RADIAL DISTRIBUTION OF COMPRESSIVE WAVES IN THE SOLAR CORONA REVEALED BY AKATSUKI RADIO OCCULTATION OBSERVATIONS
RADIAL DISTRIBUTION OF COMPRESSIVE WAVES IN THE SOLAR CORONA REVEALED BY AKATSUKI RADIO OCCULTATION OBSERVATIONS
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DOI：
10.1088/0004-637x/797/1/51
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发表时间：
2014-11
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通讯作者：
M. Miyamoto;T. Imamura;M. Tokumaru;H. Ando;H. Isobe;A. Asai;D. Shiota;T. Toda;B. Häusler;M. Pätzold;A. Nabatov;M. Nakamura
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作者：
M. Miyamoto;T. Imamura;M. Tokumaru;H. Ando;H. Isobe;A. Asai;D. Shiota;T. Toda;B. Häusler;M. Pätzold;A. Nabatov;M. Nakamura
利用航天器无线电掩星技术首次探测了日冕压缩波振幅和能流的径向变化。通过对日心距1.5-20.5RS(太阳半径)的频率时间序列进行小波分析，几乎在所有距离都检测到了准周期密度扰动。分数密度起伏的幅度随距离的增加而增大，在5RS左右达到∼的30%，表明波场的非线性是潜在的重要因素。在假设观测到的周期涨落是声波的表现形式的前提下，我们进一步估计了波能通量。能量通量在∼6RS以下随距离增加而增加，在此高度以上似乎趋于饱和，这表明声波不是从低日冕传播的，而是在扩展日冕中产生的，可能是通过阿尔芬波的非线性耗散而产生的。压缩波最终应该会通过激波产生来加热日冕而消散。
Radial variations of the amplitude and the energy flux of compressive waves in the solar corona were explored for the first time using a spacecraft radio occultation technique. By applying wavelet analysis to the frequency time series taken at heliocentric distances of 1.5–20.5 RS (solar radii), quasi-periodic density disturbances were detected at almost all distances. The period ranges from 100 to 2000 s. The amplitude of the fractional density fluctuation increases with distance and reaches ∼30% around 5 RS, implying that nonlinearity of the wave field is potentially important. We further estimate the wave energy flux on the assumption that the observed periodical fluctuations are manifestations of acoustic waves. The energy flux increases with distance below ∼6 RS and seems to saturate above this height, suggesting that the acoustic waves do not propagate from the low corona but are generated in the extended corona, probably through nonlinear dissipation of Alfvén waves. The compressive waves should eventually dissipate through shock generation to heat the corona.