Storm-time formation of a relativistic electron belt and some relevant phenomena in other magnetospheric plasma domains

An empirical formula relating the strength of a storm given by its |Dst|_max with the L-coordinate of the peak of storm-injected relativistic electrons is one of a few well-confirmed quantitative relations found in the magneto-spheric physics. We successively extended a dataset of the formula’s basic storms with several events of high Dst-amplitude up to the highest observed |Dst|_max = 600 nT. Possible applying of the formula to the predicting of the ring-current plasma-pressure distribution and the lowest westward electrojet position for a storm are discussed. We have also analyzed the 2000–2001 years’ data on relativistic electrons from our instruments installed on EXPRESS-A (geosynchronous orbit; E_e = 0.8–6 MeV), Molniya-3 (h = 500 × 40 000 km, i = 63°; E_e = 0.8–5.5 MeV) and GLONASS (h = 20 000 km, i = 64°; E_e  l MeV) along with other correlated measurements: GOES series (E_e > 2 MeV), geomagnetic indices (Dst, AE, AL) and interplanetary parameters (solar wind, IMF). The goal is to investigate which outer conditions are most responsible for the high/low output of the storm-injected relativistic electrons. For the geosynchronous orbit, two factors are found as the necessary condition of the highest electron output: high and long-lasting substorm activity on a storm recovery phase and high velocity of solar wind. On the contrary, extremely low substorm activity surely observed during whole the storm recovery phase constitutes a sufficient condition of the non-increased after-storm electron intensity. For the first time found cases of the increased after-storm electron intensity observed at the inner L-shells with no simultaneously seen increase in the geosynchronous distances are presented.     

Estimation of vertically integrated water vapor in Hungary using MODIS imagery

Information about the amount and spatial structure of atmospheric water vapor is essential in understanding meteorology and the Earth environment. Space-borne remote sensing offers a relatively inexpensive method to estimate atmospheric water vapor in the form of integrated water vapor (IWV). The research activity reported in the present paper is based on the data acquired by the HRPT/MODIS (High Resolution Picture Transmission, MODerate resolution Imaging Spectroradiometer) receiving station established in Budapest (Hungary) by the Space Research Group of the Eötvös Loránd University. Integrated water vapor is estimated by the remotely sensed data of the MODIS instrument with different methods and also by the operational numerical weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF). Radiosonde data are used to evaluate the accuracy of the different IWV fields though it has been pointed out that the in situ data also suffers from uncertainties. It was found that both the MODIS and the ECMWF based fields are of good accuracy. The satellite data represent finer scale spatial structures while the ECMWF data have a relatively poor spatial resolution. The high quality IWV fields have proved to be useful for radiative transfer studies such as the atmospheric correction of other satellite data from times different than the overpass times of satellites Terra/Aqua and the forecast times of the model data. For this purpose the temporal variability of IWV is scrutinized both using ECMWF and MODIS data. Taking advantage of Terra and Aqua overpasses, the mean rate of change of IWV estimated by the near infrared method was found to be 0.47 ± 0.45 kg m⁻² h⁻¹, while it was 0.13 ± 0.65 kg m⁻² h⁻¹ based on the infrared method. The numerical weather prediction model’s analysis data estimated −0.01 ± 0.13 kg m⁻² h⁻¹ for the mean growth rate, while using forecast data it was 0.24 ± 0.18 kg m⁻² h⁻¹. MODIS data should be used when available for the estimation of the IWV in other studies. If no satellite data are available, or available data are only from one overpass, ECMWF based IWV can be used. In this case the analysis fields (or the satellite field) should be used for temporal extrapolation but the rate of change should be calculated from the forecast data due to its higher temporal resolution.     

Geminga pulsar observations with gamma-telescope Gamma-1

The Geminga light curve obtained with the “Gamma-1” telescope features two peaks separated by 0.5 ± 0.03 period. The light curve is pronounced for γ-quanta energies higher than 400 MeV. The pulsed flux upper limit (1σ) in the energy interval 50 – 300 MeV is 6·10⁻⁷ cm⁻²sec⁻¹. For energies >300 MeV the pulsed component power law spectrum has an exponent 1.1 _−0.3^+1.1 and an integral flux (1.1±0.3)·10⁻⁶ cm⁻²sec⁻¹.     

Interplanetary shocks and geomagnetic activity during solar maximum (2000) and solar minimum (1995–1996)

Plasma and magnetic field parameter variations through fast forward interplanetary shocks were correlated with the peak geomagnetic activity index Dst in a period from 0 to 3 days after the shock, during solar maximum (2000) and solar minimum (1995–1996). Solar wind speed (V) and total magnetic field (B_t) were the parameters with higher correlations with peak Dst index. The correlation coefficients were higher during solar minimum (r² = 56% for V and 39% for B_t) than during solar maximum (r² = 15% for V and 12% for B_t). A statistical distribution of geomagnetic activity levels following interplanetary shocks was obtained. It was observed that during solar maximum, 36% and 28% of interplanetary shocks were followed by intense (Dst  −100 nT) and moderate (−50  Dst < −100 nT) geomagnetic activity, whereas during solar minimum 13% and 33% of the shocks were followed by intense and moderate geomagnetic activity. It can be concluded that the upstream/downstream variations of V and B_t through the shocks were the parameters better correlated with geomagnetic activity level, and during solar maximum a higher relative number of interplanetary shocks can be followed by intense geomagnetic activity than during solar minimum. One can extrapolate, for forecasting goals, that during a whole solar cycle a shock has a probability of around 50% to be followed by intense/moderate geomagnetic activity.     

Forecasting of DST variations from polar cap indices using neural networks

The 15-min averaged polar cap (PC) index was used as an input parameter for the Dst variation forecasting. The PC index is known to describe well the principal features of the solar wind as well as the total energy input to the magnetosphere. This allowed us to design a neural network able to forecast the Dst variations from 1 to 4 h ahead. 1998 PC and Dst data sets were used for training and testing and 1997 data sets was used for validation proposes. From the 15 moderate and strong geomagnetic storms observed during 1997, nine were successfully forecasted. In three cases the observed minimum Dst value was less than the predicted one, and only in three cases the neural network was not able to reproduce the features of the geomagnetic storm.     

Observations of diffuse galactic positron annihilation radiation

The Galactic plane was scanned nearly three times by the UCSD/MIT Hard X-Ray and Low Energy Gamma-Ray Experiment on HEAO-1 from August 1977 through September 1978. Its Medium Energy Detectors were of the NaI/CsI phoswich type and operated over the 100 keV to 2 MeV range, with a 17° FWHM field of view and a 9% energy resolution at 511 keV. Sky maps for each epoch of observation were constructed in several energy bands. After subtraction of known point sources, a component associated with the galactic plane remains, whose spectrum is consistent with a power law and a positron annihilation spectrum. In the 333 to 583 keV energy band the flux is concentrated within ±35° of the galactic center, and the ratio of flux/radian (anticenter) is high, with a 2σ lower limit of 13. The parameters of the galactic center region's annihilation spectrum are positronium fraction of 0.9±0.1 and 511 keV flux of (2.0±0.7)×10⁻³ photons/cm²-sec-rad.     

Microbial processes in frozen food

Deep freezing of food and storage at −19°C is a standard conservation procedure in food technology. The lower limit of growth of bacteria in food is from about −5°C to about −8°C, whereas the reproduction limit of yeasts is 2 to 3°C lower. Storage temperatures above −10°C should therefore not be used. At −18°C, a commonly used storage temperature, no growth of microorganisms will occur. The microorganisms mainly found at the lower growth limit are Pseudomonas sp. and basidiomycete yeasts. The reduction in the number of microorganisms due to freezing, storage, and thawing is not of practical importance. Microbial enzymes, in particular lipases and proteases, are still active at −18°C. Therefore, the quality of raw products and good hygiene at the production site are most important.     

UV photobiochemistry of anhydrobiotic organisms at extremely low temperatures

Spores of Bacillus subtilis (TKJ 3412), cells of Deinococcus radiodurans R₁ (wild type) and conidia of Aspergillus ochraceus (strain 3174) have been UV irradiated (254 nm) in the dry state (3% relative humidity, argon) or in aqueous suspension at room temperature, at −55°C to −70°C and at −165°C to −170°C. The following effects have been analyzed: decrease in viability, occurrence of DNA strand breaks (pulsed-field gel electrophoresis) and production of DNA-protein cross-links (membrane filter method). The loss in viability is usually more pronounced at around −70°C than at room temperature, but it is lowest around −170°C. The kind of prevailing DNA damage varies from organism to organism. The amount of UV induced DNA-protein cross-link products steadily decreases with the temperature and is lowest at −170°C. The decrease in highly polymeric DNA by double strand breaks follows no universal pattern. The observed hypersensitivity of the three very different species at −70°C can therefore not be simply explained on the basis of the number of DNA lesions analyzed in the course of this work. We suggest that also the changing state of cellular water below and above about −130°C significantly contributes to the change in photosensitivity.     

GEO轨道相对论电子日积分通量预报统计建模

基于辐射带相对论电子哨声波局地加速理论,将地磁AE指数作为源电子通量和通量各向异性的指标,将地磁Dst指数作为损失机制的指标,利用滑动窗口线性滤波器方法,建立了一个地球静止轨道大于2MeV相对论电子预报模型.利用该模型开展了2000-2009年地球静止轨道相对论电子通量预报试验.研究发现,这10年总预报效率为0.818,2003年的预报效率（0.633）最低,2009年的预报效率（0.856）最高.模型预报效果与持续模型相比有很大提高,略低于利用太阳风参数作为输入的同类预报模型的预报效果.这说明即使在缺少太阳风参数的情况下,该模型利用地磁扰动参数也能取得较好的预报效果.当模型输入参数增加了太阳风速度时,即综合考虑了行星际扰动和磁层扰动对辐射带粒子加速过程的影响,模型逐年的预报效率进一步提升.其中,2005年的预报效率提升了9.5%,这10年的总预报效率增加到0.848,预报值与实测值之间的线性相关系数为0.918,均方根误差为0.422.      

Cold resistance and metabolic activity of lichens below 0°C

Laboratory measurements show that lichens are extremely tolerant of freezing stress and of low-temperature exposure. Metabolic activity recovered quickly after severe and extended cold treatment. Experimental results demonstrate also that CO₂ exchange is already active at around −20°C. The psychrophilic character of polar lichen species is demonstrated by optimum temperatures for net photosynthesis between 0 and 15°C. In situ measurements show that lichens begin photosynthesizing below 0°C if the dry thalli receive fresh snow. The lowest temperature measured in active lichens was −17°C at a continental Antarctic site. The fine structure and the hydration state of photobiont and mycobiont cells were studied by low-temperature scanning electron microscopy (LTSEM) of frozen hydrated specimens. Water potentials of the frozen system are in the range of or even higher than those allowing dry lichens to start photosynthesis by water vapor uptake at +10°C. The great success of lichens in polar and high alpine regions gives evidence of their physiological adaptation to low temperatures. In general lichens are able to persist through glacial periods, but extended snow cover and glaciation are limiting factors.     

X-ray spectroscopy and variability of AGN detected in the 2 Ms Chandra Deep Field-North Survey

We investigate the nature of the faint X-ray source population through X-ray spectroscopy and variability analyses of 136 active galactic nuclei (AGN) detected in the 2 Ms Chandra Deep Field-North Survey with >200 background-subtracted 0.5–8.0 keV counts [F_{0.5–8.0 keV} = (1.4−200) × 10⁻¹⁵ erg cm⁻² s⁻¹]. Our preliminary spectral analyses yield median spectral parameters of Γ = 1.61 and intrinsic N_H = 6.2 × 10²¹ cm⁻² (z = 1 assumed when no redshift available) when the AGN spectra are fitted with a simple absorbed power-law model. However, considerable spectral complexity is apparent (e.g., reflection, partial covering) and must be taken into account to model the data accurately. Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has a pronounced effect on the derived JVH distribution and, to a lesser extent, the X-ray luminosity distribution. We also find that among the 136 AGN, 10 (≈7%) show significant Fe K emission-line features with equivalent widths in the range 0.1–1.3 keV. Two of these emission-line AGN could potentially be Compton thick (i.e., Γ < 1.0 and large Fe K equivalent width). Finally, we find that 81 (≈60%) of the 136 AGN show signs of variability, and that this fraction increases significantly (≈80–90%) when better photon statistics are available.     

Towards validation of SCIAMACHY lunar occultation NO2 vertical profiles

Vertical profiles of stratospheric nitrogen dioxide (NO₂) have been retrieved from moderate resolution lunar occultation transmission spectra measured by Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on board the European Environmental Satellite (ENVISAT). These measurements were taken over the high southern latitude of 50°–90° during the period of 2003–2005. To assess the accuracy of the retrieved NO₂ profiles, the SCIAMACHY nighttime NO₂ profiles were compared with NO₂ profiles retrieved from sunrise solar occultation spectra measured by the Halogen Occultation Experiment (HALOE) and the Stratospheric Aerosol and Gas Experiments II (SAGE II) using a photochemical correction model. The validation results show good agreement of SCIAMACHY lunar occultation NO₂ with scaled HALOE and SAGE II profiles. The relative mean differences (rmd) with scaled HALOE profiles are within −13% to +5% and standard deviations (rms) of the relative differences are within 3–19% between 25 and 38 km. The rmd and rms with scaled SAGE II NO₂ profiles are in the range of −9 to +7 and 10–17% respectively between 22 and 39 km.     

High spectral resolution Fabry-Perot interferometer measurements of comet Halley at H-alpha and 6300 Å

A 40.6 cm Newtonian telescope has been interfaced to the Fabry-Perot interferometer at the Arecibo Observatory to make high spectral resolution measurements of Comet Halley emissions at 6562.72 Å (H-alpha) and 6300.3 Å (OI). In March 1986 the H-alpha surface brightness for a 5′.9 field of view centered on the comet nucleus decreased from 39±7.8 rayleighs on 12 March to 16±3.8 rayleighs on 23 March. The atomic hydrogen production rate on 12 March 1986 was 1.62±0.5 × 10³⁰ s⁻¹, and on 23 March 1986 it was 6.76±2.3 × 10²⁹ s⁻¹. Using spectral resolution of 0.196 Å, we found the atomic hydrogen outflow velocity to be approximately 7.9±1.0 km s⁻¹. In general, the H-alpha spectra are highly structured, and indicative of a multiple component atomic hydrogen velocity distribution. An isotropic outflow of atomic hydrogen at various velocities is not adequate to explain the spectra measured at H-alpha. The 6300.3 Å emission of O(1D) had a surface brightness of 81±16 rayleighs on 15 March 1986, and 95±11 rayleighs on 17 March 1986. After adjustment for atmospheric extinction, the implied O(1D) production rate on 15 March is 6.44±3.0 × 10²⁸ s⁻¹, and the production rate on 17 March is 5.66±2.7 × 10²⁸ s⁻¹. These spectra included a feature at 6300.8 Å that we attribute to NH₂. The brightness of this emission feature was 37±11 rayleighs on 15 March.     

A comprehensive study on middle atmospheric thermal structure over a tropic and sub-tropic stations

The general characteristics of middle atmospheric thermal structure have been studied by making use of the Rayleigh lidar data collected over the period of about four years (1998–2001). Here, the data has been used from two different stations in the Indian sub-continent in tropics (Gadanki; 13.5°N, 79.2°E) and in sub-tropics (Mt. Abu; 24.5°N, 72.7°E). The observed monthly mean temperature profiles are compared with different model atmospheres (CIRA-86 and MSISE-90). We observed, the mean temperature profiles have closer agreement with MSISE-90 than CIRA-86. The temperature profiles measured by lidar and HALOE satellite overpass nearby lidar site are generally in agreement with each other. The systematic and statistical errors in deriving temperature are found to be uniform for both the stations, as 1 K at 50 km, 3 K at 60 km and 10 K at 70 km. The special features of mesospheric temperature inversion (MTI) and double stratopause structure (DBS) are also addressed for both the stations.     

Interplanetary scintillations of PKS 2314+03 during occultation by comet Halley

Strong interplanetary scintillations (IPS) of the quasar 2314+03 were recorded at 103 MHz at Thaltej-Ahmedabad, India with a transit type correlation interferometer on 18, 19 and 20 December 1985, as the radio source was predicted to be occulted by the ion tail of the comet Halley.

On 18th through 20th very strong scintillations, with periodicities of 1 sec average were observed, their amplitude progressively decreasing as the source approached the tail-end. The rms variations of scintillating flux of the source on 18, 19 & 20 were about 18, 11 & 4.7 Jy, as against 3.3 Jy on control days 17 and 21 December for solar elongation of 87°.

Assuming Gaussian irregularities with weak scattering, the rms density variations, ΔN, of 10, 6, 3 and 1 elec./cm³ on 18 through 21 December, from the comet nucleus towards its tail-end, varied as (ΔN) ∝ r^−3.3 as against (ΔN) ∝ r⁻² in the solar plasma.

Quasi-periodic modulations of the enhanced scintillating flux possibly imply 10⁴ km scale-size ion condensations and mean electron density of 10³ to 10⁴ electrons/cm³ in the Halley's plasma tail.     

Molecular and biophysical aspects of adaptation of life to temperatures below the freezing point

This review examines adaptation of life to temperatures below −2°C, from a biophysical point of view and relative to the properties of water. Different metabolic processes have different lowest temperatures. The lowest established temperature for photosynthesis and growth seems to be about −17°C. The review discusses membrane lipids from Antarctic microbial systems, and the limits to longevity of life in the cold, with coverage of permafrost microbial systems. It is directed towards readers of many backgrounds and supplements an earlier survey (L. Finegold, Adv. Space Res. 6, 257–264, 1986).     

Total electron content at low latitudes and its comparison with the IRI90

We used total electron content (TEC) data measured by Faraday rotation technique over Cachoeira Paulista (22.5°S, 45°W), in Brazil, to study the TEC variations with the solar flux at 10.7 cm (F10.7) and to compare the results with the IRI90 predictions. The data were divided into summer, equinox and winter. During the analysed period F10.7 varied from 66 up to 330. Our data shows that the observed TEC at 1600 LT (around the diurnal maximum) and at 0500 LT (around the diurnal minimum) increases with F10.7 until saturation is reached which occurs at F10.7≈210 to 220 for equinox and summer, and at F10.7≈180 for winter months. Comparison with the IRI90 predictions shows that IRI overestimates the TEC at 0500 LT for all solar flux values. At 1600 LT, IRI overestimates the observed TEC for low solar flux but underestimates it for high solar flux values.     

Response of the low latitude geomagnetic field to the major proton event of November 2001

A major solar flare eruption occurred at 16:20 UT on 4 November 2001, followed by strong solar radiation storm and proton event recorded by the SOHO and other interplanetary satellites. Coronal mass ejection associated with the flare event triggered an interplanetary shock, which impacted the geomagnetic field after about 33 h. The shock impact was quite intense to produce a SSC magnitude of 80 nT in the low latitude ground magnetic records followed by sharp and deep main phase (Dst −300 nT) in the first stage, following the density (N_p) enhancement. High time resolution digital magnetic field data from the equatorial and low latitude stations in India are analyzed to study the influence of various IP parameters on the intensity and duration of the magnetic storm. A double step storm was found to be in progress caused by the multiple injections. During the period of recovery, after a period of 8 h, a third stage of depression in the ground magnetic field was set in, which corresponded to the southward directed Bz. The energy transfer processes associated with the event is presented.     

Correlations between neutral and ionized solar wind

We report results of a statistical study correlating ionized solar wind (ISW) fluxes observed by ACE during late 2000 and throughout 2001 with neutral solar wind (NSW) fluxes observed by IMAGE/LENA over the same period. The average correlation coefficient between the neutral and ionized solar wind is 0.66 with correlations greater than 0.80 occurring about 29% of the time. Correlations appear to be driven by high solar wind flux variability, similar to results obtained by in situ multi-spacecraft correlation studies. In this study, however, IMAGE remains inside the magnetosphere on over 95% of its orbits. As a function of day of year, or equivalently ecliptic longitude, the slope of the relationship between the neutral solar wind flux and the ionized solar wind flux shows an enhancement near the upstream direction, but the symmetry point appears shifted toward higher ecliptic longitudes than the interstellar neutral (ISN) flow direction by about 20°. The estimated peak interstellar neutral upstream density inside of 1 AU is about 7 × 10⁻³ cm⁻³.     

Trapped particle energy spectrum in shuttle middeck

We describe the differential energy spectrum of trapped particles measured by a solid-state charged particle telescope in the mid-deck of the Space Shuttle during the period of solar maximum. The telescope was flown in two high altitude flights at 28.5° and 57° inclination. Assuming, as is normally done, that the variations of Shuttle orientation during the missions lead to average isotropic incident spectra, the observed spectrum disagrees significantly from AP8 model calculations. This indicates the need to take into consideration the variations of solid-angle direction relative to the magnetic field. The measurements show that there is a very significant flux of secondary light ions. The energy spectra of these ions does not agree with the production spectrum from radiation transport calculations based on omni-directional AP8 Max model as an input energy spectrum.

We also describe measurements of linear energy transfer spectra using a tissue equivalent proportional counter (TEPC) flown both in the mid-deck and the payload bay of the Space Shuttle. Comparisons are made between linear energy transfer spectral measurements AP8 model-based radiation transport predictions, and thermoluminescent dosimeter (TLD) measurements. The absorbed dose-rate measurements using TLD's are roughly 25% lower than the TEPC-measured dose rate measurements.