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Fig. 9. | Earth, Planets and Space

Fig. 9.

From: Barometric and magnetic observations of vertical acoustic resonance and resultant generation of field-aligned current associated with earthquakes

Fig. 9.

(a) Geomagnetic variation observed at Huancayo, Peru just after the origin time of the 2010 Chile earthquake. Oscillation is observed only in the declination (i.e., East-West component) which suggests the effect from a trans-equatorial field-aligned current generated in the ionosphere over the epicenter. The field-aligned current closes by the ionospheric current in the opposite hemisphere as depicted in Fig. 11(a). The arrival of the seismic wave was 8 minutes earlier (around 06:40 UT) than the onset of magnetic oscillation at 06:48 UT. (b) One second resolution geomagnetic data from Ancon observatory in Peru on the magnetic dip equator. The magnetic oscillation appears mainly in the D component, although a smaller variation is also seen in the Z (vertical) component. The small spiky variations in the H (horizontal) component are due to artificial noise caused by incomplete contact of the sensor cable. Note that the D component is expressed in units of nT.

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