A forgotten naked-eye sunspot recorded by Galileo

Several authors have shown different interesting characteristics of the long time series of solar activity reconstructed from historical naked-eye sunspot observation. For this, it is essential to make use of catalogues of this kind of observation. The aim of this note is to show a naked eye sunspot observed by Galileo. This sunspot was seen by naked eye and by telescope. It is curious that it has been forgotten until now by the compilers of the naked-eye sunspots catalogues in spite of Galileo’s fame.     

A sunspot with a peculiar motion

The development and the motion of a sunspot are described that has crossed the Sun's equator.     

A digital analysis of sunspot areas

Full-disk white light images of the Sun have been digitized, calibrated, and examined to determine objective sunspot areas for the early part of the operation of the Solar Maximum Mission satellite. We find that published sunspot areas determined from synoptic programs compare favorably with our digital areas. The mean residual between published areas and our digital areas is approximately 80 millionths of a hemisphere. The largest residual found is 642 millionths on April 1980 for Hale No. 16752.     

A model of the sunspot umbra

Equations governing the structure of the umbra of a single spot have been integrated on the spot-axis. It is shown that a consistent umbral model can be obtained only for a narrow range of the electron pressures at the spot surface. The spot center is found to be at a depth of about 400 km below the normal solar surface. The reduced energy flux observed at the surface is assumed to be due to the effect of the spot-magnetic field on subphotospheric convection and an empirical factor is introduced to take into account the reduction in the convective energy flux. With an inferred expression for as a function of the internal and magnetic-energy density it is shown that in a consistent model the physical variables in the spot approach their ambient values at about 2330 km below the undisturbed solar surface and at the same depth the energy flux approaches the normal solar value and the magnetic interference with convection vanishes. The present investigation is a refinement of an earlier paper by Chitre (1963).Supported in part by the Office of Naval Research [Nonr-220(47)] and the National Science Foundation [GP-5391].     

Polar coronal holes and the sunspot cycle. A new method to predict sunspot numbers

Twenty years ago, Ohl (1966, 1968) found a correlation between geomagnetic activity around the minimum of the solar cycle and the Wolf sunspot number in the maximum of the following solar cycle. In this paper we shall show that such a relation means indeed a relation between the polar coronal holes area around the minimum of the solar cycle and the sunspot number in the maximum of the next. In fact, a very high positive correlation exists between the temporal evolution of the size of polar coronal holes and the Wolf sunspot number 6.3. years later.     

A twin flare in symmetrical sunspot groups

Two sunspot groups in symmetrical positions relative to the Sun's equator were flaring almost simultaneously. The larger northern group was highly irregular: the two main spots were surrounded by one and the same penumbra, the magnetic polarities were inverted and the inclination of the axis was exceptionally large and of the wrong direction. The larger southern flare consisted of two parallel ribbons that developed into a loop prominence. The two ribbons were moving sideways and upwards, forming a cone. The speed of this motion amounted to 10 km s^–1 at the beginning and decreased to 2 km s^–1 in the course of one hour. The streaming along the slopes of the cone indicates the direction of the magnetic fields.     

A sunspot analysis: 1943–1977

Sunspot data from the Catania Astrophysical Observatory, covering cycles 18, 19, and 20 (1943–1977) have been analyzed, taking into account, besides the usual parameters, the number n of zones, namely latitude belts 5° wide, showing sunspot activity and the area covered by spots for each of these zones. A comparison between our conclusions and those drawn from other authors on the same subject is made.     

A new empirical model of a sunspot umbra

H and K-line spectra of quiescent prominences, taken with the slit placed normal to the limb, commonly reveal a gas streaming (5–50 km/s) that is peculiar to the upper edge of these objects. On the average this streaming is uni-directional and consistent with a hypothetical east-west wind.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

A magnetostatic sunspot model with ‘twisted’ field

It is shown that the internal structure of sunspots is affected only to a small degree by the presence of the azimuthal component of the sunspot magnetic field. The magnetostatic theory of sunspots developed by Schlüter and Temesvary (1958) is extended to include such an effect. In the present study, the radial dependence of the azimuthal component of the field is adopted from the observation of Stepanov (1965). A typical sunspot of an effective temperature of 4000K is considered and its detailed structure is presented.Publications of the Goethe Link Observatory, No. 115.     

A search for sunspot canopies using a vector magnetograph

Using a magnetograph, we examine four sunspots for evidence of a magnetic canopy at the penumbra/photosphere boundary. The penumbral edge is determined from the photometric intensity and is defined to correspond to the value of the average intensity minus twice the standard deviation from the average. From a comparison of the location of this boundary with the location of contours of the vertical and horizontal components of the magnetic field, we conclude that the data are best represented by canopy-type fields close to all four sunspots. There is some evidence that the magnetic inclination in the canopies is 5°–15° with respect to the horizontal and that the canopy base height lies in the middle/upper photosphere. The observations further suggest that the magnetic canopy of a sunspot begins at its outer penumbral boundary.     

Sunspot Positions and Areas from Observations by Galileo Galilei

Sunspot records in the seventeenth century provide important information on the solar activity before the Maunder minimum, yielding reliable sunspot indices and the solar butterfly diagram. Galilei’s letters to Cardinal Francesco Barberini and Marcus Welser contain daily solar observations on 3?–?11 May, 2 June?–?8 July, and 19?–?21 August 1612. These historical archives do not provide the time of observation, which results in uncertainty in the sunspot coordinates. To obtain them, we present a method that minimizes the discrepancy between the sunspot latitudes. We provide areas and heliographic coordinates of 82 sunspot groups. In contrast to Sheiner’s butterfly diagram, we found only one sunspot group near the Equator. This provides a higher reliability of Galilei’s drawings. Large sunspot groups are found to emerge at the same longitude in the northern hemisphere from 3 May to 21 August, which indicates an active longitude.     

A torsion-induced electric charge of the abelian higgs sunspot

One demonstrates that the Abelian Higgs sunspot acquires a non-zeroelectric charge (as well as angular momentum) in the background of a curved space-time endowed with a constant, completely antisymmetrictorsion tensor. An effective Lagrangian density is shown to contain a Chern-Simons-like term, and it leads to gauge-invariant equations of motion provided that one can neglect terms of the second order in a torsion's magnitude. The space-time torsion is also revealed to lock together the spot'selectric andmagnetic degrees of freedom.     

A refined measurement of the sunspot radiative flux deficit

New measurements of the radiative flux deficits of two large sunspots are presented, based on detailed isophotometric maps. Results are given separately for umbrae and penumbrae. The umbral and penumbral deficits are 4–5 × 10¹⁰ and 1–1.5 × 10¹⁰ erg cm^–2 s^–1 respectively, the larger figures ref to the larger spot. Over limited areas centered on the umbral cores the deficits for the two spots amount to 76 and 86% of the photospheric flux.     

Flux linkages of bipolar sunspot groups: A computer study

Past studies of the structure of solar magnetic fields have used magnetograph data to compute selected field lines for comparison with the morphology of structures seen in various spectral wavelengths. While those analyses examine one of the integral properties of magnetic fields (field lines), they are not complete since they fail to determine the other important integral property: the boundaries of the flux of field lines of given connectivity. In the present analysis we determine such a system of boundaries, called separatrices, for the current free field of two p-f spot pairs so as to exhibit the line of self-intersection, called the separator. The analysis is compared with previous analytical work. These computer results, confirming earlier studies carried out using iron fillings, show that the separatrix has the form of two intersecting ovoids, defining four flux cells. New features which have emerged from this study include the observation that the projections of the separatrix in a plane perpendicular to the separator at its highest point do not intersect at 90° as has been widely believed, but rather closer to 60° in the case studied. The separator is very nearly circular over most of its length. The two neutral points (B = 0) which appear at the photospheric ends of the separator have the mixed radial-hyperbolic form as expected, a feature requiring every field line lying on the separatrix to connect with at least one of the two neutral points. The rotation of line direction with height (shear) is graphically illustrated in the potential field case studied here. We also exhibit a magnetic arcade.     

Galileo versus Aristotle: the case of supernova 1987A

Most current supernova theories state that this phenomenon lasts a few seconds and ends with a bigfinal explosion.However, these theories do not take into account several experimental results obtained with neutrino and gravitational wave detectors during the explosion of SN1987A, the only supernova observed in a nearby galaxy in modern age. According to these experimental results the phenomenon is much more complex that envisaged by current theories, and has a duration of several hours. Indeed, SN1987A exploded on February 23, 1987, and two neutrino bursts, separated by 4.7 hours were detected: the first one at 2^h 52^m UT and the second one at 7^h 35^m UT. Furthermore, correlations between the neutrino and two gravitational wave detectors, ignored by most of the scientific community, were observed during the longer collapse time. Since the current standard theories, based on some rough simplifications, are a clear example of an Aristotelian attitude, still present in our days, we believe that a more Galilean attitude is necessary, being the only correct way for the progress of science.     

A revised listing of the number of sunspot groups made by Pastorff, 1819 to 1833

J. W. Pastorff of Drossen, Germany, made about 1477 observations of sunspots between 1819 and 1833. These observations were erroneously interpreted by A. C. Ranyard in 1874 and then used by Rudolf Wolf in his calculations of the Wolf Sunspot Numbers. The result is a noisier daily time series and overestimation of the monthly and yearly means for these years. Pastorff was actually a very good observer. In this paper, Pastorff's original observations are reexamined and more nearly correct values for the number of sunspot groups are tabulated. We show some examples of the problems created by Ranyard's interpretation and the consequences for the history of solar activity that a correct interpretation of Pastorff's observations will have. Pastorff's observations provide valuable information on the first strong cycle after the Dalton Minimum (1795–1823).     

A survey of flux transfer events recorded by the UKS spacecraft magnetometer

The UKS spacecraft operated from August 1984 through to January 1985. During that time, it made multiple crossings of the magnetopause in local time sectors extending from mid-afternoon to just behind the dawn meridian. We have surveyed the magnetometer records from these magnetopause encounters and have compiled a catalogue of flux transfer events (FTEs using criteria identical to those employed by Rijnbeek et al. (1984, J. Geophys. Res. 89, 786) in their survey of ISEE spacecraft magnetometer data. Using the catalogue, we find that FTE occurrence determined from the UKS data set is substantially less than that detected using data from the early ISEE 1/2 spacecraft orbits. The UKS data set shows a correlation between FTE occurrence and southward external magnetic field, but there are several instances of passes in which no FTEs are detected but for which the external field was unam- biguousluy southward. The passes with the largest number of events are those for which the field outside the magnetopause has a large B_M component. We conclude that the lower latitude of the UKS encounters is responsible for the discrepancy with the ISEE occurrence. The most likely source region appears to be near the subsolar region.     

A study of the green TiO band in the sunspot spectrum

The equivalent widths of the TiO lines in the α system have been measured on a high dispersion (11 mm/Å) spectrogram of large sunspot. The lines were so weak that the measurement was made by methods giving maximum and minimum equivalent widths, depending on the adopted continuum. The rotational temperature obtained in this way was about 3000 °K. The result is unaffected by stray light because there are no TiO lines in the undisturbed spectrum. The calculation of equivalent widths using several sunspot models (all of which can satisfy the observed data) shows that the logarithmic optical depth at the effective layer of molecular line formation is about -1.6.