Jet Colliding and Mixing Efficiency.

Two experimental methods, the Nile Red dye extraction and the Williamson ether synthesis in biphasic conditions, were used to characterize the mixing performance of a new cheap impinging jet colliding mixer from Gjosa and to compare it to other commercial micromixers (Caterpillar CPMM-R300, T-mixer, LTF MR-MX and LTF MR-MS). The Nile Red method shows that the Caterpillar mixer is the best one. Excellent results are also achieved with two Gjosa mixers in series. These results are not reflected in the Williamson ether synthesis, where the best mixer is the Gjosa one.

Temporal Evolution of Low-Latitude Plasma Blobs Identified From Multiple Measurements: ICON, GOLD, and Madrigal TEC.

Low-latitude plasma blobs have been studied since their first being reported in 1986. However, investigations on temporal evolution of a blob or on continental scale (>2,000 km) ionospheric contexts around it are relatively rare. Overcoming these limitations can help elucidate the blob generation mechanisms. On 21 January 2021, the Ionospheric Connection Explorer satellite encountered a typical low-latitude blob near the northeastern coast of South America. The event was collocated with a local enhancement in 135.6 nm nightglow at the poleward edge of an equatorial plasma bubble (EPB), as observed by the Global-scale Observations of the Limb and Disk (GOLD) imager. Total electron content maps from the Global Navigation Satellite System confirm the GOLD observations. Unlike typical medium-scale traveling ionospheric disturbances (MSTIDs), the blob had neither well-organized wavefronts nor moved in the southwest direction. Neither was the blob a monotonically decaying equatorial ionization anomaly crest past sunset. Rather, the blob varied following latitudinal expansion/contraction of EPBs at similar magnetic longitudes. The observational results support that mechanisms other than MSTIDs, such as EPBs, can also contribute to blob generation.

Seasonal Variation of Thermospheric Composition Observed by NASA GOLD.

We examine characteristics of the seasonal variation of thermospheric composition using column number density ratio ∑O/N 2 observed by the NASA Global Observations of Limb and Disk (GOLD) mission from low-mid to mid-high latitudes. We also use ∑O/N 2 derived from the Global Ultraviolet Imager (GUVI) limb measurements onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and estimated by the NRLMSISE-00 empirical model to aid our investigation. We found that the ∑O/N 2 seasonal variation is hemispherically asymmetric: in the southern hemisphere, it exhibits the well-known annual and semiannual pattern, with highs near the equinoxes, and primary and secondary lows near the solstices. In the northern hemisphere, it is dominated by an annual variation, with a minor semiannual component with the highs shifting toward the wintertime. We also found that the durations of the December and June solstice seasons in terms of ∑O/N 2 are highly variable with longitude. Our hypothesis is that ion-neutral collisional heating in the equatorial ionization anomaly region, ion drag, and auroral Joule heating play substantial roles in this longitudinal dependency. Finally, the rate of change in ∑O/N 2 from one solstice season to the other is dependent on latitude, with more dramatic changes at higher latitudes.

Exospheric Temperature Measured by NASA-GOLD Under Low Solar Activity: Comparison With Other Data Sets.

Exospheric temperature is one of the key parameters in constructing thermospheric models and has been extensively studied with in situ observations and remote sensing. The Global-scale Observations of the Limb and Disk (GOLD) at a geosynchronous vantage point provides dayglow limb images for two longitude sectors, from which we can estimate the terrestrial exospheric temperature since 2018. In this paper, we investigate climatological behavior of the exospheric temperature measured by GOLD. The temperature has positive correlations with solar and geomagnetic activity and exhibits a morning-afternoon asymmetry, both of which agree with previous studies. We have found that the arithmetic sum of F10.7 (solar) and Ap (geomagnetic) indices is highly correlated with the exospheric temperature, explaining ∼64% of the day-to-day variability. Furthermore, the exospheric temperature has good correlation with thermospheric parameters (e.g., neutral temperature, O2 density, and NO emission index) sampled at various heights above ∼130 km, in spite of the well-known thermal gradient below ∼200 km. However, thermospheric temperature at altitudes around 100 km is not well correlated with the GOLD exospheric temperature. The result implies that effects other than thermospheric heating by solar Extreme Ultraviolet and geomagnetic activity take control below a threshold altitude that exists between ∼100 and ∼130 km.

Pronounced Suppression and X-Pattern Merging of Equatorial Ionization Anomalies After the 2022 Tonga Volcano Eruption.

Following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter. The EIA crests variations and associated ionosphere-thermosphere disturbances were investigated using Global Navigation Satellite System total electron content data, Global-scale Observations of the Limb and Disk ultraviolet images, Ionospheric Connection Explorer wind data, and ionosonde observations. The main results are as follows: (a) Following the eastward passage of expected eruption-induced atmospheric disturbances, daytime EIA crests, especially the southern one, showed severe suppression of more than 10 TEC Unit and collapsed equatorward over 10° latitudes, forming a single band of enhanced density near the geomagnetic equator around 14-17 UT, (b) Evening EIA crests experienced a drastic deformation around 22 UT, forming a unique X-pattern in a limited longitudinal area between 20 and 40°W. (c) Thermospheric horizontal winds, especially the zonal winds, showed long-lasting quasi-periodic fluctuations between ±200 m/s for 7-8 hr after the passage of volcano-induced Lamb waves. The EIA suppression and X-pattern merging was consistent with a westward equatorial zonal dynamo electric field induced by the strong zonal wind oscillation with a westward reversal.

Variations of Lower Thermospheric FUV Emissions Based on GOLD Observations and GLOW Modeling.

Here we compare the global-scale morphology of Earth's the Far-Ultraviolet (FUV) emissions observed by NASA's Global-scale Observations of Limb and Disk (GOLD) mission to those modeled using the Global Airglow (GLOW) code with atmospheric parameters provided by Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). The O 5S oxygen (135.6 nm) and N2 Lyman-Birge-Hopfield (LBH) emissions are observed over the Western hemisphere every 30 min by the GOLD instrument. The FUV brightness of the thermosphere-ionosphere is expected to vary in systemic ways with respect to geophysical parameters, solar energy input from above, and terrestrial weather input from below. In this paper we examine the O 5S oxygen emission and the N2 LBH emission brightnesses with local time, latitude, season, tides, geomagnetic activity, and solar activity based on GOLD observations and GLOW modeling. Early GOLD observations indicate that the model effectively reproduces the brightness variations with local time and latitude but is biased low in magnitude. However, the TIEGCM is unable to accurately represent the extraordinary nighttime equatorial ionization anomaly observed by GOLD. It is also expected from these results that the signal from geomagnetic storms may obscure tidal signals.

First Global-Scale Synoptic Imaging of Solar Eclipse Effects in the Thermosphere.

A total solar eclipse occurred in the Southern Hemisphere on 2 July 2019 from approximately 17 to 22 UT. Its effect in the thermosphere over South America was imaged from geostationary orbit by NASA's Global-scale Observation of Limb and Disk (GOLD) instrument. GOLD observed a large brightness reduction (>80% around totality) in OI 135.6 nm and N2 LBH band emissions compared to baseline measurements made 2 days prior. In addition, a significant enhancement (with respect to the baseline) in the ΣO/N2 column density ratio (~80%) was observed within the eclipse's totality. This enhancement suggests that the eclipse induced compositional changes in the thermosphere. After the eclipse passed, a slight enhancement in ΣO/N2 column density ratio (~7%) was also seen around the totality path when compared to measurements before the eclipse. These observations are the first synoptic imaging measurements of an eclipse's thermospheric effects with the potential to drastically improve and test our understanding of how the thermosphere responds to rapid, localized changes in solar short wavelength radiation.