Global solar activity on long time scales

We report the results of the application of our approach to study the behavior of solar activity in the past, where:

When reconstructing the variations of solar activity, geomagnetic parameters, and the interplanetary magnetic field in the past we select a sequence of increasing time scales, which can be naturally represented by the potentials of available observational data. We select a total of four time scales: 150–200 years, 400 years, 1000 years, and 10000 years.

When constructing the series of each successive (in terms of length) time scale we use the data of the previous time scale as reference data.

We abandon, where possible, the series of traditional statistical parameters in favor of the series of physical parameters.

When deriving the relations between any parameters of solar activity, geomagnetic disturbance, and the interplanetary magnetic field, we take into account the differential nature of relations on different time scales. To this end, we use the earlier proposed MSR and DPS methods.

To verify the resulting reconstructions, we use the “principle of witnesses”, which uses independent (in some cases, indirect) information as initial data.

     

Stellar flare statistics — Physical consequences

The observational data permit us to establish clear statistical correlations between different parameters of stellar flare activity and the characteristics of quiet stars. These relations are:

1. between energies and frequencies of flares on stars of different luminosities;
2. between total radiation energies of flares and quiet stars both in X-ray and Balmer emission lines;
3. between flare decay rates just after the maxima and flare luminosities at maxima.

     

Computer simulation of observations of stars from the moon using the polar zenith telescope of the Japanese project ILOM

The paper briefly describes the purpose and features of the Japanese project ILOM (In-situ Lunar Orientation Measurement) in which it is planned to install the zenith telescope with a CCD lens on one of the poles of the Moon for the observation of stars in order to determine the physical libration of the Moon (PhLM). The studies presented in this paper are the result of the first stage of the theoretical support of the project:

1. The compilation of the list of stars within the field of view of the telescope during the precessional motion of the lunar pole.
2. Modeling and analysis of the behavior of stellar tracks during the observation period.
3. Simulation and testing of the sensitivity of the measured selenographic star coordinates to changes in the parameters of the dynamic model of the Moon and the elastic parameters of the lunar body.

Direct and inverse PhLM problems are discussed. Within the scope of the direct problem visible “daily parallels” and one-year star tracks are calculated. Their behavioral features when observed from the lunar surface are shown. At this stage of the simulation selenographic star coordinates for the four models of the gravitational field of the Moon have been compared, i.e., the model constructed on the basis of the lunar laser ranging (LLR), GLGM-2, LP150Q, and SGM100h. It is shown that even when comparing modern models LP150Q and SGM100h stellar tracks differ from the arc by more than 10 ms of arc. At the stage of the inverse problem, the manifestation of viscoelastic properties of the Moon in selenographic coordinates has been studied. In the spectrum of the simulated residual differences harmonics have been identified which can serve as indicators to refine parameters, Love number k ₂ and the delay time characterizing the viscous properties of the lunar body.     

Dwarf elliptical galaxies

Dwarf elliptical (dE) galaxies, with blue absolute magnitudes typically fainter than _MB =?16, are the most numerous type of galaxy in the nearby universe. Tremendous advances have been made over the past several years in delineating the properties of both Local Group satellite dE's and the large dE populations of nearby clusters. We review some of these advances, with particular attention to how well currently available data can constrain

1. models for the formation of dE's
2. the physical and evolutionary connections between different types of galaxies (nucleated and nonnucleated dE's, compact E's, irregulars, and blue compact dwarfs) that overlap in the same portion of the mass-spectrum of galaxies
3. the contribution of dE's to the galaxy luminosity functions in clusters and the field
4. the star-forming histories of dE's and their possible contribution to faint galaxy counts, and
5. the clustering properties of dE's.

In addressing these issues, we highlight the extent to which selection effects temper these constraints, and outline areas where new data would be particularly valuable.     

Shock remagnetization associated with meteorite impact at planetary surfaces

Shock remagnetization is a significant mode of alteration of the intensity and direction of magnetization in planetary crustal rocks subjected to the dynamic and thermochemical effects associated with meteorite impact. Shock remagnetization will take place almost instantaneously during and following the transient shock episode, and over longer times depending on residual temperature effects associated with shock heating and the production of impact melt. Remagnetization will follow certain demagnetization effects. The following transitions and residual effects will result in remagnetization of planetary crustal material:

1. First order reversible crystallographic transitions in bodycentered cubic iron-nickel alloys.
2. Second order Curie temperature transitions in face-centered cubic iron-nickel alloys.
3. Shock induced uniaxial anisotropy due to magnetoelasstic coupling of magnetic vectors to the shock wave.
4. Shock melting of iron containing silicates.
5. Subsolidus reduction and FeO decomposition.
6. Partial ther moremanence due to post-shock temperature.
7. Total thermoremanence due to post-shock temperature.
8. Production of a superparamagnetic distribution of iron which is sensitive to surface temperature fluctuation.
9. Thermal effects in metal and alloy phases.

Lunar breccia and soil samples are generally more reduced than crystalline rocks and some of th's reduction is subsolidus probably associated with the transient thermal effects due to meteorite impact in teh porous reglith.     

Evening twilight OH (7,2) band emission at Calcutta and its covariation with LI 6708 Å

Evening twilight airglow emissions of OH (7,2) band and Li 6708 Å are observed by Dunn-Manring type photometer and following important results are obtained.

1. Intensity of OH (7,2) and Li (6708 Å) decrease exponentially during evening twilight period.
2. OH (7,2) band covaries with Li (6708 Å) during evening twilight period.
3. Empirical equations of OH (7,2) band with time is obtained.
4. Possible explanations of such type of variations is also presented.

     

Lunar color boundaries and their relationship to topographic features: A preliminary survey

By combining UV negatives with IR positives of the full Moon, it is possible to suppress albedo differences and to enhance color differences between various lunar regions. Areas within the lunar maria exhibit the greatest color variations, and many have sharp boundaries. In contrast, the terrae in general show only feeble color variations, although small terra regions situated near or surrounded by maria sometimes display enhanced redness. The mare color boundaries in some cases coincide with the edges of clear-cut lava flows, the bluer material overlying the redder. One wedge-shaped area of bluer material corresponds with a prominent sinuous rille, the rille source being situated precisely in the point of the wedge. This area has obliterated portions of two ray systems, showing that the bluer material was deposited later than both the surrounding redder material and the ray material. On the other hand, rays from the crater Olbers A cross both colored areas impartially. Other examples of ray obliteration by bluer deposits are found elsewhere. From Apollo and Surveyor analyses, it is found that there is an apparent correlation between degree of blueness and titanium content of the surface materials. The following conclusions may be drawn:

1. The various maria were deposited over considerable lengths of time; this does not support the fusion-through-impact hypothesis.
2. The bluer materials, which appear to be those of high Ti content, are the more recent.
3. The hypothesis that sinuous rilles are lava drainage channels is supported.
4. The terrae covered by this study are mostly monotonous, suggesting constant composition, but a few anomalously red isolated regions may be of substantially different composition.

     

Solar flare physics enlivened by TRACE and RHESSI

The Transition Region and Coronal Explorer (TRACE) gave us the highest EUV spatial resolution and the Ramaty High Energy Solar Spectrometric Imager (RHESSI) gave us the highest hard X-ray and gammaray spectral resolution to study solar flares. We review a number of recent highlights obtained from both missions that either enhance or challenge our physical understanding of solar flares, such as:

1. Multi-thermal Diagnostic of 6.7 and 8.0 keV Fe and Ni lines
2. Multi-thermal Conduction Cooling Delays
3. Chromospheric Altitude of Hard X-Ray Emission
4. Evidence for Dipolar Reconnection Current Sheets
5. Footpoint Motion and Reconnection Rate
6. Evidence for Tripolar Magnetic Reconnection
7. Displaced Electron and Ion Acceleration Sources.

     

Multidirectional scanning of active regions with a slit-jaw spectrograph and a solar chromatograph

At the Swedish Solar Observatory in Anacapri we have simultaneously used the following combination of instruments in our investigation of active regions:

1. A spectrograph with an image rotator placed in front of the slit.
2. A subtractive double dispersive spectrograph (solar Chromatograph).
3. A Hα+0.5 Å patrol instrument. Scans over the 3b flare of August 4th 1972 are used to illustrate the method. The illustrations clearly show downflowing matter connected with bright knots and filaments in the emitting area, possibly in accordance with Hyder's infall-impact mechanism.

     

Flares and changing magnetic fields

An observational study of maps of the longitudinal component of the photospheric fields in flaring active regions leads to the following conclusions:

1. The broad-wing Hα kernels characteristic of the impulsive phase of flares occur within 10″ of neutral lines encircling features of isolated magnetic polarity (‘satellite sunspots’).
2. Photospheric field changes intimately associated with several importance 1 flares and one importance 2B flare are confined to satellite sunspots, which are small (10″ diam). They often correspond to spot pores in white-light photographs.
3. The field at these features appears to strengthen in the half hour just before the flares. During the flares the growth is reversed, the field drops and then recovers to its previous level.
4. The magnetic flux through flare-associated features changes by about 4 × 10¹⁹ Mx in a day. The features are the same as the ‘Structures Magnétiques Evolutives’ of Martres et al. (1968a).
5. An upper limit of 10²¹ Mx is set for the total flux change through McMath Regions 10381 and 10385 as the result of the 2B flare of 24 October, 1969.
6. Large spots in the regions investigated did not evince flux changes or large proper motions at flare time.
7. The results are taken to imply that the initial instability of a flare occurs at a neutral point, but the magnetic energy lost cannot yet be related to the total energy of the subsequent flare.
8. No unusual velocities are observed in the photosphere at flare time.

     

Keynote address: Outstanding problems in solar physics

Celebrating the diamond jubilee of the Physics Research Laboratory (PRL) in Ahmedabad, India, we look back over the last six decades in solar physics and contemplate on the ten outstanding problems (or research foci) in solar physics:

1. The solar neutrino problem
2. Structure of the solar interior (helioseismology)
3. The solar magnetic field (dynamo, solar cycle, corona)
4. Hydrodynamics of coronal loops
5. MHD oscillations and waves (coronal seismology)
6. The coronal heating problem
7. Self-organized criticality (from nanoflares to giant flares)
8. Magnetic reconnection processes
9. Particle acceleration processes
10. Coronal mass ejections and coronal dimming

The first two problems have been largely solved recently, while the other eight selected problems are still pending a final solution, and thus remain persistent Challenges for Solar Cycle 24, the theme of this jubilee conference.     

Climate and paleoclimate: What we can learn about solar luminosity variations

The Earth's climate is not constant, and has experienced major changes in the past on all timescales. The causes of these changes, although still incompletely understood, vary according to the timescale considered. Some of the most important causal mechanisms include continental drift, changes in the Earth's orbital parameters, volcanic activity and solar variations. Solar variations have been invoked to explain climatic change on almost all timescales from 1 to 10⁹ yr. Unfortunately, even though the Sun is a prime candidate for explaining many changes in past climate, the use of past climate as a proxy for solar luminosity changes is fraught with difficulty. For example:

1. In many cases observed changes in climate can be adequately explained without recourse to solar variations as a causal factor. In fact, on the longest timescales the Earth's climate was remarkably similar to today in spite of a considerably lower solar output.
2. For most timescales of climatic change there are, as yet, no plausible theories giving similar timescale variations in solar activity, so that a vital link between cause and effect is missing.
3. There are considerable uncertainties in the record of past climates.
4. On short timescales many proposed solar activity-climate links have failed to stand up to rigorous statistical analysis.

This paper reviews past changes in climate and proposed causal mechanisms on timescales of from 1 to 10⁹ yr. The evidence for solar activity-climate links is discussed with special reference to the above points.     

Spectral analyses of solar photospheric fluctuations

Successful subtraction of instrumental background variations has permitted spectral analyses of two-dimensional measurement arrays of granulation brightness fluctuations at the center of the disk, arrays obtained from Stratoscope I, 1959B-flight, high-resolution frames B1551 and B3241.

1. RMS's, uncorrected for instrumental blurring, are 0.0850 of mean intensity for B1551 and 0.0736 for B3241, somewhat higher than other determinations. These between-frame and between-investigation differences probably result from a combination of calibration errors, frame resolution differences, and, most likely, granulation pattern differences.
2. Significant variations over each array of mean intensities and RMS's, determined for sub-arrays with dimensions in the 2500–10000 km range, indicate spatial brightness and RMS variations larger than the ‘scale’ of the granulation pattern, supporting a turbulent interpretation of photospheric convection.
3. One-dimensional power-spectra shapes provide objective and discriminating criteria for determining granulation pattern differences and, possibly, frame resolution.
4. Two-dimensional power spectra show small, essentially random deviations from axial symmetry which lie almost entirely within the 50% confidence limits.
5. Spectral densities and fluctuation power spectra, computed from the two-dimensional power spectra and corrected for instrumental blurring, noise, and blemishes, have a useable radial wavenumber range nearly double that of earlier Stratoscope I analyses.
6. Corrected RMS's obtained from the corrected fluctuation power spectra, 0.145 ± 0.046 for B1551 and 0.136 ± 0.048 for B3241, depend critically on the accuracy of the correction.
7. The spectra's wavenumber range includes the granulation-fluctuation-producing domain but not the Kolmogoroff domain of turbulence spectra.

     

Observations of moving magnetic features near sunspots

The properties of small (< 2″) moving magnetic features near certain sunspots are studied with several time series of longitudinal magnetograms and Hα filtergrams. We find that the moving magnetic features:

1. Are associated only with decaying sunspots surrounded entirely or in part by a zone without a permanent vertical magnetic field.
2. Appear first at or slightly beyond the outer edge of the parent sunspot regardless of the presence or absence of a penumbra.
3. Move approximately radially outward from sunspots at about 1 km s^?1 until they vanish or reach the network.
4. Appear with both magnetic polarities from sunspots of single polarities but appear with a net flux of the same sign as the parent sunspot.
5. Transport net flux away from the parent sunspots at the same rates as the flux decay of the sunspots.
6. Tend to appear in opposite polarity pairs.
7. Appear to carry a total flux away from sunspots several times larger than the total flux of the sunspots.
8. Produce only a very faint emmission in the core of Hα.

A model to help understand the observations is proposed.     

Chromospheric inhomogeneities in sunspot umbrae

The properties of rapidly changing inhomogeneities visible in the H and K lines above sunspot umbrae are described. We find as properties for these ‘Umbral Flashes’:

1. A lifetime of 50 sec. The light curve is asymmetrical, the increase is faster than the decrease in brightness.
2. A diameter ranging from the resolution limit up to 2000 km.
3. A tendency to repeat every 145 sec.
4. A ‘proper motion’ of 40 km/sec generally directed towards the penumbra.
5. A Doppler shift of 6 km/sec.
6. A magnetic field of 2100 G.
7. A decrease in this field of 12 G/sec. This decrease is probably related to the flash motion.
8. At any instant an average of 3–5 flashes in a medium-sized umbra. A weak feature often persists in the umbra after the flash. This post-flash structure initially shows a blue shift, but 100–120 sec after the flash, it shows a rapid red shift just before the flash repeats.

     

Coherent mechanisms of radio emission and magnetic models of pulsars

This paper is primarily concerned with the questions of models and the mechanisms of radio emission for pulsars, the polarization of this radiation and related topic. For convenience and to provide a more complete picture of the problems involved, a short summary of the data on pulsars is also given. Besides the introduction, the paper contains the following sections:

1. Some Facts about Pulsars.
2. The Astrophysical Nature of Pulsars.
3. Coherent Mechanisms of Radio Emission from Pulsars.
4. Models of Pulsars: Magnetic, Pulsating White Dwarfs and Neutron Stars.
5. The Polarization of the Radio Emission from Pulsars.
6. A Synthesized Model of Pulsars — Magnetic, Pulsating and Rotating Neutron Stars.
7. Concluding Remarks.

     

Physical parameters of the Jovian atmosphere

The following physical parameters have been computed for the Jovian atmosphere between 270 and ?300 km: (1) Pressure, (2) Density, (3) Speed and sound, (4) Number density, (5) Density scale. It has considered that the top of the clouds is at 0 km. For the calculations of these parameters we have used:

1. for the altitudes 270-0 km data from Voyager I and II.
2. for the altitudes ?300–0 km data from Voyager II and spectroscopic observations.

     

Orbital eccentricity study for the spherical component of our galaxy

An analysis of the data concerning high-velocity stars from Eggen's catalogue aimed at a determination of the approximate slope of the mass function for the spherical component of our Galaxy, and at estimating the local circular velocity, as well as the local rotation velocity, as by-products, has been performed. Our conclusions are that:

1. A linear dependence of the mass on the radius is very likely;
2. the value of the limiting radius is most likely equal to (40±10) kpc;
3. the two local velocities are approximately equal to each other, being both equal to (230±30) km s^?1;
4. the local escape velocity appears to be most likely equal to (520±30) km s^?1;
5. the total mass of a corona, obtained in this way, is (5±1)×10¹¹ M _⊙.

     

Structure and evolutionary history of the solar system,I

1. Introduction and Survey. The method for studying the structure and evolution of the solar system is discussed. It is pointed out that theories that account for the origin of planets alone are basically insufficient. Instead one ought to aim for a general theory for the formation of secondary bodies around a central body, applicable both to planet and satellite formation. A satisfactory theory should not start from assumed properties of the primitive Sun, which is a very speculative subject, but should be based on an analysis of present conditions and a successive reconstruction of the past states.
2. Orbits of Planets and Satellites. As a foundation for the subsequent analysis, the relevant properties of planets and satellites are presented.
3. The Small Bodies. The motion of small bodies is influenced by non-gravitational forces. Collisions (viscosity) are of special importance for the evolution of the orbits. It is pointed out that the focusing property of a gravitational field (which has usually been neglected) leads to the formation of jet streams. The importance of this concept for the understanding of the comet-meteoroid relations and the structure of the asteroidal belt is shown.
4. Resonance Structure. A survey is given of the resonances in the solar system and their possible explanation. It is concluded that in many cases the resonances must already be produced at the times when the bodies formed. It is shown that resonance effects put narrow limits on the post-accretional changes of orbits.
5. Spin and Tides. Tidal effects on planetary spins and satellite orbits are discussed. It is very doubtful if any satellite except the Moon and possibly Triton has had its orbit changed appreciably by tidal effects. The isochronism of planetary and asteroidal spins is discussed, as well as its bearing on the accretional process.
6. Post-accretional Changes in the Solar System. The stability of the solar system and upper limits for changes in orbital and spin data are examined. It is concluded that much of the present dynamic structure has direct relevance to the primordial processes.

     

Distribution of active regions on the solar surface estimated by statistical methods

Statistical properties of solar active regions (AR) have been studied. In particular, (1) the distribution of ARs by their areas and importances using normal and lognormal distribution laws; (2) it was checked whether the distribution of the ARs' birth sites satisfies the Poisson distribution law (the so-called ‘law of rare events’). Observational data of 1979–1982 have been used and our conclusions are as follows:

1. As regards the areas, the distribution of the ARs that emerged near or on the borders of the large-scale background fields is normal or lognormal.
2. As regards the importances, the distribution of all ARs is lognormal.
3. The distribution of ARs that emerged far from background field borders is not normal.
4. ARs are not casual or rare events on the Sun.