ESRฦDMSPqฏ๐pขฝคdฃลถถ้ion upflowฬฏฯช
*ฌ์ ืM[1], กไ ว๊[1], S. C. Buchert[2]
์เV ๅฟ[1], ๅJ W๊[3]
ผรฎๅwพzn
ยซค[1]
IRF, Uppsala Division[2]
Applied Physics Laboratory, Johns Hopkins University[3]
Simultaneous ESR and DMSP observations of ion upflow in the dayside ionosphere
*Yasunobu Ogawa[1]
,Ryo-ichi Fujii [1],S. C. Buchert [2]
Satonori Nozawa [1],Shin-ichi Ohtani [3]
Solar-Terrestrial Environment Laboratory, Nagoya University[1]
IRF, Uppsala Division[2]
Applied Physics Laboratory, Johns Hopkins University[3]
We have examined the corresponding magnetospheric regions where
ion upflow occurs using dozen of conjunction events between ESR
and DMSP satellites. The result was that ion upflow occurs not
only in the cusp/cleft regions which have been considered as
the primary region of the ion outflow in previous studies, but
also in the region corresponding to the mantle. A common feature
of these regions is soft (< 0.5 keV) electron precipitation.
Furthermore, ion upflow is rarely found in the regions corresponding
to the boundary and central plasma sheet where energies of the
electron precipitation are higher than that in the cusp. These
results support that soft particle precipitation is the predominant
source driving F region ion upflow.
An important part in the ionosphere-magnetosphere coupling is the formation of upward ion flows from the ionosphere, as they can be a significant source of magnetospheric plasma. Numerous studies of ion outflow from the polar ionosphere to the magnetosphere have been made with satellites [Yau and Andre, 1997 and references therein]. However, the specific ionospheric source region for the ion outflow is still unclear.
Incoherent Scatter (IS) radar located at high latitude is one of the most useful tools for such a study in the polar ionosphere, because the IS radar enables us to observe ion motion along the field-aligned direction together with plasma parameters such as plasma temperature and density. EISCAT Svalbard radar (ESR) is located at the invariant latitude of 75.2 deg N, where ion upflow in the dayside ionosphere can be observed. In order to examine primary regions where the ion upflow is frequently observed in the dayside ionosphere, it is essential to know the magnetospheric region corresponding to the ionospheric region observed with the ESR. Because it is often difficult to determine the corresponding magnetospheric regions only from the IS radar, particle instruments loaded into a satellite such as DMAP satellites is used for identification of the regions. Therefore we have examined the corresponding magnetospheric regions where ion upflow occurs using dozen of conjunction events between ESR and DMSP satellites. The result was that ion upflow occurs not only in the cusp/cleft regions which have been considered as the primary region of the ion outflow in previous studies, but also in the region corresponding to the mantle. A common feature of these regions is soft (< 0.5 keV) electron precipitation. Furthermore, ion upflow is rarely found in the regions corresponding to the boundary and central plasma sheet where energies of the electron precipitation are higher than that in the cusp. These results support that soft particle precipitation is the predominant source driving F region ion upflow.
References
Yau, A. W., and M. Andre, Sources of ion outflow in the high latitude ionosphere, Space Sci. Rev., 80, 1-25, 1997.