Geoscience Reference
In-Depth Information
6
3
4
MB
0
2
1
0
-2
2
-4
IBEX-Hi
IBEX-Lo
-6
-4
-2
0
2
Energy (keV)
Fig. 4. Predicted differential spectra of H at 1 AU from the upwind direction. This
log-log plot's vertical axis is H flux in (cm
2
skeV)
−
1
. Number indices denote different
populations of protons that gave birth to the H flux. See text for definition. This figure
is adapted from the one kindly provided by V. Izmodenov and modified by the author
to indicate the energy windows of IBEX's ENA instruments, IBEX-Hi and IBEX-Lo.
3. Conclusion
In this mini-review, we tried to provide a background in the study of the
heliospheric boundaries by measuring ENA flux at 1 AU, and the current
status in modeling efforts in utilizing existing results from SoHO and in
anticipation of IBEX set for launched in 2008. In the process, we give a
basic list of references for interested readers. Due to page limitation, many
topics were not discussed; e.g., time dependence of heliospheric conditions
and the information that may be carried in ENA.
36
Now that Voyager 1 has crossed the termination shock, new data should
help modelers to refine their evermore-comprehensive models of the helio-
sphere and the ENA flux coming from the outer regions. More immediately,
ion flux in the 50-80 keV interval measured by Voyager 1 in the heliosheath
should be used to test the consistency of the ACR interpretation of the ENA
flux from the upstream direction measured by SoHO, with the reservation
that the thickness of the heliosheath upstream will not be determined for
some time to come.
While SoHO's emphasis was on ACR in the higher energies, IBEX will
be concentrating on the lower energy pre-ACR PUI. We wish IBEX great
success. Meanwhile, effort to seek opportunity to image the heliospheric
boundaries in energetic H and He in the interval 20-200 keV should be
