Ionospheric behavior over Europe during the solar eclipse of 3 October 2005

An annular eclipse occurred over Europe in the morning hours of 3 October 2005. The well-defined obscuration function of the solar radiation during the eclipse provided a good opportunity to study the ionospheric/thermospheric response to solar radiation changes. Since the peak electron density behavior of the ionospheric F2 layer follows the local balance of plasma production, loss and transport, the ionospheric plasma redistribution processes significantly affect the shape of the electron density profile. These processes are discussed here based on a comparison of vertical incidence sounding (VS) and vertical total electron content (TEC) data above-selected ionosonde stations in Europe. The equivalent slab thickness, derived with a time resolution of 10 min, provides relatively good information on the variation of the electron density profile during the eclipse. The computations reveal an increased width of the ionosphere around the maximum phase. As indicated by the available measurements over Spain, the photo production is significantly reduced during the event leading to a slower increase of the total ionization in comparison with the neighboring days. The supersonic motion of the Moon's cool shadow through the atmosphere may generate atmospheric gravity waves that propagate upward and are detectable as traveling ionospheric disturbances at ionospheric heights. High-frequency (HF) Doppler shift spectrograms were recorded during the eclipse showing a distinct disturbance along the eclipse path. Whereas the ionosonde measurements at the Ebro station/Spain in the vicinity of the eclipse path reveal the origin of the wave activity in the lower thermosphere below about 180 km altitude, the similar observations at Pruhonice/Czech Republic provide arguments to localize the origin of the abnormal waves in the middle atmosphere well below the ionospheric heights. Although ionosonde and HF Doppler measurements show enhanced wave activity, the TEC data analysis does not, which is an indication that the wave amplitudes are too small for detecting them via this interpolation method. The total ionization reduces up to about 30% during the event. A comparison with similar observations from the solar eclipse of 11 August 1999 revealed a quite different ionospheric behavior at different latitudes, a fact that needs further investigation.     

Shadow bands during the total solar eclipse of 26 February 1998

We have recorded shadow bands just before and just after the total phase of the solar eclipse of 26 February 1998, using four silicon photodiodes on the corners of a square 105 mm side. At two earlier eclipses, 11 July 1991, 3 November 1994, recordings were made using two silicon photodiodes separated by 100 mm. The analyses of these earlier eclipses have already been published in detail, and therefore here we concentrate on the analysis of the recordings made on 26 February 1998. Samples of the time series are presented, along with cross-correlation functions and power spectra. The power spectra are broadly in accord with the shadow band theory of Codona (Codona, C., 1986. The scintillation theory of eclipse shadow bands. Astron. Astrophys. 164, 415–427). This is also the case for the two earlier eclipses, but there are instructive differences between the three occasions.     

Numerical modelling of spectral sky radiance during a total solar eclipse

Ground-based observations of the spectral sky radiance within the totality region during a total solar eclipse are of significant interest because the contribution from direct and single scattered light from the solar disk is eliminated. In the present paper, we develop a numerical model of the spectral sky radiance during totality, evaluate the contribution of double scattered sunlight to the sky radiance at totality and compare it to solar corona emissions. The results show that the single scattered coronal light is the major contaminant in ground-based observations of the corona, opposite to what was believed before. For observation directions outside the corona the double scattered sun radiation dominates over the single scattered coronal light.     

The ionosphere over Genova during the solar eclipse of February 15, 1961

Summary The behaviour of the ionosphere over Genova during the solar eclipse of February 15, 1961 is investigated. For theE-layer the effect was very marked, but the value obtained for the recombination coefficient is above normal. The effect of the eclipse was also observed on theF2 layer; however, the behaviour here appears affected by the simultaneous occurrence of an ionospheric perturbation. Finally, the maximum reduction of the ionospheric absorption on 2 and 3 Mc/s during the eclipse was found to be of the order of about 12 db.This report belongs to a set of investigations on geophysical effects of the solar eclipse of February 15th, 1961 carried out by the «Istituto Geofisico, Università di Genova», and made possible through a financial support of the «Consiglio Nazionale delle Ricerche».     

Micrometeorological measurements in Nigeria during the total solar eclipse of 29 March, 2006

The total solar eclipse of 29 March, 2006 which was visible at Ibadan (7.55°N, 4.56°E), south-western Nigeria was utilized to document atmospheric surface-layer effects of the eclipse for the first time in Nigeria. The meteorological parameters measured are global radiation, net radiation, wind speed (at different heights), atmospheric pressure and soil temperature (5, 10 and 30 cm), moisture and heat flux and rainfall. The results revealed remarkable dynamic atmospheric effects. The observations showed that the incoming solar radiation, net radiation and air temperature were significantly affected.There was an upsurge of wind speed just before the first contact of the eclipse followed by a very sharp decrease in wind speed due to the cooling and stabilization of the atmospheric boundary layer. The atmospheric pressure lags the eclipse maximum by 1 h 30 min, while the soil temperature at 5 and 10 cm remain constant during the maximum phase of the eclipse.     

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.     

2009年7月22日日全食期间湖北沙洋地区电离层扰动分析

发生在2009年7月22日亚太地区的日全食,为人们研究电离层扰动提供了一次难得的机会.基于沙洋地区采集的高频(1 Hz)GPS数据,通过对日食当天与前后几天电离层VTEC(Vertical Total Electron Content)的变化分析,结果显示日食期间电离层VTEC含量均呈现出一种先下降再上升的“水槽”变化趋势,且VTEC下降达到2～5 TECU,下降幅度达33.1％,VTEC的最小值与食甚时刻延迟为25.2～147.6 s.在日全食后期有中等强度的磁暴发生,与日食相互重合叠加共同对电离层VTEC变化造成影响,使得VTEC变化明显异于前后几天,最后定量的分析了磁暴对VTEC的影响.     

High-latitude methane sulphonic acid variability and solar activity: the role of the total solar irradiance

The direct impact of solar activity on climate has been widely studied through Total Solar Irradiance (TSI). Biological processes also impact climate and are deeply affected by TSI. Marine phytoplankton emissions into the atmosphere have been proposed to change cloud albedo through cloud formation. In this work, we use wavelet analysis to investigate the decadal relation between high-latitude concentrations of methane sulphonic acid, a product of seawater algae, and TSI. We found that some of the methane sulphonic acid main periodicities coincide with periods of solar activity periods.     

Solar eclipse of August 1, 2008, over Kharkov: 3. calculation results and discussion

The calculation results of parameters of thermal and dynamical processes in the near-Earth plasma during the partial solar eclipse of August 1, 2008, over Kharkov are presented. The calculations showed that during the eclipse there occurred a decrease in the neutral temperature by approximately 17–40 K within the height range 250–350 km, respectively. At heights of 210–580 km, the eclipse resulted in an increase in the density, total plasma flux, and the flux of particles by tens of percentage points due to ambipolar diffusion. The paper presents the results of a comparative analysis of the effects in the ionospheric plasma during the partial eclipses over Kharkov of August 11, 1999; May 31, 2003; October 3, 2005; March 29, 2006; and August 1, 2008. General regularities in eclipse effects are noted.     

The solar corona during the eclipse of August 1, 2008

A new telescope has been created to investigate the solar corona during eclipses. One lens simultaneously forms three corona images occurring as coronal radiation passes through three polarizers with transmission directions rotated 0°, 60°, and 120° relative to the selected direction; in addition, one image is formed without the polarizer. The telescope was used for solar corona observation during the eclipse of August 1, 2008. We obtained the distributions of polarization brightness, K corona brightness, degree of K corona polarization, and total degree of polarization as well as polarization directions depending on the latitude and radius in the sky plane. Radial distributions of the electron density depending on latitude were calculated. The coronal plasma temperature was determined for different corona structures under the assumption of hydrostatic equilibrium.     

青藏高原对流层臭氧含量变化的太阳周期活动信号分析

利用1979~1992年卫星TOR对流层臭氧数据库资料,以及同期太阳辐照度数据序列,考察青藏高原对流层臭氧含量变化与太阳辐射周期变化之间的关系.分析表明,青藏高原对流层臭氧分布表现出与太阳辐照度相同的变化趋势,存在着明显的太阳周期变化特征.逐月线性回归分析表明,太阳辐照度增加导致青藏高原对流层臭氧增加的正效应.在太阳周期内,太阳辐射增加可使青藏高原对流层臭氧、平流层臭氧和臭氧总量分别增加1.31、4.97、6.628DU,或4.07%、2.04%、2.28%.该特征与赤道太平洋地区完全相反,分析产生差异的原因,至少应包括两方面因素：一是背景大气NOX和水汽含量的差异;二是青藏高原频繁发生的平流层-对流层大气物质交换和输送.     

Ionospheric effects of the March 29, 2006, solar eclipse over Kazakhstan

The results of studying the ionospheric effects of the March 29, 2006, solar eclipse are presented. The results were obtained in measurements of local electron density (ED) at Alma-Ata vertical ionospheric sounding station and total electron content (TEC) at the Central Asia network of two-frequency receivers of the GPS navigation system. The ED decrease at the F-layer maximum reached approximately 28%, the delay of the minimum value of EC relative to the moment of the eclipse maximum phase was about 11 min, the relaxation time was 4 min, and the duration of the EC depression at the 0.5 level was 45 min. Dynamic interlayer formations were observed in the ionosphere near the eclipse maximum phase. A traveling ionospheric disturbance, probably generated at the shock wave front during the supersonic motion of the Moon’s shadow, was detected. The disturbance period and the horizontal projection of the velocity were about 90 min and ～680 m/s, respectively. The wave vector azimuth (145°) coincides with the model value of the normal to the shock front.     

Observations of the ionosphere in the equatorial anomaly region using WISS during the total solar eclipse of 22 July 2009

An exceptionally long total solar eclipse occurred over the Yangtze River Basin in the mid-latitudes of China on 22 July 2009. The moon’s umbral shadow crossed through the ionospheric equatorial anomaly region. During the solar eclipse, new ionospheric behaviors were observed using a multi-station sounding approach. These new phenomena include: (1) visible Doppler spreading of F layer echoes at multiple group distances during the solar eclipse period, (2) strong ionospheric response near the peak of the northern equatorial anomaly crest and (3) synchronous oscillations in the E_s and F layer during the recovery phase of the solar eclipse.     

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.     

Magneto-ionospheric effects of the solar eclipse of March 20, 2015, over Kharkov

The results of observations of disturbances in the lower and middle ionosphere and in the geomagnetic field accompanying the partial solar eclipse over Kharkov are presented. The ionospheric effects have been studied with the use of an ionosonde and measurements of the phase and amplitude of a radio signal with a frequency of 66.(6) kHz on the Moscow–Kharkov route, and the effects in the magnetic field have been analyzed with the help of a magnetometer–fluxmeter in the range of periods from 1 to 1000 s. Disturbances in both the lower and middle ionosphere, as well as in the geomagnetic field, have been detected. The observation results have been compared with the results of a simulation of physical processes accompanying the solar eclipse. A good agreement has been found between observational and modeling results.     

Strong earthquake activity all over the world and strong-moderate earthquake activity within and near China （October, 2005-November, 2005）

Illustration All the data in this catalog are chosen from the ＂Preliminary Seismological Report of Chinese Seismic Stations＂ （Its abbreviation is ＂Monthly Report＂）. The catalog includes the events of M≥4.7 in and near China and M≥6 all over the world. The ＂Monthly Report＂ is monthly compiled by the Ninth Section of Institute of Geophysics, China Earthquake Administration.     

Propagation of radio waves reflected from the ionosphere during a solar eclipse

Summary The article first describes in chronological order the observations on the propagation of radio waves during the solar eclipses, and the development of the conflicting results on the similar transmissions of radio signals. The general theory of the absorption of radio waves in the ionosphere is briefly described and therefrom a method is derived to estimate the variation of the absorption of obliquely incident radio waves during a solar eclipse.The variation of field-strength can be studied in terms of the relationship between the vertical incident equivalent frequency of the signals and the critical frequencies of the ionospheric layers at the regions of reflection. The total absorption of radio waves consists of the non-deviative absorption in theD region and the deviative absorption in the higher layers of the ionosphere. During the eclipse, theD region absorption decreases in phase with the progress of the eclipse, but the variation of deviative absorption may differ in each observation. The deviative absorption is large when the equivalent frequency is close to the critical frequency of the layer reflecting the waves or of the layer just penetrated by the waves. The changes in the deviative absorption during an eclipse can be estimated on the basis of the variation of the critical frequencies of the ionospheric layers. The resultant changes in the total absorption during a solar eclipse may thus be estimated. The different types of field strength variation expected during an eclipse are given.The observations of the vertical incident absorption of radio waves and the field strength variations of obliquely incident continuous wave radio signals during the solar eclipse are described and the changes are explained on the basis of the above theory.