Measurements of flow speeds in the corona between 2 and 30 R-circle dot
Measurements of flow speeds in the corona between 2 and 30 R-circle dot
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DOI：
10.1086/304338
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发表时间：
1997-07-20
影响因子：
4.9
通讯作者：
Biesecker, DA
中科院分区：
文献类型：
--
作者：
Sheeley, NR;Wang, YM;Biesecker, DA
在1996年太阳黑子最小条件下，由太阳和日球层天文台上的大角度光谱日冕仪获得的延时白光图像序列，给人的印象是流带中物质的连续流出，就好像我们正在观察太阳风的不均匀性引起的汤姆森散射。遵循这一思路，我们跟踪了50-100个最突出的移动日冕特征的诞生和流出，发现：1。它们起源于距太阳中心约3-4公里的地方，是位于盔状飘带顶端的放射状细长结构。它们的初始尺寸在径向上约为1r，在横向上约为0.1 r。它们径向向外移动，保持恒定的角跨度，并根据它们的速度大致增加它们的长度，通常从接近5r的150公里/秒（-1）增加到接近25r的300公里/秒（-1）。它们各自的速度曲线upsilon（tau）围绕着一条接近抛物线的路径聚集，其特征是在30 r的大部分视场中恒定的加速度约为4 m s（-2）。该廓线与温度约为1.1 MK的等温太阳风扩张和5 R附近的声速点相一致，基于它们相对较小的初始尺寸，低强度，径向运动，缓慢但不断增加的速度，以及在流带中的位置，我们得出结论，这些运动具有被动跟踪缓慢太阳风流出的特征。
Time-lapse sequences of white-light images, obtained during sunspot minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory, give the impression of a continuous outflow of material in the streamer belt, as if we were observing Thomson scattering from inhomogeneities in the solar wind. Pursuing this idea, we have tracked the birth and outflow of 50-100 of the most prominent moving coronal features and find that:1. They originate about 3-4 R. from Sun center as radially elongated structures above the cusps of helmet streamers. Their initial sizes are about 1 R. in the radial direction and 0.1 R. in the transverse direction.2. They move radially outward, maintaining constant angular spans and increasing their lengths in rough accord with their speeds, which typically double from 150 km s(-1) near 5 R. to 300 km s(-1) near 25 R..3. Their individual speed profiles upsilon(tau) cluster around a nearly parabolic path characterized by a constant acceleration of about 4 m s(-2) through most of the 30 R. field of view. This profile is consistent with an isothermal solar wind expansion at a temperature of about 1.1 MK and a sonic point near 5 R..Based on their relatively small initial sizes, low intensities, radial motions, slow but increasing speeds, and location in the streamer belt, we conclude that these moving features an passively tracing the outflow of the slow solar wind.