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        검색결과 20

        1.
        2021.12 구독 인증기관 무료, 개인회원 유료
        I would like to ask you to incorporate the (Re)connection Model as a model for sustainable and inclusive change that you already use in Jeju as one of the guiding principles that could also be interesting for other countries as well. This period is decisive for the planet. UN Secretary-General António Guterres stated that the last report - ‘The Physical Science basis’ - published by the Intergovernmental Panel on Climate Change (IPCC) is a code red for humanity. “The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk,” the Secretary-General says in a statement. At the UN CBD COP 15 and COP 26 in Glasgow parties try to agree to build a biodiversity-friendly, climate-neutral and resilient planet. To keep global warming far below 2°C (idealy maximum warming of 1.5°) we need to be climate-neutral in 2050 and half the emissions of greenhouse gasses in the next decade. To stop the decline of natural ecosystems and to stop the Holocene extinction/Sixth extinction of species we need to halt the loss of biodiversity in the next decade and start immediately to restore our natural ecosystems. The (Re)connection Model can be helpful to reach these objectives. First, we need to give more space, light, food and care to nature. Second, we need to translate ‘biodiversity’ into a language that people can understand and relate to. It is only when they’ll find reasons to love the world that they’ll save it. Third, we need to adopt the (Re) connection model in which we reconnect nature with nature, people with nature, business with nature, as well as a policy with practice. It is by thinking globally, acting locally and changing personally that we’ll create the world we want, starting today, caring for nature and future generations.
        4,600원
        2.
        2016.09 구독 인증기관 무료, 개인회원 유료
        It’s a time we prepare for a reparation agenda for Jeju 4.3 victims and their families. We should approach the USA government side collectively rather than individually for their lawsuits, because most of them are elderly, over 75 years old and need intensive medical care and assistance immediately. It’s up for us to recognize some tasks of actualizing Reparation, Reconciliation and Reconnection Agenda for “Environmentally Sustainable Peace Island” beyond Trauma of the Jeju 4.3 Grand Tragedy into the next Decade.
        4,000원
        4.
        2015.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Data analysis and theoretical arguments support magnetic reconnection in a chromospheric current sheet as the mechanism of the observed photospheric magnetic ux cancellation on the Sun. Flux pile-up reconnection in a Sweet{Parker current sheet can explain the observed properties of canceling mag- netic features, including the speeds of canceling magnetic fragments, the magnetic uxes in the fragments, and the ux cancellation rates, inferred from the data. It is discussed how more realistic chromospheric reconnection models can be developed by relaxing the assumptions of a negligible current sheet curvature and a constant height of the reconnection site above the photosphere.
        3,000원
        9.
        2003.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In the present study, we have investigated morphology and evolution of small-scale Ha dynamic features on the quiet sun by analyzing video magnetograms and high resolution Ha images simultaneously taken for 5 hours at Big Bear Solar Observatory on April 18, 1997. From comparisons between time sequential longitudinal magnetograms and Hα images covering 150" × 150", several small-scale Hα dynamic features have been observed at a site of magnetic flux cancellation. A close relationship between such features and cancelling magnetic fluxes has been revealed temporarily and spatially. Our results support that material injection by chromospheric magnetic reconnect ion may be essential in supporting numerous small-scale Hα dynamical absorption features, being in line with recent observational studies showing that material injection by chromospheric magnetic reconnect ion is essential for the formation of solar filaments.
        4,000원
        10.
        2003.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Observations have indicated that magnetic reconnect ion may occur frequently in the photosphere and chromosphere as well as in the solar corona. The observed features include cancelling magnetic features seen in photospheric magnetograms, and different kinds of small-scale activities such as UV explosive events and EUV jets. By integrating the observed parameters of these features with the Sweet-Parker reconnect ion theory, an attempt is made to clarify the nature of chromospheric magnetic reconnection. Our results suggest that magnetic reconnect ion may be occurring at many different levels of the photosphere and chromosphere without a preferred height and at a faster speed than is predicted by the Sweet-Parker reconnect ion model using the classical value of electric conductivity. Introducing an anomalous magnetic diffusivity 10-100 times the classical value is one of the possible ways of explaining the fast reconnect ion as inferred from observations.
        4,000원
        12.
        2002.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Solar observations support that magnetic reconnect ion ubiquitously occurs in the chromosphere as well as in the corona. It is now widely accepted that coronal magnetic reconnect ion is fast reconnect ion of the Petschek type, and is the main driver of solar flares. On the other hand, it has been thought that the traditional Sweet-Parker model may describe chromospheric reconnect ion without difficulty, since the electric conductivity in the chromoshphere is much lower than that in the corona. However, recent observations of cancelling magnetic features have suggested that chromospheric reconnect ion might proceed at a faster rate than the Sweet-Parker model predicts. We have applied the Sweet-Parker model and Petschek model to a well-observed cancelling magnetic feature. As a result, we found that the inflow speed of the Sweet-Parker reconnect ion is too small to explain the observed converging speed of the feature. On the other hand, the inflow speeds and outflow speeds of the Petschek reconnect ion are well compatible with observations. Moreover, we found that the Sweet-Parker type current sheet is subject to the ion-acoustic instability in the chromosphere, implying the Petschek mechanism may operate there. Our results strongly suggest that chromospheric reconnect ion is of the Petschek type.
        4,000원
        13.
        2001.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Strong thermal X-ray emission, called Galactic Ridge X-ray Emission, is observed along the Galactic plane (Koyama et al. 1986). The origin of hot (~7 keV) component of GRXE is not known, while cool (~0.8 keV) one is associated with supernovae (Kaneda et al. 1997, Sugizaki et al. 2001). We propose a possible mechanism to explain the origin; locally strong magnetic fields of Blocal ~30 μG heat interstellar gas to ~7 keV via magnetic reconnection (Tanuma et al. 1999). There will be the small-scale (< 10 pc) strong magnetic fields, which can be observed as (B)obs ~3 μG by integration of Faraday Rotation Measure, if it is localized by a volume filling factor of f ~ 0.1. In order to examine this model, we solved three-dimensional (3D) resistive magnetohydrodynamic (MHD) equations numerically to examine the magnetic reconnect ion triggered by a supernova shock (fig.l). We assume that the magnetic field is Bx = 30tanh(y/20pc) μG, By = Bz = 0, and the temperature is uniform, at the initial condition. We put a supernova explosion outside the current sheet. The supernova-shock, as a result, triggers the magnetic reconnect ion, and the gas is heatd to > 7 keV. The magnetic reconnect ion heats the interstellar gas to ~7 keV in the Galactic plane, if it occurs in the locally strong magnetic fields of Blocal ~30 μG. The heated plasma is confined by the magnetic field for ~10 5.5 yr. The required interval of the magnetic reconnect ions (triggered by anything) is ~1 - 10 yr. The magnetic reconnect ion will explain the origin of X-rays from the Galactic ridge, furthermore the Galactic halo, and clusters of galaxies.
        3,000원
        15.
        1999.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Recent studies show the importance of understanding three-dimensional magnetic reconnect ion on the solar surface. For this purpose, I consider non-coplanar magnetic reconnection, a simple case of three-dimensional reconnect ion driven by a collision of two straight flux tubes which are not on the same plane initially. The relative angle e between the two tubes characterizes such reconnection, and can be regarded as a measure of magnetic shear. The observable characteristics of non-coplanar reconnection are compared between the two cases of small and large angles. An important feature of the non-coplanar reconnect ion is that magnetic twist can be produced via the re-ordering of field lines. This is a consequence of the conversion of mutual helicity into self helicities by reconnection. It is shown that the principle of energy conservation when combined with the production of magnetic twist puts a low limit on the relative angle between two flux tubes for reconnect ion to occur. I provide several observations supporting the magnetic twist generation by reconnection, and discuss its physical implications for the origin of magnetic twist on the solar surface and the problem of coronal heating.
        4,200원
        16.
        1996.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The evolution of solar magnetic arcades is investigated with the use of MHD simulations imposing resistivity on sheared magnetic fields. It is found that there is a critical amount of shear, over which magnetic reconnection can take place ill an arcade-like field geometry to create a magnetic island. The process leading to reconnect ion cannot. be solely attributed to a tearing instability, but rather to a reactive evolution of the magnetic arcade under resistivity. The natures of the arcade reconnection are governed by the spatial pattern of resistivity. A fast reconnection with a small shock angle can only be achieved when the diffusion region is localized. In this case. a highly collimated reconnect ion outflow can tear the plasmoid into a pair, and most of principal features in solar eruptive processes are reproduced.
        3,000원
        17.
        1996.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        It. has been discovered that. active regions commonly have numerous flare-like transient. loop brightenings. We use a magnetic reconnection theory driven by a ponderamotive force on account. of the basic properties of a transient. brightening: lifetime a few mins, total energy 10 25~10 29 erg. The numerical results are consistent with the observations.
        3,000원
        18.
        1990.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The magnetic reconnection mechanism is a primary candidate for "flare" processes in solar coronal regions. Numerical simulations of two-dimensional magnetic reconnection are carried out for four different cases: (1) adiabatic condition with constant resistivity, (2) adiabatic condition with temperature-dependent resistivity, (3) energetics with radiation loss and constant resistivity and (4) energetics with radiation loss and temperature-dependent resistivity. It is found that the thermal instability prompts the magnetic reconnection process, thus increasing the conversion rate of magnetic energy into kinematic energy of the fluid. We demonstrated that the observed microflares can be accounted for by our magnetic reconnection models, when the effects of the radiation loss and the temperature-dependent resistivity are taken into account.
        4,800원
        19.
        1985.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Magnetic reconnect ion is studied numerically by means of a two dimensional MHD code. The initial magnetic field configuration is the two-dimensional dipole field, and the simulation model involves magnetic reconnect ion driven by the magnetized plasma flow. Strong plasma jetting, plasmoid formation and its fast ejection are observed in the downstream region. The dependence of reconnection rate on the incoming energy flux is found to be very sensitive, while the magnitude of the resistivity does not influence much on the reconnection rate. The simulation results are discussed in the context of the geomagnetic substorm.
        4,000원
        20.
        2015.06 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        Magnetic reconnection is a fundamental process occurring in a wide range of astrophysical, heliospheric and laboratory plasmas. This process alters magnetic topology and triggers rapid conversion of magnetic energy into thermal heating and nonthermal particle acceleration. Efforts to understand the physics of magnetic reconnection have been made across multiple disciplines using remote observations of solar flares and in-situ measurements of geomagnetic storms and substorms as well as laboratory and numerical experiments. This review focuses on the progress achieved with solar flare observations in which most reconnection-related signatures could be resolved in both space and time. The emphasis is on various observable emission features in the low solar atmosphere which manifest the coronal magnetic reconnection because these two regions are magnetically connected to each other. The research and application perspectives of solar magnetic reconnection are briefly discussed and compared with those in other plasma environments.