THz photometers for solar flare observations from space

Organic semiconductors are promising materials for future electronic and electroluminescence applications. A detailed understanding of organic layers and nano-sized crystals down to single molecules can address fundamental questions of contacting organic semiconductors at the nanometer limit and obtaining luminescence from them. In this thesis, electroluminescence spectra from pentacene, a policyclic hydrocarbon (acene), are discussed. The luminescence is induced by the current from the tip of a scanning tunneling microscope (STM). Pentacene is an organic semiconductor which gained a lot of attention in technology because of its electronic properties suitable for applications in thin film devices. Moreover, recent fundamental studies employed pentacene as a standard to demonstrate sub-molecular resolution by scanning probe techniques. This work reports the first observation of light emission from nanometer-sized pentacene crystals grown on an ultrathin insulating layer on noble metal surfaces. Different STM-techniques are combined to characterize the individual systems studied with respect to topography, crystal structure, electronic properties and work function changes. The initial step of the project was the implementation of an optical system for light collection from the tunnel-junction of a low-temperature STM. In the set-up, a novel approach based on the use of in situ adjustable lenses has been realized. Three lenses placed in the vicinity of the tip-apex allow light collection into three independent channels which can be used for versatile optical analysis. An important part in the characterization of the organic system was to clarify the interaction between adsorbed molecules and substrates. We investigated individual pentacene molecules on different ultrathin insulator-metal systems. With the STM tip in tunnel contact, the molecules are situated in a double barrier junction formed by the insulating layer on one side and the vacuum gap on the other side. The metal surface and the STM-tip form the electrodes. The electronic properties of pentacene in this configuration have been characterized. Insulator-metal-systems, which provide a good electronic decoupling for pentacene from the metal, have been chosen as substrates for the growth of pentacene nanocrystals. Using the sub-molecular resolution of the STM we resolved the structure of the top-layer of the pentacene nanocrystals and found that the crystal phase agrees with the pentacene bulk structure. Moreover, the comparison of charge injection barriers between individual molecules and nanocrystals of pentacene indicates a significant change of electronic properties after the formation of ordered structure from the individual building blocks. Optical spectroscopy of the emitted light reveals an excitonic emission from the nanocrystals, which is in very good agreement with photoemission spectra of macroscopic crystals. Although a highly localized current-injection by the STM tip is used for excitation, it can be concluded that the source of light emission is delocalized. In contrast to luminescence measurements reported for other organic materials in STM, the excitation is not localized on the individual molecule, into which a charge is injected by the STM-tip. Our study indicates the importance of inter-molecular coupling leading to a high mobility of the excited state which has to be considered in the framework of STM-induced luminescence. A further result is the observation of the Stark shift of pentacene luminescence, that has so far not been measured at large electric fields of the order of 1V/nm. The evaluation of the Stark shift provides information on dipole and polarizability change during the decay of an exciton. The measured large dipole change of the lowest singlet exciton in pentacene indicates a mixing of the Frenkel exciton (FE) with a small contribution of charge-transfer (CT). Finally, we developed a set-up for photon correlation measurements in the STM. The properties of photon statistics is a means which can unambiguously prove that the luminescence is due to a single-photon source, i.e. a light source which emits no more than one photon at a time. A typical example of such a source is the emission from a single molecule. We performed photon correlations measurements of the luminescence from pentacene and C60 nanocrystals. While the excitonic bulk emission of pentacene is not expected to represent a single photon emitter, we also did not observe anticorrelations in the case of C60 indicating the importance of the local environment in the STM-junction, e.g. the short distance to the metal electrodes.

Magnetic Resonance Imaging (MRI) provides a non-invasive manner to aid clinical diagnosis, while its limitation is the slow scanning speed. Recently, due to the high costs of health care and taking account of patient comfort, some methods such as Parallel MRI (pMRI) and compressed sensing MRI have been developed to reduce the MR scanning duration under the sampling process. It is almost unavoidable to accept some doses of X-rays in computed tomography (CT scans). If one could find a more efficient way to represent the required visual information, the tasks of image processing and medical imaging would become easier and less troublesome. In this paper, first, we used pMRI on complex double data of brain magnetic resonance image. pMRI significantly reduces the number of measurements in the Fourier domain because each coil only acquires a small fraction of the whole measurements. It is important to reconstruct the original MR image efficiently and precisely for better diagnosis. In this research, we proposed a new super resolution and deblurring algorithm with dictionary learning, based on assuming a local Sparse-Land model on image patches, serving as regularization, then we validated the proposed method by using another one called the adaptive selection of sub dictionaries- adaptive reweighted sparsity regularization. Visual comparison and significant difference in psnr calculation (0.8111db) and time complexity showed that the proposed method had much better results.

Charge coupled device(CCD) is one kind of photoelectric solid-state imaging device with excellent performance. It has the features of large array and good image quality. Working under very complex driving timing, it usually has low frame frequency and can not meet the demand of high imaging frame rate. The method of equivalent high frame rate imaging technique is introduced based on normal CCD in this paper. Some CCDs can be drived via electrodes separately. To meet the imaging demands of high frame rate, high resolution and high quality of two frame imaging technique for pulse light images, the right kind of CCDs should be adopted. The most important is that the CCD electrodes must be controlled directly and respectively. The charge transfer period is a key point while designing CCD driving timing for separate pulse light integration, charge package transfer and readout for two pulse light images. The validation experiments for the principle of equivalent high frame rate exposure of two pulse light images has been accomplished. It is shown that two pulse light images with interval of about 2 μs can be distinguished while all CCD’s inherent excellent performance are retained. A kind of two framing camera system with simple structure can be developed based on this principle.

As pescarias de arrasto na costa Norte caracterizam-se por fornecerem uma grande quantidade de pescado. Devido essas pescarias capturarem grande biomassa de camarões e peixes, verificou-se a necessidade de avaliar e comparar a proporção da captura destes recursos utilizando redes de arrasto-duplo sistema “double rig”, sendo uma delas modificada. Os dados foram coletados durante o projeto inovação tecnológica para redes de arrasto seletivas à captura de peixes pela frota camaroneira. Na verificação dos recursos, optou-se avaliar a captura de pescada gó Macrodon ancylodon e dos camarões: camarão rosa Farfantepenaeus subtilis e sete barbas Xiphopenaeus kroyeri. A avaliação da proporção da captura entre peixe e camarões foram testadas para ambas as redes; testou-se ainda, a significância da captura das redes, em relação a série temporal, estimou-se a CPUE (Captura/horas de arrasto/dia) das redes, correlações lineares; normalidade da distribuição e suas diferenças significativas. A rede modificada para captura de peixes, obteve biomassa de pescado superior a rede para camarão, porém capturou uma biomassa inferior de camarões, com proporção de peixes superior, assim cumprindo sua premissa. Diferenças significativas foram encontradas nas séries temporais das redes (T:0,017; p<0,05). Em relação a CPUE, ambas as redes obtiveram correlação linear baixa, distribuições normais; diferenças significativas ANOVA (p<0,05) encontradas apenas para rede de peixes (p: 0,008). Dentre os pesqueiros, o denominado ‘zero zero’ destacou-se como principal área de esforço. Diante das resoluções obtidas no estudo, conclui-se que o uso das redes de peixe (rede modificada) mostraram-se eficazes para embarcações camanoeiras durante o período de defeso do camarão.

Paramagnetic effects are valuable structural restraints in study of structures, dynamics and interactions of proteins by means of NMR spectroscopy. Site-specific tagging of proteins with paramagnetic ions is generally required to achieve these paramagnetic effects. In this review, we first introduce the concept of paramagnetic effects including paramagnetic relaxation enhancement (PRE), pseudocontact shift (PCS) and residual dipolar couplings (RDCs), which are generally used in biomolecular NMR. Thereafter, strategies of site-specific paramagnetic tagging of proteins are outlined, and the paramagnetic effects are evaluated. On the basis of paramagnetic tagging methods described above, the applications of paramagnetic NMR in characterization of multi-domain protein replacement, 3D structural determination of unstable and low-abundance enzyme intermediate complex in real time condition, and 3D structural determination of proteins in live cells using PCSs are introduced. NMR optimized paramagnetic tags suitable for achieving high spatial resolution of distances determined by double electron-electron resonance (DEER) are reviewed. In the end, the applications of DEER measurement in characterization of protein structures in cells are demonstrated. Paramagnetic NMR and electron paramagnetic resonance (EPR) in characterization of proteins in cells is shown as a powerful technique in structural biology and chemical biology, and the development of biological compatible methods of protein modifications suitable for NMR and EPR applications are in high demand. In summary, paramagnetic tagging proteins are a powerful tool in elucidation of protein structures, dynamics and interactions in chemical and structural biology and it is surely to find wide applications in cells.

The goal of this paper is to perform simulations that capture fluid effects from small drops up to the propagation of large waves. To achieve this, we present a hybrid simulation method, that couples a two-dimensional shallow water simulation with a full three-dimensional free surface fluid simulation. We explain the approximations imposed by the shallow water model, and how to parametrize it according to the parameters of a 3D simulation. Each simulation is used to initialize double layered boundary conditions for the other one. The area covered by the 2D region can be an order of magnitude larger than the 3D region without significantly effecting the overall computation time. The 3D region can furthermore be easily moved within the 2D region during the course of the simulation. To achieve realistic results we combine our simulation method with a physically based model to generate and animate drops. For their generation we make use of the fluid turbulence model, and animate them with a simplified drag calculation. This allows simulations with relatively low resolutions.

Solar flare observations in the sub-mm spectral bands are essentially non-existent. There is evidence that some solar bursts exhibit a spectral component rising in intensity towards wavelengths shorter than 3 mm, displaying fast sub-second pulses at different repetition rates. On the other hand, the spectral features of white light flares are also unknown in the infra-red range of frequencies. In both wavelength ranges the physics of the emission processes may involve particles accelerated to high energies. The diagnostics of solar flare continuum emission in the IR and sub-mm spectral regions will provide crucial tests on various flare models and bring some clues on the initial primary energy release mechanisms. We propose the construction and operation of a ground-based telescope, operating at two sub-millimeter wavelengths (at about 210 GHz and 405 GHz), with high time resolution (one millisecond), capable of determining the spatial position of burst emission centroids with high definition (a few arcseconds) using the multiple beam technique. Final installation and operation at a high-altitude site in the Argentinian Andes mountains are planned in a joint cooperation with Argentina's Instituto de Astronomia y Fisica del Espacio, IAFE (M. Rovira and associates) and Complejo Astronomico El Leoncito, CASLEO, San Juan (H. Levato and associates); and Switzerland's University of Bern, Institute of Applied Physics, IAP, Bern (A. Magun and associates).

Several approaches to imaging hard X-rays emitted from solar flares have been proposed or are planned for the nineties including the spatial modulation collimator (SMC) and the rotating modulation collimator (RMC). A survey of current solar flare theoretical literature indicates the desirability of spatial resolutions down to 1 arcsecond, field of views greater than the full solar disk (i.e., 32 arcminutes), and temporal resolutions down to 1 second. Although the sun typically provides relatively high flux levels, the requirement for 1 second temporal resolution raises the question as to the viability of Fourier telescopes subject to the aforementioned constraints. A basic photon counting, Monte Carlo 'end-to-end' model telescope was employed using the Astronomical Image Processing System (AIPS) for image reconstruction. The resulting solar flare hard X-ray images compared against typical observations indicated that both telescopes show promise for the future.

Preliminary values for the resolutions of various figures of merit have been deduced by the SOFIA TwinMUSIC [1] for the spectra of isotopes obtained from the fission of U. The energy-loss resolution was measured to be σΔE E = 0.34% with P25 gas (Fig. 1). This leads to a charge resolution of σZ1,2 = 0.23± 0.01 for the measurements in 1 2 of the TwinMUSIC and σZ1+2 = 0.31±0.02 for the sum of both. The steep falloff of Δt,10−90% ≈ 150ps of the drift times close to the cathode measured for single anodes yields a corresponding resolution of the straight-line fit to a track through the active volume of σdt,fit = (268± 40)ps (Fig. 2). For the electrical field settings applied the measured drift velocity is well reproduced by Magboltz simulations. After fine adjustment of the drift-times with the help of an adjacent MWPC, a position resolution for the single anode of σx,PB = (28±11)μm and σx,FF = (47±13)μm for the primary beam and fission fragments, respectively, can be deduced (Fig. 3). Consequently, the angular distribution of the fragments of ≈ 40mrad could be measured with a precision of σΘ,FF = (0.13± 0.10)mrad by eventwise tracking. The analysis of the data is still ongoing, further refinements on the achieved resolutions are to be expected. Isotopic mass yields have been be deduced and published elsewhere [2]. Changes in the design of the TwinMUSIC detector system are ongoing and will allow for an even better charge, position and angular resolution. We are aiming for a full 3D tracking operation with rates of 1 − 2 MHz with a non-triggered DAQ. The potential of a low-pressure operation (0.2 − 0.3atm) and the application of other, ’faster’ gas mixtures will be tested too. The next physics run is already scheduled 2014 at CaveC looking into more details of the isotopic mass distributions. In the far future, a more complete set of measurements will be performed in the context of RB (Reaction studies with Relativistic Radioactive Beams) at the FAIR (Facility for Antiproton and Ion Research) project at GSI/Darmstadt. Dedicated detector developments will be performed for those endeavors which foster similar developments e.g. for the instrumentation of the SuperFRS.

The sudden increase of Solar X-ray and EUV emission following solar flares causes ionization and increased absorption of electromagnetic (EM) waves in the sunlit hemisphere of the Earth’s ionosphere. Solar flares are also accompanied by energetic particles which can lead to additional ionization and absorption especially at the higher latitudes (> 60 °). A novel method has been developed by Buzás et al. [1] based on the amplitude data of the EM waves measured by Digisondes to calculate and investigate the relative absorption changes (compared to quiet period) occurring during solar flares. The effect of 13 intense (>C4.8) solar flares that occurred between 06:00 and 16:30 (UT, daytime LT = UT+2 h) from 04 to 10 September 2017 have been studied using the so-called "amplitude method". Total and partial radio fade-outs, furthermore, +20%–1400% amplitude changes (measured at 2.5 and 4 MHz) were experienced at three Digisonde stations (Juliusruh (54.63° N, 13.37° E), Průhonice (49.98° N, 14.55° E) and San Vito (40.6° N, 17.8° E)) during and after the investigated flares.In the present study we compare the results of the amplitude method with the absorption changes measured by the Finnish Riometer Chain and determined by the NOAA D-RAP model during the same solar flare events. The X-class flares caused 1.5–2.5 dB attenuation at 30–32.5 MHz based on riometer data, while the absorption changes were between 10 and 15 dB in the 2.5–4.5 MHz frequency range (thus 10 times higher) according to the amplitude data measured by the Digisondes. The impact caused by the energetic particles after the solar flares are clearly seen in the riometer data, while it can be observed only at Juliusruh (~55°) at some certain cases among the Digisonde stations. Therefore, the absorption changes as a result of the particle precipitation is significant at high latitudes, but decreases rapidly with decreasing latitude, and is no longer detectable below the sub-auroral region. The main conclusion from the comparison of the amplitude method with the D-RAP model is that the model underestimates the values obtained from the Digisonde's measurements at both 2.5 and 4 MHz in almost every case. The differences varied between 0.2 and 15 dB at 2.5 MHz and 2.9–10 dB at 4 MHz and they did not show any systematic trend with the intensity of the flare, or with the latitude of the station. [1] Buzás, A., Kouba, D., Mielich, J., Burešová, D., Mošna, Z., Koucká Knížová, P., & Barta, V. (2023). Investigating the effect of large solar flares on the ionosphere based on novel Digisonde data comparing three different methods. Frontiers in Astronomy and Space Sciences, 10.

In solar flares and other astrophysical systems, a major challenge for solving the particle acceleration problem associated with magnetic reconnection is the enormous scale separation between kinetic scales and the observed reconnection scale. Because of this, it has been difficult to draw any definite conclusions by just using kinetic simulations. A particle acceleration model that solves the energetic particle transport equation can capture the main acceleration physics found in kinetic simulations and thus provide a practical way to make observable predictions and directly compare model results with observations. Here we study compression particle acceleration in magnetic reconnection by solving the Parker (diffusion–advection) transport equation using velocity and magnetic fields from two-dimensional magnetohydrodynamics (MHD) simulations of a low-β high-Lundquist-number reconnection layer. We show that the compressible reconnection layer can give significant particle acceleration, leading to the formation of power-law particle energy distributions. We analyze the acceleration rate and find that the acceleration in the reconnection layer is a mixture of first- and second-order Fermi processes. When including a guide field, we find that the spectrum becomes steeper and both the power-law cutoff energy and maximum particle energy decrease as plasma becomes less compressible. This model produces a 2D particle distribution that one can use to generate a radiation map and directly compare with solar flare observations. This provides a framework to explain particle acceleration at large-scale astrophysical reconnection sites, such as solar flares.

A brief review is given of the initial six months (October 1991 – March 1992) of solar flare observations with the Hard X-ray Telescope (HXT) aboard Yohkoh. The Yohkoh HXT has the following advanced capabilities: (i) four-band, simultaneous imaging in the X-ray energy ranges of 14–23, 23–33, 33–53, and 53–93 keV; (ii) high angular resolution of ∼ 5 arcsec with a wide Held of view covering the whole Sun; (iii) high time resolution of 0.5 s; and (iv) high sensitivity with a total effective area exceeding 50 cm2. More than 250 solar flares were observed in the initial six months, including four GOES X-class flares. It was revealed that hard X-ray sources of flares are much more complicated than expected; they sometimes vary quite rapidly, and even at the same time they show different shapes at different X-ray energies. Typical features were derived, however, from observations of several well-analyzed flares. Their implications for the particle acceleration mechanisms of solar flares are discussed.Key wordsSun: FlaresSun: Hard X-raysParticle acceleration

The future space experiment «Sun-Terahertz» is aimed at studying the Sun in the unexplored terahertz range, obtaining new data on the terahertz radiation of the Sun, solar active regions and solar flares. The scientific equipment being developed is a set of eight detectors sensitive to radiation of various frequencies in the range 0.4–12.0 THz. The Golay cell optoacoustic receiver was used as a sensitive element of the detectors. This paper examines the problem of changing the sensitivity of receivers of this type when their own temperature changes (temperature effect). Using a test bench based on a single-channel model of scientific equipment and a black body simulator, the linear section of the temperature dependence of the receiver was determined. A method for compensating the temperature effect of optoacoustic converters Golay cell has been developed and the results of its testing on a test bench are presented. This technique will be useful in the development of scientific equipment based on Golay cells, the operation of which is expected under conditions of temperature changes in the surrounding space.

This paper provides a brief description individual elements that can be included in the Solntse–Terahertz scientific apparatus that was designed for the first time to carry out an extra-atmospheric experiment onboard the International Space Station. Its purpose is to measure terahertz electromagnetic radiation both from the quiet Sun and during active processes on the Sun (solar flares, coronal mass ejections, etc.), which is necessary to establish the physical nature of solar activity and solar flares. The possibility is discussed of using optoacoustic converters (Golay cells) as receivers of terahertz radiation, the sensitivity, stability, and response time of which were determined in the course of preliminary laboratory studies under terrestrial conditions.

Evolution of magnetic field structure and particle acceleration in solar flares