Longitudinal Structure in the Altitude of the Sporadic E Observed by COSMIC in Low-Latitudes

The longitudinal structure in the altitude of the Sporadic E (Es) was investigated for the first time based on the S4 index provided by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) in low latitudes. The longitudinal structure is identified as a symmetrically located wavenumber-4 (WN4) pattern within 30°S–30°N. The WN4 occurs primarily during the daytime at the June solstice and equinoxes, with the largest amplitude at the September equinox and the smallest one at the March equinox. It moves eastward with a speed of ~90°/day. The strongest WN4 appears within 10–20°N and 5–15°S in the Northern and Southern hemispheres, respectively. At the June solstice and the September equinox, the WN4 is stronger in the Northern hemisphere than in the Southern hemisphere, while the situation is reversed at the March equinox. The altitude distribution of the convergence null in the diurnal eastward non-migrating tide with zonal wavenumber-3 (DE3) for the zonal wind is similar to that of the WN4. This and other similar features, such as the seasonal variation, eastward speed, and the symmetrical locations, support the dominant role of the DE3 tide for the formation of the WN4 structure.

Possible New Solstitial Sightline in the Stonehenge Landscape

The landscape around Stonehenge contains a number of major Early Neolithic monuments dating to the fourth millennium BC, including the Stonehenge Cursus, the Lesser Cursus, Robin Hood’s Ball causewayed enclosure and several long barrows. A previously unsuspected Early Neolithic causewayed enclosure whose northeast rim was uncovered in 2016 on the slopes of Lark Hill, just to the north of the World Heritage Site boundary, represented a major new discovery. About a millennium after the construction of the Lark Hill Enclosure, a line of at least six timber posts was erected crossing from the interior to the exterior of the old enclosure, just to one side of a wide entrance. The line is slightly curved but the last three posts in the line face directly out towards the position of June solstice sunrise. While several short and longer rows of posts are now known to have been built in this vicinity both during the Later Neolithic and at later times, there are several reasons for believing this solstitial alignment to have been intentional and meaningful. It may even have represented the “monumentalisation” of an earlier broadly solstitial alignment of natural features, as has been suggested at Stonehenge itself.

INVESTIGATING THE VARIATIONS OF HORIZONTAL (H) AND VERTICAL (Z) COMPONENTS OF THE GEOMAGNETIC FIELD AT SOME EQUATORIAL ELECTROJET STATIONS

This research is monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. It presents the variations of Horizontal (H) and vertical (Z) component of the geomagnetic field at some Equatorial Electrojet (EEJ) Stations during quiet days. Data from five (5) observatories along the magnetic equator were used for the study. Daily baseline values for each of the geomagnetic element 𝐻 and Z were obtained. The monthly average of the diurnal variation and the seasonal variations were found. Results showed that the variations of the geomagnetic element of both H and Z differ in magnitudes from one stations to another along the geomagnetic Equator due to the differences of their geomagnetic latitude. The Amplitude curves for Z) are seen to be conspicuously opposite to that of H), and there is absence of CEJ in Z- Component but present in H- Components. The values during the pre-sunrise hours are low compare to daytime hours. Minimum variations of dH was observed during June solstice and maximum variations was observed during Equinox season. This study shows that daily variations of (H) and (Z) occur in all the stations. The enhancement in H is as a result of EEJ current

INVESTIGATING THE VARIATIONS OF HORIZONTAL (H) AND VERTICAL (Z) COMPONENTS OF THE GEOMAGNETIC FIELD AT SOME EQUATORIAL ELECTROJET STATIONS

This research is monitoring equatorial geomagnetic current which causes atmospheric instabilities and affects high frequency and satellite communication. It presents the variations of Horizontal (H) and vertical (Z) component of the geomagnetic field at some Equatorial Electrojet (EEJ) Stations during quiet days. Data from five (5) observatories along the magnetic equator were used for the study. Daily baseline values for each of the geomagnetic element 𝐻 and Z were obtained. The monthly average of the diurnal variation and the seasonal variations were found. Results showed that the variations of the geomagnetic element of both H and Z differ in magnitudes from one stations to another along the geomagnetic Equator due to the differences of their geomagnetic latitude. The Amplitude curves for Z) are seen to be conspicuously opposite to that of H), and there is absence of CEJ in Z- Component but present in H- Components. The values during the pre-sunrise hours are low compare to daytime hours. Minimum variations of dH was observed during June solstice and maximum variations was observed during Equinox season. This study shows that daily variations of (H) and (Z) occur in all the stations. The enhancement in H is as a result of EEJ current.

Characteristic of daytime F-region backscatter plume structures over low latitude of China

<p>Ionospheric F‐region irregularity backscatter plumes are commonly regarded as a nighttime phenomenon at equatorial and low latitudes. At daytime, there are very few reported cases of F‐region backscatter echoes. It is still not clear what caused the daytime echoes. In order to understand the occurrence of daytime F‐region echoes, we carried out an experiment with Sanya VHF radar (18.4°N, 109.6°E, dip lat. 12.8°N) during November 2016 to August 2020. Some basic characteristics were released: (1) The daytime F‐region echoing structures have an unexpected high occurrence in June solstice of solar minimum. (2) The echoing structures could appear at any time during 0700–1800 LT, with a maximum occurrence around 0900 LT. (3) The echoing structures appeared mostly above 350 km altitude, extending up to 650 km or more (F region topside) with apparent westward drifts at times. Radar interferometry and ICON satellite in situ results show that the daytime F‐region echoes were from plume structures consisting of field‐aligned irregularities. It is suggested that the plume structures could be remnants of equatorial plasma bubble (EPB) irregularities generated on the previous night around 100–125°E. They rise to high altitudes and drift zonally together with background plasma, causing the daytime F‐region backscattering structure over Sanya. With simultaneous observations of several VHF radars at different locations, satellite in-situ measurements and/or EPB model, the dynamics of daytime F-region backscatter plume structures could be better understood in the future.</p>

The River and the Sky: Astronomy and Topography in Caral Society, America's First Urban Centers

America's first urban centers may have been located in the Supe Valley, Peru. After investigating the location and the orientation of the main built structures, we show that it is not only the presence of the Supe River that determines their orientation but also that astronomical relationships within the orientation of the buildings dictate their setting within the valley. The southernmost position of moonrise on the horizon seems to be the most important astronomical target. There is the possibility of a trend toward attributing greater importance to the June solstice sunrise and the rising of certain stars or asterisms. These orientations could relate to specific moments throughout the year, in particular to seasonal rains, subsequent river flooding, and agricultural cycles. This is one of the earliest examples of the interaction of land- and skyscapes in human cultures and indeed the first in the Americas.

Climatology of Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) Observed with GPS Networks in the North African Region

We present for the first time the climatology of medium-scale traveling ionospheric disturbances (MSTIDs) by using Global Positioning System (GPS) receiver networks on geomagnetically quiet days (Kp ≤ 3) over the North African region during 2008-2016. The ionospheric Total Electron Content (TEC) were estimated from the dual-frequency GPS measurements, and the TEC perturbations (dTEC) data were derived from the estimated TEC data. We focused on the TEC perturbations (dTEC) associated MSTIDs and statistically analyzed its characteristics, occurrence rate, diurnal and seasonal behavior as well as the interannual dependence. The results show that MSTID is a local and seasonal dependence. The results also show that MSTIDs predominantly propagates towards the South (equatorward). The daytime and nighttime MSTIDs increase with solar activity, and its event period is (12 ≤ period ≤ 53 mins), while the dominant amplitude is (0.08 ≤ amp ≤ ~1.5 dTECU). The MSTIDs propagation velocity is dominantly higher at the daytime than nighttime. The study also shows that the magnitude of MSTIDs is higher at the northwest (NW) when compared with northeast (NE), and the disturbance occurrence time is more frequent within the hours of (1200 - 1600 LT), and (1000 - 1400 LT) in December solstice at daytime for stations located in the NW and NE part of the African region, respectively. While at the nighttime, the MSTIDs also exhibits variability in disturbance occurrence time around (NW: 2100 - 0200 LT) and (NE: 1900 - 0200 LT) in June solstice, but get extended to March equinox during solar maximum (2014). The mean phase velocity in daytime MSTIDs is higher than the nighttime in every season, except during June solstice.

Reference values for biochemical analytes in feral sheep from Socorro Island, Revillagigedo Archipelago, Mexico

ABSTRACT To establish reference values for biochemical analytes related to freshwater shortage adaptation, a total of 376 blood samples were collected from feral sheep at Socorro Island, Revillagigedo Archipelago. Year-round variation was assessed by sampling at the beginning of each season defined by the March equinox, June solstice, September equinox, and December solstice. The resulting data set was analyzed using Gaussian distribution and descriptive statistics. Confidence intervals of 95% were established. Analysis of variance was used to compare the mean values of each season. Total cholesterol, triglycerides, urea, albumin, total protein, sodium ion, anion gap, creatine kinase, arginine vasopressin, and aldosterone showed concentrations above the reference range for domestic sheep. Triglycerides, urea, albumin, sodium ion, and aldosterone showed concentrations within the reference range for domestic goats. Most biochemical analytes showed differences (P<0.05) between seasons, with the highest values occurring during winter, and the lowest during spring. Results could help improve the accuracy of metabolic profiles used as a tool for evaluating dehydration indicators, and to describe the physiological mechanisms employed by feral sheep to cope with seasonal availability of freshwater.

Variations of the peak positions in the longitudinal profile of noon-time equatorial electrojet

In this study, the seasonal variations of the EEJ longitudinal profiles were examined based on the full CHAMP satellite magnetic measurements from 2001 to 2010. A total of 7537 satellite noon-time passes across the magnetic dip-equator were analyzed. On the average, the EEJ exhibits the wave-four longitudinal pattern with four maxima located, respectively, around 170° W, 80° W, 10° W and 100° E longitudes. However, a detailed analysis of the monthly averages yielded the classification of the longitudinal profiles in two types. Profiles with three main maxima located, respectively, around 150° W, 0° and 120° E, were observed in December solstice (D) of the Lloyd seasons. In addition, a secondary maximum observed near 90° W in November, December and January, reinforces from March to October to establish the wave-four patterns of the EEJ longitudinal variation. These wave-four patterns were divided into two groups: a group of transition which includes equinox months March, April and October and May in the June solstice; and another group of well-established wave-four pattern which covers June, July, August of the June solstice and the month of September in September equinox. For the first time, the motions in the course of seasons of various maxima of the EEJ noon-time longitudinal profiles have been clearly highlighted.