The flyby results are plotted below in GSM coordinates and compared against the T96/IGRF-95 field model using the average WIND values for dynamic pressure and IMF BY and BZ during the time of residence in the magnetosphere: 1.96 nPa, BY=1.95 nT, BZ=+0.53 nT. A nominal Dst of -30 nT was also assumed. Plots below show the flyby overview, the inbound magnetopause crossing and outbound magnetopause crossing.
OVERVIEW:
The first figure shows the field in GSM cartesian for the two day period January 22 and January 23, 1998. NEAR data are in green, WIND is in black and the model field is in red. The agreement of the cartesian model and measured field components throughout closest approach (see the polar and azimuth angle plots) indicates that the SPICE transformation is working fairly well. Well enough for solar wind and Eros operations. However, the angular difference in the model and measured field near closest approach is NOT constant but varies between 0.5 and 2 degrees. It is not known whether this is due to slight differences in coordinate systems, an error in SPICE attitude or sensor orientation. The outbound magnetopause crossing is fairly clear in this plot, but the inbound crossing is much harder to identify. This is better done with the angle/magnitude data shown in the next figure.
Flyby Overview: Cartesian GSM
The inbound shock crossing at 0200 UT on 22 January is apparent in the field magnitude. (See NEAR-WIND comparison as well.) The inbound magnetopause crossings are difficult to judge but occur near the time of the model field crossing. The outbound crossing is easier to see. The outbound shock crossing corresponds to the cessation of fluctuations shortly before 1200 UT on the 23rd.
Flyby Overview: Azimuth-Polar-Total GSM
INBOUND MAGNETOPAUSE:
The inbound magnetopause is almost impossible to identify from the cartesian coordinates but is easier to see in the azimuth and polar angle plots. The first magnetopause encounter appears to be near 2235 UT or so on Jan. 22. The initial crossing is messy and finishes around 2245 UT. Two more encounters with the current layer occur, near 2305-2315 UT and 2355-0000 UT. The inner edge of the T96 magnetopause occurs near the second re-encounter with the current sheet. Although the measured field strength varies considerably, the model field is comparable. The orientation of the measured and model fields is however significantly different, the measured field being tilted about 20 degrees more northward.
Inbound:
OUTBOUND MAGNETOPAUSE:
The outbound magnetopause is clear even in the cartesian coordinates. The current layer is first grazed at 1015 UT on Jan. 23. This is also associated with a low field strength. The outbound crossing is completed by 1025 UT. The sheath field is highly variable in orientation and strength. The shock crossing is clear at about 1135 UT and there appears to be a 'foot' in the field magnitude in front of the shock (the scale does not show it well) that lasts until about 1145 UT.
Outbound:
