Question from Joe Kan: (Feb. 16, 2001)

Are your Figures 1 and 2 for reflection from the ionosphere? Have you test your results against mine?

Reply from L. H. Lyu:

• Figure 1 is a sketch for a general case in which Alfven wave is generated from a region with dynamo effect (E dot J < 0).
• Figure 2 can be considered as a sketch of Alfven wave reflected from ionosphere.
• I remembered that in your M-I coupling model, you have assumed that electric field is curl free in ionosphere. I have shown you that it is not applicable to a system in which an Alfven wave has a finite extended wave front, i.e., a fully 3-D wave structure. (Figure 7)

How do you handle reflection from the plasma sheet? Are you assuming the reflection from the plasma sheet is the same as reflection from the ionosphere?

Reply from L. H. Lyu:

I have decided not to use the phrase: “reflection from the plasma sheet.” I prefer to consider this electric field is generated from a pre-exist electric field (it may come from Alfven wave or fast-mode wave) in a very thin current sheet. i.e.,

After explosive thinning, …

1. If Bn is greater than zero and plasma sheet thickness is much greater than the electron gyro radius, but smaller than the ion gyro radius (or in the same order of magnitude), then electrons will move along E cross Bn direction but ions will move nearly along the E-field direction (with a small component along E cross Bn direction). This type of plasma motion can generate an electric field (i.e., a dynamo effect). This electric field can propagate along magnetic field line by Alfven wave.
2. If Bn is equal to zero or if the current sheet thickness is close to electron gyro radius, then magnetic reconnection may take place at this thin current sheet..