联合太阳和行星际物理参数预测行星际激波能否到达地球

选取第23太阳活动周（1997—2006年）期间542例由太阳爆发活动驱动的行星际激波事件,分析确定了太阳源头和行星际空间中影响行星际激波能否到达地球轨道的关键物理参数;在此基础上,建立了预测行星际激波能否到达地球的新预报模型（EdEaSPM）. 回溯预报结果表明,EdEaSPM模型的预报成功率约为66%,略高于国际一流预报模型的预报成功率;EdEaSPM模型的虚报率未超过50%,改善了当前国际主流模型虚报率较大的情况;对于偏度指标,虽然当前所有模型的偏度值均大于1,但EdEaSPM模型的偏度值最接近于1且明显小于其他模型的偏度值;EdEaSPM模型的其他评价指标也都高于国际主流模型的相应指标. 此外,选取2012年期间的激波事件对EdEaSPM模型进行了预报检验,预测结果与实际情况吻合. EdEaSPM模型不仅能够提前约1～3天进行预报,而且预报效果与国际一流模型具有可比性,尤其是在提高预报成功率及降低虚报率方面具有一定优势.     

A new approach to solar cycle forecasting

We describe a novel approach for determining the timing of the solar cycle and tracking its evolution relative to other cycles. This method also has predictive capability for forecasting the cycle “onset.” Based on current trends, we expect that Cycle 23 will be about 1 year longer than the previous two cycles.     

A Brief Review of Interplanetary Investigations in China from 2014 to 2016

Great progress has been made in the research of solar corona and interplanetary physics by the Chinese scientists during the past two years (2014-2016). Nearly 100 papers were published in this area. In this report, we will give a brief review to these progresses. The investigations include:solar corona, solar wind and turbulence, superhalo electron and energetic particle in the inner heliosphere, solar flares and radio bursts, Coronal Mass Ejections (CMEs) and their interplanetary counterparts, Magnetohydrodynamic (MHD) numerical modeling, CME/shock arrival time prediction, magnetic reconnection, solar variability and its impact on climate. These achievements help us to better understand the evolution of solar activities, solar eruptions, their propagations in the heliosphere, and potential geoeffectiveness. They were achieved by the Chinese solar and space scientists independently or via international collaborations.     

Properties of solar X-ray flares and proton event forecasting

X-ray flares and acceleration processes are in one complex of sporadic solar events (together with CMEs, radio bursts, magnetic field dissipation and reconnection). This supposes the connection (if not physical, but at least statistical) between characteristics of the solar energetic proton events and flares. The statistical analysis indicates that probability and magnitude of the near-Earth proton enhancement depends heavily on the flare importance and their heliolongitude. These relations may be used for elaboration of the forecasting models, which allow us to calculate probability of the solar proton events from the X-ray observations.     

Cosmic radiation exposure of aircraft occupants on simulated high-latitude flights during solar proton events from 1 January 1986 through 1 January 2008

From 1 January 1986 through 1 January 2008, GOES satellites recorded 170 solar proton events. For 169 of these events, we estimated effective and equivalent dose rates and doses of galactic cosmic radiation (GCR) and solar cosmic radiation (SCR), received by aircraft occupants on simulated high-latitude flights. Dose rate and dose estimates that follow are for altitudes 30, 40, 50, and 60 kft, in that order.     

Interplanetary Physics in Mainland China

During the past two years (2016-2018), great achievements have been made in the Chinese research of interplanetary physics, with nearly 100 papers published in the academic journals. The achievements are including but not limited to the following topics:solar corona; solar wind and turbulence; filament/prominence and jets; solar flare; radio bursts; particle acceleration at coronal shocks; magnetic flux ropes; instability; instrument; Coronal Mass Ejections (CMEs) and their interplanetary counterparts; Magnetohydrodynamic (MHD) numerical modeling; solar energetic particles and cosmic rays. The progress further improves our understanding of the eruptions of solar activities, their evolutions and propagations in the heliosphere, and final geoeffects on our Earth. These results were achieved by the Chinese solar and space scientists independently or via international collaborations. This paper will give a brief review of these achievements.     

Interplanetary shocks and geomagnetic activity during solar maximum (2000) and solar minimum (1995–1996)

Plasma and magnetic field parameter variations through fast forward interplanetary shocks were correlated with the peak geomagnetic activity index Dst in a period from 0 to 3 days after the shock, during solar maximum (2000) and solar minimum (1995–1996). Solar wind speed (V) and total magnetic field (B_t) were the parameters with higher correlations with peak Dst index. The correlation coefficients were higher during solar minimum (r² = 56% for V and 39% for B_t) than during solar maximum (r² = 15% for V and 12% for B_t). A statistical distribution of geomagnetic activity levels following interplanetary shocks was obtained. It was observed that during solar maximum, 36% and 28% of interplanetary shocks were followed by intense (Dst  −100 nT) and moderate (−50  Dst < −100 nT) geomagnetic activity, whereas during solar minimum 13% and 33% of the shocks were followed by intense and moderate geomagnetic activity. It can be concluded that the upstream/downstream variations of V and B_t through the shocks were the parameters better correlated with geomagnetic activity level, and during solar maximum a higher relative number of interplanetary shocks can be followed by intense geomagnetic activity than during solar minimum. One can extrapolate, for forecasting goals, that during a whole solar cycle a shock has a probability of around 50% to be followed by intense/moderate geomagnetic activity.     

Interplanetary shocks and sudden impulses during solar maximum (2000) and solar minimum (1995–1996)

In this work a study is performed on the correlation between fast forward interplanetary shock parameters at 1 Astronomical Unit and sudden impulse (SI) amplitudes in the H-component of the geomagnetic field, for periods of solar activity maximum (year 2000) and minimum (year 1995–1996). Solar wind temperature, density and speed, and total magnetic field, were taken to calculate the static pressures (thermal and magnetic) both in the upstream and downstream sides of the shocks. The variations of the solar wind parameters and pressures were then correlated with SI amplitudes. The solar wind speed variations presented good correlations with sudden impulses, with correlation coefficients larger than 0.70 both in solar maximum and solar minimum, whereas the solar wind density presented very low correlation. The parameter better correlated with SI was the square root dynamic pressure variation, showing a larger correlation during solar maximum (r = 0.82) than during solar minimum (r = 0.77). The correlations of SI with square root thermal and magnetic pressure were smaller than with the dynamic pressure, but they also present a good correlation, with r > 0.70 during both solar maximum and minimum. Multiple linear correlation analysis of SI in terms of the three pressure terms have shown that 78% and 85% of the variance in SI during solar maximum and minimum, respectively, are explained by the three pressure variations. Average sudden impulse amplitude was 25 nT during solar maximum and 21 nT during solar minimum, while average square root dynamic pressure variation is 1.20 and 0.86 nPa^1/2 during solar maximum and minimum, respectively. Thus on average, fast forward interplanetary shocks are 33% stronger during solar maximum than during solar minimum, and the magnetospheric SI response has amplitude 20% higher during solar maximum than during solar minimum. A comparison with theoretical predictions (Tsyganenko’s model corrected by Earth’s induced currents) of the coefficient of sudden impulse change with solar wind dynamic pressure variation showed excellent agreement, with values around 17 nT/nPa^1/2.     

Research Progress of Interplanetary Physics in Mainland China

Significant progress has been made by Chinese scientists in research of interplanetary physics during the recent two years (2018-2020). These achievements are reflected at least in the following aspects:Activities in solar corona and lower solar atmosphere; solar wind and turbulence; filament/prominence, jets, flares, and radio bursts; active regions and solar eruptions; coronal mass ejections and their interplanetary counterparts; other interplanetary structures; space weather prediction methods; magnetic reconnection; Magnetohydrodynamic (MHD) numerical modeling; solar energetic particles, cosmic rays, and Forbush decreases; machine learning methods in space weather and other aspects. More than one hundred and forty papers in the academic journals have been published in these research directions. These fruitful achievements are obtained by Chinese scholars in solar physics and space physics either independently or through international collaborations. They greatly improve people's understanding of solar activities, solar eruptions, the corresponding space weather effects, and the Sun-Earth relations. Here we will give a very brief review on the research progress. However, it must be pointed out that this paper may not completely cover all achievements in this field due to our limited knowledge.     

On the correlation of the solar wind observed at the L5 point and at the Earth

The L5 point is a promising location for forecasting co-rotating high-speed streams in the solar wind arriving at the Earth. We correlated the solar wind data obtained by the Nozomi spacecraft in interplanetary space and by the Advanced Composition Explorer (ACE) at the L1 point, and found that the correlation is significantly improved from that of the 27-day recurrence of ACE data. Based on the correlation between the two spacecraft observations, we estimated the correlation of the solar wind velocity between the L5 point and at the Earth, and found that the correlation coefficient was about 0.78 in late 1999, while that of the 27-day recurrence was 0.51. Eighty-eight percent of the velocity difference falls within 100 km/s between the L5 point and the Earth. This demonstrates the potential capability of solar wind monitoring at the L5 point to forecast the geomagnetic disturbances 4.5 days in advance.     

Propagation and interaction of interplanetary transient disturbances. Numerical simulations

We study the heliocentric evolution of ICME-like disturbances and their associated transient forward shocks (TFSs) propagating in the interplanetary (IP) medium comparing the solutions of a hydrodynamic (HD) and magnetohydrodynamic (MHD) models using the ZEUS-3D code [Stone, J.M., Norman, M.L., 1992. Zeus-2d: a radiation magnetohydrodynamics code for astrophysical flows in two space dimensions. i – the hydrodynamic algorithms and tests. Astrophysical Journal Supplement Series 80, 753–790]. The simulations show that when a fast ICME and its associated IP shock propagate in the inner heliosphere they have an initial phase of about quasi-constant propagation speed (small deceleration) followed, after a critical distance (deflection point), by an exponential deceleration. By combining white light coronograph and interplanetary scintillation (IPS) measurements of ICMEs propagating within 1 AU [Manoharan, P.K., 2005. Evolution of coronal mass ejections in the inner heliosphere: a study using white-light and scintillation images. Solar Physics 235 (1–2), 345–368], such a critical distance and deceleration has already been inferred observationally. In addition, we also address the interaction between two ICME-like disturbances: a fast ICME 2 overtaking a previously launched slower ICME 1. After interaction, the leading ICME 1 accelerates and the tracking ICME 2 decelerates and both ICMEs tend to arrive at 1 AU having similar speeds. The 2-D HD and MHD models show similar qualitative results for the evolution and interaction of these disturbances in the IP medium.     

Advances in modeling gradual solar energetic particle events

Solar energetic particles pose one of the most serious hazards to space probes, satellites and astronauts. The most intense and largest solar energetic particle events are closely associated with fast coronal mass ejections able to drive interplanetary shock waves as they propagate through interplanetary space. The simulation of these particle events requires knowledge of how particles and shocks propagate through the interplanetary medium, and how shocks accelerate and inject particles into interplanetary space. Several models have appeared in the literature that attempt to model these energetic particle events. Each model presents its own simplifying assumptions in order to tackle the series of complex phenomena occurring during the development of such events. The accuracy of these models depends upon the approximations used to describe the physical processes involved in the events. We review the current models used to describe gradual solar energetic particle events, their advances and shortcomings, and their possible applications to space weather forecasting.     

Comparison of heliospheric conditions near the earth during four recent solar maxima

Statistical properties of the daily averaged values of the solar activity (sunspot numbers, total solar irradiance and 10.7 cm radio emission indices), the solar wind plasma and the interplanetary magnetic field parameters near the Earth’s orbit are investigated for a period from 1964 to 2002 covering the maxima of four solar cycles from 20th to 23rd. Running half-year averages show significant solar cycle variations in the solar activity indices but only marginal and insignificant changes in comparison with background fluctuations for heliospheric bulk plasma and magnetic field parameters. The current 23rd cycle maximum is weaker than 21st and 22nd maxima, but slightly stronger than 20th cycle in most of solar and heliospheric manifestations.     

Research Advances of Solar Corona and Interplanetary Physics in China: 2012–2014

Solar transients and their related interplanetary counterparts have severe effects on the space environments of the Earth. Therefore, the research of solar corona and interplanetary physics has become the focus of study for both solar and space scientists. Considerable progress has been achieved in these aspects by the solar and space physics community of China during 2012–2014, which will be given in this report. The brief report summarizes the research advances of solar corona and interplanetary physics into the following parts: solar wind origin and turbulence, coronal waves and seismology, solar eruptions, solar energetic particle and galactic cosmic ray, magnetic reconnection,Magnetohydrodynamic(MHD) models and their applications, waves and structures in solar wind,propagation of ICMEs/shocks and their arrival time predictions. These research achievements have been achieved by Chinese solar and space scientists independently or via international collaborations.     

An empirical model to predict the 1-AU arrival of interplanetary shocks

We extend the empirical coronal mass ejection (CME) arrival model of Gopalswamy et al. [Gopalswamy, N. et al. Predicting the 1-AU arrival times of coronal mass ejections, J. Geophys. Res. 106, 29207, 2001] to predict the 1-AU arrival of interplanetary (IP) shocks. A set of 29 IP shocks and the associated magnetic clouds observed by the Wind spacecraft are used for this study. The primary input to this empirical shock arrival model is the initial speed of white-light CMEs obtained using coronagraphs. We use the gas dynamic piston–shock relationship to derive the ESA model which provides a simple means of obtaining the 1-AU speed and arrival times of interplanetary shocks using CME speeds.     

A new parameter to define interplanetary coronal mass ejections

The interplanetary manifestations of coronal mass ejections, ICMEs, have many signatures in the solar wind but none of these signatures in the velocity, density, temperature, magnetic field, plasma composition or energetic particles uniquely and unambiguously identifies the occurrence of an ICME. Different investigators identify different events when confronted with the same data. Herein, we present a single physical parameter that combines information from multiple plasma components and that holds the promise of defining a beginning and an end of the region of influence ICME and an indication of the location of the encounter with the ICME relative to its central meridian. This parameter is the total plasma pressure perpendicular to the magnetic field, consisting of the sum of the magnetic pressure and plasma kinetic or thermal pressure. It provides a vehicle for classifying the nature of the ICME encounter and, in many cases, provides an unambiguous start and stop time of the event. However, it does not provide a start and stop time for any embedded flux rope. This identification depends on examination of the magnetic field.     

Comparing proton fluxes of central meridian SEP events with those predicted by SOLPENCO

We have developed an operational code, SOLPENCO, that can be used for space weather prediction schemes of solar energetic particle (SEP) events. SOLPENCO provides proton differential flux and cumulated fluence profiles from the onset of the event up to the arrival of the associated traveling interplanetary shock at the observer’s position (either 1.0 or 0.4 AU). SOLPENCO considers a variety of interplanetary scenarios where the SEP events develop. These scenarios include solar longitudes of the parent solar event ranging from E75 to W90, transit speeds of the associated shock ranging from 400 to 1700 km s⁻¹, proton energies ranging from 0.125 to 64 MeV, and interplanetary conditions for the energetic particle transport characterized by specific mean free paths. We compare the results of SOLPENCO with flux measurements of a set of SEP events observed at 1 AU that fulfill the following four conditions: (1) the association between the interplanetary shock observed at 1 AU and the parent solar event is well established; (2) the heliolongitude of the active region site is within 30° of the Sun–Earth line; (3) the event shows a significant proton flux increase at energies below 96 MeV; (4) the pre-event intensity background is low. The results are discussed in terms of the transit velocity of the shock and the proton energy. We draw conclusions about both the use of SOLPENCO as a prediction tool and the required improvements to make it useful for space weather purposes.     

One-up on L1: Can X-rays provide longer advanced warning of solar wind flux enhancements than upstream monitors?

Observations of strong solar wind proton flux correlations with ROSAT X-ray rates along with high spectral resolution Chandra observations of X-rays from the dark Moon show that soft X-ray emission mirrors the behavior of the solar wind. In this paper, based on an analysis of an X-ray event observed by XMM-Newton resulting from charge exchange of high charge state solar wind ions and contemporaneous neutral solar wind data, we argue that X-ray observations may be able to provide reliable advance warning, perhaps by as much as half a day, of dramatic increases in solar wind flux at Earth. Like neutral atom imaging, this provides the capability to monitor the solar wind remotely rather than in situ.     

Flight safety implications of the extreme solar proton event of 23 February 1956

There is considerable speculation about the effects at aircraft altitudes resulting from extreme solar proton events. The ground level event (GLE) of 23 February 1956 (GLE 5), remains the largest solar proton event of the neutron monitor era in terms of its influence on count rates at monitors near sea level. During this GLE the count rate was increased by as much as 4760% (15-min average) at the Leeds monitor relative to the count rate from galactic cosmic radiation (GCR). Two modern models of the event cumulative solar proton spectrum for this event, a 6-parameter fit in energy and a 4-parameter Band fit in rigidity, are compared with 1-h of GCR at solar minimum. While effective doses calculated with CARI-7A for both models at low geomagnetic cutoff rigidities are indeed high when compared with GCR and can exceed recommended exposure limits, both GLE spectra exhibit a much stronger dependence on cutoff rigidity than GCR, and a larger fraction of the dose from neutrons. At locations with cutoff rigidities above 4.2 and 6.4?GV, respectively, the GLE effective doses are smaller than the GCR hourly dose. At locations with cutoff rigidities above about 4?GV, GCR was the dominant source of exposure in 10?h or less at all altitudes examined. This suggests that if a similar event occurs in the future, low- and mid-latitude flights at modern jet flight altitudes could be well-protected by Earth’s magnetic field.     

Force-free magnetic field in a cylindrical flux rope without a constant alpha

It is generally assumed that magnetic fields inside interplanetary magnetic clouds and flux ropes in the solar photosphere are force-free. In order to model such fields, the solution of rot B = B is commonly used where  = const. But comparisons of this solutions with observations show significant difference. To treat this problem,we examine the solutions with .