On a sequence of remarkable fine structures in the type IV burst of 24 April, 1985

During the type IV burst on 24 April, 1985 we observed at 234 MHz an untypical, strong, nearly six hours lasting continuum emission incorporating several groups of broadband pulsations, zebra patterns, fiber bursts, and a new fine structure phenomenon. The power spectra of the groups of broadband pulsations reveal no simple structure. There is only one common periodic component between 0.3 s and 0.4 s. Slowly drifting chains of narrowband fiber bursts are described as a new fine structure by spectrograms and simultaneously recorded single frequency intensity profiles. A qualitative model of this new fine structure is suggested.     

Ultraviolet solar irradiance measurement from 200 to 358 nm during spacelab 1 mission

The paper presents the results obtained from the UV-spectrometer of the Solar Spectrum Experiment during the Spacelab 1 mission in December 1983. The irradiance data concern 492 passbands, which are located between 200 and 358 nm at almost equidistant wavelengths separated by about 0.3 nm. The passbands have a well-defined, bell-shaped profile with a full width at half maximum of about 1.3 nm. The data, which have an error budget between 4 and 5%, agree closely with the spectral distributions observed by Heath (1980) and Mentall et al. (1981) and confirm that the solar irradiance and the fluxes of Sun-like stars show about the same spectral distribution down to at least 240 nm.     

Observations of longperiod mass velocity oscillations in the Sun's chromosphere

Observations made by the differential method in the H line have revealed longperiod (on a timescale of 40 to 80 min) line-of-sight velocity oscillations which increase in amplitude with distance from the centre to the solar limb and, as we believe, give rise to prominence oscillations. As a test, we present some results of simultaneous observations at the photospheric level where such periods are absent.Oscillatory processes in the solar chromosphere have been studied by many authors. Previous efforts in this vein led to the detection of shortperiod oscillations in both the mass velocities and radiation intensity (Deubner, 1981). The oscillation periods obtained do not, normally, exceed 10–20 min (Dubov, 1978). More recently, Merkulenko and Mishina (1985), using filter observations in the H line, found intensity fluctuations with periods not exceeding 78 min. However, the observing technique they used does not exclude the possibility that those fluctuations were due to the influence of the Earth's atmosphere. It is also interesting to note that in spectra obtained by Merkulenko and Mishina (1985), the amplitude of the 3 min oscillations is anomalously small and the 5 min period is altogether absent, while the majority of other papers treating the brightness oscillations in the chromosphere, do not report such periods in the first place. So far, we are not aware of any other evidence concerning the longperiod velocity oscillations in the chromosphere on a timescale of 40–80 min.Longperiod oscillations in prominences (filaments) in the range from 40 to 80 min, as found by Bashkirtsev et al. (1983) and Bashkirtsev and Mashnich (1984, 1985), indicate that such oscillations can exist in both the chromosphere and the corona (Hollweg et al., 1982).In this note we report on experimental evidence for the existence of longperiod oscillations of mass velocity in the solar chromosphere.     

Hydrogen emission from moving solar prominences

Brightness variations of the lines arising from a five-level hydrogen model atom, depending upon prominence velocities, have been investigated using a combination of two non-LTE techniques. The importance of the Doppler brightening and/or Doppler dimming effects is demonstrated for the lines of the Lyman and Balmer series.On leave from Wroclaw University Observatory, Poland.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Evidence for interacting loop process in a phase of the May 16, 1981 flare

The behaviour of the flare in the period of enhancement and maximum of hard X-ray, microwave and decimetric type IV continuum is analysed. The elongation of the H ribbons and microwave source disclose that the energy release site was shifting through a system of loops with a velocity less than 200 km s^-1, and that the energy was carried down the field lines with a velocity of about 1000 km s^-1, implying the thermal conduction front mechanism of energy transport. Several processes of energy release are considered and it is concluded that an explanation in terms of succeeding interactions of neighbouring loops, involving fast reconnection of their poloidal components is in best agreement with the observations.Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.     

A photometric search for solar giant convection cells

We limit the photometric contrast of solar giant convection cells using 525.6 nm continuum images obtained on 15 days in May 1985. The r.m.s. of the giant cell intensity pattern must be less than or equal to the observed r.m.s. on spatial scales 80 to 240 Mm which is 0.023% or, equivalently, 0.33 K. However, the spatial scale and time-scale dependence of the variance demonstrate that giant cells are not the source of the observed variance. Consequently, a tighter constraint on the r.m.s. of the giant cell pattern may be placed, namely 0.016% or 0.23 K. This limit is consistent with temperature perturbations estimated from recent nonlinear simulations of global-scale solar convection. We use this limit on the r.m.s. of the giant cell pattern to estimate that the contribution of giant cells to the fluctuation of the solar irradiance on a one-month time-scale is less than 3 × 10^–5 S.     

Group Doppler effect in anisotropic plasmas

In anisotropic plasmas, the radiative power emitted and the power observed per unit solid angle should be calculated along the direction of the group velocityv _g . The two power functions referred differ by a product of two factors: one is the group Doppler factor and the other is the squeezing effect of the radiative energy due to the dependence ofv _g on direction. In this paper, the group Doppler factor is derived using two different methods, and the relevant physical concepts are analyzed in details. A number of numerical examples pertaining to astrophysical situations are presented, to illustrate the significance of the group Doppler effect with respect to the wave Doppler effect which is valid in isotropic media.     

Velocity-height relation for antimatter meteors

A general velocity-height relation for both antimatter and ordinary matter meteor is derived. This relation can be expressed as % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaacq% aHfpqDdaWgaaWcbaGaamOEaaqabaaakeaacqaHfpqDdaWgaaWcbaGa% eyOhIukabeaaaaGccqGH9aqpcaqGLbGaaeiEaiaabchacaqGGaWaam% WaaeaacqGHsisldaWcaaqaaiaadkeaaeaacaWGHbaaaiaabwgacaqG% 4bGaaeiCaiaabIcacaqGTaGaamyyaiaadQhacaGGPaaacaGLBbGaay% zxaaGaeyOeI0YaaSaaaeaacaWGdbaabaGaamOqaiabew8a1naaBaaa% leaacqGHEisPaeqaaaaakmaacmaabaGaaGymaiabgkHiTiaabwgaca% qG4bGaaeiCamaadmaabaGaeyOeI0YaaSaaaeaacaWGcbaabaGaamyy% aaaacaqGLbGaaeiEaiaabchacaqGOaGaaeylaiaadggacaWG6bGaai% ykaaGaay5waiaaw2faaaGaay5Eaiaaw2haaiaacYcaaaa!64FD!\[\frac{{\upsilon _z }}{{\upsilon _\infty }} = {\text{exp }}\left[ { - \frac{B}{a}{\text{exp( - }}az)} \right] - \frac{C}{{B\upsilon _\infty }}\left\{ {1 - {\text{exp}}\left[ { - \frac{B}{a}{\text{exp( - }}az)} \right]} \right\},\]where _z is the velocity of the meteoroid at height z, its velocity before entrance into the Earth's atmosphere, is the scale-height, and C parameter proportional to the atom-antiatom annihilation cross- section, which is experimentally unknown. The parameter B (B = DA₀/m) is the well known parameter for koinomatter (ordinary matter) meteors, D is the drag factor, ₀ is the air density at sea level, A is the cross sectional area of the meteoroid and m its mass.When the annihilation cross-section is zero — in the case of ordinary meteors — the parameter C is also zero and the above derived equation becomes % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaacq% aHfpqDdaWgaaWcbaGaamOEaaqabaaakeaacqaHfpqDdaWgaaWcbaGa% eyOhIukabeaaaaGccqGH9aqpcaqGLbGaaeiEaiaabchacaqGGaWaam% WaaeaacqGHsisldaWcaaqaaiaadkeaaeaacaWGHbaaaiaabwgacaqG% 4bGaaeiCaiaabIcacaqGTaGaamyyaiaadQhacaGGPaaacaGLBbGaay% zxaaGaaiilaaaa!4CF5!\[\frac{{\upsilon _z }}{{\upsilon _\infty }} = {\text{exp }}\left[ { - \frac{B}{a}{\text{exp( - }}az)} \right],\]which is the well known velocity-height relation for koinomatter meteors.In the case in which the Universe contains antimatter in compact solid structure, the velocity-height relation can be found useful.Work performed mainly at the Nuclear Physics Laboratory of the National University of Athens, Greece.     

Direct generation of solar and stellar radio bursts by energetic electron maser

A fully relativistic electron maser is proposed for the explanation of certain non-thermal solar and stellar radio bursts. This mechanism (maser synchrotron) is based on a gyroresonant interaction between waves and electrons of high energies and uses the free energy contained in an electronic distribution function that peaks for energies around 1 MeV.By a calculation of the growth rates of the three electromagnetic modes, we show that the X-mode prevails for values of _p/ _cup to 2 or 3. This result is very different from the standard cyclotron maser case where such values of _p/ _clead to quench the X-mode growth. Hence, the synchrotron maser instability appears to be a direct and efficient amplification process for considerably larger physical conditions than the cyclotron maser. In addition, the radiation, emitted over the second gyroharmonic, freely propagates without a strong reabsorbtion at the 2 _clayer. All these points can constitute major advantages of this mechanism in an astrophysical context.Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.     

Annual variation of atmospheric carbonyl sulfide in the marine atmosphere in the Southern Indian Ocean

Measurements of the concentrations of carbonyl sulfide (COS) in the marine atmosphere were made over a period of two years in the southern Indian Ocean (Amsterdam Island, 37°50 S–77°31 E; March 1987–February 1988 and April 1989–February 1990). The mean atmospheric COS concentration for the whole period was 475±48 pptv (n=544). Atmospheric COS concentrations show no significant seasonal variation with a summer to winter ratio of 1.05. Taking into account the observed variability of the atmospheric COS concentration (10%), a value of 1.4 yr is estimated as a lower limit for the atmospheric COS lifetime. A comparison of the COS data at Amsterdam Island with those obtained in the Southern Hemisphere in the past 12 yr does not reveal any significant trend in the tropospheric background COS mixing ratio.