The Scientific Foundations of Forecasting Magnetospheric Space Weather

The magnetosphere is the lens through which solar space weather phenomena are focused and directed towards the Earth. In particular, the non-linear interaction of the solar wind with the Earth's magnetic field leads to the formation of highly inhomogenous electrical currents in the ionosphere which can ultimately result in damage to and problems with the operation of power distribution networks. Since electric power is the fundamental cornerstone of modern life, the interruption of power is the primary pathway by which space weather has impact on human activity and technology. Consequently, in the context of space weather, it is the ability to predict geomagnetic activity that is of key importance. This is usually stated in terms of geomagnetic storms, but we argue that in fact it is the substorm phenomenon which contains the crucial physics, and therefore prediction of substorm occurrence, severity and duration, either within the context of a longer-lasting geomagnetic storm, but potentially also as an isolated event, is of critical importance. Here we review the physics of the magnetosphere in the frame of space weather forecasting, focusing on recent results, current understanding, and an assessment of probable future developments.Peer reviewe

POTENTIAL OF CHLOROPHYLL FLUORESCENCE AND VIS/NIR SPECTROSCOPY MEASUREMENT USE FOR THE DETECTION OF NITROGEN CONTENT AND DISEASE INFECTION OF APPLE LEAVES

Abstract SPÁČILOVÁ, V., ŠAFRÁNKOVÁ, I.: Potential of chlorophyll fl uorescence and VIS/NIR spectroscopy measurement use for the detection of nitrogen content and disease infection of apple leaves. Acta univ. agric. et silvic. Mendel. Brun., 2011, LIX, No. 6, pp. 317-328 A possibility of using spectral methods for determining a nutritional status and detecting pathogens in apple-tree cvs. 'Jonagold' and 'Idared' was verifi ed in an orchard and pot experiments in 2007-2010. Treatments diff ered in the fertilizer or fungicide dose. Leaf samples were collected from the experimental variants to determine nitrogen content and to measure spectral refl ectance (spectrophotometer Avantes USB 2000) and chlorophyll fl uorescence imaging (FluorCam). Results of the measurements were correlated to leaf analyses for nitrogen content in dry matter. At the same time, a health status (the occurrence of fungal pathogens Venturia inaequalis and Podosphaera leucotricha) was assessed and changes of photochemical effi ciency of PSII of infected leaves were evaluated. The parameters providing the best description of diff erences in the photosynthetic activity of leaves depending on treatments (parameter Fv/Fm and parameter GENTY, known as PSII -eff ective quantum yield of PSII) were selected. The values of correlation coeffi cients of Fv/Fm and PSII depending on fertilization treatments were as follows: Fv/Fm: r = −0.4735, p<0.000089, = 0.05; PSII : r = 0.755; p < 0.00038, = 0.05. Data obtained from measuring with a spectrophotometer was used for the calculation to normalized diff erence vegetation indices NDVI; a signifi cant relationship was found for the index GNDVI (r = 0.4691, p < 0,0002, = 0.05). The signifi cant diff erence between healthy leaves and leaves infected by the pathogens V. inaequalis and P. leucotricha was confi rmed using the spectrophotometer, and the largest diff erences in refl ectances were found in wavelengths around 400 nm. The values of indices GNDVI, RNDVI and NDVI 450 obtained from measuring refl ectance of leaves with symptoms of V. inaequalis and P. leucotricha infections were signifi cantly lower compared to the indices of healthy leaves. The values of indices NDVI were as follows: GNDVI 0.930; RNDVI 0.912; NDVI 450 0.917 for healthy leaves and GNDVI 0.519/0.623; RNDVI 0.428/0.540; NDVI 450 0.432/0.499 for leaves infected by pathogens V. inaequalis/P. leucotricha, respectively. There was found signifi cant diff erence between infected and healthy leaves for all indices ( = 0.05). Also, the PSII exhibited signifi cant responses to the presence of V. inaequalis and P. leucotricha ( PSII : healthy leaves 0.182; V. inaequalis/P. leucotricha presence 0.232/0.222; = 0.05). apple tree, spectral refl ectance, chlorophyll fl uorescence, Venturia inaequalis, Podosphaera leucotricha, nitrogen content Light energy absorbed by chlorophyll molecules in chloroplasts of green plant leaves is used in the three ways: for synthesis of simple sugars in photosynthesis, for thermal energy, and it is released to the environment or emitted in the form of red fl uorescence radiation. Thes

The effect of abscisic acid and benzylaminopurine on photosynthesis and transpiration rates of maize ( Zea mays L.) under water stress and subsequent rehydration

The young plants of maize were cultivated as sand culture under controlled conditions in a greenhouse. The water stress caused by interruption of irrigation for a period of 8 days had the effect of statistically significant decrease of the photosynthesis rate (P N ) and the transpiration rate (E) as compared with plants under no stress. When the plants were treated with a 100 μM abscisic acid (ABA) solution before the interruption of irrigation, this had the effect of further decrease of the levels of P N and E during the first period of measurement (3 to 4 days after interruption of irrigation) and the effect of slowing down the development of water stress in the following period (7 to 8 days after interruption of irrigation). ABA applied through irrigation was more effective than the one applied by sprinkling because it significantly increased the water use efficiency (WUE) in the treated plants. Benzylaminopurine (BAP) used as a 10 μM solution brought about an increase of P N and E in comparison with the plants under stress, not treated phytohormones. The result of the combined application of both growth regulators were steady levels of P N during the entire eight-day evaluation of water stress imposed on maize plants. However, during the second period of measuring, the higher levels of E were reflected in a decrease of the WUE level. Two days after irrigation was resumed, the subsequent saturation of plants with water was manifested by an increase of P N in all groups of plants under stress. However, the fairly steady levels remained below the level of P N measured in the control sample under no stress. Rehydration had various effects on E. The level of E increased the most in the case where ABA was used as irrigation. It also increased moderately in the case where ABA was applied by sprinkling and in the case of the plants under stress, not treated phytohormones. On the contrary, E stagnated in the cases with BAP and decreased in the cases where ABA and BAP were applied together

An application of the dust grain charging model to determination of secondary electron spectra

Dust grains – objects of different shapes with a size distribution from micro to nanometers – are generally considered as a part of many space as well as laboratory plasmas. Among various dust charging processes, electron-induced secondary emission plays an important role in plasmas containing a noteworthy portion of high-energy electrons. Since a part of secondary electrons has not the energy high enough to overcome the surface potential barrier, the resulting grain charge is determined not only by the secondary emission yield (related to the grain material and size) but also by the secondary electron spectrum. We have developed a model of secondary electron emission from small dust grains. In the present contribution, we discuss the profile of a secondary emission yield that can be received from the model and the measured equilibrium grain charge, both as functions of an incident electron beam energy. A comparison of these quantities leads to an estimation of secondary electron spectra. We have found that: (1) the energy spectrum of secondary electrons does not change with the energy of primary electrons and (2) the energy spectrum depends on the target material being harder for gold and silver than for glass grains

Secondary electron emission from highly charged carbon grains

Surfaces in contact with a plasma can influence its characteristics and, on the other hand, the impact of plasma particles can change surface properties of materials immersed in a plasma. Carbon is often present in plasma systems either as a building material or a product of technological processes, thus its behavior is an important factor of these applications. The paper deals with investigations of secondary emission of 1–6 μm spherical grains from amorphous carbon under the electric field of the order of 108 V/m. We have found that the secondary emission yield increases with the electric field at the sample surface nearly linearly and does not depend on the grain diameter. Long-lasting (hours) electron irradiation of the sample surface leads to a significant decrease of the yield that was attributed to the removal of an absorbed layer from the grain surface. This conclusion is supported by the fact that a similar effect was achieved after several minutes of simultaneous electron and ion treatments