中国最早的观象台发掘

在山西襄汾县陶寺镇附近发掘出距今约4000年的最早观象台兼祭祀台遗址,它是由观测点、夯土柱和柱间狭缝组成,用于观测日出方位变化,确定回归年长度来制订历法。模拟观测结果表明,位于东南和东北的二狭缝可准确测定冬至和夏至日期,而此二狭缝之间有10个土柱,应象征着视太阳向北和向南每位移一个土柱为一个节气。由此推之,帝尧时的历法特征是将一岁分成20个节气的阳历,上古时的阴阳五行历即十月太阳历是源于它奠定的基础。     

Prediction of solar cycle 24 and beyond

In the previous study (Hiremath, Astron. Astrophys. 452:591, 2006a), the solar cycle is modeled as a forced and damped harmonic oscillator and from all the 22 cycles (1755–1996), long-term amplitudes, frequencies, phases and decay factor are obtained. Using these physical parameters of the previous 22 solar cycles and by an autoregressive model, we predict the amplitude and period of the present cycle 23 and future fifteen solar cycles. The period of present solar cycle 23 is estimated to be 11.73 years and it is expected that onset of next sunspot activity cycle 24 might starts during the period 2008.57±0.17 (i.e., around May–September 2008). The predicted period and amplitude of the present cycle 23 are almost similar to the period and amplitude of the observed cycle. With these encouraging results, we also predict the profiles of future 15 solar cycles. Important predictions are: (i) the period and amplitude of the cycle 24 are 9.34 years and 110 (±11), (ii) the period and amplitude of the cycle 25 are 12.49 years and 110 (±11), (iii) during the cycles 26 (2030–2042 AD), 27 (2042–2054 AD), 34 (2118–2127 AD), 37 (2152–2163 AD) and 38 (2163–2176 AD), the sun might experience a very high sunspot activity, (iv) the sun might also experience a very low (around 60) sunspot activity during cycle 31 (2089–2100 AD) and, (v) length of the solar cycles vary from 8.65 years for the cycle 33 to maximum of 13.07 years for the cycle 35.     

ROSA: A High-cadence,Synchronized Multi-camera Solar Imaging System

The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument is a synchronized, six-camera high-cadence solar imaging instrument developed by Queen’s University Belfast. The system is available on the Dunn Solar Telescope at the National Solar Observatory in Sunspot, New Mexico, USA, as a common-user instrument. Consisting of six 1k × 1k Peltier-cooled frame-transfer CCD cameras with very low noise (0.02 – 15 e s⁻¹ pixel⁻¹), each ROSA camera is capable of full-chip readout speeds in excess of 30 Hz, or 200 Hz when the CCD is windowed. Combining multiple cameras and fast readout rates, ROSA will accumulate approximately 12 TB of data per 8 hours observing. Following successful commissioning during August 2008, ROSA will allow for multi-wavelength studies of the solar atmosphere at a high temporal resolution.     

Influence of the moon on the earth’s magnetosphere at various phases of a solar activity cycle

We studied the dependence of the A _p -index describing the geomagnetic disturbance on the Moon’s phase. We processed available data for cycles 20–23 of the solar activity by the epoch super-position method. We discovered that, in the declining branch of the solar cycle, the highest values of the A _p -index relative to an average value are observed near new moon. The difference of the A _p -index values for new moon and full moon is approximately 18%. In the branch of increase and maximum of the solar cycle, we observed minimum values of the A _p -index during several days before full moon, and maximum values of the A _p -index take place during several days after full moon. The conclusion follows from this that the mechanism of the Moon’s effect on the earth’s magnetosphere is different essentially for intervals near new moon and full moon.     

Solar cycle variation of interplanetary coronal mass ejection latitudes

With the use of interplanetary coronal mass ejections (ICMEs) compiled by Richardson and Cane from 1996 to 2007 and the associated coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO), we investigate the solar cycle variation of real ICME-associated CME latitudes during solar cycle 23 using Song et al.’s method. The results show the following:

Some notes concerning the prediction of the amplitude of the solar activity cycles

The parameter G, which is determined from the general number of sunspots groups N _g according to the daily observations G=∑(1/N _g )², is offered. This parameter is calculated for the days when there is at least one sunspots group. It characterizes the minimum epoch solar activity. Parameter G mounts to the maximum during the epoch close to the minimal activity of sunspots. According to the data of the sequence of sunspots group in Greenwich–USAF/NOAA observatory format, observation data of Kislovodsk solar station and also daily Wolf number, the changes of parameter G during 100 years were reconstructed. It is demonstrated in the paper that parameter G’s amplitude in minimal solar activity n is linked with the sunspot cycle’s amplitude W _n+1 or one and half cycles. The 24th activity cycle prediction is calculated, which makes W ₂₄=135(±12).     

Statistical Assessment of Photospheric Magnetic Features in Imminent Solar Flare Predictions

In this study we use the ordinal logistic regression method to establish a prediction model, which estimates the probability for each solar active region to produce X-, M-, or C-class flares during the next 1-day time period. The three predictive parameters are (1) the total unsigned magnetic flux T _flux, which is a measure of an active region’s size, (2) the length of the strong-gradient neutral line L _gnl, which describes the global nonpotentiality of an active region, and (3) the total magnetic dissipation E _diss, which is another proxy of an active region’s nonpotentiality. These parameters are all derived from SOHO MDI magnetograms. The ordinal response variable is the different level of solar flare magnitude. By analyzing 174 active regions, L _gnl is proven to be the most powerful predictor, if only one predictor is chosen. Compared with the current prediction methods used by the Solar Monitor at the Solar Data Analysis Center (SDAC) and NOAA’s Space Weather Prediction Center (SWPC), the ordinal logistic model using L _gnl, T _flux, and E _diss as predictors demonstrated its automatic functionality, simplicity, and fairly high prediction accuracy. To our knowledge, this is the first time the ordinal logistic regression model has been used in solar physics to predict solar flares.     

Effects of the solar eclipse of August 1, 2008, on the earth’s lower atmosphere

The paper presents results of optical observations and analysis of dynamics of effects on the earth’s lower atmosphere of the partial solar eclipse (of magnitude 42%) of August 1, 2008, near Kharkov. This is compared with the effects induced by the partial solar eclipses on August 11, 1999, and October 3, 2005. All three eclipses occurred around midday. The standard deviation of the solar-limb displacement σ _S during the eclipses on October 3, 2005, August 1, 2008, and August 11, 1999, was established to decrease by 0.13, 0.30, and 0.68″ at the maximum of the solar obscuration function 0.13, 0.31, and 0.73, respectively, so that the temperature drop in the earth’s lower atmosphere t _a was 1.3, 2.0, and 7.3 K. The time lags of decreases of σ _S and t _a was found to be 15 and 5 minutes.     

Seeing-Induced Errors in Solar Doppler Velocity Measurements

Imaging systems based on a narrow-band tunable filter are used to obtain Doppler velocity maps of solar features. These velocity maps are created by taking the difference between the blue- and red-wing intensity images of a chosen spectral line. This method has the inherent assumption that these two images are obtained under identical conditions. With the dynamical nature of the solar features as well as the Earth’s atmosphere, systematic errors can be introduced in such measurements. In this paper, a quantitative estimate of the errors introduced due to variable seeing conditions for ground-based observations is simulated and compared with real observational data for identifying their reliability. It is shown, under such conditions, that there is a strong cross-talk from the total intensity to the velocity estimates. These spurious velocities are larger in magnitude for the umbral regions compared to the penumbra or quiet-Sun regions surrounding the sunspots. The variable seeing can induce spurious velocities up to about 1 km s⁻¹. It is also shown that adaptive optics, in general, helps in minimising this effect.     

Phase Space Analysis: The Equilibrium of the Solar Magnetic Cycle

We present the results of a statistical study of the solar cycle based on the analysis of the superficial toroidal magnetic field component phase space. The magnetic field component used to create the embedded phase space was constructed from monthly sunspot number observations since 1750. The phase space was split into 32 sections (or time instants) and the average values of the orbits on this phase space were calculated (giving the most probable cycle). In this phase space it is shown that the magnetic field on the Sun’s surface evolves through a set of orbits that go around a mean orbit (i.e., the most probable magnetic cycle that we interpret as the equilibrium solution). It follows that the most probable cycle is well represented by a van der Pol oscillator limit curve (equilibrium solution), as can be derived from mean-field dynamo theory. This analysis also retrieves the empirical Gnevyshev – Ohl’s rule between the first and second parts of the solar magnetic cycle. The sunspot number evolution corresponding to the most probable cycle (in phase space) is presented.     

Variations of 14C around AD 775 and AD 1795 – due to solar activity

The motivation for our study is the disputed cause for the strong variation of ¹⁴C around AD 775. Our method is to compare the ¹⁴C variation around AD 775 with other periods of strong variability. Our results are: (a) We see three periods, where 14C varied over 200 yr in a special way showing a certain pattern of strong secular variation: after a Grand Minimum with strongly increasing ¹⁴C, there is a series of strong short‐term drop(s), rise(s), and again drop(s) within 60 yr, ending up to 200 yr after the start of the Grand Minimum. These three periods include the strong rises around BC 671, AD 775, and AD 1795. (b) We show with several solar activity proxies (radioisotopes, sunspots, and aurorae) for the AD 770s and 1790s that such intense rapid ¹⁴C increases can be explained by strong rapid decreases in solar activity and, hence, wind, so that the decrease in solar modulation potential leads to an increase in radioisotope production. (c) The strong rises around AD 775 and 1795 are due to three effects, (i) very strong activity in the previous cycles (i.e. very low ¹⁴C level), (ii) the declining phase of a very strong Schwabe cycle, and (iii) a phase of very weak activity after the strong ¹⁴C rise – very short and/or weak cycle(s) like the suddenly starting Dalton minimum. (d) Furthermore, we can show that the strong change at AD 1795 happened after a pair of two packages of four Schwabe cycles with certain hemispheric leadership (each package consists of two Gnevyshev‐Ohl pairs, respectively two Hale‐Babcock pairs). We show with several additional arguments that the rise around AD 775 was not that special. We conclude that such large, short‐term rises in ¹⁴C (around BC 671, AD 775, and 1795) do not need to be explained by highly unlikely solar super‐flares nor other rare events, but by extra‐solar cosmic rays modulated due to solar activity variations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Exact relativistic model for a superdense star

Assuming that the physical 3-spacet = const in a superdense star is spheroidal, a static spherically symmetric model based on an exact solution of Einstein’s equations is given which will permit densities of the order of 2 × 10¹⁴ gm cm^-3, radii of the order of a few kilometers and masses up to about four times the solar mass.     

The case for the Universe to be a quantum black hole

We present a necessary and sufficient condition for an object of any mass m to be a quantum black hole (q.b.h.): “The product of the cosmological constant Λ and the Planck’s constant ℏ, Λ and ℏ corresponding to the scale defined by this q.b.h., must be of order one in a certain universal system of units”. In this system the numerical values known for Λ are of order one in cosmology and about 10¹²² for Planck’s scale. Proving that in this system the value of the cosmological ℏ _c is of order one, while the value of ℏ for the Planck’s scale is about 10⁻¹²², both scales satisfy the condition to be a q.b.h., i.e. Λℏ≈1. In this sense the Universe is a q.b.h. We suggest that these objects, being q.b.h.’s, give us the linkage between thermodynamics, quantum mechanics, electromagnetism and general relativity, at least for the scale of a closed Universe and for the Planck’s scale. A mathematical transformation may refer these scales as corresponding to infinity (our universe) and zero (Planck’s universe), in a “scale relativity” sense.     

Influence of the hot oxygen corona on the satellite drag in the Earth’s upper atmosphere

Calculation results on the possible influence of the hot oxygen fraction on the satellite drag in the Earth’s upper atmosphere on the basis of the previously developed theoretical model of the hot oxygen geocorona are presented. Calculations have shown that for satellites with orbits above 500 km, the contribution from the corona is extremely important. Even for the energy flux Q ₀ = 1 erg cm⁻² s⁻¹, the contribution of the hot oxygen can reach tens of percent; and considering that real energy fluxes are usually higher, one can suggest that for extreme solar events, the contribution of hot oxygen to the atmospheric drag of the satellite will be dominant. For lower altitudes, the contribution of hot oxygen is, to a considerable degree, defined by the solar activity level. The calculations imply that for the daytime polar atmosphere, the change of the solar activity level from F _10.7 ∼ 200 to F _10.7 ∼ 70 leads to an increase in the ratio of the hot oxygen partial pressure to the thermal oxygen partial pressure by a factor of almost 30, from 0.85 to 25%. The transition from daytime conditions to nighttime conditions almost does not change the contribution from suprathermal particles. The decrease of the characteristic energy of precipitating particles, i.e., for the case of charged particles with a softer energy spectrum, leads to a noticeable increase of the contribution of the suprathermal fraction, by a factor of 1.5–2. It has been ascertained that electrons make the main contribution to the formation of the suprathermal fraction; and with the increase of the energy of precipitating electrons, the contribution of hot oxygen to the satellite drag also increases proportionally. Thus, for a typical burst, the contribution of the suprathermal fraction is 30% even at relatively high solar activity F _10.7 = 135.     

Orbit of an Astrometric Binary System

We present a new method to solve the problem of initial orbit determination of any binary system. This method is mainly based on the material available for an observer, for example relative positions at a given time of the couple in the “plane of sky”, namely the tangent plane to the celestial sphere at the position of the primary component. The problem of orbit determination is solved by splitting in successive stages in order to decorrelate the parameters of each other as much as possible. On one hand, the geometric problem is solved using the first Kepler’s law from a single observing run and, on the other hand, dynamical parameters are then inferred from the fit of the Kepler’s equation. At last, the final stage consists in determining the main physical parameters involved in the secular evolution of the system, that is the spin axis and the J₂ parameter of the primary if we assume that it is a quasi-spherical body. As a matter of fact there is no need to make too restrictive initial assumptions (such as circular orbit or zero eccentricity) and initial guesses of parameters required by a non-linear least-squares Levenberg–Marquardt algorithm are finally obtained after each stage. Such a protocol is very useful to study systems like binary asteroids for which all of the parameters should be considered a priori as unknowns. As an example of application, we used our method to estimate the set of the Pluto–Charon system parameters from observations collected in the literature since 1980.     

Solar Magnetic Activity and Total Irradiance Since the Maunder Minimum

We develop a model for estimating solar total irradiance since 1600 AD using the sunspot number record as input, since this is the only intrinsic record of solar activity extending back far enough in time. Sunspot number is strongly correlated, albeit nonlinearly with the 10.7-cm radio flux (F _10.7), which forms a continuous record back to 1947. This enables the nonlinear relationship to be estimated with usable accuracy and shows that relationship to be consistent over multiple solar activity cycles. From the sunspot number record we estimate F _10.7 values back to 1600 AD. F _10.7 is linearly correlated with the total amount of magnetic flux in active regions, and we use it as input to a simple cascade model for the other magnetic flux components. The irradiance record is estimated by using these magnetic flux components plus a very rudimentary model for the modulation of energy flow to the photosphere by the subphotospheric magnetic flux reservoir feeding the photospheric magnetic structures. Including a Monte Carlo analysis of the consequences of measurement and fitting errors, the model indicates the mean irradiance during the Maunder Minimum was about 1 ± 0.4 W m⁻² lower than the mean irradiance over the last solar activity cycle.     

Multispacecraft Observations of Magnetic Clouds and Their Solar Origins between 19 and 23 May 2007

We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing the structure of in situ events and relating them to their solar sources. The investigated period was characterized by two high-speed solar wind streams and magnetic clouds observed in the vicinity of the sector boundary. The observing satellites were separated by a longitudinal distance comparable to the typical radial extent of magnetic clouds at 1 AU (fraction of an AU), and, indeed, clear differences were evident in the records from these spacecraft. Two partial-halo coronal mass ejections (CMEs) were launched from the same active region less than a day apart, the first on 19 May and the second on 20 May 2007. The clear signatures of the magnetic cloud associated with the first CME were observed by STEREO B and Wind while only STEREO A recorded clear signatures of the magnetic cloud associated with the latter CME. Both magnetic clouds appeared to have interacted strongly with the ambient solar wind and the data showed evidence that they were a part of the coronal streamer belt. Wind and STEREO B also recorded a shocklike disturbance propagating inside a magnetic cloud that compressed the field and plasma at the cloud’s trailing portion. The results illustrate how distant multisatellite observations can reveal the complex structure of the extension of the coronal streamer into interplanetary space even during the solar activity minimum. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

A New Way that Planets Can Affect the Sun

We derive a perturbation inside a rotating star that occurs when the star is accelerated by orbiting bodies. If a fluid element has rotational and orbital components of angular momentum with respect to the inertially fixed point of a planetary system that are of opposite sign, then the element may have potential energy that could be released by a suitable flow. We demonstrate the energy with a very simple model in which two fluid elements of equal mass exchange positions, calling to mind a turbulent field or natural convection. The exchange releases potential energy that, with a minor exception, is available only in the hemisphere facing the barycenter of the planetary system. We calculate its strength and spatial distribution for the strongest case (“vertical”) and for weaker horizontal cases whose motions are all perpendicular to gravity. The vertical cases can raise the kinetic energy of a few well positioned convecting elements in the Sun’s envelope by a factor ≤7. This is the first physical mechanism by which planets can have a nontrivial effect on internal solar motions. Occasional small mass exchanges near the solar center and in a recently proposed mixed shell centered at 0.16R _s would carry fresh fuel to deeper levels. This would cause stars like the Sun with appropriate planetary systems to burn somewhat more brightly and have shorter lifetimes than identical stars without planets. The helioseismic sound speed and the long record of sunspot activity offer several bits of evidence that the effect may have been active in the Sun’s core, its envelope, and in some vertically stable layers. Additional proof will require direct evidence from helioseismology or from transient waves on the solar surface.     

A transient event in AD 775 reported by al‐Tabarī: A bolide – not a nova,supernova, or kilonova

Given that the cause for the strong increase in ¹⁴C in AD 774/5 in Japanese and German trees is still a matter of debate (e.g. short gamma‐ray burst or solar super‐flare), we have searched in Arabic chronicles for reports about unusual transient celestial events. In the History of al‐Tabarī we found two (almost identical) reports about such an event. The group around caliph al‐Mansūr observed a transient event while on the way from Baghdad to Mecca on AD 775 Augusst 29– September 1 (Julian calendar). A celestial object (kawkab) was seen to fall or set (inqadda), and its trace (atharuhu) was seen for at least tens of minutes (up to 70–90 min) during morning twilight. The reports use the Arabic words kawkab and athar(uhu), which were also used in the known Arabic reports about supernovae SN 1006 and 1054, so that one might consider an interpretation as a nova‐like event. The kawkab (celestial object) was observed only during the morning twilight at a brightness of probably between about –3 and 0 mag. Such a brightness and time‐scale would be expected for optical kilonovae (at ∼3 to 9 kpc) in the context of short gamma‐ray bursts. There are no similar reports from eastern Asia for this time. However, the short reports are fully consistent with a bolide: The word kawkab can be used for meteor, the verb inqad_. d_. a normally means falling down, the word atharuhu can mean its trace. We therefore prefer the interpretation as bolide. We discuss in detail how to convert the Muslim calendar date to a date in the Julian calendar using first the calculated Islamic calendar and then considering the time when the crescent new moon could be visible at the given location. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Magnetic Correspondence between the Photosphere and the Heliosphere

The solar magnetic field maps every point in the corona to a corresponding place on the solar surface. Identifying the magnetic connection map is difficult at low latitudes near the heliospheric current sheet, but remarkably simple in coronal hole interiors. We present a simple analytic magnetic model (‘pseudocurrent extrapolation’) that reproduces the global structure of the corona, with significant physical advantages over other nearly analytic models such as source-surface potential field extrapolation. We use the model to demonstrate that local horizontal structure is preserved across altitude in the central portions of solar coronal holes, up to at least 30 R_s, in agreement with observations. We argue that the preserved horizontal structure may be used to track the magnetic footpoint associated with the location of a hypothetical spacecraft traveling through the solar corona, to relate in situ measurements of the young solar wind at ∼10–30 R_s to particular source regions at the solar surface. Further, we discuss the relationship between readily observable geometrical distortions and physical parameters of interest such as the field-aligned current density.