Ionospheric control of polarization of low-latitude geomagnetic micropulsations at sunrise |
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| Affiliation: | 1. University of São Paulo, “Luiz de Queiroz” College of Agriculture, Avenida Pádua Dias, 11, CEP 13418-900 Piracicaba, São Paulo, Brazil;2. Embrapa Trigo, Rodovia BR 285, km 294, P.O. Box 451, CEP 99001-970 Passo Fundo, Rio Grande do Sul, Brazil;3. Federal University of Pelotas, Department of Soil Science, Campus Universitário s/n, P.O. Box 354, CEP 96010-900 Pelotas, Rio Grande do Sul, Brazil;1. Department of Advanced Interconnection Materials, The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan;2. E-ThermoGentek Co., Ltd., 102 Kujyo CID bld., 13, Shimotonodacho, Higashikujo, Minami-ku, Kyoto, 601-8047, Japan;1. Department of Pathology, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil;2. Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil;3. Department of Mental Health, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil;4. Department of Radiology, Columbia University Medical Center, New York, NY, USA;1. Aalto University, School of Chemical Engineering, Department of Chemical and Metallurgical Engineering, P.O. Box 16200, 00076 Aalto, Helsinki, Finland;2. Lappeenranta University of Technology, School of Engineering Science, P.O. Box 20, FI-53851 Lappeenranta, Finland |
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| Abstract: | Continuous observations of low-latitude Pc3 and Pc4 geomagnetic micropulsations were carried out at ASO (22.0°N, 198.0° geomagnetic coordinates) from November 1979 to July 1980 to confirm the ionospheric control of polarization characteristics of low-latitude pulsations presented by Saka etal. (1980). The present study confirms the previous result that D-component amplitude starts to increase with sunrise. From the present study, the following results are obtained : (1) the D-component amplitude, which is much smaller than the H-component amplitude before sunrise, increases as much as that of the H-component after sunrise, and this brings about the tilting of the major axis of the polarization ellipse from north to northwest; (2) the onset-time of the D-component increment (or tilting of the major axis) coincides with the appearance of the E-layer in the ionosphere within an hour, and the time of the coincidence shifts from season to season, in parallel with the change of sunrise ; and (3) the ellipticity of the polarization in the horizontal plane is not affected appreciably by sunrise.It is suggested that the Hall conductivity increment associated with the E-layer sunrise enhancement affects the characteristics of the D-component on the ground. |
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