Plasma waves and field-aligned currents in the Venus plasma mantle


J. Geophys. Res., 101, 17,313-17,324, 1996
(Received October 30, 1995; revised March 15, 1996; accepted March 21, 1996)
Copyright 1996 by the American Geophysical Union.
Paper number 96JA00927.


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Figure Captions

Figure 1a, Figure 1b.     100 Hz peak amplitude as a function of altitude and local time for orbits 125-248. The data are shown for (a) inbound and (b) outbound portions of each orbit. The gray scale indicates the peak amplitude per 24-s interval, with 12-s spacing between samples. The circles indicate the altitude of the orbiter electron temperature probe (OETP) ionopause.

Figure 2.     Relationship between flow-aligned coordinates and Venus solar orbital (VSO) coordinates.

Figure 3.     High resolution plasma wave and magnetic field data from orbit 169 outbound. Fifteen minutes of data are shown, with the top four panels showing wave intensity for the four wave channels, using a logarithmic scale. The bottom four panels show the magnetic field, cast into radial-flow-perp components. The vertical line in Figure 3 marks the OETP ionopause.

Figure 4.     Wave and magnetic field data for the inbound portion of orbit 157. Similar in format to Figure 3.

Figure 5.     Wave and magnetic field data for the periapsis portion of orbit 201. Similar in format to Figure 3. This orbit was also discussed by Luhmann [1988].

Figure 6.     Wave and magnetic field data for the outbound portion of orbit 171. Similar in format to Figure 3. This orbit was also discussed by Law and Cloutier [1995].

Figure 7a, Figure 7b.     Wave and plasma variations as a function of altitude with respect to the OETP ionopause for solar zenith angles (SZA) <30°. In Figure 7a, 7b and subsequently (Figures 8a, 8b and 9a, 9b) we have used data from the Unified Abstract Data System database for the first three seasons of dayside periapsis. The wave data are peak amplitudes. The plasma data are from the Langmuir probe. In calculating the plasma beta we assume that the ion temperature (T) = T/1.8 for altitudes > 350 km, where T is the electron temperature. The top panel of Figure 7a shows the wave amplitude for the four wave channels, while the bottom panel shows magnetic field strength, electron density, and plasma beta. The symbols show the median values per 25-km-altitude bin, while the shaded regions mark the upper and lower quartiles per bin. In Figure 7b we show the angle the magnetic field makes with the presumed flow direction () and the angle the field makes with respect to the vertical (). Both angles have been folded into the range 0°- 90°. The bottom panel of Figure 7b shows the parallel and perpendicular current density, calculated assuming horizontal currents and neglecting the vertical component of the magnetic field.

Figure 8a, Figure 8b.     Wave and plasma variations as a function of altitude with respect to the OETP ionopause for 30° < SZA < 60°. Similar in format to Figure 7a, 7b.

Figure 9a, Figure 9b.     Wave and plasma variations as a function of altitude with respect to the OETP ionopause for 60° < SZA < 90°. Similar in format to Figure 7a, 7b.

Figure 10.     Magnetic field orientation and rotation at the OETP ionopause. The solid circles indicate the median, while the error bars mark the upper and lower quartile.

Figure 11.     Schematic of the magnetic field geometry in the mantle and upper ionosphere.

Figure 12.     The relationship between the magnetic field perturbation and velocity perturbation for a shear Alfvén wave standing in the magnetosheath flow. Figure 12 shows (a) magnetic field pointing away from the subsolar point, and (b) magnetic field pointing toward the subsolar point. The unprimed vectors are above the current layer, while the primed vectors are below. For each case the upper plot shows the projection in the radial-flow plane, with the lower plot showing the projection in the horizontal plane.


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Text and figures by R. J. Strangeway
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Last modified: Sept. 19, 1996