Equatorial F-region vertical ion drifts during quiet solar maximum

Median values of ionosonde h′F data acquired at Ibadan (Geographic:7.4°N, 3.9°E, Magnetic: dip 6°S, and magnetic declination, 3°W), Nigeria, West Africa, have been used to determine vertical ion drift (electric field) characteristics in the postsunset ionosphere in the African region during a time of high solar activity (average F_10.7 −208). The database spans from January and December 1958 during the era of International Geophysical Year (IGY) for geomagnetic quiet conditions. Bimonthly averaged diurnal variations patterns are very similar, but differ significantly in magnitude and in the evening reversal times. Also, monthly variations of F-region vertical ion drift reversal times inferred from the time of h′F maximum indicates early reversal during equinoxes and December solstice months except for the month of April. Late reversal is observed during the June solstice months. The equatorial evening prereversal enhancement in vertical ion drift (V_zp) occurs largely near 1900 LT with typical values 20–45 m/s. Comparison of Ibadan ionosonde V_zp with the values of prereversal peak velocity reported for Jicamarca (South America), Kodaikanal (India), and Scherliess and Fejer global model show considerable disparity. The changes of postsunset peak in virtual height of F-layer (h′F_P) with prereversal velocity peak V_zp are anti-correlated. Investigation of solar effects on monthly values of V_zp and h′F_P revealed that these parameters are independent of monthly averaged solar flux intensity during quiet-time sunspot maximum conditions.     

Nighttime cloud properties retrieval using MODIS and artificial neural networks

In this work a methodology for inferring water cloud macro and microphysical properties from nighttime MODIS imagery is developed. This method is based on the inversion of a theoretical radiative transfer model that simulates the radiances detected in each of the sensor infrared bands. To accomplish this inversion, an operational technique based on Artificial Neural Networks (ANNs) is proposed, whose main characteristic is the ability to retrieve cloud properties much faster than conventional methods. Furthermore, a detailed study of input data is performed to avoid different sources of errors that appear in several MODIS infrared channels. Finally, results of applying the proposed method are compared with in-situ measurements carried out during the DYCOMS-II field experiment.     

对流层顶变化对上对流层/下平流层臭氧分布的影响

上对流层和下平流层(UT／LS)，位于8-25km高度之间，是大气中一个很特殊的区域．大部分的臭氧分布在下平流层，在下平流层臭氧的含量发生一个很小的变化，就会对气候和地面的紫外辐射产生很大的影响．而作为气象参数的对流层顶，是充分混合、缺乏臭氧的上对流层和层结稳定、臭氧丰富的下平流层之间的边界或过渡层，其变化对臭氧总量和分布有直接和明显的影响．本文使用二维模式模拟研究对流层顶变化对臭氧在UT／LS分布的影响．模拟结果表明对流层顶的季节变化对UT/LS的臭氧分布有明显的影响，臭氧的局地变化可以超过10％在冬季北半球中纬度对流层顶高度升高1km时，模式结果表明对臭氧分布的影响比较显著，局地变化可超过6％，但是对臭氧总量的影响较小，变化不超过5DU，小于观测资料统计分析的结果。     

Modeling large solar flares

The basic ideas to model the large solar flares are reviewed and illustrated. Some fundamental properties of potential and non-potential fields in the solar atmosphere are recalled. In particular, we consider a classification of the non-potential fields or, more exactly, related electric currents, including reconnecting current layers. The so-called ‘rainbow reconnection’ model is presented with its properties and predictions. This model allows us to understand main features of large flares in terms of reconnection. We assume that in the two-ribbon flares, like the Bastille-day flare, the magnetic separatrices are involved in a large-scale shear photospheric flow in the presence of reconnecting current layers generated by a converging flow.     

High resolution time profile of decimetric type-III bursts

Type-III bursts are signatures of the electron beams accelerated during the solar flares, their observation and investigation provide information of the acceleration processes, the characteristics of the exciting agent and the acceleration site. The Brazilian Solar Spectroscope (BSS), in operation at INPE, Brazil, have recorded type-III radio bursts in decimetric range (2050–2250 MHz) with high time resolution of 20 ms. Decimetric reverse drift bursts are possibly generated in a dense loop by electron beams travelling towards the photosphere. Hence their time profiles should carry signatures of the density inhomogenities in the loop. Here the temporal and spectral characteristics of decimetric type-III bursts are presented.     

Solar maximum mission experiment: Ultraviolet spectroscopy and polarimetry on the solar maximum mission

We describe the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM) spacecraft. The instrument, which operates in the wavelength range 1150 – 3600 Å, has a spatial resolution of 2–3 arc sec and a spectral resolution of 0.02 Å FWHM in second order. A Gregorian telescope, focal length 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F₂ waveplates can be inserted behind the spectrometer entrance slit and allows all four Stokes parameters to be determined. The observing modes include rasters, spectral scans, velocity measurements, and polarimetry. Finally, we present examples of initial observations made since launch.     

Shock protection of penetrator-based instrumentation via a sublimation approach

It is often necessary for space-borne instrumentation to cope with substantial levels of shock acceleration both in the initial launch phase, as well as during entry, descent and landing in the case of planetary exploration. Current plans for a new generation of penetrator-based space missions will subject the associated on-board instrumentation to far greater levels of shock, and ways must therefore be found to either ruggedize or else protect any sensitive components during the impact phase. In this paper, we present an innovative method of shock protection that is suited for use in a number of planetary environments, based upon the temporary encapsulation of said components within a waxy solid which may then be sublimated to return the instrument back to its normal operation. We have tested this method experimentally using micromachined silicon suspensions under applied shock loads of up to 15,000g, and found that these were able to survive without incurring damage. Furthermore, quality factor measurements undertaken on these suspensions indicate that their mechanical performance remains unaffected by the encapsulation and subsequent sublimation process.     

Solar rhythms in the characteristics of the Arctic frontal zone in the North Atlantic

Long-term changes of the Arctic frontal zone characteristics near the south-eastern coasts of Greenland were considered, the NCEP/NCAR reanalysis data being used. It was found that in the cold half of the year the temperature gradients in the layer 1000–500 hPa in the region under study reveal strong ∼10-yr and ∼22-yr periodicities that seem to be related to solar activity cycles. The results obtained suggest the influence of solar activity and cosmic ray variations on the structure of the temperature field of the troposphere resulting in the changes of the temperature contrasts in the Arctic frontal zone that, in turn, may affect the intensity of cyclogenesis at middle latitudes. The detected effects seem to indicate an important part of frontal zones in the mechanism of solar activity and cosmic ray variation influence on the development of extratropical baric systems. It is suggested that the variations of the temperature gradients revealed in the Arctic frontal zone are due to the radiative forcing of cloudiness changes which may be associated with geomagnetic activity and cosmic ray variations.