Effective Conductivity of a Cloudy Ionosphere - Hydromagnetic Waves in the Magnetosphere and the Ionosphere - page 308

Fig. 10.5. Geometry of the applied electric E and magnetic B 0 fields, as well as the
Pedersen current J P (alongtheelectricfield),Hallcurrent J H (across E and B 0 )
and a total current J T . The magnetic field oriented inside the page. a) Open Hall
circuit. Non-conductive walls prevent the J H flow. The vertical thin arrow represents
the applied electrical field, while the bold arrow represents the total current as a
consequence of the combined Pedersen current produced by the initial electric field
as well as of the Hall current due to the polarized electric field between the walls.
A potential difference was applied to the side surfaces of the rectangular plate. b)
Closed Hall circuit in which J H can leak independently of J P . c) The measurements
on the closed Hall circuit were taken on a thin (0.05 cm) disk-shaped plate with an
aperture at the center. An electric field between large and small radii of the disk
excites a circular ring of Hall current enclosed and circulating around the axis of the
disk. d) Enlarged fragment of the mask (0.4 × 0.4 cm). Different areas of the mask
had different transparency

Free carriers were generated by an illumination passing through a filter of
pure Si and a mask pressed to the sample. The mask was a thin sapphire plate
200 µm thick. On a mask sized 4 × 4 mm there were 100 transparent spots sized

2 L p ∼ 440 µm

(see Fig. 10.5). The detailed description of the experiment may be found in
[7]. The variability of inhomogeneities, that is, the ratio of transparency in a
spot to transparency outside the spot (in the negative mask) was 0 . 8.
The magnetic field was in the range 0 <B< 30kGs ( 0 <β e < 15).

200 µm. The mean distance between the spot centers was 2 L c ∼