On the formation and origin of substorm growth phase/onset auroral arcs inferred from conjugate space-ground observations
Document Type
Article
Publication Date
10-1-2015
Abstract
Magnetotail processes and structures related to substorm growth phase/onset auroral arcs remain poorly understood mostly due to the lack of adequate observations. In this study we make a comparison between ground-based optical measurements of the premidnight growth phase/onset arcs at subauroral latitudes and magnetically conjugate measurements made by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe B (RBSP-B) spacecraft crossing L values of ~5.0-5.6 in the premidnight inner tail region. The conjugate observations offer a unique opportunity to examine the detailed features of the arc location relative to large-scale Birkeland currents and of the magnetospheric counterpart. Our main findings include (1) at the early stage of the growth phase the quiet auroral arc emerged ~4.3 equatorward of the boundary between the downward Region 2 (R2) and upward Region 1 (R1) currents; (2) shortly before the auroral breakup (poleward auroral expansion) the latitudinal separation between the arc and the R1/R2 demarcation narrowed to ~1.0; (3) RBSP-B observed a magnetic field signature of a local upward field-aligned current (FAC) connecting the arc with the near-Earth tail when the spacecraft footprint was very close to the arc; and (4) the upward FAC signature was located on the tailward side of a local plasma pressure increase confined near L ~5.2-5.4. These findings strongly suggest that the premidnight arc is connected to highly localized pressure gradients embedded in the near-tail R2 source region via the local upward FAC.
Identifier
84954388700 (Scopus)
Publication Title
Journal of Geophysical Research Space Physics
External Full Text Location
https://doi.org/10.1002/2015JA021676
e-ISSN
21699402
ISSN
21699380
First Page
8707
Last Page
8722
Issue
10
Volume
120
Grant
NAS5-02099
Fund Ref
National Science Foundation
Recommended Citation
Motoba, T.; Ohtani, S.; Anderson, B. J.; Korth, H.; Mitchell, D.; Lanzerotti, L. J.; Shiokawa, K.; Connors, M.; Kletzing, C. A.; and Reeves, G. D., "On the formation and origin of substorm growth phase/onset auroral arcs inferred from conjugate space-ground observations" (2015). Faculty Publications. 6759.
https://digitalcommons.njit.edu/fac_pubs/6759
