典型的太阳质子事件峰值流量的一种预报方法

分析了1988~2006年中62个典型的太阳质子事件,发现其归一化后峰值流量变化具有很好的统计规律,根据该规律提出了一种对太阳质子事件峰值流量进行预报的方法.试验预报结果表明,太阳质子事件峰值流量的预报值和实测值都在同一个量级以内,平均相对误差为32％,预报误差在可接受范围内.本文方法对于日常预报业务而言是实用和可行的.     

Stratospheric ozone response to a solar proton event: Hemispheric asymmetries

Ozone depression in the polar stratosphere during the energetic solar proton event on 4 August 1972 was observed by the backscattered ultraviolet (BUV) experiment on the Nimbus 4 satellite. Distinct asymmetries in the columnar ozone content, the amount of ozone depressions and their temporal variations above 4 mb level (38 km) were observed between the two hemispheres. The ozone destroying solar particles precipitate rather symmetrically into the two polar atmospheres due to the geomagnetic dipole field These asymmetries can be therefore ascribed to the differences mainly in dynamics and partly in the solar illumination and the vertical temperature structure between the summer and the winter polar atmospheres. The polar stratosphere is less disturbed and warmer in the summer hemisphere than the winter hemisphere since the propagation of planetary wave from the troposphere is inhibited by the wind system in the upper troposphere, and the air is heated by the prolonged solar insolation. Correspondingly, the temporal variations of stratospheric ozone depletion and its recovery appear to be smooth functions of time in the (northern) summer hemisphere and the undisturbed ozone amount is slighily, less than that of its counterpart. On the other hand, the tempotal variation of the upper stratospheric ozone in the winter polar atmosphere (southern hemisphere) indicates large amplitudes and irregularities due to the disturbances produced by upward propagating waves which prevail in the polar winter atmosphere. These characteristic differences between the two polar atmospheres are also evident in the vertical distributions of temperature and wind observed by balloons and rocker soundings.     

Solar proton event in December 2006

The variations in the rigidity spectrum and anisotropy of cosmic rays in December 2006 have been studied based on the surface measurements of the cosmic ray intensity at the global network of stations, using the method of global spectrographic survey. It has been indicated that the highest degree of anisotropy (to ～50%) with the maximal intensity of particles with a rigidity of 4 GV in the direction from the Sun (an asymptotic direction of about ?25° and 160°) was observed at 0400 UT on December 13. The parameters of the cosmic ray rigidity spectrum, which reflect the electromagnetic characteristics of the heliospheric fields during the studied period, have been determined when the surface and satellite measurements of protons in the energy range from several megaelectronvolts to several tens of gigaelectronvolts were jointly analyzed. The observed anisotropy and variations in cosmic rays in a wide energy range have been explained based on an analysis of the results.     

The influence of solar activity on the stratospheric ozone layer

Pure and Applied Geophysics -     

Changes of the first Schumann resonance frequency during relativistic solar proton precipitation in the 6 November 1997 event

The variations of the first mode of Schumann resonance are analyzed using data from Kola peninsula stations during the solar proton event of 6 November 1997. On this day the intensive flux of energetic protons on GOES-8 and the 10% increase of the count rate of the neutron monitor in Apatity between 1220 and 2000 UT were preceded by a solar X-ray burst at 1155 UT. This burst was accompanied by a simultaneous increase of the Schumann frequency by 3.5%, and the relativistic proton flux increase was accompanied by 1% frequency decrease. These effects are explained by changes of the height and dielectric permeability of the Earth-ionosphere cavity.     

Studies on the shift in the frequency of the first Schumann resonance mode during a solar proton event

The variation of the first Schumann resonance (SR) frequency spectra observed from the recorded data over Kolkata (22.56°N, 88.5°E) during a solar proton event (SPE) on July 14, 2000 has been presented. It shows increase in frequency during X-ray bursts and decrease during the period of occurrence of an SPE. The results from some other locations for the same event are also reported. The severe X-ray bursts recorded just before the proton event exhibit enhancement in frequency of the first mode due to enhancement of ionization in the D-region of the ionosphere. Some attempts are made to explain the observed variation during solar proton events in terms of the perturbations within the Earth–ionosphere waveguide on the basis of two-layer-model.     

Distribution of extreme solar energetic proton fluxes

The knowledge of the high intensity tails of probability distributions that determine the rate of occurrence of extreme events of solar energetic particles is a critical element in the evaluation of hazards for human and robotic space missions. Here instead of the standard approach based on fitting a selected distribution function to the observed data we investigate a different approach, which is based on a study of the scaling properties of the maximum particle flux in time intervals of increasing length. To find the tail of the probability distributions we apply the “Max-Spectrum” method (Stoev, S.A., Michailidis, G., 2006. On the estimation of the heavy-tail exponent in time series using the Max-Spectrum. Technical Report 447, Department of Statistics, University of Michigan) to 1973–1997 IMP-8 proton data and the 1987–2008 GOES data, which cover a wide range of proton energies. We find that both data sets indicate a power-law tail with the power exponents close to 0.6 at least in the energy range 9–60 MeV. The underlying probability distribution is consistent with the Fréchet type (power-law behavior) extreme value distribution. Since the production of high fluxes of energetic particles is caused by fast Coronal Mass Ejections (CMEs) this heavy-tailed distribution also means that the Sun generates more fast CMEs than would be expected from a Poissonian-type process.     

A deep stratospheric intrusion associated with an intense cut-off low event over East Asia

European Centre for Medium-Range Weather Forecasts Re-Analysis Interim(ERA-Interim)reanalysis data and satellite data,and trajectory model were applied to analyze the dynamical,thermo-dynamical,and chemical structure in the upper troposphere and lower stratosphere(UTLS)of an intense cut-off low(COL)event occurring over East Asia during June 19-23,2010,and to characterize the process and transport pathway of deep stratospheric intrusion.The Atmospheric Infrared Sounder(AIRS)ozone data and the Global Positioning System Ozone(GPSO3)sonde data showed that the air mass originating from the polar formed a region with relatively high values of potential vorticity(PV)and ozone in the center of COL,and a secondary ozone peak appeared in the upper troposphere during mature stage of the COL.Forward trajectory simulation suggested that during the first stage of COL,deep stratospheric intrusion associated with strong northerly wind jet on the west side of the upper-level trough transported ozone-rich air from the polar lower stratosphere into the middle and lower troposphere in the mid-latitude,and increased the ozone concentration there.During the mature stage of the COL,stratospheric air was transported counterclockwise into the troposphere.Backward trajectory model was used to find the source regions of air mass within the COL during its mature stage.Model results show that air masses with high ozone concentration in the center of the COL have two source regions:one is the subpolar vortex which lies in northern part of Center Siberia,where ozone-rich air plays a major role in increasing the ozone concentrations,and the other is the strong shear region which is near by the cyclonic side of the extratropical jet axis(west of 90°E,near 50°N).The air masses with low ozone concentration around the COL also have two source regions:one is the anticyclonic side of the extratropical jet axis,where the air mass with the relatively low ozone concentration at the bottom of the COL is mainly controlled by horizontal movement,and the other is the warm area of the south side of COL,where the air mass on the east and west side of the COL is mainly dominated by upward motion.     

Mismatch between variations of solar indices, stratospheric ozone and UV-B observed at ground

In solar cycles 22–23, all solar indices showed maxima near 1990 and 2000 and minima in 1996. The maximum to minimum variation was only 1–2% in the UV range 240–350 nm. Dobson ozone intensities did not show any clear relationship with solar cycle and ozone variations were less than 10%. The UV-B (295–325 nm) observed at ground by Brewer spectrophotometers at some locations had variations of 50–100% for 295–300 nm, and 20–50% for 305–325 nm. The maxima were in different years at different locations (even with separations of only 300 km), did not match with the solar cycle, and were far too large to be explained on the basis of ozone changes (1% decrease of ozone is expected to cause 2% increase of UV-B). Thus, if the data are not bad, the UV-B changes do not match with solar activity or ozone changes and must be mostly due to other local effects (clouds, etc.?). When data are averaged over wide geographical regions, UV-B variation ranges are smaller (10–20%, probably because localised, highly varying cloud effects get filtered out), and are roughly as expected from ozone variations.     

Certain features of UHF propagation during solar proton events

Results of the experimental reception of the UHF signal from geostationary satellite, visible at a low elevation angle from the receiving point, have been considered. It has been noted that the fluctuation intensity considerably increases during powerful solar proton events. The observed effect can be caused by interference between direct and secondary rays related to tropospheric irregularities. The hypothesis explaining obtained results based on the optical model of solar-tropospheric coupling is proposed.     

2013年平流层爆发性增温期间高纬电离层半日潮汐波研究

基于Sondrestrom站(67°N, 51°W)非相干散射雷达观测数据, 研究了2013年平流层爆发性增温(SSW)事件发生后高纬地区电离层F层和E层半日潮汐波.同时, 对1月非SSW发生期间和不同太阳活动期间高纬电离层中的半日潮汐波进行了统计分析, 并和2013年SSW事件发生后的结果进行了比较.研究发现, SSW发生后F层经向风中的半日潮汐波有显著增强, 其振幅大于80 m·s^-1的时间持续了至少60 h, 最大值达到109 m·s^-1.在180~330 km范围内, 半日潮汐波振幅平均大了24 m·s^-1.在E层高度上, 经向风中的半日潮汐波也在SSW发生后迅速增强, 最大值达到109 m·s^-1, 在108~117 km范围内, 其振幅平均大了33 m·s^-1.在E层纬向风中, 半日潮汐波振幅在120 km处连续超过36 h的时间内大于70 m·s^-1, 最大值达到92 m·s^-1.不同太阳活动期间的半日潮汐波统计结果显示, 和低太阳活动期间相比, 高太阳活动期间半日潮汐波在F层和E层平均增强14 m·s^-1.这明显小于SSW期间24和33 m·s^-1的增幅, 表明高太阳活动不是2013年SSW期间高纬电离层半日潮汐波增强的主要原因.我们的研究表明2013年高纬电离层半日潮汐波的增强很可能是受到SSW事件的影响.

     

Simulation of the stratospheric ozone and temperature response to the solar irradiance variability during sun rotation cycle

Despite substantial progress in atmospheric modeling, the agreement of the simulated atmospheric response to decadal scale solar variability with the solar signal in different atmospheric quantities obtained from the statistical analysis of the observations cannot be qualified as successful. An alternative way to validate the simulated solar signal is to compare the sensitivity of the model to the solar irradiance variability on shorter time scales. To study atmospheric response to the 28-day solar rotation cycle, we used the chemistry–climate model SOCOL that represents the main physical–chemical processes in the atmosphere from the ground up to the mesopause. An ensemble simulation has been carried out, which is comprised of nine 1-year long runs, driven by the spectral solar irradiance prescribed on a daily basis using UARS SUSIM measurements for the year 1992. The correlation of zonal mean hydroxyl, ozone and temperature averaged over the tropics with solar irradiance time series have been analyzed. The hydroxyl has robust correlations with solar irradiance in the upper stratosphere and mesosphere, because the hydroxyl concentration is defined mostly by the photolysis. The simulated sensitivity of the hydroxyl to the solar irradiance changes is in good agreement with previous estimations. The ozone and temperature correlations are more complicated because their behavior depends on non-linear dynamics and transport in the atmosphere. The model simulates marginally significant ozone response to the solar irradiance variability during the Sun rotation cycle, but the simulated temperature response is not robust. The physical nature of this is not clear yet. It seems likely that the temperature (and partly the ozone) daily fields possess their own internal variability, which is not stable and can differ from year to year reflecting different dynamical states of the system.     

Increase in the carbon dioxide infrared emissions during solar proton events

Increase in the nighttime high-latitude nonthermal emissions in the mesosphere and lower thermosphere in the 4.3 and 15 μm CO₂ bands during solar proton events has been estimated for the first time. The estimations have been performed for protons with energies not lower than 1 MeV precipitating into the atmosphere. A strong increase in the 4.3 μm emission can be anticipated during the above events; however, a substantial increase in the 15 μm emission is improbable. The 4.3 μm emission can increase only above approximately 80 km regardless of the energy of precipitating protons. The excitation of CO₂ vibrational states, transitions from which generate the 4.3 μm emission, is caused by the vibrational excitation of N₂ molecules due to collisions with secondary electrons, produced during solar proton events, and the following transfer of this excitation to CO₂(00⁰1) molecules during N₂-CO₂ collisions. Original Russian Text ? V.P. Ogibalov, S.N. Khvorostovskii, G.M. Shved, 2006, published in Geomagnetizm i Aeronomiya, 2006, Vol. 46, No. 2, pp. 159–167.     

Generalized thermostatistics and wavelet analysis of solar wind and proton density variability

In this paper, we analyze the probability density function (PDF) of solar wind velocity and proton density, based on generalized thermostatistics (GT) approach, comparing theoretical results with observational data. The time-series analyzed were obtained from the SOHO satellite mission where measurements were sampled every hour. We present in the investigations data for two years of different solar activity: (a) moderate activity (MA) period (1997) and (b) high activity (HA) period (2000). For the MA period, the results show good agreement between experimental data and GT model. For the HA period, the agreement between experimental and theoretical PDFs was fairly good, but some distortions were observed, probably due to intermittent characteristics of turbulent processes. As a complementary analysis, the global wavelet spectrum (GWS) was obtained, allowing the characterization of the predominant temporal variability scales for both periods and the stochastic aspects of the nonlinear solar wind variability are discussed.     

Possible solar forcing of interannual and decadal stratospheric planetary wave variability in the northern hemisphere: An observational study

The variability of stratospheric planetary waves and their possible connection with the 11-year solar cycle forcing have been investigated using annual-mean temperatures for the period of 1958–2001 derived from two reanalysis data sets. The significant planetary waves (wavenumbers 1–3) can be identified in the northern mid-high latitudes (55–75°N) in the stratosphere using this data. Comparisons with satellite-retrieved products from the Microwave Sounding Unit (MSU) confirm the significant planetary wave variability seen in the reanalyses. A planetary wave amplitude index (PWAI) is defined to indicate the strength of the stratospheric planetary waves. The PWAI is derived from Fourier analysis of the temperature field for wavenumbers 1–3 and averaged over 55–75°N latitude and the 70–20 hPa layers. The results include two meaningful inter-annual oscillations (2- and 8-year) and one decadal trend (16-year) that was derived from wavelet analysis. The stratospheric temperature structure of the wave amplitudes appear associated with the Arctic Oscillation (AO) which explicitly changed with the PWAI. The temperature gradients between the polar and mid-high latitudes show opposite tendencies between the top-10 strong and weak wave regimes.The variation of the planetary wave amplitude appears closely related to the solar forcing during the recent four solar cycles (20–23). The peak of the 2-year oscillation occurs synchronously with solar minimum, and is consistent with the negative correlation between the PWAI and the observed solar UV irradiance. The UV changes between the maxima and minima of the 11-year solar cycle impact the temperature structure in the middle-lower stratosphere in the mid-high latitudes and hence influence the planetary waves. During solar maximum, the dominant influence appears to be exerted through changes in static stability, leading to a reduction in planetary wave amplitude. During solar minimum, the dominant influence appears to be exerted through changes in the meridional temperature gradient and vertical wind shear, leading to an enhancement of planetary wave amplitude.     

Variations in the 557.7-nm atmospheric emission during stratospheric warming events under conditions of high and low solar activity

The effect of anomalously high average nighttime intensities of the atomic oxygen 557.7-nm atmospheric emission (luminescence heights 85–115 km) during sudden winter stratospheric warming events (SWEs) in Eastern Siberia is considered. Analysis of the variations in the 557.7-nm emission intensity (I _557.7) revealed the interdaily I _557.7-nm variations during SWEs and high average monthly I _557.7-nm values in the winter months in conditions of high solar activity. It has finally been found that the variations with periods of several days, at a maximum of which anomalously high daily values of I _557.7 are observed, are superposed on the average I _557.7-level during SWEs at high solar activity. A high average level of I _557.7 in the winter months in Eastern Siberia can be related to the fact that the atomic oxygen concentration at altitudes of the 557.7 nm emission luminescence increases by a factor of 2–3 in years of high solar activity.     

Characteristics of relativistic solar cosmic rays during the event of December 13, 2006

The characteristics of relativistic solar protons have been obtained using the methods of optimization based on the data of ground detectors of cosmic rays during the event of December 13, 2006, which occurred under the conditions of solar activity minimum. The dynamics of relativistic solar protons during the event has been studied. It has been indicated that two populations (components) of particles exist: prompt and delayed (slow). The prompt component with a hard energy spectrum and strong anisotropy manifested itself as a pulse-shaped enhancement at Apatity and Oulu stations, which received particles with small pitch-angles. The delayed component had a wider pitch-angle distribution, as a result of which an enhancement was moderate at Barentsburg station and at most neutron monitors of the worldwide network. The energy spectra obtained from the ground-based observations are in good agreement with the direct measurements of solar protons on balloons and spacecraft.     

Relativistic solar protons in the event of January 20, 2005: Model studies

Using the optimization methods, the characteristics of relativistic solar protons (RSPs) have been obtained from the data of ground-based cosmic ray detectors in the event of January 20, 2005, which was the largest event in the last 50 years since the event of February 23, 1956. The RSP dynamics during the event has been studied. The existence of two populations (components) of particles, fast and delayed (slow) has been shown. The fast component with a hard exponential energy spectrum and strong anisotropy was shown as a giant pulselike enhancement at several southern polar stations. The delayed component had a power-law energy spectrum and a wider pitch-angle distribution, which caused the enhancement effect at the majority of stations at the global network.     

On the solar/QBO effect on the interannual variability of total ozone and the stratospheric circulation over Northern Europe

Based on total ozone data from the World Ozone Data Center and stratospheric geopotential height data from the Meteorological Institute of Berlin Free University for the months of January through March for the time period of 1958–1996, the influence of the 11-year solar cycle and the equatorial quasi-biennial oscillation (QBO) on total ozone and the stratospheric circulation at 30 hPa over Northern Europe is investigated. The analysis is performed for different levels of solar activity. The relationship of the equatorial QBO with ozone and the stratospheric circulation over the study region exhibits unique features attributed to strong opposite connections between the equatorial zonal wind and ozone/stratospheric dynamics during periods of solar minimum and maximum. Using the Solar/QBO effect, a statistical extraction of the interannual variations of total ozone and stratospheric circulation over Northern Europe has been attempted. The variations extracted and observed for late winter show very good correspondence. The solar/QBO effect in total ozone and stratospheric dynamics over Northern Europe appears to be related to planetary wave activity.