The response of the azimuthal component of the ionospheric electric field to auroral arc brightening

We have analyzed the response of azimuthal component of the ionospheric electric field to auroral arc activity. We have chosen for analysis three intervals of coordinated EISCAT and TV observations on 18 February, 1993. These intervals include three kinds of arc activity: the appearance of a new auroral arc, the gradual brightening of the existing arc and variations of the arc luminosity. The arcs were mostly east-west aligned. In all cases, the enhancement of arc luminosity is accompanied by a decrease in the westward component of the ionospheric electric field. In contrast, an increase of that component seems to be connected with arc fading. The observed response is assumed to have the same nature as the short circuit of an external electric field by the conductor. The possible consequence of this phenomenon is discussed.     

Diurnal Variation of Gravity Wave Activity at Midlatitudes in the Ionospheric F Region

We investigate the short-term fluctuations in the period range from 15 to 180 minutes in the electron density variations of the F region ionosphere. Electron density profiles obtained at the ionospheric stations of Pruhonice (49.9° N, 14.5° E) and Ebro (40.8° N, 0.5° E) at five minute time sampling have been used for this analysis. The diurnal changes of the activity of the acoustic gravity wave fluctuations (AGW) show a clear enhancement during and several hours after sunrise. The periods of such AGW's are about 60 to 75 minutes and these waves propagates vertically through the ionosphere from a source located at an altitude of 180-220 km. The most likely source for these events seems to be passage of the Solar terminator.     

Distribution of ionospheric O<Superscript>+</Superscript> ion in synchronous altitude region

Based on satellite observation data, using dynamics equation, the ionospheric O⁺ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK _p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O⁺ ion’s density and flux versus longitude in the synchronous altitude region for differentK _p are given. The main results show that in the synchronous altitude region: (i) The O⁺ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic activity indexK _p is, the higher the O⁺ ion’s density and flux, and their variation amplitude will be. The O⁺ ion’s density and flux whenK _{p ≥} 6 will be about ten times as great as that whenK _p = 0. (iii) WhenK _p = 0 orK _{p ≥} 6, the O⁺ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK _p = 3−5, the O⁺ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O⁺ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK _p value.     

Ionospheric measurements of relative coronal brightness during the total solar eclipses of 11 August, 1999 and 9 July, 1945

Swept-frequency (1/10 MHz) ionosonde measurements were made at Helston, Cornwall (50°06N, 5°18W) during the total solar eclipse on August 11, 1999. Soundings were made every three minutes. We present a method for estimating the percentage of the ionising solar radiation which remains unobscured at any time during the eclipse by comparing the variation of the ionospheric E-layer with the behaviour of the layer during a control day. Application to the ionosonde date for 11 August, 1999, shows that the flux of solar ionising radiation fell to a minimum of 25±2% of the value before and after the eclipse. For comparison, the same technique was also applied to measurements made during the total solar eclipse of 9 July, 1945, at Sörmjöle (63°68N, 20°20E) and yielded a corresponding minimum of 16 ± 2%. Therefore the method can detect variations in the fraction of solar emissions that originate from the unobscured corona and chromosphere. We discuss the differences between these two eclipses in terms of the nature of the eclipse, short-term fluctuations, the sunspot cycle and the recently-discovered long-term change in the coronal magnetic field.     

液体闪烁计数技术测氡在铀矿勘查中的应用研究

在火山岩、花岗岩地区和中新生代盆地铀矿勘查中进行了大量的液体闪烁测氡工作，发现该方法探测效率高、抗干扰能力强、重复性好、异常清晰，取得了较好的地质找矿效果，证实了该方法的有效性和可行性。     

Interplanetary scintillation observations of interaction regions in the solar wind

Co-rotating interaction regions (CIRs) between fast and slow streams of plasma are a prominent feature of the solar wind. Measurements of interplanetary scintillation (IPS) using the three widely separated antennas of the EISCAT facility have been used to detect the compression regions at the leading edges of interaction regions and to determine the location and velocity of the structure. Observations show that interaction regions have developed as close to the Sun as 25–30 solar radii, a result supported by theoretical modelling which shows that the conditions needed for CIRs to develop exist inside 30 solar radii.     

Reinvestigation of the irregularities in the 3H decay

Having in mind the potential impact of the results presented by Veprev and Muromtsev (2012) [13] on our knowledge of the universe, we reinvestigated the liquid scintillation measurement of the count rate variations of ³H. Making use of the sophisticated Quantulus liquid scintillation spectrometer, we found that the measurement of the high-energy tail of ³H spectrum may be significantly influenced by instrumental instability. Thus, the possible explanation for the relatively high count rate variations of Veprev and Muromtsev (2012) [13] can be attributed mainly to the walk of the cut-off in the integrated spectrum, although weak variations of different origin could be masked by such cut-off drifts. In our experiment we have also registered the oscillatory behavior of measured high-energy tail of ³H spectrum, but with very small amplitude (less than 0.5%), which cannot be easily explained only by instrumental instability. When the total ³H spectrum was measured, no significant variations in the count rate were found.     

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iGMAS全球电离层TEC格网产品精度分析

为了分析与评估国际GNSS监测评估系统(iGMAS)全球电离层TEC格网产品精度,该文基于iGMAS及IGS各电离层分析中心发布的全球电离层TEC格网产品,进行了精度比较分析,结果表明:iGMAS与IGS、CODE、JPL、ESOC、UPC等IGS电离层工作组发布的全球电离层TEC格网产品,在全球、不同纬度带和欧洲等不同区域均表现出较高的一致性和强相关性,互差为0~2.0 TECU;JPL分析中心GIM的内符合精度约为2.5 TECU,iGMAS、IGS、CODE、ESOC和UPC等分析中心GIM的内符合精度均小于1.5 TECU;在2~8 TECU的精度范围内,iGMAS全球电离层TEC格网产品的精度总体与IGS、CODE、JPL、ESOC、UPC等IGS电离层工作组的精度相当。     

液闪法测量水中氚放射性活度的淬灭效应

采用液体闪烁计数法进行放射性同位素测量时存在淬灭效应,而且几乎每个样品的淬灭程度都不同,并影响测量精度。采用液体闪烁计数法测量水中氚的放射性活度,淬灭是难以避免的,因此要进行淬灭校正,才能使不同淬灭程度的样品的测量结果具有可比性。淬灭校正的方法有很多,外标准校正法是一种比较可靠的方法。文章采用氚外标准校正法进行实验,得出淬灭校正曲线即探测效率E与淬灭参数SQP(E)的关系式为E=0.001 3SQP(E)-0.707 6,经过样品验证,该曲线是可靠的。采用外标准校正法适合于大批样品的测量。