Charge-transfer induced EUV and soft X-ray emissions in the heliosphere
Charge-transfer induced EUV and soft X-ray emissions in the heliosphere
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DOI：
10.1051/0004-6361:20065250
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发表时间：
2006-09
影响因子：
6.5
通讯作者：
D. Koutroumpa;R. Lallement;V. Kharchenko;A. Dalgarno;R. Pepino;V. Izmodenov;E. Quémerais
中科院分区：
文献类型：
--
作者：
D. Koutroumpa;R. Lallement;V. Kharchenko;A. Dalgarno;R. Pepino;V. Izmodenov;E. Quémerais
研究了太阳风重离子与星际中性原子之间的电荷转移产生的EUV/软X射线辐射，以及X射线强度和光谱随视线方向、观测者位置、太阳周相位和太阳风各向异性的变化，以及太阳风的暂时增强，类似于斯诺登等人（2004年）在XMM-哈勃深场北曝光期间观察到的事件。方法：利用最近的中性原子的观测，结合更新的截面和级联光子光谱，我们计算了稳定太阳风的星际氢、氦和高电荷太阳风离子的自洽分布，并构建了单色辐射图和光谱。我们分别评估了日鞘和日尾的贡献，并包括X射线发射的激发太阳风离子产生的连续碰撞的信号。结果：在大多数实际观测中，低纬和中纬的X射线辐射在最低活动时明显高于最高活动时，特别是在12月前后。这是由于在高活动阶段中性粒子的强烈耗尽，而太阳风通量的增加并不能弥补这一点。对于高纬度地区，发射以复杂的方式取决于离子种类。一般来说，强度图对于间隔六个月的观测是显著不同的。发现二次离子对X射线视线强度的贡献可以忽略不计，因为它们的密度只有在很远的距离上才会变得显着。日鞘-日尾的贡献总是小于5%。我们可以重现的强度范围和时间变化的XMM-HDFN发射线在0.52-0.75 keV的间隔，使用一个简单的增强太阳风螺旋流。这表明这些线在事件发生之前、期间和之后都有一个主要的日光层起源。
We study the EUV/soft X-ray emission generated by charge transfer between solar wind heavy ions and interstellar neutral atoms and variations of the X-ray intensities and spectra with the line of sight direction, the observer location, the solar cycle phase and the solar wind anisotropies, and a temporary enhancement of the solar wind similar to the event observed by Snowden et al. (2004) during the XMM-Hubble Deep Field North exposure. Methods.Using recent observations of the neutral atoms combined with updated cross-sections and cascading photon spectra we have computed self-consistent distributions of interstellar hydrogen, helium and highly charged solar wind ions for a stationary solar wind and we have constructed monochromatic emission maps and spectra. We have evaluated separately the contribution of the heliosheath and heliotail, and included X-ray emission of the excited solar wind ions produced in sequential collisions to the signal. Results.In most practicable observations, the low and medium latitude X-ray emission is significantly higher at minimum activity than at maximum, especially around December. This occurs due to a strong depletion of neutrals during the high activity phase, which is not compensated by an increase of the solar wind flux. For high latitudes the emission depends on the ion species in a complex way. Intensity maps are in general significantly different for observations separated by six-month intervals. Secondary ions are found to make a negligible contribution to the X-ray line of sight intensities, because their density becomes significant only at large distances. The contribution of the heliosheath-heliotail is always smaller than 5%. We can reproduce both the intensity range and the temporal variation of the XMM-HDFN emission lines in the 0.52-0.75 keV interval, using a simple enhanced solar wind spiral stream. This suggests a dominant heliospheric origin for these lines, before, during and also after the event.