Detailed comparison between sunspot activity in ‘hot spots’ and galactic cosmic-ray intensity

The influence of sunspot activity on the condition of the solar-terrestrial environment during cycle 21 was examined using the data of sunspots and the modulation of the galactic cosmic-ray intensity. The hot spots discussed by Ichimoto et al. (1985) and Bai (1987a, 1988) were also found by analyzing the longitudinal distribution of sunspot groups.A detailed comparison between the time change of the sunspot activity in hot spots and that of the galactic cosmic rays observed by the neutron monitor reveals that several transient diminutions of the GCR intensity (with much longer duration than a Forbush decrease) occur at nearly the same time as the sporadic enhancement of sunspot area in the hot spots.Contributions from Kwasan and Hida Observatories, Kyoto University No. 303.     

Simultaneous observation of whistlers and emissions during a geomagnetically quiet period at low latitude

A unique night-time natural electromagnetic disturbances in the VLF/ELF range received during a magnetically quite period at a low latitude Indian ground station, Jammu (geomag. lat. 19°26′ N, L=1.17) has been reported. During the routine observation of VLF waves at Jammu, whistlers and different types of VLF/ELF emissions such as whistlers of varying dispersion confined to a small band limited frequency range, hisslers, pulsing hiss, discrete chorus emissions of rising and falling tones with multiple bands, oscillating tone discrete emission, whistler-triggered hook and discrete chorus risers emissions, etc. have been observed simultaneously during the quiet period on a single night. Such type of unique simultaneous observations has never been reported from any of the low latitude ground stations and this is the first observation of its kind. The results are discussed in the light of recorded features of whistlers and emissions. Generation and propagation mechanism are discussed briefly. Plasma parameters are further derived from the dispersion analysis of nighttime whistlers and emissions recorded simultaneously during magnetically quiet periods.     

The heliocentric radial gradient in cosmic ray density and the ‘swinson’ sidereal time variation

The sidereal time variation reported by Swinson depends on the existence of a heliocentric radial gradient of cosmic ray density in the rigidity range ? 100 GV and appears because of the inclination of the axis of rotation of the Earth to the normal to the ecliptic plane. It is sensitive to the polarity of the interplanetary magnetic field. Meson detectors on the surface of the Earth near the equator and at shallow underground depths can be used to measure this effect.In this paper results obtained at Makerere on the Earth's surface and at Kilembe (50 m.w.e.) in Uganda, East Africa, are compared with data previously reported by Swinson from Chacaltaya (25 m.w.e.) and Embudo (40 m.w.e.).From the relationship between the sidereal time variation and the heliocentric radial gradient it is concluded that the data are consistent with a local radial gradient of ($\text{(41 ± 8)}\text{P)}\text{\% A.U.}{}^{\mathrm{?1}}$ in the rigidity range 15 < P ? 100 GV during 1967–1971, a period including the most recent solar maximum. This estimate is consistent with modulation theory and the prevailing power spectrum in the interplanetary magnetic field.The Swinson effect is not appreciable at depths of more than 50 m.w.e. underground.     

The observation of a ‘negative burst’ with high spatial resolution

The case of a short-time disappearance of the S-component source over the active region is described and its association with events in H is discussed. Under the assumption that in this case the radio source was observed to be covered by coronal mass ejection caused by filament eruption, estimates are made of the velocity of the ejection, its linear size and of the optical thickness.     

Generalized ‘dependencies’ and parameter variance

The autodependence, (a special case of the — now quite obsolete — dependences, which had been introduced for very specialized astrometric purposes) is proportional to the parameter variance which is the expectation of the variance of the systematic error of a function evaluated with estimated parameters.     

On two different types of sunsports-‘vortices’ and ‘sources’-within A U(1)-symmetric Yang-Mills-Higgs system

An intimate link between the structure of the sunspot's magnetic field contiguration and the behaviour of the Higgs field phase at large distances from spot's center is discussed within a U(1)-symmetric Yang-Mills-Higgs gauge theory. It is shown, in particular, that the total magnetic flux of standard sunspots can acquirediscrete values only. A conclusion is also arrived at that, in addition to standard sunspots (magneticvortices), a new sort of sunspots (magneticsources (sinks)), whose total magnetic flux iszero, could principally be observed on the Sun; the two sorts of spots are shown to stand in adual orcomplementary relation to each other. In this connection, finally, a question about the possible role of the divergence of electromagnetic potential — the field violating a gauge invariance of the theory — in physics of two-dimensional solar phenomena is briefly touched.     

A class of exact isotropic solutions of Einstein’s equations and relativistic stellar models in general relativity

In this paper we have studied a particular class of exact solutions of Einstein’s gravitational field equations for spherically symmetric and static perfect fluid distribution in isotropic coordinates. The Schwarzschild compactness parameter, GM/c ² R, can attain the maximum value 0.1956 up to which the solution satisfies the elementary tests of physical relevance. The solution also found to have monotonic decreasing adiabatic sound speed from the centre to the boundary of the fluid sphere. A wide range of fluid spheres of different mass and radius for a given compactness is possible. The maximum mass of the fluid distribution is calculated by using stellar surface density as parameter. The values of different physical variables obtained for some potential strange star candidates like Her X-1, 4U 1538–52, LMC X-4, SAX J1808.4?3658 given by our analytical model demonstrate the astrophysical significance of our class of relativistic stellar models in the study of internal structure of compact star such as self-bound strange quark star.     

Pitch angle scattering of solar particles: Comparison of ‘particle’ and ‘field’ approach

In the quasi-linear theory of pitch angle scattering the power spectrum of magnetic field fluctuations is related to the shape of the pitch angle diffusion coefficient D(), the absolute value of the mean free path , and the rigidity dependence of the mean free path (R). We discuss these relations in detail during the solar particle event of 11 April, 1978 which was observed on HELIOS-2 at a distance of 0.49 AU from the Sun. Magnetic field measurements obtained during the time of the event are used as a basis for the layer model in which the method of particle trajectories in an actually measured field is used to simulate pitch angle diffusion. The values of D() and based on the trajectory simulation for 100 MeV protons (field approach) are compared with results obtained from solar proton data (particle approach) and with predictions from quasi-linear theory based on the additional assumption of the slab model for magnetic field fluctuations (QLT approach). The time of the event is characterized by a high level of field fluctuations, the observed mean free path of about 0.03 AU for 100 MeV protons is smaller than the average value near 1 AU. Results from the field and particle approaches agree surprisingly well. The remaining difference in the mean free path of about a factor of 2 could be due to tangential discontinuities which are measured by the magnetometer, but not seen by the real particles traveling along the average field. The results from the field and QLT approaches based on the same set of magnetic field measurements differ by about a factor of 4. One of the reasons for this discrepancy is that the conditions for resonance scattering are only marginally valid. In addition, the wave vectors representing Alfvén-type fluctuations may not be totally field aligned. This deviation from the slab model would cause an increase of the theoretically predicted mean free path and lead to better agreement with the other two approaches.     

A distinctive type of ascending prominence — ‘fountain’

Cinematographic observations of solar prominences made at Mauna Loa during the past couple of years suggest that there is a well-defined sub-class of ascending prominences characterized by closed-system transference of chromospheric material along an arch or loop (up one leg and down the other); meanwhile the entire prominence envelope steadily rises upward and expands through the corona. We denote these prominences as fountains. Several examples are described. Fountains appear to be well contained by coronal magnetic fields. Their total kinetic energy is in the order of 10³⁰ erg but dissipation is typically quite slow (over time periods like 100 min) so that the correlative disturbances (radio bursts, coronal transients, chromopsheric brightenings, etc.) are generally unspectacular or non-existent.This research was started when E. T.-H. was still on the staff of the High Altitude Observatory.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Mass and particle ‘loading’ in plasma-neutral gas interaction

Qualitative considerations of mass and particle loading in plasma-neutral gas interaction are made by the help of a one-dimensional steady model. In the case of particle loading the plasma flow behind a strong shock is accelerated as in the case of mass loading regarded by Biermannet al. (1967) whereas behind a weak shock the flow is decelerated. As an example, one-dimensional time-dependent flows with ionization of the neutral gas by Alfvén's critical velocity effect are calculated. Because of the acceleration of the subsonic flow by loading processes, the existence of a tangential discontinuity in the flow around comets seems questionable.     

Coronal magnetic storms: A new perspective on flares and the ‘solar flare myth’ debate

Recently Gosling (1993) examined the interplanetary consequences of solar activity, and suggested that the coronal mass ejection (CME) was the prime driver of most disturbances (i.e., interplanetary shocks, high-energy particles, geomagnetic storms, etc.) and that the solar flare was relatively unimportant in this context. He coined the phrase Solar Flare Myth. Since that paper there has been much debate on the origin of interplanetary disturbances - most people sitting squarely in the flare or CME camp. vestka (1995) has attacked Gosling's conclusions on the grounds that it is misleading to ignore the flare, and that past flare classifications were perfectly adequate for explaining the observations described by Gosling. This paper is a comment on vestka's report and an attempt to put the Solar Flare Myth into perspective - indeed it is an attempt to view the solar flare/CME phenomena in a more constructive light.     

Variations of ‘wavelengths’ and ‘bisector indices’ of 70 solar spectral lines between 3300 and 3960 Å in Kitt Peak FTS spectra

Wavelengths and bisector indices (a special measure for the asymmetry of a line near its bottom) are determined for 70 lines in each of 47 high-dispersion spectra. The spectra were obtained with the Fourier Transform Spectrograph connected to the McMath Telescope at Kitt Peak National Observatory; they all cover the same spectral range from 3200 to 4000 Å and concern either the full disk (19 disk spectra), or the disk center (9 center spectra), or two areas at sin = 0.85 on the west- and east-side of the disk (19 limb spectra). The main observing seasons were June 1986, June 1987, April and June/July 1988. The - relative - position of an individual line in one spectrum can be established with a precision of about 4 m s^-1, the precision of one bisector index is 1–2 m s^-1.Wavelengths and bisector indices show of course the typical characteristics which result from the familiar effects known as blueshift, limb effect and line asymmetry. However, concerning their variations in time, unexpected results are obtained:(1) Even in disk spectra the time-scales of the wavelength variations are often in the order of one hour or less. (2) For all 3 types of spectra (disk, center, limb) the variations depend not only on the known parameters such as line depth and - occasionally - excitation potential, but also - often even primarily - on wavelength. (3) In center spectra, the wavelength differences between strong and faint lines can vary by as much as 500 m s^-1, in disk spectra short-time variations of wavelength differences can amount to more than 50 m s^-1. (4) For most spectra there is not only a very pronounced and narrow correlation between line shift and line temperature (a special measure for the line depth), but also a significant correlation between line shift and variation of the bisector index.Clearly, the observed effects must be attributed to variations of the velocity fields in the upper photosphere/lower chromosphere (super-granulation cells, overshooting, oscillations), which either influence the line wavelengths directly via the Doppler-effect, or indirectly by changing the contrast between the blue-shifted granules and the red-shifted intergranular lanes. Because of the snapshot character of the observations, no reliable conclusions can be drawn on the actual time-dependency.     

Short-term periodicities of the sun's ‘mean’ and differential rotation

We have looked for periodicities in solar differential rotation on time scales shorter than the 11-year solar cycle through the power- spectrum analysis of the differential rotation parameters determined from Mt. Wilson velocity data (1969–1994) and Greenwich sunspot group data (1879–1976). We represent the differential rotation by a set of Gegenbauer polynomials (()= + (5sin₂–1)+ (21sin₄–14sin₂+1)). For the Mt. Wilson data, we focus on observations obtained after 1981 due to the reduced instrumental noise and have binned the data into intervals of 19 days. We calculated annual averages for the sunspot data to reduce the uncertainty and corrected for outliers occuring during solar cycle minima. The power spectrum of the photospheric mean rotation , determined from the velocity data during 1982–1994, shows peaks at the periods of 6.7–4.4 yr, 2.2 ± 0.4 yr, 1.2 ± 0.2 yr, and 243 ± 10 day with 99.9% confidence level, which are similar to periods found in other indicators of solar activity suggesting that they are of solar origin. However, this result has to be confirmed with other techniques and longer data sets. The 11-yr periodicity is insignificant or absent in . The power spectra of the differential rotation parameters and , determined from the same subset, show only the solar cycle period with a 99.9% confidence level.The time series of determined from the yearly sunspot group data obtained during 1879–1976 is very similar to the corresponding time series of . After correcting for data with large error bars (occurring during cycle minima), we find periods, which are most likely harmonics of the solar cycle, such as 18.3 ± 3.0 yr and 7.5 ± 0.5 yr in and confirmed these and the 3.0 ± 0.1 yr period in . The original time series show in addition some shorter periods, absent in the corrected data, representing temporal variations during cycle minimum. Given their large error bars, it is uncertain whether they represent a solar variation or not. The results presented here show considerable differences in the periodicities of and determined from the velocity data and the spot group data. These differences may be explained by assuming that the rotation rates determined from velocity and sunspot data represent the rotation rates of the Sun's surface layers and of somewhat deeper layers.     

‘Similar’ coordinate systems and the Roche geometry: application

A new equivalence relation, named relation of ‘similarity’ is defined and applied in the restricted three-body problem. Using this relation, a new class of trajectories (named ‘similar’ trajectories) are obtained; they have the theoretical role to give us new details in the restricted three-body problem. The ‘similar’ coordinate systems allow us in addition to obtain a unitary and an elegant demonstration of some analytical relations in the Roche geometry. As an example, some analytical relations published by Seidov (in Astrophys. J. 603:283, 2004) are demonstrated.     

Determining parameters of Moon’s orbital and rotational motion from LLR observations using GRAIL and IERS-recommended models

The aim of this work is to combine the model of orbital and rotational motion of the Moon developed for DE430 with up-to-date astronomical, geodynamical, and geo- and selenophysical models. The parameters of the orbit and physical libration are determined in this work from lunar laser ranging (LLR) observations made at different observatories in 1970–2013. Parameters of other models are taken from solutions that were obtained independently from LLR. A new implementation of the DE430 lunar model, including the liquid core equations, was done within the EPM ephemeris. The postfit residuals of LLR observations make evident that the terrestrial models and solutions recommended by the IERS Conventions are compatible with the lunar theory. That includes: EGM2008 gravitational potential with conventional corrections and variations from solid and ocean tides; displacement of stations due to solid and ocean loading tides; and precession-nutation model. Usage of these models in the solution for LLR observations has allowed us to reduce the number of parameters to be fit. The fixed model of tidal variations of the geopotential has resulted in a lesser value of Moon’s extra eccentricity rate, as compared to the original DE430 model with two fit parameters. A mixed model of lunar gravitational potential was used, with some coefficients determined from LLR observations, and other taken from the GL660b solution obtained from the GRAIL spacecraft mission. Solutions obtain accurate positions for the ranging stations and the five retroreflectors. Station motion is derived for sites with long data spans. Dissipation is detected at the lunar fluid core-solid mantle boundary demonstrating that a fluid core is present. Tidal dissipation is strong at both Earth and Moon. Consequently, the lunar semimajor axis is expanding by 38.20 mm/yr, the tidal acceleration in mean longitude is \(-25.90 {{}^{\prime \prime }}/\mathrm{cy}^2\), and the eccentricity is increasing by \(1.48\times 10^{-11}\) each year.     

Rapid changes in the fine structure of a coronal ‘bright point’ and a small coronal ‘active region’

A coronal bright point is resolved into a pattern of emission which, at any given time, consists of 2 or 3 miniature loops (each 2500 km in diameter and 12 000 km long). During the half-day lifetime of the bright point individual loops evolved on a time scale 6 min. A small ctive region seemed to evolve in this way, but the occasional blurring together of several loops made it difficult to follow individual changes.     

Guide and examples for users of the ‘spacekap’ style file

Guide and examples for users of the spacekap style fileBasic instructions     

Guide and examples for users of the ‘SPACEKAP’ style file

Guide and examples for users of the SPACEKAP style fileBasic instructions     

Guide and examples for users of the ‘SPACEKAP’ style file

Guide and examples for users of the SPACEKAP style fileBasic instructions