No abstract

The east–west component of magnetic field variation (∆D-component) at Davao station (Philippines, geomagnetic latitude: – 2.22˚N) are used to investigate the characteristics of the long-term Inter-Hemispheric Field-Aligned Currents (IHFACs) based on the time-series analysis from August 1998 to July 2020. Recent in situ satellite and ground-based observations have reported that dusk-side current polarity of IHFAC is often opposite to that of the noon IHFAC, being inconsistent with Fukushima's IHFACs model. We investigated the consistency of the dusk-side IHFAC polarity derived from the observations with the polarity expected from Fukushima’s IHFACs model and examined the solar cycle dependence of IHFACs. It was confirmed that the dusk-side IHFACs during June and December solstices flow in the same direction of the noontime IHFACs, which was consistent with the IHFAC polarities suggested by the Fukushima model. The dusk-side IHFACs around March and September–November months disagreed with the Fukushima model. The ∆D variations clearly showed seasonal asymmetry in the dawn and noon sectors, whereas the ∆D variations in the dusk sector demonstrated seasonal symmetry. Solar cycle dependence of IHFACs was exhibited in the dusk sector. For the dawn and noon sectors, the yearly peak-to-peak ∆D amplitude in the later solar cycle SC24 decreased by about 35% in comparison with the earlier solar cycle SC23. In contrast, the dusk-side yearly peak-to-peak ∆D amplitude increased by about 200%. The dusk-side IHFAC yearly amplitude tended to be in inverse proportion to solar activity.

We developed a new numerical model to constrain the interior structure of rocky Exoplanets, and applied it to the nearby planets Proxima Centauri b and Ross-128 b. The recently measured elemental abundances of red dwarfs and Alpha Centauri were utilized to infer the bulk composition of each planet, and to measure their core mass fractions (CMF). The results of our model predicted that the radius of Proxima b at its minimum mass may be 1.036 ± 0.040R⊕, and if its mass is as high as 2M⊕, 1.170 ± 0.040R⊕. The radius of Ross-128 b at minimum mass may be 1.034 ± 0.040R⊕, with its radius at an upper-bound mass of 2M⊕ being 1.150 ± 0.040R⊕. Both planets may have thin mantles with similar conditions to Earth’s, but not convecting as vigorously. The CMF's might lie in the ranges of 20% - 59% and 34% - 59% for Proxima b and Ross-128 b respectively, making it very likely they have massive iron cores. Their central temperatures may be high enough to partially melt the cores, and possibly generate magnetic fields. If they have magnetic fields at present, they are most likely to be multipolar in nature due to slow rotation speeds resulting from stellar tidal effects. The field strengths were predicted to have values of 0.06 G - 0.23 G for Proxima b, and 0.07 G - 0.14 G for Ross-128 b. If either planet contains more than 10% of their mass in volatiles, magnetic fields would either be non-existent or very weak. The conditions of both planets may be hostile for habitability.

We report the validation of a new planetary system around the K3 star EPIC 212737443 using a combination of K2 photometry, follow-up high-resolution imaging and spectroscopy. The system consists of two sub-Neptune sized transiting planets with radii of 2.6R⊕ and 2.7R⊕, with orbital periods of 13.6 and 65.5 d, equilibrium temperatures of 536 and 316 K, respectively. In the context of validated K2 systems, the outer planet has the longest precisely measured orbital period, as well as the lowest equilibrium temperature for a planet orbiting a star of spectral type earlier than M. The two planets in this system have a mutual Hill radius of ΔRH  = 36, larger than most other known transiting multiplanet systems, suggesting the existence of another (possibly non-transiting) planet, or that the system is not maximally packed.

Researching on urban heat island (UHI) is a hot topic among urban designers due to its adverse impacts. This paper focuses on studying spatial and temporal dynamicity of surface UHI in the Colombo district based on correlations between land surface temperatures (LST) with normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) using Landsat data from 1988 to 2019. Image processing and statistical analysis were done using QGIS Desktop 3.16.0 and RStudio softwares respectively. The mean of LSTs were continuously increasing from 1988 to 2019. The highest LSTs were observed at the Colombo harbour area in both 1997 and 2007. After initiation of the port city project in 2015, these values have been increased rapidly around the Colombo port city area. The expansion of UHI area was 71.55% between 1988 to 2019, and they were distributed from the western coastal belt to the east along with the central part of the district. The urban hot spots (UHS) were compacted at harbour and port city area. Additionally, new hot spots have been generated since 2017 adjacent to “Seethagama”. These small pockets are too hot and not very conducive for human settlements. Parking lots, compacted built-up areas, and ongoing industrial construction areas influence the formation of UHS. Considering this critical situation, it is highly recommended that to move mitigation strategies like urban greening methods, cooling pavements and cooling roofs, etc.  These results could be used towards a well-designed urban planning system to maintain the ecological balance within the study area.