Effects of charged dust grains

Dust grains expelled by radiation pressure of stars are charged to potentials in the range 30–40 V in Hi clouds. These grains may be responsible for the following phenomena which are otherwise hardly explicable. (1) A considerable fraction of electrons knocked-out by charged grains of high speeds have energies around 15 eV and produce singly ionized ions but not doubly ionized ones in accord with an ultraviolet observation of interstellar atoms and ions. (2) Transverse momentum transferred to grains by Coulomb scattering of ambient electrons and protons is greater than that by multiple scattering of cosmic ray protons, thus the former being more effective for the grain alignment than the latter. (3) At a shock front charge separation due to a large inertial mass of grains produces an electric field, thus accelerating charged particles and causing a drift of interstellar matter.     

Soft X-ray observation of theϱ ophiuchus dark cloud region

Soft X-rays (0.1–0.8 keV) from the region including the Oph dark cloud were observed with the SAS-3 low-energy X-ray telescope. No X-ray absorption by the cloud was observed. This indicates that the diffuse component of soft X-rays in this region is mostly from the foreground of the Oph cloud which is located at a distance of 160–200 pc.     

Recession rates of waterfalls in Boso Peninsula,Japan, and a predictive equation

Rates of waterfall recession, and major factors that influence the rate, were studied using waterfalls in Boso Peninsula, Japan. The mean rate of waterfall recession was estimated by determining the age and original location. The principal factor in determining the rate of waterfall recession is the ratio of the erosive force of stream to the bedrock resistance. This is expressed in terms of measurable variables, which include the discharge (drainage area and precipitation), the width and height of the waterfall, and the unconfined compressive strength of the bedrock. An empirical equation connecting the force/resistance ratios and the rates of waterfall recession is derived. Copyright © 2003 John Wiley & Sons, Ltd.     

Probing the lower ionospheric perturbations associated with earthquakes by means of subionospheric VLF/LF propagation

There have been reports for many years that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes (EQs) attracts a lot of attention as a very promising candidate for short-term EQ prediction. In this review we present a possible use of VLF/LF (very low frequency (3–30 kHz)/low frequency (30–300 kHz)) radio sounding of seismo-ionospheric perturbations. In order to avoid the overlapping with my own previous reviews, we first show some pioneering results for the Kobe EQ and we try to present the latest results including the statistical evidence on the correlation between the VLF/LF propagation anomalies (ionospheric perturbations) and EQs (especially with large magnitude and with shallow depth), medium-distance (6-8 Mm) propagation anomalies, the fluctuation spectra of subionospheric VLF/LF data (the effect of atmospheric gravity waves, the effect of Earth's tides, etc.), and the mechanism of lithosphere-atmosphere-ionosphere coupling. Finally, we indicate the present situation of this kind of VLF/LF activities going on in different parts of the globe and we suggest the importance of international collaboration in this seismo-electromagnetic study.     

Erratum to:Schumann resonance observation in China and anomalous disturbance possibly associated with Tohoku M9.0 earthquake

正Erratum to:Earthq Sci(2013)26(2):137–145DOI 10.1007/s11589-013-0009-0In the published article,first author’s name was misspelt.The correct name appears in this erratum.     

Estimation of lightning and sprite parameters based on observation of sprite-producing lightning power spectra

Spectrograms and ELF power spectra of magnetic variations originated from sprite-producing lightning discharges have been analyzed to extract both parent lightning and sprite parameters. Some of the spectrograms and power spectra have been found to have approximately quasi-oscillatory shape in the frequency range 0–40 Hz with maximum repetition period about 15–20 Hz. A theory predicts that this interesting peculiarity of the power spectra can be due to interference between electromagnetic fields originated from the parent lightning discharge and from the sprite. A smooth envelope of the power spectrum was shown to have a form of damped oscillations with period close to reciprocal value of sprite lag time. A technique of extracting sprite parameters based on the sprite-producing lightning power spectrum is proposed. The lack of the first Schumann resonance and other features occasionally observed in spectral resonance structure were also discussed.     

Q-Bursts: Natural ELF Radio Transients

We overview resonance spectra and present analytical expressions for the waveforms of natural extremely low frequency transient events (Q-bursts). It is shown that model and observed waveforms are similar when a wideband receiver is used at a place with low level of industrial interference. We also describe how to detect a natural ELF transient signal embedded in the man-made noise by using the singular spectral analysis.     

Ionization of interstellar matter by suprathermal dust grains

Suprathermal dust grains as suggested by Wickramasinghe produce electrons of energies not higher than 20 eV by Coulomb collisions with free electrons in an interstellar medium. These electrons are responsible for the production of singly ionized ions but not effective for that of highly ionized ones. This explains a general feature of the composition of atoms and ions as observed from the Copernicus satellite.