Abstract
Morphological characteristics of daytime mid-latitude sporadic-E (Es) patches are studied by two-dimensional total electron content (TEC) maps drawn using the Japanese dense network of Global Positioning System (GPS) receivers. By analyzing over 70 cases, we found that their horizontal shapes are characterized by frontal structure typically elongated in east-west by ~100 km. They are observed to migrate mainly northward in the morning and southward in the afternoon with speeds of 30–100 m/s. This may reflect the velocities of neutral winds controlled by the atmospheric tides. Such frontal structures are often found to include smaller scale structures.
Highlights
Sporadic-E (Es) is a thin densely ionized plasma patch, and its occurrence is highly unpredictable. It often appears in the E region of the ionosphere most frequently during the local summer in mid-latitude regions (Whitehead 1989, and references therein)
We modeled the long-period changes of STEC assuming that the vertical total electron content (TEC) (VTEC) obeys a cubic polynomial of time and estimated their coefficients together with phase ambiguities following the method of Ozeki and Heki (2010)
The distribution of the occurrence hour from the ionosonde during 2010, the same period as the Global Positioning System (GPS)-TEC study, shows morning peaks at 10 and 12 local time (LT) followed by a drop of 13–15 LT and the evening peak at 17 LT
Summary
Observation results 2-D horizontal structures Figure 1a–c shows VTEC anomaly maps with Es patches in three areas of different geographic latitudes, namely (a) Wakkanai, ~45 N, (b) Kokubunji, ~35 N, and (c) Yamagawa, ~30 N. The distribution of the occurrence hour from the ionosonde during 2010, the same period as the GPS-TEC study, shows morning peaks at 10 and 12 LT followed by a drop of 13–15 LT and the evening peak at 17 LT.
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