From April 24 to October 25, 2011, an Acoustic Doppler Velocimeter （ADV） continually running for 185 d was mounted on the smooth ridge at the edge of Monterey Canyon to observe turbulence in the bottom boundary laye...From April 24 to October 25, 2011, an Acoustic Doppler Velocimeter （ADV） continually running for 185 d was mounted on the smooth ridge at the edge of Monterey Canyon to observe turbulence in the bottom boundary layer. The ADV was set at 1.4 m above the bed bottom, continuously run for 1 min with a 2-minute interval with sampling frequency 64 Hz. The long-time continual observation is significant to reveal variations of turbulent characteristics and show some differences from the classic traditional tur- bulent theory. Eliminating the noise by the ＇Phase-Space Thresholding Method＇, rotating the coordinate and low-pass filtering the velocity were applied for data processing. This paper was mainly to estimate the turbulent kinetic energy dissipation rate by the iner- tial dissipation method, friction velocity, drag coefficient and significant periods of the turbulent characteristics with the ADV data. The results show that there is a strong, rotating bottom flow up to 0.398 ms-1 with predominantly semidiumal period and less sig- nificantly diurnal and semilunar period. The turbulent kinetic energy dissipation rate ranges from 1.09× 10-8W kg-1 to 6.62× 10-8W kg-1, which can vary with 2 or 3 orders of magnitude in one day. The daily averaged variations of friction velocity and drag coeffi- cient are 6.50×10-3-2.32× 10-2ms-1 and 6.30×10-3-4.36×10-2, respectively. All the characteristics have a remarkable semidiurnal period. In the bottom boundary layer with a rotating tide, the parameterized coefficients to describe ε-μ. and ε-Et relationships are much smaller than the traditional value.展开更多
Using observations from the EUV Imaging Spectrometer （EIS） onboard Hinode, we exam the plasma dynamics around the edge of the active region 10977, possibly associated with the source of nascent slow/intermediate sol...Using observations from the EUV Imaging Spectrometer （EIS） onboard Hinode, we exam the plasma dynamics around the edge of the active region 10977, possibly associated with the source of nascent slow/intermediate solar wind. The correlation between the temporal profiles of the radiation intensity and Doppler shift for each emission line are analyzed. And three small regions with positive correlations for all the five emission lines are selected for a detailed analysis. In this work, Doppler blue （red） shift is defined as negative （positive）. We find that in Region 1, the radiation intensity （Doppler velocity） decreases by about 15% （about 3 km s-X）, and logarithmical differential emission measures （lg（DEMs）） reduces by about 0.06-0.10% at all temperatures, called ＂weak dimming＂, during a 30-min interval. In Region 2 and Region 3, however, the radiation intensity （Doppler velocity） increases by about 15% （about 3 km s-l）, and lg（DEMs） increases by about 0.06%~0.10% at all tempera- tures, called ＂weak brightening＂. Such weak dimming （weak brightening） could reflect a slow draining （replenishing） of plas- ma in the solar wind flux tubes, possibly due to a larger （smaller） outflow flux at high altitude than at low altitude. These sug- gest that the plasma supply could be intermittent with an alternation of draining and replenishing, for which the underlying physical process is yet unknown, at the source region of slow/intermediate solar wind.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 41476002 and 41076005)Program for New Century Excellent Talents in University NCET-11-0470National High-tech Research and Development Program (863 Torch Program)2012AA09A403
文摘From April 24 to October 25, 2011, an Acoustic Doppler Velocimeter （ADV） continually running for 185 d was mounted on the smooth ridge at the edge of Monterey Canyon to observe turbulence in the bottom boundary layer. The ADV was set at 1.4 m above the bed bottom, continuously run for 1 min with a 2-minute interval with sampling frequency 64 Hz. The long-time continual observation is significant to reveal variations of turbulent characteristics and show some differences from the classic traditional tur- bulent theory. Eliminating the noise by the ＇Phase-Space Thresholding Method＇, rotating the coordinate and low-pass filtering the velocity were applied for data processing. This paper was mainly to estimate the turbulent kinetic energy dissipation rate by the iner- tial dissipation method, friction velocity, drag coefficient and significant periods of the turbulent characteristics with the ADV data. The results show that there is a strong, rotating bottom flow up to 0.398 ms-1 with predominantly semidiumal period and less sig- nificantly diurnal and semilunar period. The turbulent kinetic energy dissipation rate ranges from 1.09× 10-8W kg-1 to 6.62× 10-8W kg-1, which can vary with 2 or 3 orders of magnitude in one day. The daily averaged variations of friction velocity and drag coeffi- cient are 6.50×10-3-2.32× 10-2ms-1 and 6.30×10-3-4.36×10-2, respectively. All the characteristics have a remarkable semidiurnal period. In the bottom boundary layer with a rotating tide, the parameterized coefficients to describe ε-μ. and ε-Et relationships are much smaller than the traditional value.
基金supported by the National Natural Science Foundation of China(Grant Nos.41174148,41222032,40931055,41231069,41274172)supported by a foundation for the Author of National Excellent Doctoral Dissertation of China(FANEDD)(Grant No.201128)
文摘Using observations from the EUV Imaging Spectrometer （EIS） onboard Hinode, we exam the plasma dynamics around the edge of the active region 10977, possibly associated with the source of nascent slow/intermediate solar wind. The correlation between the temporal profiles of the radiation intensity and Doppler shift for each emission line are analyzed. And three small regions with positive correlations for all the five emission lines are selected for a detailed analysis. In this work, Doppler blue （red） shift is defined as negative （positive）. We find that in Region 1, the radiation intensity （Doppler velocity） decreases by about 15% （about 3 km s-X）, and logarithmical differential emission measures （lg（DEMs）） reduces by about 0.06-0.10% at all temperatures, called ＂weak dimming＂, during a 30-min interval. In Region 2 and Region 3, however, the radiation intensity （Doppler velocity） increases by about 15% （about 3 km s-l）, and lg（DEMs） increases by about 0.06%~0.10% at all tempera- tures, called ＂weak brightening＂. Such weak dimming （weak brightening） could reflect a slow draining （replenishing） of plas- ma in the solar wind flux tubes, possibly due to a larger （smaller） outflow flux at high altitude than at low altitude. These sug- gest that the plasma supply could be intermittent with an alternation of draining and replenishing, for which the underlying physical process is yet unknown, at the source region of slow/intermediate solar wind.
