Browsing by Author "Foster, J. C."

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    Prompt effects of solar wind variations on the inner magnetosphere and midlatitude ionosphere
    (Elsevier, 2005) Huang, Chao-Shong; Foster, J. C.; Yumoto, K.; Chau Chong Shing, Jorge Luis; Veliz, Oscar
    It is well known that the solar wind can significantly affect high-latitude ionospheric dynamics. However, the effects of the solar wind on the middle- and low-latitude ionosphere are much less studied. In this paper, we report observations that large perturbations in the middle- and low-latitude ionosphere are well correlated with solar wind variations. In one event, a significant (20–30%) decrease of the midlatitude ionospheric electron density over a large latitudinal range was related to a sudden drop in the solar wind pressure and a northward turning of the interplanetary magnetic field, and the density decrease became larger at lower latitudes. In another event, periodic perturbations in the dayside equatorial ionospheric E × B drift and electrojet were closely associated with variations in the interplanetary electric field. Since the solar wind is always changing with time, it can be a very important and common source of ionospheric perturbations at middle- and low-latitudes. The relationship between solar wind variations and significant ionospheric perturbations has important applications in space weather.
    Palabras clave:Solar windElectric fieldIonospheric density perturbations
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    Variations of low-latitude geomagnetic fields and Dst index caused by magnetospheric substorms
    (American Geophysical Union, 2004-05-25) Huang, Chao-Song; Foster, J. C.; Goncharenko, L. P.; Reeves, G. D.; Chau Chong Shing, Jorge Luis; Yumoto, K.; Kitamura, K.
    We present observations of periodic magnetospheric substorms and corresponding ionospheric disturbances. Since the periodic substorms occur during a stable interplanetary magnetic field, we are able to identify which ionospheric signatures are caused solely by substorms. We find that the low-latitude ionospheric electric field perturbation after substorm onsets is eastward on the dayside and westward on the nightside and that the ground magnetometer northward (H) deviations at middle and low latitudes show an increase (a positive bay) after each substorm onset, no matter whether the magnetometers are located on the dayside or on the nightside. The nightside magnetometer H deviations are closely correlated with the inner magnetospheric magnetic field Bz component during the dipolarization process. The Dst index shows a significant increase of 20–40 nT after each substorm onset. We propose that the increase in the magnetometer H field and Dst index in response to substorm onsets is related to the field dipolarization. In this scenario the nightside magnetosphere earthward of the near-Earth neutral line is highly compressed during the dipolarization, and the magnetic flux density within the inner magnetosphere is greatly enhanced, resulting in an increase in the ground magnetometer H component and in Dst.
    Palabras clave:Magnetic stormsSubstormsDipolarization