太阳质子事件与太阳耀斑的关系

通过对0°W-39°W,40°W-70°W,71°W-90°W经度范围内太阳质子事件与太阳耀斑的相关性计算分析,发现太阳质子事件与太阳耀斑的相关系数依赖于经度.太阳耀斑积分与地球磁链接区域（40°W-70°W）太阳质子事件强度的相关系数最大.相关系数的这种特点与耀斑加速粒子的最大流量只出现在磁链接区域的特征相吻合.计算结果表明,太阳耀斑对太阳质子事件具有贡献,即耀斑对E ≥ 10MeV的质子加速有贡献.耀斑和CME在磁链接区域对太阳质子事件的贡献相同,这说明太阳质子事件是混合型事件.     

Large geomagnetic storms of extreme solar event periods in solar cycle 23

During extreme solar events such as big flares or/and energetic coronal mass ejections (CMEs) high energy particles are accelerated by the shocks formed in front of fast interplanetary coronal mass ejections (ICMEs). The ICMEs (and their sheaths) also give rise to large geomagnetic storms which have significant effects on the Earth’s environment and human life. Around 14 solar cosmic ray ground level enhancement (GLE) events in solar cycle 23 we examined the cosmic ray variation, solar wind speed, ions density, interplanetary magnetic field, and geomagnetic disturbance storm time index (D_st). We found that all but one of GLEs are always followed by a geomagnetic storm with D_st  −50 nT within 1–5 days later. Most(10/14) geomagnetic storms have D_st index  −100  nT therefore generally belong to strong geomagnetic storms. This suggests that GLE event prediction of geomagnetic storms is 93% for moderate storms and 71% for large storms when geomagnetic storms preceded by GLEs. All D_st depressions are associated with cosmic ray decreases which occur nearly simultaneously with geomagnetic storms. We also investigated the interplanetary plasma features. Most geomagnetic storm correspond significant periods of southward B_z and in close to 80% of the cases that the B_z was first northward then turning southward after storm sudden commencement (SSC). Plasma flow speed, ion number density and interplanetary plasma temperature near 1 AU also have a peak at interplanetary shock arrival. Solar cause and energetic particle signatures of large geomagnetic storms and a possible prediction scheme are discussed.     

Characteristics of solar particle events at Mars relative to Earth

While not specifically designed to detect solar energetic particle radiation, the Electron Reflectometer onboard Mars Global Surveyor (MGS/ER) collected such data from January 1999 through October 2006. Energetic protons (?25 MeV) and other ions penetrated the MGS/ER shielding and registered counts within the instrument’s electronics. During solar particle events (SPE’s), prolonged enhancements in the particle background were observed at Mars with time intensity profiles similar to Earth based SPE observations. Throughout the lifespan of MGS/ER, 85 distinct SPE’s were observed. Basic characteristics of Mars based SPE observations and the frequency of SPE occurrences at Mars are compared to corresponding Earth based observations. Approximately 22% of SPE’s that occurred during MGS/ER operation were observed at Earth but not Mars. Similarly, 19% of SPE’s were observed at Mars but not Earth. Time intensity profiles at Earth and Mars match predictions provided in the literature, based on the physical location of the detector with respect to the motion of the interplanetary shock wave. Note: The work described herein was largely conducted as part of a doctoral dissertation produced by the author.     

CME-geometry and cosmic-ray anisotropy observed by a prototype muon detector network

We analyze the cosmic-ray anisotropy observed by a prototype network of muon detectors during geomagnetic storms associated with coronal mass ejections (CMEs). The network currently consists of multidirectional surface muon detectors at Nagoya (Japan) and Hobart (Australia), together with a prototype detector at São Martinho (Brazil) which has been in operation since March, 2001. In this report, we analyze the anisotropy recorded in both the muon detector and neutron monitor (the Spaceship Earth) networks and find significant enhancements of cosmic-ray anisotropy during geomagnetic storms. Following the analysis by Bieber and Evenson [Bieber, J.W., Evenson, P. CME geometry in relation to cosmic ray anisotropy. Geophys. Res. Lett. 25 (1998) 2955–2958] for the neutron monitor data at 10 GeV, we also derive cosmic-ray density gradients from muon data at higher-energy (50 GeV), possibly reflecting the larger-scale geometry of CMEs causing geomagnetic storms. We particularly find in some events the anisotropy enhancement clearly starting prior to the storm onset in both the muon and neutron data. This is the first result of the CME-geometry derived from simultaneous observations of the anisotropy with networks of multidirectional muon detectors and neutron monitors.     

太阳风对流效应对CME渡越时间的影响

基于Gopalswamy预报日冕物质抛射（CME）渡越时间的经验模型,选取1996-2007年间52个与地磁效应Dst<-50nT相关的CME事件以及10个引起特大磁暴（Dst<-200nT）的CME事件,结合ACE卫星在1AU处的太阳风观测资料,分析背景太阳风对流效应对CME到达1AU处渡越时间预报的影响.对于52个CME事件,考虑太阳风对流效应的影响后,预报的标准偏差由16.5h降为11.4h,修正后的误差分布趋向于高斯分布,并且68%事件的预报误差小于15h.对于10个引起特大磁暴的CME事件,考虑太阳风对流效应的影响后,预报的标准偏差由10.6h降低到6.5h,其中6个事件的预报误差小于5h.研究结果表明,对于CME事件,考虑背景太阳风对流效应的影响可以降低预报CME渡越时间的标准偏差,说明太阳风对流效应对预报CME事件渡越时间具有重要作用.     

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.     

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.     

Solar flares,CMEs and solar energetic particle events during solar cycle 24

We present here a study of Solar Energetic Particle Events (SEPs) associated with solar flares during 2010–2014 in solar cycle 24. We have selected the flare events (≥GOES M-class), which produced SEPs. The SEPs are classified into three categories i.e. weak (proton intensity?≤?1?pfu), minor (1?pfu?<?proton intensity?<?10?pfu) and major (proton intensity?≥?10?pfu). We used the GOES data for the SEP events which have intensity greater than one pfu and SOHO/ERNE data for the SEP event less than one pfu intensity. In addition to the flare and SEP properties, we have also discussed different properties of associated CMEs.     

Solar and interplanetary precursors of geomagnetic storms in solar cycle 23

Estimating the magnetic storm effectiveness of solar and associated interplanetary phenomena is of practical importance for space weather modelling and prediction. This article presents results of a qualitative and quantitative analysis of the probable causes of geomagnetic storms during the 11-year period of solar cycle 23: 1996–2006. Potential solar causes of 229 magnetic storms (Dst ? −50 nT) were investigated with a particular focus on halo coronal mass ejections (CMEs). A 5-day time window prior to the storm onset was considered to track backward the Sun’s eruptions of halo CMEs using the SOHO/LASCO CMEs catalogue list. Solar and interplanetary (IP) properties associated with halo CMEs were investigated and correlated to the resulting geomagnetic storms (GMS). In addition, a comparative analysis between full and partial halo CME-driven storms is established. The results obtained show that about 83% of intense storms (Dst ? −100 nT) were associated with halo CMEs. For moderate storms (−100 nT < Dst ? −50 nT), only 54% had halo CME background, while the remaining 46% were assumed to be associated with corotating interaction regions (CIRs) or undetected frontside CMEs. It was observed in this study that intense storms were mostly associated with full halo CMEs, while partial halo CMEs were generally followed by moderate storms. This analysis indicates that up to 86% of intense storms were associated with interplanetary coronal mass ejections (ICMEs) at 1 AU, as compared to moderate storms with only 44% of ICME association. Many other quantitative results are presented in this paper, providing an estimate of solar and IP precursor properties of GMS within an average 11-year solar activity cycle. The results of this study constitute a key step towards improving space weather modelling and prediction.     

CMEs and active regions on the sun

The relationship between active regions (ARs) and coronal mass ejections (CMEs) is studied. For this purpose a statistical analysis of 694 CMEs associated with ARs was carried out. We considered the relationship between properties of the CMEs and ARs characterized using the McIntosh classification. We demonstrated that CMEs are likely to be launched from ARs in the mature phase of their evolution when they have complex magnetic field. The fastest and halo CMEs can be ejected only from the most complex ARs (when an AR is a bipolar group of spots with large asymmetric penumbras around the main spot with many smaller spots in the group). We also showed that the wider events have a tendency to originate from uncomplicated magnetic structures. This tendency was used for estimation of the real angular widths of the halo CMEs. The probability of launching of fast CMEs increases together with increase of the complexity and size of ARs. The widest, but slow, CMEs originate from the simplest magnetic structure which are still able to produce CMEs. Our results could be useful for forecasting of space weather.     

Solar extreme events 2005–2006: Effects on near-Earth space systems and interplanetary systems

Extreme events are defined as those events in which the characteristics (e.g. field strength, speed, intensity of radiation, energies) of the associated phenomena (e.g. solar flares, coronal mass ejections, solar proton events) are some orders of magnitude larger than in other events. Such strong events commonly occur about two years before and after sunspot maximum and some strong events occur as well in the declining phase before the solar activity minimum [Bothmer V., Zhukov A. The 11 Sun as the prime source of space weather, in: Bothmer, V., Daglis, I. (Eds.), Space Weather: Physics and Effects, Springer Praxis Books, 12 pp. 438, 2007]. In the first part of the paper the characteristics of the Jan. 2005 and Dec. 2006 events are given. This is followed by a presentation of the effects that were encountered on technological systems and also addresses the issue of what could have occurred on biological systems during such events. The second part of the paper deals with how one should go about analyzing solar extreme events - as part of the global distribution of all events or as ”outliers” with their own special characteristics.     

Short-term periodicities in the downward longwave radiation and their associations with cosmic ray and solar interplanetary data

In this study downward longwave (LW) atmospheric radiation data for the period of 2014–2020 were used to search for short-term periodicities using fast Fourier transform (FFT). Several local peaks in the power spectrum density were found and established. The time series exhibits a series of significant peaks (exceeding the 95% confidence limit), such as at 273 days, 227 days, 200 days, 178 days, 157 days, 110 days, 120 days, 87 days, 73 days, 53–56 days, 35–30 days, 25–27 days, 21 days, 13 days, and 9–10 days.Moreover, cosmic ray data from KACST muon detector and the Oulu neutron monitor, as well as the data for the solar radio flux at 10.7 cm (F10.7 cm), Dst index, and solar wind speed for the same period as the LW data, were used to look for common cyclic variations and periodicities matching those found in the LW radiation. This was done to investigate the possible effect of the solar activity parameters on LW radiation. Several common periodicities were observed in the spectra of all the variables considered, such as 227 days, 154–157 days, 25–27 days, and 21 days. Some of the periodicities found in the LW radiation spectrum can be attributed to the modulation of the cosmic ray intensity by solar activity. Others are attributed to the disturbances in the interplanetary magnetic field. Based on the spectral results, we suggest that the solar signals may directly or indirectly affect the variations of the downward longwave radiation, which in turn may affect climate change.     

Enhancement of solar wind low-energy energetic particles as precursor of geomagnetic disturbance in operational geomagnetic forecast

A study of the relationship between solar wind low-energy energetic particles using data from the Electron, Proton, and Alpha Monitor (EPAM) onboard the Advanced Compositional Explorer spacecraft (ACE) and geomagnetic activity using data from Canadian magnetic observatories in Canada’s polar cap, auroral zone, and subauroral zone was carried out for a period spanning 1997–2005. Full halo coronal mass ejections (CMEs) were used to gauge the initial particle enhancements and the subsequent geomagnetic activity. It was found that maximum geomagnetic activity is related to maximum particle enhancements in a non-linear fashion. Quadratic fit of the data results in expressions that can be easily used in an operational space weather setting to forecast geomagnetic disturbance quantitatively. A superposed epoch analysis shows increase in particle flux level starts hours before geomagnetic activity attains its peak, affirming the precursory nature of EPAM particles for the impending geomagnetic impact of CME. This can supplement the decision process in formulating geomagnetic warning after the launch of CME from the Sun but before the arrival of shock at Earth. The empirical relationships between solar wind low-energy energetic particles and geomagnetic activity revealed in this statistical study can be easily codified, and thus utilized in operational space weather forecast to appraise the geoeffectiveness of the CME and to provide a quantitative forecast for maximum geomagnetic activity in Canada’s polar cap, auroral zone, and subauroral zone after the occurrence of a CME.     

The effect of solar–geomagnetic activity during hospital admission on coronary events within 1 year in patients with acute coronary syndromes

Some evidence indicates the deterioration of the cardiovascular system during space storms. It is plausible that the space weather conditions during and after hospital admission may affect the risk of coronary events in patients with acute coronary syndromes (ACS). We analyzed the data of 1400 ACS patients who were admitted to the Hospital Lithuanian University of Health Sciences, and who survived for more than 4 days. We evaluated the associations between geomagnetic storms (GS), solar proton events (SPE), and solar flares (SF) that occurred 0–3 days before and after hospital admission and the risk of cardiovascular death (CAD), non-fatal ACS, and coronary artery bypass grafting (CABG) during a period of 1 year; the evaluation was based on the multivariate logistic model, controlling for clinical data. After adjustment for clinical variables, GS occurring in conjunction with SF 1 day before admission increased the risk of CAD by over 2.5 times. GS 2 days after SPE occurred 1 day after admission increased the risk of CAD and CABG by over 2.8 times. The risk of CABG increased by over 2 times in patients admitted during the day of GS and 1 day after SPE. The risk of ACS was by over 1.63 times higher for patients admitted 1 day before or after solar flares.     

Advance of interplanetary physics study in China: 2008—2010

Interplanetary physics study is an important ingredient in space weather research. Considerable progress this aspect has been achieved by the space physics community of China in recent years. This brief report summarizes the latest advances of the interplanetary physics research in China during the period of 2008--2010. This report includes solar corona and solar wind, interplanetary transients, energetic particles, MHD simulation, space plasma, and prediction methods for physical phenomena originating from both solar corona and interplanetary space.     

Solar energetic particle events during the rise phases of solar cycles 23 and 24

We present a comparative study of the properties of coronal mass ejections (CMEs) and flares associated with the solar energetic particle (SEP) events in the rising phases of solar cycles (SC) 23 (1996–1998) (22 events) and 24 (2009–2011) (20 events), which are associated with type II radio bursts. Based on the SEP intensity, we divided the events into three categories, i.e. weak (intensity < 1 pfu), minor (1 pfu < intensity < 10 pfu) and major (intensity ? 10 pfu) events. We used the GOES data for the minor and major SEP events and SOHO/ERNE data for the weak SEP event. We examine the correlation of SEP intensity with flare size and CME properties. We find that most of the major SEP events are associated with halo or partial halo CMEs originating close to the sun center and western-hemisphere. The fraction of halo CMEs in SC 24 is larger than the SC 23. For the minor SEP events one event in SC23 and one event in SC24 have widths < 120° and all other events are associated with halo or partial halo CMEs as in the case of major SEP events. In case of weak SEP events, majority (more than 60%) of events are associated with CME width < 120°. For both the SC the average CMEs speeds are similar. For major SEP events, average CME speeds are higher in comparison to minor and weak events. The SEP event intensity and GOES X-ray flare size are poorly correlated. During the rise phase of solar cycle 23 and 24, we find north–south asymmetry in the SEP event source locations: in cycle 23 most sources are located in the south, whereas during cycle 24 most sources are located in the north. This result is consistent with the asymmetry found with sunspot area and intense flares.     

Effective non-vertical and apparent cutoff rigidities for a cosmic ray latitude survey from Antarctica to Italy in minimum of solar activity

In this paper we will report the results of the computation of cutoff rigidities of vertical and non-vertical incident cosmic ray particles. Non-vertical effective cutoff rigidities have been computed by tracing particle trajectories through the “real” geomagnetic magnetic field comprising the International Geomagnetic Reference Field model (IGRF95, IAGA Division 5 Working Group 8, 1996: Sabaka, T.J., Langel, R.A., Baldwin, R.T., Conrad, J.A. The geomagnetic field, 1900–1995, including the large scale fields from magnetospheric sources and NASA candidate models for the 1995 IGRF revision. J. Geomag. Geoelect. 49, 157–206, 1997.) and the Tsyganenko [Tsyganenko, N.A. A magnetospheric magnetic field model with a warped tail current sheet. Planet. Space Sci. 37, 5–20, 1989.] magnetosphere model. The computation have been done for the backward route (from Antarctica to Italy) of the Italian Antarctic ship survey 1996–1997, for geographic points corresponding to the daily average coordinates of the ship; for zenith angles 15°, 30°, 45° and 60°, and azimuth angles from 0° to 360° in steps of 45°. By means of the obtained non-vertical cutoffs the apparent cutoff rigidities have been calculated. The information on integral multiplicities of secondary neutrons detected by the neutron monitor in dependence of the zenith angle of incoming primary cosmic ray particles have also been used. This information is based on the theoretical calculations of meson-nuclear cascades of primary protons with different rigidities arriving to the Earth’s atmosphere at the zenith angles of 0°, 15°, 30°, 45°, 60° and 75°. The difference between the computed apparent and vertical cutoff rigidities reaches ∼1 GV at rigidities >7–8 GV. At rigidities of 10–16 GV, the difference between the apparent and vertical cutoff rigidities is larger than that obtained earlier by Clem et al. [Clem, J.M., Bieber, J.W., Duldig, M., Evenson, P., Hall, D., Humble, J.E. Contribution of obliquely incident particles to neutron monitor counting rate. J. Geophys. Res. 102, 26919–26926, 1997.] and Dorman et al. [Dorman, L.I., Villoresi, G., Iucci, N., Parisi, M., Tyasto, M.I., Danilova, O.A., Ptitsyna, N.G. Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996–1997), 3. Geomagnetic effects and coupling functions. J. Geophys. Res. 105, 21047–21056, 2000.].     

Solar proton enhancements in different energy channels and coronal mass ejections during the last solar cycle

The main properties of 11622 coronal mass ejections (CMEs) observed by the Solar and Heliospheric Observatory (SOHO) mission’s Large Angle and Spectrometric Coronagraph (LASCO-C2) from January 1996 through December 2006 are considered. Moreover, the extended database of solar proton enhancements (SPEs) with proton flux >0.1 pfu at energy >10 MeV measured at the Earth’s orbit is also studied. A comparison of these databases gives new results concerning the sources and acceleration mechanisms of solar energetic particles. Specifically, coronal mass ejections with width >180° (wide) and linear speed >800 km/s (fast) seem they have the best correlation with solar proton enhancements. The study of some specific solar parameters, such as soft X-ray flares, sunspot numbers, solar flare index etc. has showed that the soft X-ray flares with importance >M5 may provide a reasonable proxy index for the SPE production rate. From this work, it is outlined that the good relation of the fast and wide coronal mass ejections to proton enhancements seems to lead to a similar conclusion. In spite of the fact that in the case of CMEs the statistics cover only the last solar cycle, while the measurements of SXR flares are extended over three solar cycles, it is obvious for the studied period that the coronal mass ejections can also provide a good index for the solar proton production.