considered. It is shown that the presence of sub-Alfvénic Evershed flows in the sunspot penumbra has almost no effect on the temperature distribution in the dense photospheric layers of the sunspot but significantly lowers the temperature of the chromosphere and the lower corona above the sunspot penumbra up to heights of 5–6 Mm.     

Spatial pattern of photospheric granules in a sunspot neighborhood

Based on high-resolution (0.3 arcsec) observations, we studied the behavior of solar granulation in the neighborhood of a sunspot. The bright granules’ spatial distribution and the granules’ surface density as a function of distance from the center of the sunspot umbra were determined.Bright granules distribute delimiting cells of dimensions in the mesogranular scale. The mean diameter of these cells does not show significant variation with the variation of the magnetic field of the sunspot. The granules’ surface density does not show significant variation with distance to the sunspot umbra. Both results point to a very weak, if any, influence of the sunspot magnetic field at distances greater than 20 arcsec.     

Reconstruction of Centennial Series of Solar Activity

Geomagnetism and Aeronomy - The results of the digitalization of the centennial series of solar activity are considered. The data contain information on sunspots since 1918, sunspot umbra since...     

Solar corona top heating

The solar magnetic field fragmentation into thin magnetic tubes above the photosphere makes it possible to transform and factorize MHD equations analytically and to obtain explicit expressions for Alfvén and magnetosonic fields. A physical model that enables an explanation of the effect of strong heating of the solar chromosphere and corona has been proposed. This model makes it possible to estimate analytically a powerful Alfvén disturbance entering the chromosphere due to convective motions of the photosphere and a thermal release due to a three-wave interaction within the chromosphere.     

Sunspots

Abstract

Some examples of research on structure and formation of sunspots are briefly recollected in historical sequence. They relate to many facets of sunspots, first: magnetic inhibition of convection, the conjecture of a fiat penumbra, the stratification beneath the umbra, the observable magnetic profile, the Evershed effect as syphon flow, the concept of a magnetopause; next: cooling by Alfven waves, evolution and stability, the “bright ring”, the observed change of umbra brightness with the phase of the sunspot cycle, the hypothetical cluster of separate flux strands underneath the umbra, the profile of the magnetopause, the structure of the penumbra and the inclination of its field and finally: the concept of a deep penumbra with volume currents, exchange convection and the concept of a second current sheet separating umbra and penumbra.

Of course, the rigorous theoretical modeling of local magnetoconvection is an essential tool for our understanding of all these processes. I do not deal with it here, but the reader has a fascinating review of magnetoconvection already in his hands (Weiss, 1991).     

Magnetic field variations in the umbra of single sunspots during their passage across the solar disk

Temporal variations of the maximum (B _max) and average (〈B〉) magnetic inductions, minimum (α _min) and average (〈α〉) inclination angles of the field lines to the radial direction from the center of the Sun, and areas of the sunspot umbra S in the umbra of single sunspots during their passage across the solar disk are investigated. The variation of the properties of single sunspots has been considered at different stages of their existence, i.e., during formation, the “quiet” period, and the disappearance stage. It has been found that, for the majority of the selected single sunspots, there is a positive correlation between B _max and S and between 〈B〉 and S defined at different times during the passage of sunspots across the solar disk. It is shown in this case that the nature of the dependence between the parameters α _min and B _max, α _min and S, as well as between 〈α〉 and 〈B〉, 〈α〉 and S, can vary from sunspot to sunspot, but for many sunspots the inclination angle of the field lines decreases on average with the growth of the sunspot umbra area and the field strength.     

Anticorrelation of Variations of the Magnetic Field of a Sunspot and the Brightness of Its Umbra in Long-Period Sunspot Oscillations

Geomagnetism and Aeronomy - Changes in the umbra brightness and in the magnetic field over time should occur on long-period sunspot oscillations in accordance with Birman’s idea of inhibition...     

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 B_max, the minimum inclination angle of the field lines to the radial direction from the center of the Sun α_min (i.e., the inclination angle of the axis of the magnetic tube from the sunspot umbra), and values of these parameters B_mean and α_mean 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.     

The effects of climatic variability on estimates of recharge from temperature profiles

Using heat as a tracer allows for estimation of ground water recharge rates based on subsurface temperature measurements. While possible in theory, it may be difficult in practice to discriminate the effects of climate from the effects of ground water advection. This study uses synthetic simulations to determine the influence of variability of ground surface temperature (GST) on the ability to estimate vertical specific discharge from temperature profiles. Results suggest that in cases where temperature measurements are sufficiently deep and specific discharge is sufficiently high, estimates of specific discharges will be reasonably accurate. Increasing the number of times temperatures are measured, or producing models that incorporate variations in GST, will increase the reliability of any studies using temperatures to estimate specific discharge. Furthermore, inversions of temperature measurements should be combined with other methods of estimating recharge rates to improve the reliability of recharge estimates.     

中国地区地磁异常静日（AQD）的初步分析

本文将G.M.Brown等人对离S_q电流体系焦点较远处台站的异常静日（AQD）的H分量分析,发展为对包括S_q电流体系焦点附近台站和Z、D分量在内的AQD分析。主要分析了中国五个地磁台D、H、Z三要素静日最大值和最小值出现时间的分布,及其季节变化和逐年变化规律。结果表明,D、Z也有和H类似的AQD现象,其出现的年频度,也有与太阳黑子数反相变化的趋势。在有三个多太阳周资料的佘山台,太阳极小年AQD(Z_max)出现的频度,和随后的太阳极大年的黑子数R呈近似线性的关系。最后,本文对今后我国开展变化磁场的分析研究提出了建议。     

Chromospheric and Coronal Radio Sources from Observations of the Partial Solar Eclipse of March 20, 2015, at the Mountain Astronomical Station of the Central Astronomical Observatory

This paper presents the results of processing the data on the partial solar eclipse that occurred on March 20, 2015, and was observed with the RT-3 (λ = 4.9 cm) and RT-2 (λ = 3.2 cm) radio telescopes of the Kislovodsk Mountain Astronomical Station, Central Astronomical Observatory, Russian Academy of Sciences (MAS CAO RAS). They were compared with observations in the optical and X-ray ranges. The local radio sources at the limb and on the disc of the Sun were identified: an eruptive and a quiet prominence; filaments; a coronal hole; facular plages; and a sunspot group. The curves of the center-to-limb variations in the radio brightness of the undisturbed regions of the Sun were plotted for λ = 4.9 and λ = 3.2 cm. The solar radio maps were presented. The altitude of the radiating layer in the chromosphere above the sunspot and the facular sources for λ = 4.9 cm λ = 3.2 cm was compared.     

An analysis of heat transfer in the solar photosphere and chromosphere

The prevailing heat transfer processes—convection in the photosphere and wave propagation in the chromosphere—are principally different. Despite this fact, there is a direct link between these processes: it is precisely convective photospheric flows that excite intense Alfven waves in the chromosphere. A physical model explaining the effect of strong chromospheric and coronal heating is improved in this work. The model is based on synchronous propagation and interaction in the chromosphere of photospheric spicules and Alfven waves. The results of observations of the last decade and the analytical solution of the equations of magnetohydrodynamics are used. It is established that the heating of the solar atmospheric plasma proceeds not in the corona but in the upper chromosphere.     

The Ratio Between the Number of Sunspot and the Number of Sunspot Groups

Data from three solar observatories (Learmonth, Holloman, and San Vito) are used to study the variations in the average number of sunspots per sunspot group. It is found that the different types of sunspot groups and the number of sunspots in these groups have different solar cycle and cycle to cycle variations. The varying ratio between the average number of sunspots and the number of sunspot groups is shown to be a real feature and not a result of changing observational instruments, observers’ experience, calculation schemes, etc., and is a result of variations in the solar magnetic fields. Therefore, the attempts to minimize the discrepancies between the sunspot number and sunspot group series are not justified, and lead to the loss of important information about the variability of the solar dynamo.     

On a Magnetic Anomaly in the Umbra of the Following Spot of an NOAA 12192 Active Region

This paper examines the evolution and morphology of a magnetic anomaly: the appearance and disappearance of a longitudinal magnetic flux with opposite polarity at an area of about 10 arc seconds in the umbra of the following sunspot of an NOAA 12192 active region, which was observed from 21 to 26 October 2014 in the SDO/HMI and SOLIS/VSM magnetograms. Information collected by spacecraft and under on-ground observations including data from the Sun Service of the Crimean Astrophysical Observatory of the Russian Academy of Sciences are analyzed. Based on the methods of observation and determination of longitudinal magnetic fields in SDO/HMI in line FeI 6173.34 Å it was revealed, that combinations of contours appearing due to magnetic force lines inclinations relative to the line-of-sight and line-of-sight velocities can cause a significant undervalue of the magnetic field intensity in magnetograms, but polarity does not reverse. The fine spatial structure, evolution features, close correlation with ultraviolet loops system in SDO/AIA images, “moustaches”, and no temporal and spatial correlation with flares point to a connection between the detected anomaly and the new magnetic flux emergence of opposite polarity in a spot’s umbra at an earlier decay stage. We analyze magnetic force lines reconnection and show that annigilation of the magnetic fields of opposite polarities can take place for many hours at small (~30 km) scales and this fact is verified by observation results. There are additional facts in favor of the cluster model of a solar spot by Severny-Parker.

     

Dynamic Characteristics of Area Variations of Small and Large Sunspots and Quasi-Biennial Oscillations in Solar Activity

The spatiotemporal and chaotic dynamics of variations in area of sunspot groups related conventionally to small (area <50 Msh) and large (area >50 Msh) populations is analyzed. The Greenwich Observatory–Marshall Space Flight Center data were used. The results show that both sunspot populations have a single initial source, which is a magnetic flux generated by the dynamo process (presumably at the bottom of the convective zone) and is responsible for the 11—22-year periodicity of solar activity. A possible explanation of the revealed different behavior of the considered populations is that the magnetic flux is partially involved in another process responsible for the shaping of primarily very large sunspot groups. This process develops presumably in the upper layer of the convective zone with an unstable amplitude and a period varying within 1–2 years. The analysis of power spectrum of the Wolf number time series has indicated the difference between dynamic characteristics of the two studied processes.     

The sunspot cycle, the QBO, and the total ozone over Northeastern Europe: a connection through the dynamics of stratospheric circulation

The interaction between the factors of the quasi-biennial oscillation (QBO) and the 11-year solar cycle is considered as an separate factor influencing the interannual January–March variations of total ozone over Northeastern Europe. Linear correlation analysis and the running correlation method are used to examine possible connections between ozone and solar activity at simultaneous moment the QBO phase. Statistically significant correlations between the variations of total ozone in February and, partially, in March, and the sunspot numbers during the different phases of QBO are found. The running correlation method between the ozone and the equatorial zonal wind demonstrates a clear modulation of 11-y solar signal for February and March. Modulation is clearer if the QBO phases are defined at the level of 50 hPa rather than at 30 hPa. The same statistical analyses are conducted also for possible connections between the index of stratospheric circulation C₁ and sunspot numbers considering the QBO phase. Statistically significant connections are found for February. The running correlations between the index C₁ and the equatorial zonal wind show the clear modulation of 11-y solar signal for February and March. Based on the obtained correlations between the interannual variations of ozone and index C₁, it may be concluded that a connection between solar cycle – QBO – ozone occurs through the dynamics of stratospheric circulation.     

Long-range forecasts of River Po discharges based on predictable solar activity and a fuzzy neural network model / Prévisions à long terme des débits du Fleuve Pô basées sur l’activité solaire prévisible et sur un modèle de réseau de neurones flou

Abstract

Abstract Is it possible to make seasonal and interannual forecasts of hydrological variables if one cannot predict next week’s rainfall? Contrary to common view, some scientists support the hypothesis that variations in mean global temperature and precipitation are controlled more by external forcing (solar variability and volcanic eruptions) than by increasing atmospheric concentration of greenhouse gases. Temperature and precipitation are connected with special phases of the 11-year sunspot cycle, which coincide with significant accumulation of energetic solar eruptions. Because of the possibility of identifying years with many solar eruptions, the attractive prospect emerges of the long-term hydrological forecasting based on cycles of solar activity. Starting from this assumption, an expert system was built based on a fuzzy neural network model for seasonal and interannual forecasting of the Po River discharge. It was found that indices of solar activity and of global circulation are sufficient to yield useful forecasts of hydrological variables.     

An attempt to the explanation and to the prediction of the eleven-year cycle of solar activity

Summary According to the author the reason of the subsistence of the 11 years' sunspot cycle is to be found in the conjunction of the planets. As a result of the investigations it has been stated that from among the nine planets the joint tidal effect of Venus-Jupiter-Earth is a decisive factor in the variations of sunspot activity. The above three planets are every 10.4 years and 12.0 years respectively, in a close conjunction. The mean value (11.2 years) is in an almost full accordance with the average cycle-period. The fluctuations of the period of the cycle come from the fact that the planets' getting into approximately one line takes a different time within each cycle. This time delay is the cause of the stronger or weaker sunspot activity, and of the shorter or longer cycles.