On the lunar node resonance of the orbital plane evolution of the Earth’s satellite orbits

This paper aims to investigate the effects of lunar node resonance on the circular medium Earth orbits (MEO). The dynamical model is established in classical Hamiltonian systems with the application of Lie transform to remove the non-resonant terms. Resonant condition, stability and phase structures are studied. The lunar node resonance occurs when the secular changing rates of the orbital node (with respect to the equator) and the lunar node (with respect to the ecliptic) form a simple integer ratio. The resonant conditions are satisfied for both inclined and equatorial orbits. The orbital plane would have long period (with typical timescales of several centuries) fluctuation due to the resonance.     

Fractal Structure of the Heliospheric Plasma Sheet at the Earth''''s Orbit

An analysis of the data from the Wind and IMP-8 spacecraft revealed that a slow solar wind, flowing in the heliospheric plasma sheet, represents a set of magnetic tubes with plasma of increased density (N > 10cm-3 at the Earth's orbit). They have a fine structure at several spatial scales (fractality), from 2°-3°(at the Earth's orbit, it is equivalent to 3.6-5.4h, or (5.4-8.0)×106km) to the minimum about 0.025°, i.e. the angular size of the nested tubes is changed nearly by two orders of magnitude. The magnetic tubes at each observed spatial scale are diamagnetic, i.e. their surface sustains a flow of diamagnetic (or drift) current that decreases the magnetic field within the tube itself and increases it outside the tube. Furthermore, the value of β= 8π[N(Te + Tp)]/B2 within the tube exceeds the value of βoutside the tube. In many cases total pressure P = N(Te + Tp) + B2/8πis almost constant within and outside the tubes at any one of the aforementioned scales.     

Advances in the Researches of the Middle and Upper Atmosphere in China

In this paper we summarize the research results by Chinese scientists in 2016-2018. The focuses are placed on the researches of the middle and upper atmosphere, specifically the researches associated with groundbased observation capability development, dynamical processes, and properties of circulation and chemistryclimate coupling of the middle atmospheric layers.      

Advances in the Researches of the Middle and Upper Atmosphere in China

In this report we summarize the research results by Chinese scientists in 2018-2020. The focuses are placed on the researches of the middle and upper atmosphere, specifically the researches on atmospheric structure and composition, climate and chemistry-climate coupling and climate modelling, dynamics in particular those inducing the coupling of the atmospheric layers.      

Why should the latitude of the observer be considered when modeling gradual proton events? An insight using the concept of cobpoint

The shape of flux profiles of gradual solar energetic particle (SEP) events depends on several not well-understood factors, such as the strength of the associated shock, the relative position of the observer in space with respect to the traveling shock, the existence of a background seed particle population, the interplanetary conditions for particle transport, as well as the particle energy. Here, we focus on two of these factors: the influence of the shock strength and the relative position of the observer. We performed a 3D simulation of the propagation of a coronal/interplanetary CME-driven shock in the framework of ideal MHD modeling. We analyze the passage of this shock by nine spacecraft located at ∼0.4 AU (Mercury’s orbit) and at different longitudes and latitudes. We study the evolution of the plasma conditions in the shock front region magnetically connected to each spacecraft, that is the region of the shock front scanned by the “cobpoint” (Heras et al., 1995), as the shock propagates away from the Sun. Particularly, we discuss the influence of the latitude of the observer on the injection rate of shock-accelerated particles and, hence, on the resulting proton flux profiles to be detected by each spacecraft.     

On the 3D structure of the nebula around η-Carinae

The asymmetric shape of the nebula around η-Carinae (Homunculus) can be explained by a spherical expansion in a non-homogeneous medium. Two models are analyzed: an exponential and an inverse power law dependence for the density as a function of distance from the equatorial plane. The presence of a medium with variable density along the polar direction progressively converts the original spherical shell into a bipolar nebula. In the case of the nebula around η-Carinae, we know the time elapsed since the great outburst in 1840. An exact match between observed radii and velocities can be obtained by fine tuning the parameters involved, such as initial radius, initial velocity and the typical scale that characterizes the gradient in density. The observed radius and velocity of the Homunculus as a function of the polar angle in spherical coordinates can be compared with the corresponding simulated data by introducing the efficiency in a single or multiple directions. Once the 3D spatial structure of the Homunculus is obtained, we can compose the image by integrating along the line of sight. In order to simulate the observed image, we have considered a bipolar nebula with constant thickness and an optically thin emitting layer. Some simulated cuts of the relative intensity are reported and may represent a useful reference for the astronomical cuts.     

Satellite-observed biological variability in the equatorial Pacific during the 2009–2011 ENSO cycle

The event of 2009–2011 El Niño Southern Oscillation (ENSO) provides an opportunity to gain insight into the biological variability of the equatorial Pacific Ocean for an entire ENSO cycle with satellite and in situ observations. Even though El Niño and La Niña in general led to respectively weakened and enhanced chlorophyll-a concentration and net primary production (NPP) along the equatorial Pacific Ocean during the 2009–2011 ENSO cycle, biological responses were highly disparate along the equator and attributed to different driving mechanisms. In the eastern equatorial Pacific east of 150°E, the El Niño-La Niña biological change was in general small except for the transition period even though sea surface temperature (SST) showed over ∼5 °C drop from El Niño to La Niña. In the central-eastern (170°W–140°W) equatorial Pacific, moderate change of biological activity is attributed to the changes of thermocline driven by the eastward propagating equatorial Kelvin waves and changes of zonal currents and undercurrents. Highest biological response in this ENSO cycle was located in the central (170°E–170°W) and central-western (150°E–170°E) equatorial Pacific with quadruple chlorophyll-a concentration and over ∼400 mg C m⁻² d⁻¹ increase of NPP from El Niño in 2009 to La Niña in 2010. However, spatial pattern of ENSO biological variability as represented with NPP is not exactly the same as chlorophyll-a variability. Wind-driving mixing of nutrients and eastward advection of the oligotrophic warm pool waters are attributed to this significant biological variability in this region.     

Introduction to the Payloads and the Initial Observation Results of Chang＇E-1

Chang'E-1,the orbiter circling the moon 200km above the moon surface,is the first Chinese Lunar exploration satellite.The satellite was successfully launched on 24th October 2007.There are 8 kinds of scientific payloads onboard,including the stereo camera,the laser altimeter,the Sagnac-based interferometer image spectrometer,the Gamma ray spectrometer,the X-ray spectrom-eter,the microwave radiometer,the high energy particle detector,the solar wind plasma detector and a supporting payload data management system.Chang'E-1 opened her eyes to look at the moon and took the first batch of lunar pictures after her stereo camera was switched on in 20th November 2007.Henceforth all the instruments are successfully switched on one by one.After a period of parameter adjustment and initial check out,all scientific instruments are now in their normal operating phase.In this paper,the payloads and the initial observation results are introduced.     

Comparative anatomy of the day- and night-time radar echoes from the 130–170 km region of the low latitude ionosphere

Recent observations of daytime 150 km echoes made from Gadanki have revealed ‘descending layer type’ echoing pattern, which are remarkably different from their well known ‘necklace’ pattern. These descending layer type echoing pattern have close resemblance to those of the nighttime valley region echoes that are presumably linked with the intermediate layer formed by the meridional wind shear associated with the semidiurnal/terdiurnal tidal winds. The observed close resemblance between the two echoing patterns reminds the plausible role of the semidiurnal/terdiurnal tidal wind and metallic ions in the governing physical processes. We present a comparative anatomy of these two echoing phenomena by making a close examination of the radar observations from Gadanki. Importantly, we bring out the similarities and dissimilarities in their characteristics and discuss the results in the light of currently available theoretical frameworks in an effort to further our understanding on the origin of these echoing phenomena, which have been addressed so far in isolation.     

Brief Introduction about the SVOM Mission

SVOM is a mission dedicated for studying γ-Ray Bursts, and will also be a powerful target-ofopportunity observatory for the whole astronomy community. The mission has been approved jointly by both Chinese and French space agencies. It is planned to be in the orbit in 2021 with an altitude ≤ 600 km and an inclination ≤ 30°.      

Deformation of the ionosphere structure during the space weather events on October–November 2003

We present the spatial maps of the ionosphere–plasmasphere slab thickness τ (ratio of the vertical total electron content, TEC, to the F-region peak electron density, NmF2) during the intense ionospheric storms of October–November 2003. The model-assisted technology for estimate of the upper boundary of the ionosphere, hup, from the slab thickness components in the bottomside and topside ionosphere – eliminating the plasmasphere contribution of τ – is applied at latitudes 35° to 70°N and longitudes −10° to 40°E, from the data of 20 observatories of GPS-TEC and ionosonde networks, for selected days and hours of October and November 2003. The daily–hourly values of NmF2, hmF2 and TECgps are used as the constrained parameters for the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, during the ionospheric quiet days, positive and negative storm phases for estimate of τ and hup. Good correlation has been found between the slab thickness and the upper boundary of the ionosphere for the intense ionospheric storms at October–November 2003. During the negative phase of the ionospheric storm, when the ionospheric plasma density is exhausted, the nighttime upper boundary of the ionosphere is greatly uplifted towards the magnetosphere tail, while the daytime upper boundary of the ionosphere is reduced below 500 km over the Earth.     

Variations in the thermosphere and ionosphere response to the 17–20 April 2002 geomagnetic storms

The responses of the thermospheric density and ionospheric foF2 to the intense magnetic storms event on 17–20 April were analyzed by using data from CHAMP/STAR and ionosonde stations respectively, and NRLMSISE-00 and IRI-2007 models were used to simulate. The models can capture the tendency of changes, especially under quiet or moderate geomagnetic conditions, but are less accurate under geomagnetic storms. The thermospheric density is sensitive to the EUV emission and geomagnetic activity, and double-peak structure appeared in the dayside. On 19 April dayside, TADs traveled toward the equator with phase speeds of the order of 300–750 m/s, interfered near the equator to produce a total density perturbation of 25%, and then passed through each other and into the opposite hemisphere. For ionospheric foF2, there are non-symmetric hemispheres’ features during the intense geomagnetic activities. In details, middle latitudes in the north and high latitudes in both hemispheres are negative ionospheric storms, and the maximum amplitudes of δfoF2$\delta \mathit{foF}2$ is about 60%, but the amplitudes decrease from the higher to lower latitudes in the Southern Hemisphere. Meanwhile, the equatorial station shows positive phase, and the maximum value is about 100%. Finally, the mechanisms for these features will be discussed in this study.     

Advances in the Researches of the Middle and Upper Atmosphere in China in 2014—2016

In this report the research results by Chinese scientists in 2014-2016 are summarized. The focuses are placed on the researches of the middle and upper atmosphere, specifically the researches associated with ground-based observation capability development, dynamical processes, and properties of circulation and chemistry-climate coupling of the middle atmospheric layers.      

Advances in the Researches of the Middle and Upper Atmosphere in China in 2012–2014

In this report we summarize the research results by Chinese scientists in 2012–2014. The focuses are placed on the researches of the middle and upper atmosphere, specifically the researches related to ground-based observation capability development, dynamical processes, the property of circulation and chemistry-climate coupling of the middle atmospheric layers.     

Status of the Advanced Space-based Solar Observatory

The Advanced Space-based Solar Observatory (ASO-S) was formally approved at the end of 2017. In the past two years, ASO-S underwent its official Phase-B and Phase-C studies. The Phase-B study was successfully accomplished by the end of April 2019, and the Phase-C study is being now undertaken until August 2020. Then the flight model is planned to finish within 16 months. Around the end of 2021, ASO-S will be ready in the launch state. We briefly summarize the history of ASO-S, the phase-B studies, and the phase-C studies.      

Planetary wave coupling of the atmosphere–ionosphere system during the Northern winter of 2008/2009

This paper presents the global spatial (latitude and altitude) structure and temporal variability of the ∼23-day ionospheric zonally symmetric (s = 0) planetary wave (PW) seen in the Northern winter of 2008/2009 (October 2008–March 2009). It is shown that these ∼23-day ionospheric oscillations are forced from PWs propagating from below. The COSMIC ionospheric parameters f_oF2 and h_mF2 and electron density at fixed altitudes and the SABER temperatures were utilized in order to define the waves which are present simultaneously in the atmosphere and ionosphere. The long-period PWs from the two data sets have been extracted through the same data analysis method. The similarity between the lower thermospheric ∼23-day (s = 0) temperature PW and its ionospheric electron density response provides valuable and strong experimental evidence for confirming the paradigm of atmosphere–ionosphere coupling.