검색결과

검색조건
좁혀보기
검색필터
결과 내 재검색

간행물

    분야

      발행연도

      -

        검색결과 10

        2.
        2021.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Observations of line of sight (LOS) Doppler velocity and non-thermal line width in the o -limb solar corona are often used for investigating the Alfven wave signatures in the corona. In this study, we compare LOS Doppler velocities and non-thermal line widths obtained simultaneously from two di erent instruments, Coronal Multichannel Polarimeter (CoMP) and Hinode/EUV Imaging Spectrometer (EIS), on various o -limb coronal regions: aring and quiescent active regions, equatorial quiet region, and polar prominence and plume regions observed in 2012{2014. CoMP provides the polarization at the Fe xiii 10747 A coronal forbidden lines which allows their spectral line intensity, LOS Doppler velocity, and line width to be measured with a low spectral resolution of 1.2 A in 2-D o limb corona between 1.05 and 1.40 RSun, while Hinode/EIS gives us the EUV spectral information with a high spectral resolution (0.025 A) in a limited eld of view raster scan. In order to compare them, we make pseudo raster scan CoMP maps using information of each EIS scan slit time and position. We compare the CoMP and EIS spectroscopic maps by visual inspection, and examine their pixel to pixel correlations and percentages of pixel numbers satisfying the condition that the di erences between CoMP and EIS spectroscopic quantities are within the EIS measurement accuracy: 3 kms􀀀1 for LOS Doppler velocity and 9 kms􀀀1 for non-thermal width. The main results are summarized as follows. By comparing CoMP and EIS Doppler velocity distributions, we nd that they are consistent with each other overall in the active regions and equatorial quiet region (0.25  CC  0.7), while they are partially similar to each other in the overlying loops of prominences and near the bottom of the polar plume (0.02  CC  0.18). CoMP Doppler velocities are consistent with the EIS ones within the EIS measurement accuracy in most regions ( 87% of pixels) except for the polar region (45% of pixels). We nd that CoMP and EIS non-thermal width distributions are similar overall in the active regions (0.06  CC  0.61), while they seem to be di erent in the others (􀀀0:1  CC  0.00). CoMP non-thermal widths are similar to EIS ones within the EIS measurement accuracy in a quiescent active region (79% of pixels), while they do not match in the other regions ( 61% of pixels); the CoMP observations tend to underestimate the widths by about 20% to 40% compared to the EIS ones. Our results demonstrate that CoMP observations can provide reliable 2-D LOS Doppler velocity distributions on active regions and might provide their non-thermal width distributions.
        4,300원
        4.
        2010.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We investigate how plasma structures in the solar chromosphere and corona can extend to altitudes much above hydrostatic scale heights from the solar surface even under the force of gravity. Using a simple modified form of equation of motion in the vertical direction, we argue that there are two extreme ways of non-hydrostatic support: dynamical support and magnetic support. If the vertical acceleration is downward and its magnitude is a significant fraction of gravitational acceleration, non-hydrostatic support is dynamical in nature. Otherwise non-hydrostatic support is static, and magnetic support by horizontal magnetic fields is the only other possibility. We describe what kind of observations are needed in the clarification of the nature of non-hydrostatic support. Observations available so far seem to indicate that spicules in the quiet regions and dynamic fibrils in active regions are dynamically supported whereas the general chromosphere as well as prorninences is magnetically supported. Moreover, it appears that magnetic support is required for plasma in some coronal loops as well. We suspect that the identification of a coronal loop with a simple magnetic flux tube might be wrong in this regard.
        4,000원
        8.
        2004.10 구독 인증기관·개인회원 무료