The Low-Latitude Boundary Layer in the Tail-Flanks
Abstract
Geotail observations of the low-latitude boundary layer (LLBL) in the tail-flanks show that it is where the cold-dense ions appear with stagnant flow signatures accompanied by bi-directional thermal electrons (<300 eV). It is concluded from these findings that the tail-LLBL is the site of capturing the cold-dense plasma of the magnetosheath origin on to the closed field lines of the magnetosphere. There are also cases suggesting that the cold-dense plasma entry from the flanks can be significant to fill a substantial part of the magnetotail. In such cases, which are detected mostly during northward IMF intervals, the cold-dense plasma is not spatially restricted to a layer attached to the magnetopause (LLBL) but continues to well inside the magnetotail, constituting the cold-dense plasma sheet. The continuity of the cold-dense plasma all the way from the magnetospheric boundary strongly supports the idea that the magnetosheath ions are directly supplied into the cold-dense plasma sheet from the flank. This cold-dense plasma in the near-Earth region shows significant contrast with the nominal hot-tenuous plasma presumably transported from the distant tail. A statistical study showing significant control on the near-Earth plasma sheet status by the IMF Bz component supports the idea that the cold-dense ion supply to the near-Earth tail from the flanks dominates over the hot-tenuous ion transport from the distant tail during northward IMF periods. We suggest that the formation processes of the plasma sheet differ according to the IMF Bz component.
- Publication:
-
Geophysical Monograph Series
- Pub Date:
- 1998
- DOI:
- 10.1029/GM105p0033
- Bibcode:
- 1998GMS...105...33F