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Results of experiments on the evolution of the Peregrine breather (PB) in a wave tank are presented and compared with numerical simulations based on the Nonlinear Schrödinger (NLS) and the Dysthe equations. The experiments demonstrate notable deviation from the NLS solution due to significant asymmetric widening of the spectrum. Good agreement of measurements with the solutions of the Dysthe equation is obtained. Contrary to the PB NLS soliton, no return to the initial undisturbed wave train can be expected.

A flux gate magnetometer with an amplitude resolution of 6 pT/LSB was installed at Huancayo, Peru (12øS, 750øW in geographic coordinates, 0.8øN, 335.6 ø in geomagnetic coordinates) in December 1985 and recorded field variations for 1 year with 3-s sampling intervals. Horizontal field variations of Pc 3-4 pulsations (periods from 150 to 30 s) were studied and it was found that the oscillations were observed predominantly in the H component (magnetic north-south), though oscillations in the D component (magnetic east-west) are superimposed temporarily at local sunrise. The D component signals, which last for •2 hours after local sunrise, bring about a large tilt of the polarization azimuth angles in the H-D plane without a significant change in the ellipticity. The azimuth at sunrise lies in the NW-SE quadrant during local summer (November to January), while it lies in the NE-SW quadrant for local winter (March to September). On the basis of the observed seasonal change of the azimuth angles, we present a model of the ionospheric current system setup by the incident Pc 3-4 pulsations in the dayside region of the dawn terminator at the dip-equator.

[1] A new self-consistent version of a time-dependent magnetospheric paraboloid model is presented and tested on the 24-27 September 1998 magnetic storm interval (minimum Dst = À207 nT). The model uses DMSP satellite data to identify the location of the inner boundary of the magnetotail current sheet and the magnetic flux in the lobes and their variations with time. These inputs plus upstream solar wind dynamic pressure and IMF B z values are used to iteratively model the Earth's field during the storm. Several interesting results with important consequences are obtained: (1) the model tail field strength at the Earth's surface (DT = À134 nT) is a significant fraction of the ring current value (DR = À167 nT); (2) the movement of the tail current sheet inward to L = 3.5-4.0 at storm maximum is consistent with geosynchronous magnetic field data; (3) at the Earth's surface the Chapman-Ferraro magnetopause current field (DCF = 117 nT) is almost equal at storm maximum to the value from the tail current, thus the fields from the two systems nearly cancel; (4) the magnetic flux from the polar cap in the course of the magnetic storm main phase approximately doubles in comparison with the magneto-quiet interval just before the storm onset; this fact shows that the driven processes prevail over dissipation processes throughout the storm main phase; (5) the large-scale internal currents in the magnetosphere (ring current, field-aligned currents, and magnetotail current) have significant influence on the shape and size of the magnetosphere; the location of the magnetopause subsolar point is different from that obtained by extrapolation of empirical results taken during high geomagnetic activity intervals and from magnetospheric models that do not include feedback from internal magnetospheric currents.

Abstract. In this paper, perturbations of the ionospheric Total Electron Content (TEC) are compared with geomagnetic oscillations. Comparison is made for a few selected periods, some during earthquakes in California and Japan and others at quiet periods in Israel and California. Anomalies in TEC were extracted using Global Positioning System (GPS) observations collected by GIL (GPS in Israel) and the California permanent GPS networks. Geomagnetic data were collected in some regions where geomagnetic observatories and the GPS network overlaps. Sensitivity of the GPS method and basic wave characteristics of the ionospheric TEC perturbations are discussed. We study temporal variations of ionospheric TEC structures with highest reasonable spatial resolution around 50 km. Our results show no detectable TEC disturbances caused by right-lateral strike-slip earthquakes with minor vertical displacement. However, geomagnetic observations obtained at two observatories located in the epicenter zone of a strong dip-slip earthquake (Kyuchu, M = 6.2, 26 March 1997) revealed geomagnetic disturbances occurred 6-7 h before the earthquake.