Dynamics of auroral absorption in the midnight sector—The movement of absorption peaks in relation to the substorm onset

The movement of peaks of auroral radio absorption is studied using observations made with networks of spaced riometers in Canada and Alaska. It is found that on the average the movement of absorption peaks differs significantly from that of the onset of the A.A. substorm and in individual cases the motions of onset and subsequent peaks appear to be independent. This is taken to indicate that the time-structure of auroral absorption with periods between several minutes and an hour or two represents in general a space-time structure within the envelope of the overall substorm, involving additional mechanisms.Two classes of absorption peak are identified within the substorm. Those occurring within 10 min of the onset move more rapidly and may travel towards or away from the pole; those occurring after 30 min are of longer duration and move relatively slowly and only towards the equator. By comparison with the recovery phase of the substorm in luminous aurora it is speculated that the late peaks may indicate magnetospheric electric fields.     

Radial dependence of solar wind parameters in the ecliptic (1.1 R ⊙−61 AU)

The radial dependencies of four solar wind parameters (plasma density N, velocity V, temperature T, and magnitude of the interplanetary magnetic field B) are derived from remote sensing data of the solar corona and from in situ measurements in the heliosphere (Helios-1, 2, Pioneer-10, 11, and Voyager-1, 2). Using doubly logarithmic scaling (solar wind parameter vs radial distance from the Sun) one finds two distinct intervals in the ecliptic, i.e., an exponential section within, approximately, the inner heliosphere and a linear section - up to at least 61 AU - in the outer heliosphere.     

Frequency dependence of solar flare occurrence rates—inferred from power-law distribution

Based on the frequency dependence of the power-law distribution of the peak fluxes in 486 radio bursts in 1–35 GHz observed by Nobeyama Radio Polarimeters (see Song et al. in Astrophys. J. 750:160, 2012), we have first suggested in this paper that the events with power-law behaviors may be emitted from the optically-thin regions, which can be considered as a good measure for the flare energy release. This result is supported by that both the power-law and optical-thin events gradually increase with radio frequencies, which are well fitted by a power-law function with similar indices of 0.48 and 0.80, respectively. Moreover, a flare occurrence rate is newly defined by the power-law event number in per unit frequency. Its values in lower frequencies are evidently larger than those in higher frequencies, which just imply that most flares are trigged in higher corona. Hence, the frequency variation of power-law event number may indicate different energy dissipation rates on different coronal heights.     

Infrared spectroscopy of micro-organisms near 3,4 μm in relation to geology and astronomy

Microorganisms sealed in KBr dises have an absorption spectrum over the 2.5–15 m waveband that shows thermal stability as they are heated in an inert atmosphere to temperatures of about 400°C. Microfossils tightly sealed within cavities in rocks could be endowed with similar properties of thermal stability. The observed absorption of interstellar material along the line of sight from the solar system to the galactic centre is remarkably similar to the spectrum of dry micro-organisms over the 3.15–3.7 m waveband.     

On the centre-to-limb variation and latitude dependence of the asymmetry and wavelength shift of the solar line λ 5576

Low noise photoelectric measurements of the line profile of the g = 0 Fe line gl 5576.097 combined with determinations of the wavelength shift of its centre calibrated by use of an I ₂ absorption tube are reported. Measurements taken at various limb distances (1.0 cos 0.2) and along 4 different diameters of the Sun are used to investigate the behaviour of the line asymmetry (C-shape) and wavelength shift of the line centre as functions of cos and of latitude and to search for possible pole-equator differences.An accuracy of approx. 0.8 mÅ r.m.s. is achieved for the determination of the centre of the solar line relative to the iodine lines and of 0.3 mÅ to 1 mÅ r.m.s. for the relative variations of the C-shape. The analysis shows a significant difference between the limb-effect curves along polar and equatorial diameters for cos 0.4 and changes of the C-shape for 0.9 cos 0.6 with a rather strong indication of a latitude dependence of the C-shape. This latitude dependence may account for the so-called ears observed by Howard et al. (1980) who used the well-known Doppler compensator method which integrates the line asymmetry from the line wings to the core.Mitteilungen aus dem Kiepenheuer-Institut Nr. 207.     

Role of the solar wind parameters in changing orbital motion of the Earth’s satellites

The investigation of the solar wind and geomagnetic activity parameters' effect on variations of the orbital motion periods of artificial satellites has been continued. The periods of orbital motion of uncontrolled satellites from the database of the Ukrainian network of optical stations (UNOS) for 2012–2014 was used. The data have been compared with the values of geomagnetic planetary index K and the energy spectra of protons and electrons obtained by the GEOS satellites in events during which the orbital periods have changed. It is shown that, in the energy spectra of the proton and electron fluxes, there is no effect of softening the spectrum with time at the time of the flare appearance. This indicates the possibility of particle accumulation above the active region (AR), which entails further continuous energy emission of the solar flare from AR. Dependences have been obtained between the geomagnetic activity and the solar wind speed at a given interplanetary magnetic field strength during the periods under study for the changes in the orbital motion periods of satellites. The corresponding correlation coefficients are 0.93–0.96.     

The effects of solar and ionospheric parameters on seasonal variation of 6300 Å line emission at Calcutta

The purpose of this paper is to find correlation between OI 6300 Å line intensity with solar and ionospheric parameters. A critical study have been made and the following important results are obtained:

Heating and acceleration of α-particles in the solar wind

The non-linear saturation of whistler mode instability in the solar wind is considered here. The resulting heating and acceleration are calculated. It is shown that this instability heats predominantly the -particles and the ratio of heating rates of -particles to ions have been calculated. This instability is shown to be effective in accelerating -particles than ions. However, this process cannot account for V /V _i 1.     

A comparative study of Hα-flares of different visual features in relation to radio bursts and sunspots

Solar H-flares now reported with their distinctive visual features have been statistically examined for a period of about eight years in relation to their different characteristics, flare-burst and flare-sunspot association. Important results obtained are: (i) Integrated intensity changes from the highest to the lowest values in the order F, H, E, and D flare type, whereas, impulsiveness in the order H, F, E, and D type, (ii) Flare-burst association is frequency dependent and is highest and lowest for H and D types respectively in almost all the frequencies, (iii) Most of the flares of D, E, and F types are associated with sunspots of _p , _p , and configurations having field strength 1500–2500 G, while that of H type with _p and configurations having field strength 1000–2000 G.     

GETEMME—a mission to explore the Martian satellites and the fundamentals of solar system physics

GETEMME (Gravity, Einstein??s Theory, and Exploration of the Martian Moons?? Environment), a mission which is being proposed in ESA??s Cosmic Vision program, shall be launched for Mars on a Soyuz Fregat in 2020. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive Laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine Laser range measurements to the reflectors on Phobos and Deimos. Also, asynchronous two-way Laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellite system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter ?? as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame.     

Mass—luminosity relation and pulsational properties of Wolf—Rayet stars

The evolution of Population I stars with initial masses 70M _⊙ ≤ M _ZAMS ≤ 130M _⊙ is considered. The computations were performed under various assumptions about the mass loss rate and were terminated at the phase of gravitational contraction after core helium exhaustion. The mass loss rate at the helium burning phase, ?_3α , is shown to be the main parameter that determines the coefficients of the mass—luminosity relation for Wolf—Rayet stars. Several more accurate mass—luminosity relations for mass loss rates ? = f _3α ?_3α , where 0.5 ≤ f _3α ≤ 3, are suggested, along with the mass—luminosity relation that combines all of the evolutionary sequences considered. The results of the stellar evolution computations were used as initial conditions in solving the hydrodynamic equations describing the spherically symmetric motions of a self-gravitating gas. The outer layers of massive Population I stars are unstable against radial oscillations throughout the helium burning phase. The oscillation amplitude is largest at enhanced carbon and oxygen abundances in the outer stellar layers, i.e., at a lower initial stellar mass M _ZAMS or a lower mass loss rate during the entire preceding evolution. In the course of evolution, the radial oscillation amplitude decreases and the small nonlinearity of the oscillations at M < 10M _⊙ allow the integral of mechanical work W done by an elementary spherical layer of gas in a closed thermodynamic cycle to be calculated with the necessary accuracy. The maximum of the radial dependence of W is shown to be located in layers with a gas temperature T ～ 2 × 10⁵ K, where the oscillations are excited by the iron Z-bump κ-mechanism. Comparison of the radial dependences of the integral of mechanical work W and the amplitude of the radiative flux variations suggests that the nonlinear radial oscillations of more massive Wolf—Rayet stars are also excited by the κ-mechanism.     

Properties of energetic electrons of magnetospheric origin in the magnetosheath and in the solar wind—correlation with geomagnetic activity

Bursts of energetic electrons (from >40keV up to 2MeV) as distinct from the magnetopause electron layer observed by Domingo et al. (1977) have been observed in the magnetosheath and in the solar wind by HEOS-2 at high-latitudes. Although these electrons are occasionally found close to the bow shock and simultaneously with low frequency (magnetosonic) upstream waves our observations strongly indicate that these electrons are of exterior cusp origin. Indeed, the flux intensity is highest in the exterior cusp region and decreases as the spacecraft moves away from it both tailward or upward. The energy spectrum becomes harder with increasing radial distance from the exterior cusp. The measured anisotropy indicates that the particles are propagating away from the exterior cusp. The magnetic field points to the exterior cusp region when these electrons are observed, being, for solar wind observations, centred at longitude 0° or 180° rather than along the spiral and in the magnetosheath, being usually different from the 90° or 270° orientation typical of that region. We exclude, therefore, that acceleration in the bow shock is the source of these particles because $\text{B}$ is not tangent to the shock when bursts are observed. We have also found a one to one correlation between geomagnetic storms' recovery phases and intense, continuous observations of >40 keV electrons in the magnetosheath, while, on the other hand, during geomagnetically quiet (Dst) periods bursts are observed only if AE is much larger than average.     

High resolution observation of Hα solar flares and temporal relation between Hα and X-ray,microwave emission

We studied the evolutional characteristics of fine structures in H flare emitting regions and their relation to X-ray and microwave emissions for selected events observed with the 60 cm Domeless Solar Telescope at Hida Observatory, University of Kyoto. The principal conclusions of this investigation are: (1) H kernel consists of some finer bright points or Hflare points whose individual size is less than 1 arc sec. (2) Impulsive brightnenings of H flare points occurred simultaneously with the spikes of the hard X-ray and microwave bursts within the time resolution of our H observations which varied from 1 to 10 s. (3) It is concluded that fast electron beams must be the principal mechanism of heating H flares during the impulsive phase of a flare.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. Contributions from the Kwasan and Hida Observatories, University of Kyoto, No. 265.     

Periodic and quasi-periodic motions of a solar sail close to SL 1 in the Earth–Sun system

Solar sails are a proposed form of spacecraft propulsion using large membrane mirrors to propel a satellite taking advantage of the solar radiation pressure. To model the dynamics of a solar sail we have considered the Earth–Sun Restricted Three Body Problem including the Solar radiation pressure (RTBPS). This model has a 2D surface of equilibrium points parametrised by the two angles that define the sail orientation. In this paper we study the non-linear dynamics close to an equilibrium point, with special interest in the bounded motion. We focus on the region of equilibria close to SL ₁, a collinear equilibrium point that lies between the Earth and the Sun when the sail is perpendicular to the Sun–sail direction. For different fixed sail orientations we find families of planar, vertical and Halo-type orbits. We have also computed the centre manifold around different equilibria and used it to describe the quasi-periodic motion around them. We also show how the geometry of the phase space varies with the sail orientation. These kind of studies can be very useful for future mission applications.     

Structure of the region of solar wind—Interstellar medium interaction and its influence on H atoms penetrating the solar wind

The structure of the region of interaction between the solar wind and the interstellar medium in the two-shocks model (TSM), first suggested by Baranovet al. (1970), is numerically calculated.For this problem our model is true only for charged particles of the interstellar medium interacting with the solar wind, since the free paths of neutral particles are very long and any hydrodynamical approximation would be incorrect.The shapes of the outer and inner shocks, the shape of the contact surface and the distribution of the parameters inside the interaction region are calculated, and are universal and correct for other astrophysical applications such as interstellar bubbles (Weaveret al., 1977), the stellar wind flow around a globule (Dyson, 1975), the interaction of stellar winds in binaries (Prilutzky and Usov, 1976), and so on.The problem of the effect of the charge exchange of H atoms with interstellar gas protons decelerated by an outer shock on H atoms penetrating the solar system is considered using the calculated results (Wallis, 1975). This effect is shown to influence essentially the estimate of H-atom concentration in the interstellar medium based on theL -scattering data.     

Numerical simulations of kinetic Alfvén waves to study spectral index in solar wind turbulence and particle heating

We present numerical simulations of the modified nonlinear Schrödinger equation satisfied by kinetic Alfvén waves (KAWs) leading to the formation of magnetic filaments at different times. The relevance of these filamentary structures to solar wind turbulence and particle heating has also been pointed out.