Comparison between the NEIC broadband radiated energy catalogue and the Harvard CMT catalogue provides information about the properties of apparent stress. Based on the numerical studies of Shaw (1998) we examined the ratio of broadband radiated energy and scalar seismic moment of shallow earthquakes worldwide from 1987 to 1998. It is observed that for different focal mechanisms, scaling of apparent stress or ‘scaled energy’ with seismic moment is different. For thrust and normal events, apparent stress decreases with seismic moment; while for strikeslip events, apparent stress increases with seismic moment. On average, for thrust events, the apparent stress of aftershocks is higher than that of main shocks; for strike-slip events, the apparent stress of aftershocks is lower than that of main shocks; while the situation of normal events is in between.

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The prototype of a ⁴He pumped vector magnetometer is presented. Large auxiliary coils systems used in previously developed apparatus to allow vector measurements from a scalar (atomic or nuclear resonance) sensor are replaced by a light triaxial modulation system associated with advanced techniques of signal processing. The performances of the helium scalar sensor are first briefly recalled; then the principle of the vector measurement, obtained by adding three (approximately) orthogonal modulations of different frequencies (all of the order of 10 Hz) is explained. Afterwards a second part of the paper is devoted to the calibration process, and a first estimate of the performances of the vector magnetometer is obtained. They confirm that this instrument could be a good candidate for an automatic absolute magnetic observatory: after the calibration process completion and a proper installation, it would provide by itself the absolute value of three orthogonal components of the field. In addition to that, the ⁴He vector magnetometer appears to be also promising for space applications.

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Four sunspot-minimum periods (1963-1966, 1971-1977, 1983-1987 and 1992-1997) have been examined for the results which are presented. Using several different weather parameters, tropospheric gravity waves, enhanced cold fronts and two rainfall data sets in Eastern Australia, associations at reasonably high levels of significance have been found with enhanced geomagnetic activity (EGA). Statistically this EGA involved either short delays of several days or long delays of about 20 days. The geomagnetic parameters used were (a) the AE index (b) the hourly H component for a number of stations and (c) the daily K_P-sum value. The K_P-sum analyses have shown that the EGA associated with the delays form part of four or five cycles of recurrent geomagnetic activity for 27-day periodicities. Furthermore statistically two recurrent cycles are found to exist concurrently, one apparently related to the short delays and the other to the long delays. Periodicities of 13.5 days are created because the two sets are displaced from each other by approximately this interval. A brief reference is made to the 13.5 periodicity known to exist for geomagnetic activity and the evidence in the literature for active regions on the sun to be displaced by 180 degrees of solar longitude.

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The paper describes the differences in the magnetic disturbance effect on horizontal geomagnetic field (H) and declination (D) at Alibag (India), Lunping (Taiwan), Chichijima (Japan) and Kakioka (Japan). It is suggested that the trapped particles in the earth's magnetic field lines are guided by the dipole declination and not by the ground declination and follow the direction towards the geomagnetic pole. The disturbance vector is given by sin (ψ - D) where ψ and D are dipole and ground declinations of the station respectively. The mean disturbance daily variation (SD) of H field is similar at all stations but SD of eastward field (Y) is negative at Alibag but positive at Lunping, Chichijima and Kakioka. Similarly, the daily mean values of H field systematically decrease with increasing ring current index (decreasing value of Dst index) for all stations. But declination values are positively related with Dst index at Alibag and negatively related at Lumping, Chichijima and Kakioka. The SSC amplitude in Y field shows negative values at Alibag but positive values at Kakioka. The storm-time variations Dst(H) show negative excursion during the main phase of the storm at Alibag, Lunping, Chichijima and Kakioka. On the other hand, the Dst variations in declination during the main phase show negative excursions at Alibag but positive excursions at Lumping and Chichijima. This shows a very significant longitudinal inequality in storm-time behavior of eastward geomagnetic field at any place on the earth.

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From analyses of magnetic data from the Circum-pan Pacific Magnetometer Network (CPMN) stations, we can find the following wave characteristics of Pi 2 magnetic pulsations. (1) Pi 2 pulsations observed on the ground are an ensemble of various hydromagnetic modes excited at high, middle, low, and equatorial latitudes. Each mode exhibits its own propagation (timing) and spatial illumination. (2) There are apparent longitudinal propagation and latitudinal time delays of the maximum Pi 2 magnetic energy among the CPMN stations within 100 sec. (3) When a single low-latitude station is located in the sectors of 00-24 hr LT, 20-03 hr local time (LT), and 23-01 hr LT, respectively, 62%, 79%, and 100% of auroral breakups identified by the Polar satellite have associated Pi 2s. 66% of the low-latitude Pi 2s occur within 1 min of the auroral breakups, and 85% within 2 min. Pi 2s are still a good indicator of substorm onsets, but they should be used with care.

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The cosmic-ray decreases and interplanetary disturbances, that occurred at 1 AU during the period, June 8-July 21, 1969, have been investigated by using the cosmic-ray intensity data recorded with ground-based monitors at Mt. Washington and Deep River, as well as the Interplanetary Magnetic Field (magnitude and direction) and the SolarWind Plasma bulk speed, density and temperature at 1 AU. We observed a two-step Forbush decrease on June 8-9, 1969, which was due to the structure within the shock and sheath preceding the interplanetary coronal mass ejection. We also observed two cosmic-ray depressions on June 16-20 and July 13-15, 1969, which were attributed to a long-lived corotating high-speed solar wind stream. The outward propagating interplanetary shock waves that occurred at about 0700 UT on June 16, 1969, and at about 1400 UT on July 13, 1969 and which were associated with the long-lived corotating high-speed solar wind stream, most probably swept away the galactic cosmic rays, causing the delay in the Forbush decrease recovery at 1 AU, and, hence, the unusually long recovery of the two-step Forbush decrease at 1 AU with onset on June 8, 1969. The additional depressions by the interplanetary shocks associated with the long-lived corotating high-speed solar wind streams which were superposed on the recovery phase of the Forbush decrease of June 8, 1969, were shown to be larger on the lower energy galactic cosmic-ray particles, and therefore the duration of the recovery phase would be much longer in the lower energy region, an expectation which is consistent with the observations.

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Between late 1994 and early 2001 the Wind orbiter, generally targeted to stay in the solar wind, passed through the Earth's magnetosphere -50 times. About 450 distinct bow shock crossings were collected during the inbound and outbound bracketing each Wind perigee. These crossings and corresponding vectorial upstream solar wind measurements by the Wind MFI and SWE instruments are used to study the 3-D shape of the bow shock and its motion. Mapping of bow shock crossings to the Sun-Earth line and to the terminator plane is realized using a recent analytical model of the planetary bow shock. The asymmetry of the terrestrial bow shock in the terminator plane is studied as a function of Friedrichs diagram anisotropy. Analysis of the subsolar bow shock position as a function of Alfvenic Mach number Ma during intervals of magnetic field aligned solar wind flow shows that the shock tends to approach the Earth when Ma is decreasing, while for non field-aligned flows bow shock moves from the planet.

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We present the temporal evolution of magnetic field topology in the magnetotail with a southward IMF in order to identify the magnetic reconnection. The magnetic field topology is uniquely determined by the eigenvalues of the critical points, if they are not degenerated. This is because the critical points, their number, and the rules between them characterize the whole magnetic field pattern. At the critical points, the magnetics become zero. The magnetic vector field curves and surfaces are both integrated out along the principal directions of certain classes of critical points including the Earth's dipole magnetic field. The skeleton that includes the critical points, characteristic curves, and surfaces provides the three-dimensional topological structure of the reconnection. The change of the skeleton, i.e. the change of the topology, has revealed the occurrence of magnetic reconnection. Namely, threedimensional“X-points” or the more-than-two critical points that are saddle and connected each other are unstable and can move, vanish, and generated.

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We demonstrate that a real-time based moment tensor analysis using broadband seismic waveforms provides us with the information about the spatio-temporal change of stress field. Such a capability is crucial when monitoring the volcanic activity during the eruption if it causes seismic swarm. We estimated the moment tensors of earthquakes occurring during the swarm activity before the eruption of Usu volcano in March 2000 as well as those during the swarm activity of Miyakejima volcano starting in June 2000. In both cases, we detected the stress change due to the movement of magma reservoir.

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