In general, nighttime thermospheric 557.7 nm emission over mid-latitudes is predominantly masked by significantly larger mesospheric component, and hence, F-region plasma structures are rarely ...observed in this emission. This paper reports the first rare simultaneous detection of F-region plasma depleted structure in O(\(^1\)D) 630.0 nm and O(\(^1\)S) 557.7 nm airglow images from Hanle, India, a mid-latitude station (32.7{\deg}N, 78.9{\deg}E; Mlat. ~24.1{\deg}N) on a geomagnetically quiet night (Ap=3) of 26 June 2021. This indicates significant enhancement of thermospheric 557.7 nm emission. Interestingly, thermospheric 557.7 nm emission was not significant on the following geomagnetically quiet night as MSTID bands were only observed in 630.0 nm images. We show that enhanced dissociative recombination caused by descent of F-layer peak over the observation region coupled with the significant increase of the electron density at thermospheric 557.7 nm emission altitude enabled the detection of the plasma depleted structure on 26 June 2021.
Air and sea surface temperature increases due to global warming have been widely observed around the world at various rates. This temperature rising has also been documented in many subsurface ...records recently. The air-ground temperature coupling system introduces an important factor in disturbing the original thermal balance and provides a new dimension to comprehend the effects of global warming on the Earth system. Ten meteorological stations of Central Weather Bureau in Taiwan that have been routinely measured for air (1.5 m above the ground) and subsurface (at depths of 0, 5, 10, 20, 30, 50, 100, 200, 300 and 500 cm below the ground) temperatures are used for in-depth comparison in this study. These stations have a mean observation period of 82 years (as of 2008) to provide good coverage for a preliminary examination of air-ground temperature coupling relationship in a century scale. Results show that patterns and variations of air and subsurface temperature are quite different among stations in Taiwan. In general, air and subsurface temperatures exhibit consistent linear trends after 1980 due to accelerating global warming, but display complex and inconsistent tendencies before 1980. When surface air temperature is subtracted from subsurface one, the differences in the eastern Taiwan are generally larger than those in the western Taiwan. This observation is possibly caused by (1) heat absorption of dense high-rise buildings, and/or (2) cut off heat propagating into deep depths in the urban area of western Taiwan. By comparing temperature peaks at various layers from shallow to deep, rates of thermal propagation can be estimated. The distinct time shifts among stations suggest that thermal propagations have to be taken into account when constructing historical temperature records.
This work explores the results of applying Square Euclidean and Correlation k-means cluster analysis on ion density irregularity profiles observed by the Advanced Ionospheric Probe (AIP) onboard the ...Formosat-5 (F-5) satellite from November 2017 to November 2020. The Square Euclidean cluster analysis yielded separate clusters each for ion density irregularities consistent with Equatorial Plasma Bubbles (EPBs) occurring over the southern low-latitude, northern low-latitude and equator. The Correlation k-means cluster analysis only yielded one cluster characterized by ion density irregularities consistent with EPBs occurring over the equator. Thus, this work suggests that a cluster analysis preferably a Square Euclidean Cluster analysis can be used to find and classify ion density irregularities consistent with EPBs. This work also shows that the F-5/AIP can perform multi-year observations of ion density irregularities at ~710 km altitude and at ~2230 pm local-time that are consistent with irregularities due to EPBs.
We report data quality of a micro barometer which observes atmospheric infrasonic waves at Ogasawara islands, approximately 1000 kilometers south of Tokyo, Japan, showing the cases of three different ...natural events including volcanic eruption, tsunami, strong wind and signals from one ordinary day. With considering weather conditions, the wavelet spectrum analysis showed different features. The good quality of Ogasawara data is verified, partly because microbarom caused by the nonlinear interaction of large-amplitude storm-generated waves on the surface of the ocean has been clearly observed.
PDF
