FIRST COMPLETE DETERMINATION OF PLASMA PHYSICAL PARAMETERS ACROSS A CORONAL MASS EJECTION-DRIVEN SHOCK
FIRST COMPLETE DETERMINATION OF PLASMA PHYSICAL PARAMETERS ACROSS A CORONAL MASS EJECTION-DRIVEN SHOCK
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DOI：
10.1088/0004-637x/720/1/130
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发表时间：
2010-09
期刊：
影响因子：
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通讯作者：
A. Bemporad;S. Mancuso
中科院分区：
文献类型：
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作者：
A. Bemporad;S. Mancuso
我们报道了与2002年3月22日太阳喷发有关的一个由日冕物质抛射(CME)驱动的快速激波的研究。太阳和日球层天文台上的LASCO和UVCS仪器在白光和极端紫外线(EUV)的中间日冕中观测到了这一事件，并通过空间和地面射电观测站在米波和十米波中观测到了这一事件。激波过境的明显特征是：(1)CME开始后观测到较强的II型发射通道；(2)与激波穿越UVC狭缝视场有关的强Oviλλ1032、1037谱线增宽(最高可达∼2×107K)；(3)位于CME锋面上方的LASCO图像中的密度增强。由于UVCS狭缝的中心在4.1R☉，与正在膨胀的CME的侧翼相对应，这次观测代表了迄今为止用UVCS仪器获得的对激波的最高紫外线探测。为了估计激波压缩比和等离子体温度，以及所涉及的日冕磁场强度，我们将白光和EUV资料结合起来，应用于一般斜激波情形的Rankine-Hugoniot方程。结果表明，当压缩比X=2.06时，从初始温度2.3×105K到1.9×106K，日冕等离子体在激波过程中被加热，同时激波前磁场从∼0.02G到激后磁场∼0.04G经历压缩，激波时的磁场和动能密度增量相当(符合能量均分的思想)，都比热能密度增量大两倍以上。这是首次在日冕中得到激波前后等离子体物理参数的完整表征。
We report on the study of a fast coronal mass ejection (CME)-driven shock associated with the solar eruption of 2002 March 22. This event was observed in the intermediate corona both in white light and the extreme ultraviolet (EUV) by the LASCO and UVCS instruments on board the Solar and Heliospheric Observatory, as well as in metric and decametric wavelengths through space- and ground-based radio observatories. Clear signatures of shock transit are (1) strong type II emission lanes observed after the CME initiation, (2) strong O vi λλ1032, 1037 line profile broadenings (up to ∼2 × 107 K) associated with the shock transit across the UVCS slit field of view, and (3) a density enhancement located in LASCO images above the CME front. Since the UVCS slit was centered at 4.1 R☉, in correspondence with the flank of the expanding CME, this observation represents the highest UV detection of a shock obtained so far with the UVCS instrument. White-light and EUV data have been combined in order to estimate not only the shock compression ratio and the plasma temperature, but also the strength of the involved coronal magnetic fields, by applying the Rankine–Hugoniot equations for the general case of oblique shocks. Results show that, for a compression ratio X = 2.06 as derived from LASCO data, the coronal plasma is heated across the shock from an initial temperature of 2.3 × 105 K up to 1.9 × 106 K, while at the same time the magnetic field undergoes a compression from a pre-shock value of ∼0.02 G up to a post-shock field of ∼0.04 G. Magnetic and kinetic energy density increases at the shock are comparable (in agreement with the idea of equipartition of energy), and both are more than two times larger than the thermal energy density increase. This is the first time that a complete characterization of pre- and post-shock plasma physical parameters has been derived in the solar corona.