We give the results of parameter fitting of the magnetic clouds (MCs) observed by the Wind spacecraft for the three year period – 2004 to the end of 2006 (the “Present period”) using the force-free MC model of Lepping, Jones, and Burlaga ( J. Geophys. Res. 95 , 11957, 1990 ). There were 19 MCs identified in the Present period, which was mainly in the declining phase of the solar cycle. The long-term occurrence rate of MCs is 10.3/year (1995-2015), whereas the occurrence rate for the Present period is only 6.3/year, similar to that for the period 2007-2009. Hence, the MC occurrence rate has had an appreciable decrease for the six years 2004-2009. The MC modeling gives such basic MC quantities as size, axial orientation, field handedness, axial magnetic field strength, center time, and closest approach vector. A statistically based modification of the modeled field intensity is tested. Also calculated are derived quantities, such as axial magnetic flux, axial current density, and axial current. Quality ( Q 0 $Q_{0}$ ) estimates are assigned representing excellent (1), good/fair (2), and poor (3). We provide error estimates on the specific fit parameters for the individual MCs for the Q 0 = 1 , 2 $Q_{0} =1,2$ cases, and give a distribution of MC types (i.e. N ⇒ S, S ⇒ N, All N, All S, etc., ten categories in all). There is an inordinately large percentage of the N ⇒ S type in the Present period (32%). The Present period basic model fitting results are compared to the results of the full Wind mission and other 3-year periods. First, we notice that during the Present period the MCs are, on average, significantly faster (by 21%), distinctly stronger in axial magnetic field (by 37%), and smaller in diameter (by 5.5%), than those in the Long-term period. The quality of the MCs in the Present period is significantly better than that of the Long-term period, where the ratio N ( Q 0 = 1 , 2 ) / N ( Q 0 = 1 , 2 , 3 ) $N(Q_{0} =1,2)/N(Q_{0} =1,2,3)$ for each is 0.79 and 0.58, respectively. The Present period is quite different from the Long-term period (1995-2015), it is from the other three 3-year periods between 2006 and the end of 2015. In the Present period upstream shocks occur for the first 12 MCs of the 19 cases (63%); for comparison the Long-term rate is 56%.

中文翻译：

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2004-2006年风磁云模型拟合

我们使用 Lepping、Jones 的无力 MC 模型给出了 Wind 航天器在 2004 年至 2006 年底（“当前时期”）三年期间观测到的磁云（MCs）的参数拟合结果。和 Burlaga (J. Geophys. Res. 95, 11957, 1990)。本期共发现19个MC，主要处于太阳活动周期的衰退期。MCs的长期发生率为10.3/年（1995-2015年），而本期的发生率为6.3/年，与2007-2009年相似。因此，MC 发生率在 2004-2009 的六年间有明显的下降。MC 建模给出了诸如尺寸、轴向方向、磁场旋向性、轴向磁场强度、中心时间和最接近向量等基本 MC 量。测试建模场强的基于统计的修改。还计算导出量，例如轴向磁通量、轴向电流密度和轴向电流。质量 ( Q 0 $Q_{0}$ ) 估计值被指定为优秀 (1)、良好/一般 (2) 和差 (3)。我们为 Q 0 = 1 , 2 $Q_{0} =1,2$ 情况下的单个 MC 的特定拟合参数提供误差估计，并给出 MC 类型的分布（即 N ⇒ S，S ⇒ N，全N、全S等，共十类）。在当前时期，N ⇒ S 型的比例非常大（32%）。本期基本模型拟合结果与全 Wind 任务和其他 3 年期的结果进行了比较。首先，我们注意到在当前时期，MC 平均要快得多（21%），轴向磁场明显强（37%），直径更小（5.5%），与长期相比。当前时期的 MC 质量明显优于长期时期，其中比率 N ( Q 0 = 1 , 2 ) / N ( Q 0 = 1 , 2 , 3 ) $N(Q_{ 0} =1,2)/N(Q_{0} =1,2,3)$ 分别为 0.79 和 0.58。当前时期与长期时期（1995-2015 年）有很大不同，它与 2006 年至 2015 年底的其他三个 3 年时期不同。在当前时期，前 12 个 MC 发生了上游冲击。 19例（63%）；相比之下，长期利率为 56%。其中比率 N ( Q 0 = 1 , 2 ) / N ( Q 0 = 1 , 2 , 3 ) $N(Q_{0} =1,2)/N(Q_{0} =1,2,3)每个的 $ 分别为 0.79 和 0.58。当前时期与长期时期（1995-2015）有很大不同，它与 2006 年至 2015 年底的其他三个 3 年时期不同。在当前时期，前 12 个 MC 发生了上游冲击。 19例（63%）；相比之下，长期利率为 56%。其中比率 N ( Q 0 = 1 , 2 ) / N ( Q 0 = 1 , 2 , 3 ) $N(Q_{0} =1,2)/N(Q_{0} =1,2,3)每个的 $ 分别为 0.79 和 0.58。当前时期与长期时期（1995-2015）有很大不同，它与 2006 年至 2015 年底的其他三个 3 年时期不同。在当前时期，前 12 个 MC 发生了上游冲击。 19例（63%）；相比之下，长期利率为 56%。