Investigation on the Variability of the Geomagnetic Daily Current During Sudden Stratospheric Warmings

• Published in: Journal of geophysical research. Space physics 2019-07, Vol.124 (7), p.6156-6172
• Main Authors: Owolabi, Charles, Lei, Jiuhou, Bolaji, O. S., Jimoh, Oluwaseyi, Ruan, Haibing, Li, Na, Niu, Xiaojuan, Yoshikawa, Akimasa
• Format: Article
• Language: English
• Subjects: Counter electrojet; Diurnal variations; Electrojets; Equatorial electrojet; equatorial electrojet current; Evolution; geomagnetic field variation; Geomagnetism; Investigations; ionospheric current; Ionospheric currents; Longitude; Magnetic fields; Stratospheric warming; Strength; sudden stratospheric warming; tidal variability; Tides
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2019JA026667

The magnetic field records of the magnetometer networks in the American, East Asian‐Australian, and European‐African sectors were employed in this present work. We used them to investigate equatorial electrojet (EEJ), counter electrojet (CEJ), tidal variability in EEJ strength and ionospheric current during the 2005/2006 and 2008/2009 sudden stratospheric warming (SSW) events. In addition to the well‐investigated tidal variability in EEJ strength over the American and East Asian sectors, we investigated that of the African sector for the first time. Interestingly, the tidal components in EEJ strength during both SSW events clearly exhibit marked longitudinal differences with high, moderate, and low amplitudes in the American, East Asian, and African sectors, respectively. An exception found around day 71 in the African sector after the 2008/2009 SSW event had higher solar diurnal tidal component as compared to that of the Asian sector. Over the American sector, solar and lunar semidiurnal tides were strongly associated with CEJ current during both SSW events, whereas at the African and East Asian sectors such variabilities are not evident. A solar diurnal tidal component was strongly related to a reduction in the EEJ strength over the East Asian sector. In addition, a prolonged period of CEJ occurrence that begins during the SSW precondition and ends when the SSW was evolving characterized the African sector during both SSW events. There is a steady shift in phase at later hours when both SSW events are evolving. Key Points Varying patterns of the zonal mean wind in the stratosphere play a major role in modulating the equatorial electrojet current strength Counter electrojet occurrence is noticeable during the sudden stratospheric warming as compared to the precondition period The lunar tide can be larger than the solar tide in electrojet current strength during the sudden stratospheric warming