Editorial: Geospace Observation of Natural Hazards

This collection of technical papers aims to bring recent data from many sources into the study of natural hazards. They represent a multi-instrumental approach using both ground observations: Global Navigation Satellite System (GNSS); and Low Earth Orbiting Electromagnetic (LEO EM) satellites missions together with Earth Observations (EO), which could reveal new information. Results from latest satellite missions, [(NPP/NASA/NOAA(US), CENTINEL, Swarm/ESA (EU), HIMAWARI (JMA, Japan), FORMOSAT-5 (Taiwan, August 2017), CSES1 (China/Italy, Feb 2018), and FORMOSAT-7/COSMIC-2 (Taiwan/United States, May 2019)], are represented in this volume

A Statistical Comparison of Zonal Mean and Tidal Signatures in FORMOSAT-3/COSMIC and Ground-Based GPS TECs

Atmospheric tidal components in the ionosphere can reflect either the in-situ generated quiet-time variation in the ionosphere, or vertically propagating tidal components generated through coupling to lower or middle atmosphere phenomena. Frequency-wavenumber tidal decomposition is a valuable tool for isolating the primary tidal components that drive the dynamics of the middle and upper atmosphere, allowing temporal and spatial variability to be quantified in a systematic manner, provided sufficient local time sampling. To date, two commonly used data sources for such tidal studies in the ionosphere are the FORMOSAT-3/COSMIC (F3/C) satellite constellation and ground-based GPS-derived Global Ionosphere Maps (GIMs). In this study, the migrating diurnal and semidiurnal tidal components, the nonmigrating diurnal eastward 3 (DE3) component, as well as the zonal mean component that dominate quiet-time ionospheric variability are extracted from 2008 F3/C and GIM Total Electron Content (TEC) data, using integration times of 20 days. We find that the zonal mean and tidal TEC components in F3/C and ground-based GIM data show qualitatively similar seasonal variability and spatial structure. However, the maximum amplitudes of the zonal mean and migrating tidal components computed from F3/C are consistently smaller than those from the ground-based GIMs, revealing a systematic difference between the two datasets. Conversely, the DE3 amplitudes are generally larger in F3/C compared to GIM, potentially due to the higher zonal wavenumber of that component

Seismo-Traveling Ionospheric Disturbances Triggered by the 12 May 2008 M 8.0 Wenchuan Earthquake

A network of 6 ground-based GPS receivers in East Asia was employed to study seismo-traveling ionospheric disturbances (STIDs) triggered by an M 8.0 earthquake which occurred at Wenchuan on 12 May 2008. The network detected 5 STIDs on the south side of the epicenter area. A study on the distances of the detected STIDs to the epicenter versus their associated traveling times shows that the horizontal speed is about 600 m s-1. Applying the circle method, we find that the 5 circles intercept at a point right above the epicenter when the horizontal speed of 600 m s-1 is given. Global searches of the ray-tracing and the beam-forming techniques confirm that the STIDs are induced by vertical motions in the Earth¡¦s surface during the Wenchuan Earthquake

Introduction to the Special Issue on “Earth Observation FORMOSAT-5”

The National SPace Organization (NSPO) was founded in 1991 to pursue self-reliant space technology to nurture the domestic space industry and promote space science research in Taiwan. As an extension of the widely-accepted FORMOSAT-2 remote sensing satellite, NSPO is self-reliantly developing FORMOSAT-5 to continue its international earth observation image and space science research services. FORMOSAT-5 will offer state-of-the-art ionospheric space science data for geoscience research. It will also provide two-meter panchromatic and four-meter multi-spectrum images at various processing levels. Using the heritage and lessons-learned from the FORMOSAT-1/Ionospheric Plasma and Electrodynamics Instrument (IPEI), FORMOSAT-5/Advanced Ionospheric Probe (AIP) becomes an all-in-one plasma sensor with a sampling rate up to 8192 Hz to measure ionospheric plasma concentrations, velocities, temperatures, and ambient magnetic fields over a wide range of spatial scales. FORMOSAT-5’s global coverage capability, smart agility feature and pioneer use of a Complementary Metal-Oxide-Semiconductor (CMOS) sensor for commercial optical earth observation satellites (Chang et al. 2012a) will bring even broader research applications to the geoscience community. The 500-kg FORMOSAT-5 satellite, as shown in Fig. 1, will soon be launched into a two-day revisit Sun-synchronous orbit at 720 km altitude and 98.28° inclination

Ionospheric GPS TEC Anomalies and M ≧ 5.9 Earthquakes in Indonesia during 1993 - 2002

Indonesia is one of the most seismically active regions in the world, containing numerous active volcanoes and subject to frequent earthquakes with epicenters distributed along the same regions as volcanoes. In this paper, a case study is carried out to investigate pre-earthquake ionospheric anomalies in total electron content (TEC) during the Sulawesi earthquakes of 1993 - 2002, and the Sumatra-Andaman earthquake of 26 December 2004, the largest earthquake in the world since 1964. It is found that the ionospheric TECs remarkably decrease within 2 - 7 days before the earthquakes, and for the very powerful Sumatra-Andaman earthquake, the anomalies extend up to about 1600 km from the epicenter

The impact of FORMOSAT-5/AIP observations on the ionospheric space weather

This paper assimilates the in-situ O+ fluxes observations obtained from the Advanced Ionospheric Probe (AIP) onboard the upcoming FORMOSAT-5 (FS-5) satellite and evaluates its possible impact on the ionospheric space weather forecast model. The Observing System Simulation Experiment (OSSE), designed for the global O+ fluxes, is shown to improve the electron density specification in the vicinity of satellite orbits. The root-mean-square-error (RMSE) of the ionospheric electron density obtained from assimilating the daytime O+ fluxes could be improved by ~10 and ~5% for the forecast and nowcast, respectively. Although the improvement of nighttime O+ flux assimilation is less significant compared to the daytime assimilation, it still reveals impacts on the model result. This suggests that nighttime observations might not be sufficient to alter the model trajectory in the positive direction as with the daytime result. Alternative data assimilation approaches, such as assimilation of the empirical model built by using the nighttime FS-5/AIP together with other existing satellite observations of O+ flux could obtain better accuracy of the electron density forecast

Spatial analyses on seismo-ionospheric precursors observed by GIM TEC and DEMETER during the 2008 M8.0Wenchuan earthquake

An abstract of the Spatial analyses on seismo-ionospheric precursors observed by GIM TEC and DEMETER during the 2008 M8.0Wenchuan earthquake paper presented at EGU General Assembly in 2015

Ionospheric Responses to the July 15 - 16, 2000 Magnetic Storm around Geographic Longitude 121˚E

This study presents observed behavior of ionospheric responses using vertical total electron contents (VTEC) and NmF2. The data were collected from global positioning system (GPS) networks and ionosondes around the geographic longitude of 121°E from mid- to low-latitudes for the severe magnetic storm on 15 July 2000. The results show that the severe magnetic storm caused significant density depletion and a G-condition occurrence in the western Pacific region on 15 - 16 July 2000. The G-condition is observed on the ionograms at Chung-Li station around 2330 UT on July 15. Furthermore, the variation of the F-peak height (HmF2) at Cebu indicates that a zonal electric field produced an upward drift and enhanced the fountain effect from 1000 UT on July 15. The observation of a G-condition indicates that a storm-induced neutral-wind circulation was the main cause of compositional change; i.e., an increase in the N2/O ratio and its associated loss coefficients that produced a negative storm phase along the chain of geographic longitude 121°E