Observations of large scale steady magnetic fields in the dayside Venus ionosphere
Although the dayside ionosphere of Venus is often field-free except for fine scale features, large scale, steady iosospheric magnetic fields with magnitudes sometimes exceeding 100 gammas are occasionally observed by the Pioneer Venus Orbiter magnetometer. These fields are mainly horizontal and can assume any angle in the horizontal plane. The orientation of the field may change along the spacecraft trajectory. The field magnitude in the upper ionosphere usually shows a distinct minimum near approx.200 km altitude, but the altitude profile is otherwise arbitrary. With few exceptions, the observations of these large scale fields occur when periapsis is at solar zenith angles < 50/sup 0/. The occurrences of large scale fields is often coincident with the observation of high solar wind dynamic pressures by the Pioneer Venus Orbiter plasma analyzer closely following the ionosphere encounter. However, the detection of this phenomenon even during some orbits for which the dynamic pressure is not extraordinarly high suggests that other factors, such as hysteresis effects, must also play a role in determining the occurrence frequency of large scale magnetic fields in the dayside Venus ionosphere.
- Research Organization:
- Univ. of California, Los Angeles
- OSTI ID:
- 6565125
- Journal Information:
- Geophys. Res. Lett.; (United States), Vol. 7:11
- Country of Publication:
- United States
- Language:
- English
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