Geotail was at (-85.4, 3.7, -4.3) Re GSM at 2000 UT on Jan. 18, 1993. It observed a plasmoid starting at 2020 UT, and another one at 2120 UT. Electric and magnetic field data at one minute resolution show that in Figure 1. There are some spikes on the plots that require removal mentally. I can work on 4s resolution plots, along with a computation of the convective flow velocity. Geotail also observed energetic particle enhancements at 2135, 2200, 2220 UT in addition to the ones associated with the two plasmoids. This is shown in Figure 2. The figure is taken from the APL www server, courtesy of Dr. D. J. Williams and R. McEntire. It seems to me that there were two substorms in that interval with several intensifications near the high latitude oval between the two onsets. Finally, CPI (plasma) measurements taken from the Univ. of Iowa web page and provided through the efforts of Dr. L. A. Frank as a service to the community show in Figure 3 that in the periods of interest that the field was steady (lobe-like) there was mantle plasma present (10^2 eV/Q), streaming tailward. This results in a steady tailward flow outside the plasma sheet that is of the order of 150-200 km/s. Inside the plasma sheet, naturally, the plasma flow was tailward, and generally larger than at the mantle, in association with the observed plasmoids.
The high resolution (3s) magnetic field and electric field data are presented in Figure 4. Filtering the electric field by removing an offset can provide the convective component of the flow in the X-direction. This is shown in Figure 5. The latter one shows the X-component of the flow computed from Eygse and Bxyz_gsm for times that the field points in a direction that the most significant ocntribution to Vx is from Ey. This figure shows that the flow velocity was small initialy but became larger at around 20:30 UT. Careful classification of the Bz and By perturbation suggests that three bipolar signatures were observed: 1) 2018-2028 UT: The Vxperp flow cannot be completely detemined but indications are that it is small. This may be a quasistagnant plasmoid. 2) 2028-2037 UT: Vxperp peaks at -400 km/s with an average of about 200 km/s. This can be considered a more classical plasmoid. 3) 2037-2100 UT: Although a unipolar signature at 2037-2040 UT can be seen there is no strong indication for a flux rope/plasmoid here. The negative Bz during the interval suggests the possibility for a post-plasmoid plasma sheet phase, although the flow is not strong at all. Thus, it seems that the plasmoid seen between 2028-2034 UT was not followed by strong plasma sheet/lobe reconnection. Finally, the plasma sheet activity increased at 2100 UT as evidence by the field variability and inferred tailward flow. The actual flow magnitude here is a little more uncertain because a different background may need to be subtracted from Ey. This can be done by special processing. However, I think that we can trust that there was significant convective tailward flow of the order of 400-500 km/s.
In addition to the magnetic field and electric field data, Figure 5 presents high resolution data from the energetic particle instrument EPIC. A postscript version of the figure appears here. Channels are: E3 (ions, 62-74 keV), E4 (ions, 74-89 keV), He2 (Helium, 70-96 keV), and ED1 (electrons, >34 keV). [Courtesy: D. J. Williams and Stu Nylund].
Furthere analysis of the time delays in arrival of the ion and electron beams can be done by using line plots rather than color plots. The following series of line plots allows one to do so. They are labeled by STartUT to ENdUT in HHMM as: lineplotSTUTENUT.gif (.ps).
lineplot22152225a(GIF) or (PS)
lineplot22152225b(GIF) or (PS)
The last two plots differ in that lineplot22152225a has no running average applied to the electron data, whereas lineplot22152225b has a 3point running average applied. The electron data are 3 second resolution.
Note that the electron pulse that may show up when printing the color plot ics_mgf_efd.ps at 22:18:20 UT, is not apparent in the line plot. However, the case can be made for that time of onset from the timing based on ion arrival times. Ions are safer to use in this case because they have more sharply defined onsets and by doing a linear fit to the arrival times you can find the times of onset of an infinite speed particle. That will be the onset time of the acceleration process.
