[(7)] ~ 140 km. Thus, the Ar+ charge-exchange altitude can be taken as 280 km. This is due to charge exchange with atomic oxygen, which is the main neutral thermospheric constituent. With [[spi:math]] = RE + 280 km, we can use (4) to calculate the loss-cone angle ([[spi:math]]) for given field line L [[spi:math]] R/RE and for various locations of injection r0 on the same field line. The relationship between [[spi:math]] and r0 is shown in Figure 7. From this figure, we determine that prompt precipitation of substantial numbers of Ar+ of 3.5 keV energy is unlikely for source radial distances greater than ~ 2000 km from LEO, primarily because the beam pitch-angle is not likely to be much less than ~ 30°. Consideration of the impacts due to precipitation of 3.5 keV Ar+ is given in Section IV.A. B. Beam-Magnetosphere Interactions In the rest of the magnetosphere at radial distances > 2000 km from LEO and up to GEO, trapping of the argon plasma, as depicted in Figure 1, is likely to occur for substantial length of time if the argon plasma beam does not pass entirely out of the magnetosphere. For this case, we must consider beam-plasma interactions. The plasma interactions can be roughly divided into the largest spatial scale interaction with the magnetospheric shell as a whole and into the spectrum of smaller scale plasma instabilities, although the two are not unrelated. Here we shall deal only with the former; discussion of the latter is found in Section IV.E. The physics of a plasma beam propagating transverse to a homogeneous vacuum magnetic field is very simple: if the beam is sufficiently dense so that polarization currents can maintain the charge separation electric field necessary to satisfy [[spi:math]] ([[spi:math]] is the beam velocity), the beam will propagate across the magnetic field. An alternative view of the effects of 15
RkJQdWJsaXNoZXIy MTU5NjU0Mg==