晕状日冕物质抛射的地球有效性
Geoeffectiveness of halo CMEs
摘要：
来自太阳中心附近区域的晕日冕物质抛射（HCME）可能具有地球效应。假设HCME的形状是一个圆锥体，并且它们以恒定的角宽度和速度传播，至少在它们的早期阶段，我们已经开发了一种技术（Michalek等人，2003），使我们能够获得空间速度，宽度和源位置。我们应用这种技术，以获得所有完整的太阳和日光层天文台（SOHO）任务的大角度和光谱日冕物质抛射（LASCO）的实验，直到2002年底观察到的HCME的参数。使用这些数据，我们研究哪些参数决定HCME的地理有效性。结果表明，在所考虑的时间段内，只有来自太阳中心附近西半球的快晕日冕物质抛射（空间速度大于$\sim 1000{km\over s}$）才能引起强烈的磁暴。我们说明了如何HCME参数可以用于空间天气预报。它还表明，磁暴的强度不依赖于所确定的宽度HCME。这意味着HCME不一定要非常大才能引起重大的地磁风暴。
英文摘要：
Halo coronal mass ejections (HCMEs) originating from regions close to the center of the Sun are likely to be geoeffective. Assuming that the shape of HCMEs is a cone and they propagate with constant angular widths and velocities, at least in their early phase, we have developed a technique (Michalek et al. 2003) which allowed us to obtain the space speed, width and source location. We apply this technique to obtain the parameters of all full HCMEs observed by the Solar and Heliospheric Observatory (SOHO) mission's Large Angle and Spectrometric Coronagraph (LASCO) experiment until the end of 2002. Using this data we examine which parameters determine the geoeffectiveness of HCMEs. We show that in the considered period of time only fast halo CMEs (with the space velocities higher than $\sim 1000{km\over s}$ and originating from the western hemisphere close to the solar center could cause the severe geomagnetic storms. We illustrate how the HCME parameters can be used for space weather forecast. It is also demonstrated that the strength of a geomagnetic storm does not depend on the determined width of HCMEs. This means that HCMEs do not have to be very large to cause major geomagnetic storms.
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