Study on the system of night hours for decoding Korean astronomical records of 1625–1787

This paper presents a study of the dates and times of astrophysical phenomena seen in the night time hours in Korea between 1625 and 1787. This is a period when two different calendars were used and it is important to know which calendar was used to record events such as lunar eclipses. It is known that the Joseon court adopted Shixianli (a Chinese calendar of Adam Schall) in 1654, the fifth reign of King Hyojong. However, the year when the court introduced the calendar into the system of night hours has not yet been determined. To know the enforcement year is very important for studies on astronomical events that are presented in Korean historical documents. From Seungjeongwon Ilgi (Daily Records of the Royal Secretariat), we compile a total of 90 lunar eclipse records referring to the observation time of the eclipses and calculate the times of occurrence of the eclipses with respect to the calendrical methods: Chiljeongsan Naepyeon (a Korean calendar) and Shixianli. As a result, we find that the system of night hours by the former calendrical method was used in the Joseon dynasty until as late as 1710. We also verify that the times of sunrise and sunset were considered as the moments when the center of the Sun reached the horizon according to Chiljeongsan Naepyeon at least. Therefore, we think that this study will contribute to the studies on astronomical phenomena of the Joseon dynasty, particularly on the estimate of the observation time.     

Revised upper limit on the internal magnetic moment of Venus

Over four Venus years of low altitude nightside PVO magnetometer observations are used to establish a new upper limit for the magnetic moment of Venus. Improvements over previous studies include data coverage and new instrument calibration information. The upper limit on an internal dipole moment is determined to be 8.4 × 10¹⁰ T m³.     

Study of hot flow anomalies using Cluster multi-spacecraft measurements

Hot flow anomalies (HFAs) were first discovered in the early 1980s at the bow shock of the Earth. In the 1990s these features were studied, observed and simulated very intensively and many new missions (Cluster, THEMIS, Cassini and Venus Express) focused the attention to this phenomenon again. Many basic features and the HFA formation mechanism were clarified observationally and using hybrid simulation techniques. We described previous observational, theoretical and simulation results in the research field of HFAs. We introduced HFA observations performed at the Earth, Mars, Venus and Saturn in this paper. We share different observation results of space mission to give an overview to the reader.     

金星火山与气候探测任务

金星火山和气候探测任务（Venus Volcano Imaging and Climate Explorer,VOICE）聚焦金星火山与热演化历史、水与板块运动、内部结构和动力学、气候演化和生命信息探索等重大科学问题,提出采用极化合成孔径雷达（Polarimetric Synthetic Aperture Radar,PolSAR） 、下视与临边结合的微波辐射探测仪（Microwave Radiometric Sounder,MWRS）和紫外–可见–近红外多光谱成像仪（Ultraviolet-Visible-Near Infrared Multispectral Imager,UVN-MSI）等三个先进的有效载荷,在350 km圆轨道上对金星全球表面和大气联合探测。 PolSAR将对金星全球表面进行高分辨多极化雷达成像;MWRS将对金星全球云下大气的热力结构和化学组成,云中可能的宜居环境及与生命相关大气成分进行探测;UVN-MSI则实现大气全貌成像、表面光谱成像和闪电检测。通过多种先进探测载荷和技术手段的结合,VOICE任务将揭示金星构造热演化历史和超温室效应机理,探索其宜居性和生命信息。VOICE任务的实施将实现国际金星研究探索中许多“零”的突破,为理解行星宜居性和太阳系演化提供极为关键的观测支持,对提升中国在国际深空探测与空间科学研究中的地位产生重大影响。      

Temporal and spatial variations observed in the ionospheric composition of Venus: Implications for empirical modelling

In situ measurements of the thermal ion composition of the ionosphere of Venus have been obtained for a period of two Venus years from the Bennett rf ion mass spectrometer on the Pioneer Venus Orbiter. Ion measurements within an altitude interval of 160 to 300 kilometers, corresponding to an overall latitude interval of about ?4° to 34°N, are assembled from the interval December 1978 to March 1980. This time interval corresponds to two revolutions of Venus about the Sun, designated as two “diurnal cycles”. The distributions of several ion species in this data base have been sorted to identify temporal and spatial variations, and to determine the feasibility of an analytical representation of the experimental results. The first results from the sorting of several prominent ions including O⁺, O₂⁺, and H⁺ and several minor ions including CO₂⁺, C⁺, and H₂⁺ reveal significant diurnal variations, with superimposed modulation associated with solar activity and solar wind variations. The diurnal variation consists of strong day to night contrast in the ion concentrations, with differences of one to two orders of magnitude, depending upon ion mass and altitude. The concentrations of O₂⁺, O⁺, CO₂⁺ and C⁺ peak throughout the dayside decreasing sharply at the terminators to nightside levels, lower by one to two orders of magnitude relative to the dayside. The diurnal variations of the light ions H⁺ and H₂⁺ peak during the night, exhibiting asymmetric nightside bulges favoring the pre-dawn sector, near 0400 solar hour angle. Superimposed upon the diurnal distributions are modulation signatures which correlate well with modulation in the F_10.7 index, indicating a strong influence of solar variability on the ion production and distribution. The influence of solar wind perturbations upon the ion distributions are also indicated, by a significant increase in the scatter of the observations with increasing altitude as higher altitudes, approaching 300 kilometers, are sampled. Together, these temporal and spatial variations make the task of modelling the ionosphere of Venus both very interesting and challenging.     

Solar wind governing the response of Venusian atmosphere and ionosphere

The ionosphere of Venus is primarily formed by photoionization of a gaseous blanket around Venus. The impact ionization by energetic solar charged particles also plays an important role in the variability of Venusian ionospheric ion, electron density and their temperature profiles. The microscopic variations in the solar wind velocity, particle flux and orientations of frozen-in interplanetary magnetic field determine the solar wind interaction with the Venusian ionosphere. The ion and electron density profiles obtained by Pioneer Venus Orbiter and Pioneer Venus Entry Probes have been analysed in the light of simultaneous solar wind velocity and particle flux. Marked changes in height profiles of ion, electron densities and their temperatures have been found to correlate with the simultaneous changes in the solar wind velocity and particle flux. It is shown that the solar wind plays a more important role in controlling the physical properties and behavior of daytime as well as nighttime ionosphere of Venus, whereas the solar xuv sustains the primary ionization process.     

Coordinated lidar and TIMED observations of the quasi-two-day wave during August 2002–2004 and possible quasi-biennial oscillation influence

The Colorado State University sodium lidar, located in Fort Collins, CO (41N, 105W), is capable of both daytime and nighttime operations and has conducted a number of continuous multiple-day observational campaigns over the past few years. Three such campaigns, lasting between 80 and 90 h, were conducted during August 2002–2004 when mesospheric winds and temperature observations were collected simultaneously. These data were processed to extract the vertical structure and temporal evolution of the quasi-two-day wave, which was found to be significant in the power spectra. The quasi-two-day wave in temperature, zonal wind and meridional wind was analyzed for each year, indicating that the wave activity in 2003 was weaker than the other two years. Concurrent TIMED/SABER (2002–2004) and TIMED/TIDI observations (2004) in August were also processed. The SABER temperature shows a quasi-two-day wave with a dominant westward propagating zonal wavenumber four (s = −4) component in 2002 and 2004 but not in 2003. Analysis of the TIDI winds in August 2004 also indicates significant quasi-two-day wave activity, with the zonal wavenumber three and four components of comparable strength. The results of this coordinated ground-based lidar and TIMED satellite observations during August are presented. The possible influence of quasi-biennial oscillation on the inter-annual variability of the quasi-two-day wave is investigated.     

SOHO observations relating to the associationbetween flares and coronal mass ejections

Campaigns to investigate the solar coronal mass ejection (CME) onset have been run using the Solar andHeliospheric Observatory (SOHO) since 1996. These have included coronagraph and extreme-ultraviolet (EUV) disc imaging, along with magnetic mapping of the photosphere, in concert with EUV and UV spectroscopic observations. These campaigns have included co-ordination with ground-based observatories, and with other spacecraft, especially Yohkoh and the Transition Region and Corona Explorer (TRACE). This multi-instrument, multi-spacecraft effort has provided many rewards, with some spectacular observations of countless eruptions. It has included the discovery of unexpected phenomena such as EUV waves and groundbreaking work on coronal dimming, and the development of sigmoidal shaped structures. Much has been learnt about the CME onset yet the most basic questions still remain. We have an unprecedented view of CME eruptions, yet we are still unable to identify clearly the onset process and we do not fully understand the CME-flare relationship. With all of the campaigns producing excellent multi-wavelength observations of CMEs, how far have we progressed in the understanding of the CME onset and, in particular, the CME-flare relationship? Can we identify lines of research using the SOHO data, which will provide the answers we seek — or do we need fundamentally different observation scenarios? It is the author's opinion that we actually have the observational tools required to understand much about the onset process and the CME/flare links, and the emphasis should be on understanding the limitations of our instrumentation and on removing any preconceived ideas from our interpretations.     

Venus atmospheric circulation: Observations and implications of the thermal structure

Continued analysis of Pioneer Venus imaging and polarimetry data indicates that the average cloud-top level circulation is mainly zonal (east to west) with a small meridional component. Presence of planetary scale waves and a possible sun-related component are evident in the data. If the tracked features refer to the same vertical level, then some variability of the circulation would have to be present to account for the Pioneer and Mariner 10 cloud-tracking results. However, the implied balanced flow from the observed thermal structure analysis strongly suggests that at least some of the variations in these observations is due to apparent cloud-top variations and that the circulation itself is relatively stable.Direct cyclostrophic calculations based on the observed thermal structure of the atmosphere yield a balanced zonal circulation with distinct mid-latitude jets (peak velocities about 110–120 ms^?1) located between 50 and 40 mb in each hemisphere of the planet near 45° latitude. The calculations which extend to about 40 km altitude from 80 km above the surface agree well with the observed entry probe zonal components and indicate breakdown of the balance condition near the upper and lower boundaries at low latitudes.The balanced flow results are consistent with the Mariner 10 and Pioneer cloud tracked estimates of the zonal circulation provided the effective altitude of the tracked features is slightly different at different observation periods. The features in the Pioneer Venus data would then lie on a sloping surface that extends from about 68 km (40 mb) at low latitudes to about 75 km (10 mb) in mid-latitudes. The polarization features would occur on a roughly parallel surface that is 1–2 km above the effective cloud-height surface, and Mariner 10 features would have effective altitudes somewhat lower than the Pioneer ultraviolet features. A slight asymmetry is evident in the balanced zonal circulation arising out of an asymmetry in the thermal field.Finally, the solenoids formed by intersecting isobaric and isosteric (constant specific volume) surfaces deduced from the Pioneer Venus radio occultation data show distinct evidence of a direct meridional circulation that may be important in sustaining the Venus atmospheric circulation.     

A comparison of seasonal variations of sea level in the southern Baltic Sea from altimetry and tide gauge data

In this paper, seasonal sea level variations have been determined at five locations in the Baltic Sea from satellite altimetry for the period 1993–2015. The results were compared to tide gauge water level data. Annual and semi-annual amplitudes have been investigated for both sea level anomalies and tide gauge water level. It was found that the two independent observations of sea level variations along the Polish coast are in good agreement both in terms of their annual and semi-annual amplitudes and their annual and semi-annual phases. The annual cycles in the sea level variations measured by altimetry and tide gauge reach maximum values at approximately the same month (November/December).Moreover, this article shows the differences between the annual and semi-annual amplitudes and phases in the sea level anomalies and water level data within the same time frame. The difference in the annual amplitudes between the satellite altimetry and the tide gauge results is between 0.33?cm and 1.53?cm. The maximum differences in the annual cycle of the sea level changes were found at the Swinoujscie station. The correlations between the original series and the calculated curves were determined, and the relationship between the amplitudes and the phases were investigated. The correlation between the annual variations observed from the two independent observation techniques is 0.92.To analyse the dynamics of the change in sea level, the linear trend was estimated from the satellite altimetry and tide gauge time series both in the original time series of the data and in the time series in which seasonal variations were removed. In addition, we calculated the estimated errors of regression and how many years’ worth of data are needed to obtain an accuracy of 0.1?mm per year. The estimated errors of regression showed that to get an accuracy of 0.1?mm per year, we need 100?years of data.     

第23太阳活动周行星际磁场扇形结构对中低纬地磁场的影响

用特征向量分析法对第23太阳活动周天津静海磁场强度水平分量H的时均值进行研究,分析行星际磁场扇形结构的地磁效应（简称扇形效应）对中低纬地磁场H分量日变化的贡献.研究结果表明,中低纬扇形效应为3～11nT,在太阳活动高年扇形效应达到最大值（约11nT）,低年达到最小值（约3nT）.太阳活动高年扇形效应引起的地磁H分量值变化与太阳活动低年的情况相反,但是扇形效应在夏季对地磁H分量的影响较小.太阳活动高年扇形效应日均值的增减与上升年的相反,与下降年相同,夏季扇形效应平均增量最小且无规律.春、夏和秋三个季节的扇形效应最大值都出现在太阳活动高年,冬季的扇形效应在太阳活动峰年两年后才出现最大值（约11nT）.在太阳活动低年（或高年）,当扇形磁场背离（或指向）太阳时,夏季扇形效应白天引起地磁H分量增大（或减小）,夜间导致地磁H分量减小（或增大）,其他季节全天都会导致地磁H分量减小（或增大）.用特征向量推断行星际磁场扇形极性的符合率在春夏秋三个季节高达60%,在冬季为55%.      

Atmospheric dynamics on Venus and Mars

New results from Pioneer Orbiter observations indicate a continued vortex organization of the cloud level atmosphere in either hemisphere, centered over respective poles. Significant changes in the magnitude of the cloud level zonal circulation over a period of several years have been detected. A strong signature of the solar tidal circulation has been detected in the atmospheric circulation with the lowest speeds occurring in equatorial latitudes about 20° upstream of the sub-solar point. Finally, a solar-locked persistent spatial structure has been discovered in the variance of the ultraviolet brightness measured from brightness normalized images of Venus. Vega balloons (drifting at about 53 km altitude near 7°N and 7°S latitudes) have also provided some unique observations of atmospheric circulation, significant among them being the strong vertical motions, the zonality of their drift speeds as well as a significant temperature difference between the two balloons. The temperature difference which amounts to 6.5°K on average is currently being interpreted as a temperature variation with longitude or time.

Diagnostic modelling efforts towards simulating the atmospheric circulation on Venus are continuing and have provided some clues about the processes that maintain them but have not yet been successful in explaining the superrotation of the atmosphere.

Knowledge of the Martian atmospheric dynamics on the other hand is still limited by lack of adequate observations. Numerical modelling of the Martian atmosphere continues to provide most of the information about the atmospheric circulation. The situation regarding the paucity of observations should improve with the completion of the proposed Mars Observer mission. The low circular polar orbit planned provides an excellent opportunity to study the Martian atmosphere.     

Evidence for mass-loading of the Venus magnetosheath

The observed magnetic field configuration in the Venus magnetosheath contains information about the solar wind mass-loading processes occurring as a result of the extension of the neutral atmosphere into the magnetosheath. In this paper, magnetic field signatures of various mass-loading processes are discussed and experimental results from the Pioneer Venus Orbiter magnetometer experiment are examined for evidence of these signatures. The data suggest that the ?$\text{V}$X$\text{B}$ acceleration process, stochastic pickup of ionospheric ions, and $\text{J}$X$\text{B}$ force “scavenging” at the ionopause all occur at various times.     

Behavior of the atomic oxygen 557.7 nm atmospheric emission in the solar cycle 23

We present the results of nightglow observation of the atomic oxygen 557.7 nm line emission in the solar cycle 23. We use the experimental data obtained at Geophysical observatory near Irkutsk (52°N, 103°E), Russia, for the 1997–2006 period. The 557.7 nm emission observations data are compared with atmospheric and solar parameters. We note a difference in correlation coefficients between the 557.7 nm emission intensity and the solar activity indices in different phases of the solar cycle. Airglow observation results are compared with the observational data obtained by other authors.     

Modeling of ionospheric parameter variations in East Asia during the moderate geomagnetic disturbances

The results of modeling of ionospheric disturbances observed in the East Asian region during moderate storms are presented. The numerical model for ionosphere–plasmasphere coupling developed at the ISTP SB RAS is used to interpret the data of observations at ionospheric stations located in the longitudinal sector of 90–130°E at latitudes from auroral zone to equator. There is obtained a reasonable agreement between measurements and modeling results for winter and equinox. In the summer ionosphere, at the background of high ionization by the solar EUV radiation in the quiet geomagnetic period the meridional thermospheric wind strongly impacts the electron concentration in the middle and auroral ionosphere. The consistent calculations of the thermospheric wind permit to obtain the model results which are closer to summer observations. The actual information about the space-time variations of thermosphere and magnetosphere parameters should be taken into account during storms.     

The VEGA Venus balloon experiment

In June 1985, two instrumented balloons were placed in the atmosphere of Venus as part of the VEGA mission. Each balloon traveled about 30 percent of the way around the planet at a float altitude near 54 kilometers. In situsensors measured pressure, temperature, vertical wind velocity, cloud particle backscatter, ambient light level, and frequency of lightning. A ground-based network of 20 radio antennas tracked the balloons by very long baseline interferometry (VLBI) techniques to monitor the Venus winds. The history, organization, and principal characteristics of this international balloon experiment are described.     

Variation of monthly mean foF2 and hmF2 over a mid latitude station during the period 1997–2006

Ionosonde data of a mid latitude station Novosibirsk (Geog. Lat. 54.6°N, Geog. Long. 83.2°E) has been analyzed for the years 1997–2006 that covers the major part of solar cycle 23. Our results show the presence of winter anomaly in the daytime F2 layer critical frequency during different phases of solar activity. Results also reveal a semiannual variation of foF₂ with two maxima and a minimum that always appears in summer. While the first maximum is in the spring equinox, the second one is found to shift from autumn to winter with the increase of solar activity. The maximum height of F2 layer during the daytime shows variation with the solar activity. It is higher during the higher activity periods and lower during the periods of low activity. Results of ionosonde observations have been compared with those obtained from IRI-2007 model and it is found that model reproduces gross features of foF₂ variation. However, the modeled hmF₂ variations during equinoxes are significantly different from the ones derived using the ionosonde data. The model also underestimates the hmF₂ values.     

Studies of the configuration of the Venus ionospheric magnetic field

The dayside ionospheric magnetic field of Venus has been modelled from two different points of view. The Cloutier et al. electrodynamic model makes specific predictions about the behavior of the global magnetic field configuration that can be compared with those expected from the alternate diffusion/convection model. Although the diffusion/convection model is currently only one-dimensional, it is found that it is consistent with the observations in several areas where the 3-dimensional electrodynamic model is not.     

Composition of the Venus atmosphere below 100 km altitude

Our current knowledge on the composition of the Venus atmosphere in the altitude range from the surface to 100 km is compiled. Gases that have been measured, and whose mixing ratios are assumed to be constant with altitude, are CO₂, N₂, He, Ne, Ar, and Kr. Gases that have been identified in the lower and/or middle atmosphere, but whose mixing ratios may depend on altitude, latitude and/or local time, are CO, H₂O, HCl, HF, and SO₂. Conflicting data or only upper limits exist on some important trace gases, such as O₂, H₂, and Cl₂. The latter two are key constituents in the photochemistry of the middle atmosphere of Venus. The chapter concludes with a listing of the isotopic abundances of elements measured in the Venus atmosphere.     

Ionospheric and geomagnetic Pc5 oscillations as observed by the ionosonde and magnetometer at Sodankylä

The study is based on the data of the rapid-run ionosonde at the Sodankylä Geophysical Observatory at auroral latitude (L?=?5.25) which routinely performs one-minute sounding since 2007. This dataset allows a unique opportunity for investigating possible effects of ultra-low frequency (ULF, 1–7?mHz) waves in the auroral ionosphere. Suitable observations were made during moderately disturbed geomagnetic conditions typically at recovery of the geomagnetic storms caused by solar wind high-speed streams, in the daytime between 9 and 16 MLT. The ionospheric oscillations corresponding to Pc5 geomagnetic pulsations were found in variations of the virtual height of the F layer and the power of ionosonde reflections from E and F layers. The later are most probably caused by modulation of electron precipitation, which is also manifested in weak (about 0.01–0.06?dB) variations of cosmic noise absorption. The most important and novel result is that the pulsations of power of reflection from E and F layers typically has a spectral maximum at nearly half the periodicity of the Pc5 geomagnetic pulsations, whereas such spectral peak is negligible in the geomagnetic pulsations.