On the simultaneity of substorm onset between two hemispheres

A Morioka (1) , Y Miyoshi (2) , F Tsuchiya (1) , H Misawa (1) , Y Kasaba (3) , T Asozu (4, 1) , S Okano (1) , A Kadokura (5) , N Sato (5) , H Miyaoka (5) , K Yumoto (6) , G. K. Parks (7) , F Honary (8) , Jean-Gabriel Trotignon (9) , Pierrette Décréau (9) , B. W. Reinisch (10)

1 PPARC - Planetary Plasma and Atmospheric Research Center [Sendai]
2 STEL - Solar-Terrestrial Environment Laboratory [Nagoya]
3 Tohoku University [Sendai]
4 Japan Atomic Energy Agency
5 NiPR - National Institute of Polar Research [Tokyo]
6 SERC - Space Environment Research Center [Kyushu]
7 SSL - Space Sciences Laboratory [Berkeley]
8 Department of Physics [Lancaster]
9 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
10 UMLCAR - Center for Atmospheric Research [Lowell]

[1] Simultaneous observations of auroral kilometric radiation from the Northern and Southern Hemispheres showed some cases in which the buildup of field‐aligned acceleration occurred only in one hemisphere at the substorm onset. This indicates that a substorm does not always complete the current system by connecting the cross‐tail current with both northern and southern ionospheric currents. Conjugate auroral observations showed that in one case, the auroral breakup in the Northern and Southern Hemispheres was not simultaneous; rather, they occurred a few minutes apart. This time difference in the breakup between two hemispheres suggests that the local auroral ionosphere controls auroral breakup in each hemisphere independently. The evidence in this study may indicate that the buildup of the field‐aligned acceleration region at the auroral breakup does not result only from the magnetospheric process and that the auroral ionosphere finally controls and/or ignites the substorm onset, that is, the auroral breakup.

Domains: Sciences of the Universe [physics]

A Morioka, Y Miyoshi, F Tsuchiya, H Misawa, Y Kasaba, et al.. On the simultaneity of substorm onset between two hemispheres. Journal of Geophysical Research Space Physics, 2011, 116, A04211 (15 p.). ⟨10.1029/2010JA016174⟩. ⟨insu-01180185⟩