Investigation of the Magnetosphere of Ganymede with Galileo's Energetic Particle Detector
Ph.D. dissertation by Shawn M. Stone, University of Kansas,
1999.
Copyright 1999 by Shawn M. Stone. Used with permission.
8.4 Pitch Angle Scattering Results for G2 and G7
During the closest approach and outbound portions of the G2 encounter, and all portions of the G7 encounter, the loss cones and anti-loss cones were exhibiting characteristics that could not be replicated by magnetic field alone, or by secondary interactions with Ganymede. Anti-loss cones such as the bounce shadow shown in Figure 6.87 that were near empty for the F2 channel but nearly filled in for the lower energy E1 and E3 channels are thought to be due to scattering. Using the implementation of pitch angle scattering presented in section 2.4 and section 5.3, the extent of the scattering effect was measured by the simulation for both models.
The first feature suspected of being under the influence of scattering is Feature G2-18:56:31. Only the F2 channel exhibits a bounce shadow. Under extended bounce mode with scattering, model M1 predicts that all electron channels will have a bounce shadow. Model M2 predicts only F2 will have one as is observed in the real data. Tables 8.9 and 8.10 summarize the scattering results for feature G2-18:56:31 and G2-18:58:31 during closest approach.
Table 8.9 Closest approach feature G2-18:56:31. The simulated run is performed in extended bounce mode with scattering implemented.
| Model | Result | Figure |
| M1 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. These values seem to be a little high. | 6.62 |
| M1 | Channel F2 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. These values seem to be much closer. | 6.63 |
| M2 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. The value of 5´10-3 1/s seems to be a little high but 1´10-3 1/s is right on. | 6.64 |
| M2 | Channel F2 electrons. The scattering coefficients used are 1´10-3 1/s and .6´10-3 1/s. The value of 1´10-3 1/s is right on but 6´10-3 1/s seems a little low. | 6.65 |
| M1 | Channel E3 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. Even though the observed data does not show evidence for a bounce shadow one is predicted by model M1. | 6.66 |
| M1 | Channel E3 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. Even though the observed data does not show evidence for a bounce shadow one is predicted by model M1. | 6.67 |
| M2 | Channel E3 electrons. In extended bounce mode with scattering model M2 does produce a bounce shadow. | 6.68 |
Table 8.10 Closest approach feature G2-18:58:31. The simulated run is performed in extended bounce mode with scattering implemented.
| Model | Result | Figure |
| M1 | Channel E3 electrons. The scattering coefficients used are 5´10-3 1/s and 2´10-3 1/s. These values seem to be a little high. | 6.90 |
| M1 | Channel E3 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. The value of 1´10-3 1/s seems to match the observed data. | 6.91 |
| M1 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. The value of 5´10-3 1/s seems to be a little high and 1´10-3 1/s is close. | 6.92 |
| M1 | Channel F2 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. The value of .6´10-3 1/s is still too high, but .2´10-3 1/s seems to match nicely. | 6.93 |
| M2 | Channel E3 electrons. The scattering coefficients used are 5´10-3 1/s and 2´10-3 1/s. The value of 5´10-3 1/s is too high, and 2´10-3 1/s is also. | 6.94 |
| M2 | Channel E3 electrons. The scattering coefficients used are 2´10-3 1/s and 1´10-3 1/s. The value of 1´10-3 1/s seems to match the observed data. | 6.95 |
| M2 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. These values seem to be a little high. | 6.96 |
| M2 | Channel F2 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. The value of .2´10-3 1/s seems to match the observed data. | 6.97 |
Scattering plays an important part in the outbound portion of the G2 encounter, as was shown in section 6.4. For the bounce shadow features such as G2-19:08:51 (Figure 6.106), the effects of scattering are also evident. The high energy F2 electron channel is deeper than the lower energy electron channels. For the loss cone features such as Feature G2-19:10:51, the observed loss cone is wider than the simulated absorption signature predicted by model M2. Scattering solves these problems. Tables 8.11 and 8.12 summarize the scattering results for models M1 and M2 for these features. The results of the correlations are tabulated in Table 8.14.
Table 8.11 Outbound feature G2-19:08:51. The simulated run is performed in extended bounce mode with scattering implemented.
| Model | Result | Figure |
| M1 | Channel E3 electrons. The scattering coefficients used are 5´10-3 1/s and 2´10-3 1/s. The value of 5´10-3 1/s brings simulated feature into agreement. | 6.111 |
| M1 | Channel E3 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. The bounce shadow becomes more shallow with decreasing scattering coefficient. This is contrary to what is physically observed. | 6.112 |
| M1 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 2´10-3 1/s. Both values seem too high. | 6.113 |
| M1 | Channel F2 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. The value of .6´10-3 1/s brings simulated feature into agreement. | 6.114 |
| M2 | Channel E3 electrons. The scattering coefficients used are 5´10-3 1/s and 2´10-3 1/s. The value of 5´10-3 1/s is too high. The value of 1´10-3 1/s seems to match. | 6.115 |
| M2 | Channel E3 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. These values are too low, resulting in a simulated feature that is too deep. | 6.116 |
| M2 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. Both values seem too high. | 6.117 |
| M2 | Channel F2 electrons. The scattering coefficients used are .6´10-3 1/s and .2´10-3 1/s. The value of .6´10-3 1/s seems to match the observed data. | 6.118 |
Table 8.12 Outbound feature G2-19:10:51. The simulated run is performed in extended bounce mode with scattering implemented.
| Model | Result | Figure |
| M1 | Channel E3 electrons. The scattering coefficients used are .6´10 -3 1/s and .2´10 -3 1/s. These values are both too small to deplete the loss cone of the particles in order to match the feature. | 6.143 |
| M1 | Channel E3 electrons. The scattering coefficients used are 5´10 -3 1/s and 1´10 -3 1/s. These values get closer but are still not enough. | 6.144 |
| M2 | Channel E3 electrons. The scattering coefficients used are .6´10 -3 1/s and .2´10 -3 1/s. Both these values are too small to fill the feature to the observed depth and shape. | 6.145 |
| M2 | Channel E3 electrons. The scattering coefficients used are 5´10 -3 1/s and 1´10 -3 1/s. The value of 1´10 -3 1/s seems to fit the feature well. | 6.146 |
For G7, scattering seems to have even a more pronounced effect than at G2. In order to match the observed bounce shadow features a scattering coefficient as much as a factor of 10 greater must be implemented. The one prime example is Feature G7-07:22:14 which is similar to all the features at G7 and is shown in Figure B.8. The high energy electron channel F2 shows a relatively deep anti-loss cone, but the low energy electron channels are almost completely filled in. Simulated runs in extended bounce mode with scattering are summarized in Table 8.13.
Table 8.13 Outbound feature G7-07:22:14. The simulated run is performed in extended bounce mode with scattering implemented.
| Model | Result | Figure |
| M1 | Channel E1 electrons. The scattering coefficients used are 50´10-3 1/s and 10´10-3 1/s. These values are both too small to fill the simulated loss cone. | B.33 |
| M1 | Channel E3 electrons. The scattering coefficients used are 50´10-3 1/s and 10´10-3 1/s. These values are both too small to fill the simulated loss cone. | B.35 |
| M1 | Channel F2 electrons. The scattering coefficients used are 50´10-3 1/s and 10´10-3 1/s. The location in time of this feature is predicted incorrectly by model M1. | B.37 |
| M2 | Channel E1 electrons. The scattering coefficients used are 30´10-3 1/s and 10´10-3 1/s. The value of 30´10-3 1/s seems to match the depth of the anti-loss cone feature. | B.39 |
| M2 | Channel E3 electrons. The scattering coefficients used are 30´10-3 1/s and 10´10-3 1/s. The value of 30´10-3 1/s seems to match the depth of the anti-loss cone feature. | B.41 |
| M2 | Channel F2 electrons. The scattering coefficients used are 5´10-3 1/s and 1´10-3 1/s. A value between 5´10-3 1/s and 1´10-3 1/s seems to match the depth of the anti-loss cone feature. | B.43 |
Table 8.14 Scattering coefficients for the G2 and G7 loss cone and anti-loss cone features derived from the correlations in chapter 6.
| Feature/Energy Channel | M1 Daa x 10-3 l/s | M2 Daa x 10-3 l/s |
| G2-18:56:31/F2 | 2 | 6 |
| G2-18:58:31/E1 | .6 | 2 |
| G2-18:58:31/E3 | .2 | 1 |
| G2-18:58:31/F2 | .1 | .2 |
| G2-19:08:51/E1 | 1 | 2 |
| G2-19:08:51/E3 | 2 | 1 |
| G2-19:08:51/F2 | 2 | .6 |
| G2-19:10:51/E1 | 1 | 3 |
| G2-19:10:51/E3 | 3 | 1 |
| G2-19:10:51/F2 | 5 | .6 |
| G7-07:22:14/E1 | -- | 30 |
| G7-07:22:14/E3 | -- | 30 |
| G7-07:22:14/F2 | -- | 5 |
Next: 8.5 Corotational and Parallel Electric Field Implications
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Updated 8/23/19, Cameron Crane
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