Observations have shown that the chromosphere networks are rich in features with density higher than the ambient atmosphere. To investigate the effect of horizontal density-inhomogeneity on spicules, here we carry out two-dimensional magnetohydrodynamic (MHD) simulations based on the shock scenario. In a gravitationally stratified solar atmosphere, we insert a vertical preexisting density structure (PeDS) that has higher density than the ambient regions, and then we drive a spicule by a velocity pulse at the bottom of the chromosphere. We find a horizontal flow of 2 km s⁻¹ caused by a rarefaction wave that may have a certain material supplement effect for the spicules and a V-shaped shock front in the chromosphere. An interesting feature found in our experiment is that the existence of PeDS leads to the formation of multiple threads in spicules. Their formation results from the larger density, lower transition region, and higher speeds of magnetoacoustic waves in the PeDS than at its outer boundaries. Parameter studies show that multiple threads of a spicule can be more pronounced in cases with wider velocity pulses and a larger internal/external density ratio in the PeDS. Our study shows that the horizontal density-inhomogeneity in the solar atmosphere is an important factor that is responsible for the complexity of a spicule.

观测表明，色球网络具有丰富的特征，其密度高于周围大气。为了研究水平密度不均匀性对针状体的影响，我们基于冲击场景进行了二维磁流体动力学（MHD）模拟。在重力分层的太阳大气中，我们插入一个垂直的预先存在的密度结构（PeDS），其密度高于周围区域，然后我们通过色球层底部的速度脉冲驱动针状体。我们发现稀疏波引起的2 km s ^-1的水平流动可能对针状体有一定的物质补充作用，并在色球层中出现了V形激波锋。我们的实验中发现的一个有趣的特征是，PeDS 的存在导致骨针中形成多条线。它们的形成是由于 PeDS 中比其外边界具有更大的密度、更低的过渡区域和更高的磁声波速度。参数研究表明，在 PeDS 中具有更宽的速度脉冲和更大的内部/外部密度比的情况下，骨针的多线会更加明显。我们的研究表明，太阳大气中的水平密度不均匀性是造成针状体复杂性的一个重要因素。