The characteristics of terdiurnal tides in the ionosphere
- PDF / 8,791,800 Bytes
- 13 Pages / 595.276 x 790.866 pts Page_size
- 15 Downloads / 167 Views
ORIGINAL ARTICLE
The characteristics of terdiurnal tides in the ionosphere Jing Liu1,2
· Wenbin Wang2 · Xuemin Zhang1
Received: 1 March 2020 / Accepted: 19 September 2020 / Published online: 29 September 2020 © Springer Nature B.V. 2020
Abstract Studying the characteristics of terdiurnal tides in the ionosphere provides an important pathway to understand the dynamic coupling between the low atmosphere and the ionosphere. Based on the TEC data from the Madrigal database at the Massachusetts Institute of Technology Haystack Observatory, a decomposition and nonlinear fitting method is used to derive ionospheric terdiurnal tides. Statistical analysis is then carried out to study the variability of ionospheric terdiurnal tides. Both the absolute and relative amplitudes of terdiurnal tides are large near the equator and in the equatorial ionization anomaly (EIA) region. The relative amplitude of terdiurnal tides in the Northern Hemisphere is larger than that in the Southern Hemisphere at low latitude, exhibiting hemispheric asymmetry. The amplitudes of terdiurnal tides at magnetic middle latitudes (∼35 °N MLat) at the east hemisphere (142 °E), west hemisphere (90 °W) and zero degree longitude sites all have annual, semiannual and 4-month cycles. Furthermore, our analysis shows that there are longitudinal variations of terdiurnal tides and these variations appear to be dependent on solar activity. Terdiurnal tides show two peaks near the equinoxes, one in March and April, and the other between October and November. The terdiurnal tides with characteristics of large amplitudes in the equator and EIA regions, and their correlation with the diurnal and semidiurnal components suggest that terdiurnal tides and their intra-annual variations are likely related to the nonlinear interaction be-
B J. Liu
[email protected]
1
Institute of Earthquake Forecasting, China Earthquake Administration, No. 63 Fuxing Road, Haidian district, Beijing, China
2
High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
tween diurnal and semidiurnal tides, which also show strong intra-annual variations. Keywords Terdiurnal tides · Ionosphere · TEC
1 Introduction Tides are common phenomena in the atmosphere. They have been studied for decades (e.g., Forbes 1984; Hagan and Forbes 2002; Pancheva et al. 2013). There are two types of tidal oscillations predicted by the classical tidal theory (Chapman and Lindzen 1970), the migrating and nonmigrating tides. Migrating tides are induced by gravitation or the heating associated with solar radiation and are synchronized with the sun (or moon) (Schunk and Nagy 2009). They propagate westward relative to a fixed location on the rotating Earth. The nonmigrating tides can propagate in the eastward or westward direction (Hagan and Forbes 2002). The latent heat release due to deep tropical convection and nonlinear wave-wave interactions are believed to be the causes of the nonmigrating tides (Forbes et al. 2003; Hagan and Forbes 2002, 2003). Because atmospheric density decre
Data Loading...
