Pi2 pulsations observed around the dawn terminator

S. Imajo, A. Yoshikawa, T. Uozumi, S. Ohtani, A. Nakamizo, R. Marshall, B. M. Shevtsov, V. A. Akulichev, U. Sukhbaatar, A. Liedloff, K. Yumoto

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


We examined Pi2 pulsations observed simultaneously at low-latitude stations (L = 1.15 - 2.33) around the dawn terminator. Those Pi2 pulsations observed in the sunlit region were polarized in the azimuthal (D, positive eastward) direction. We found that the D component oscillations in the dark and sunlit regions were in antiphase, whereas the H component oscillated in phase. A statistical analysis indicates that these D component phase reversals occurred about 0.5 h sunward of the dawn terminator at 100 km in altitude, corresponding to the highly conducting E layer. The azimuthal polarization and D component phase reversals related to the dawn terminator cannot be explained by the existing models of low-latitude Pi2s (e.g., cavity resonance or substorm current wedge oscillations). Similar D component phase reversals were also found on the dusk side although the amplitude of the D component is smaller than that of the H component. We suggest that the meridional ionospheric current in the sunlit region adjacent to the dawn terminator drives the D component oscillations in antiphase with those D oscillations produced by the oscillatory field-aligned current (FAC) on the postmidnight side. The meridional current is expected to form a part of a current system that extends from the postmidnight FAC to the equatorial Cowling current. The D component oscillations in the Northern and Southern Hemispheres are also in antiphase, indicating that the current system is symmetric with respect to the equator.

Original languageEnglish
Pages (from-to)2088-2098
Number of pages11
JournalJournal of Geophysical Research: Space Physics
Issue number3
Publication statusPublished - Mar 1 2015

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Space and Planetary Science


Dive into the research topics of 'Pi2 pulsations observed around the dawn terminator'. Together they form a unique fingerprint.

Cite this