Abstract
We have investigated the variations of sporadic E (Es) layer using the
measurements of digisondes at Icheon (37.14°N, 127.54°E, IC) and Jeju (33.4°N, 126.30°E,
JJ) in 2011–2018. The Es occurrence rate and its critical frequency (foEs) have peak
values in summer at both IC and JJ in consistent with their known seasonal variations at
mid-latitudes. The virtual height of the Es layer (h’Es) during equinox months is
greater than that in other months. It may be related to the similar variation of meteor
peak heights. The h’Es shows the semidiurnal variations with two peaks at early in the
morning and late in the afternoon during equinoxes and summer. However, the semi-diurnal
variation is not obvious in winter. The semi-diurnal variation is generally thought to
be caused by the semi-diurnal tidal variation in the neutral wind shear, whose
measurements, however, are rare and not available in the region of interest. To
investigate the formation mechanism of Es, we have derived the vertical ion drift
velocity using the Horizontal Wind Model (HWM) 14, International Geomagnetic Reference
Field, and Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar-00
models. Our results show that h’Es preferentially occur at the altitudes where the
direction of the vertical ion velocity changes. This result indicates the significant
role of ion convergence in the creation of Es.
Publisher
The Korean Space Science Society
Subject
General Earth and Planetary Sciences,General Physics and Astronomy
Cited by
8 articles.
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