Morphology and dynamics of daytime mid-latitude sporadic-E patches revealed by GPS total electron content observations in Japan

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.

3D tomography of midlatitude sporadic-E in Japan from GNSS-TEC data

“…Figures 8 and 9 show the three cases in Kanto (Cases 1-3) and two cases in Kyushu (Cases 4, 5), respectively. In Cases 1 and 2, the Es move southward, while in Cases 3-5 they move northward, maintaining their altitude of ~ 100 km, with speeds (30-100 m/s) consistent with the earlier report by Maeda and Heki (2015). …”

“…First, we show formal errors, i.e., the square root of the diagonal components of the covariance matrix, the inverse of the normal matrix, which is related to the non-uniform distribution of the accuracy of the tomography results. Additional file 1: Figure S2 shows relatively high accuracy for blocks at lower (Maeda and Heki 2015). Black curves in a describe the tracks (moving southward) of the intersection of LoS with a thin layer at 100-km altitude (black dots show the positions at 3:51 UT) for the station-satellite pairs shown in e. We show the map views of the results at altitudes 90-120 km (a) and 180-210 km (b), and latitude-height profiles at 31.8° N (c) and 32.0° N (d).…”

“…By utilizing GEONET, Maeda and Heki (2015) found that GNSS-TEC can detect Es patches with critical frequencies (foEs) exceeding 20 MHz as short-term localized enhancements in TEC. They also showed that Es patches often show frontal structure extending dominantly in the east-west direction over tens of kilometers or more.…”

Strong Sporadic E Occurrence Detected by Ground‐Based GNSS

“…Since the nighttime spread‐ F can significantly disturb the GNSS signal, to avoid the confounded effect from simultaneous E s and spread‐ F , we only examine data in daytime in our study. In comparison with the earlier studies (Maeda & Heki, , ; Maeda et al, ), our study will be of significance as follows: (1) Maeda and Heki (, ) and Maeda et al () mainly used the TEC data from GNSS Earth Observation Network (GEONET) over Japan; we will use the TEC data from a broader region in China that would benefit for study of larger scale E s occurrence. (2) In this study, we will make comparison between GNSS and ionosonde for all the detected E s cases, which enable the evaluation and validation statistically.…”

“…Due to the dense coverage of global GNSS stations, it could be easily used to monitor the structure and evolution of ionosphere such as traveling ionospheric disturbances (Ding et al, ) or postmidnight equatorial F region irregularities (Li et al, ). Recently, Maeda and Heki (, ) and Maeda et al () innovatively proposed a method to monitor regional E s occurrence and its evolution using dense ground‐based GNSS network total electron content (TEC). They did independent evaluations through comparing E s cases with simultaneous ionosonde and interferometric synthetic aperture radar observations and proved the validity of their method.…”