Solar energetic particle event onsets at different heliolongitudes: The effect of turbulence in Parker spiral geometry
Solar energetic particle event onsets at different heliolongitudes: The effect of turbulence in Parker spiral geometry
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DOI：
10.1051/0004-6361/202346384
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发表时间：
2023-03
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影响因子：
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通讯作者：
T. Laitinen;S. Dalla;C. Waterfall;A. Institute;U. C. Lancashire;UK.
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作者：
T. Laitinen;S. Dalla;C. Waterfall;A. Institute;U. C. Lancashire;UK.
太阳高能粒子（SEP），在太阳爆发期间加速，被观察到迅速达到行星际空间的一个广泛的日长范围。为了进入这些位置，SEP必须在宽粒子源处被加速，或者穿过平均帕克螺旋磁场传播。我们研究了SEP在一个新的模型中的传播，该模型考虑了平均磁场的螺旋几何形状，以评估这种改进的描述如何影响SEP的路径长度和SEP强度在1~Au的整体演变。我们使用全轨道测试粒子模拟的100兆电子伏的质子在湍流模型占主导地位的模式是横向和二维相对于帕克螺旋。我们发现SEP在注入太阳后的一小时内沿着弯曲磁力线沿着传播，到达1~Au的60 μ m的日长波范围，与弯曲磁力线的范围一致。SEP开始时间相对于沿帕克螺旋沿着连接到源的位置是不对称的，向西的位置看到更早的到达和更高的峰值强度。初至SEP的路径长度为1.5-1.7~Au，比帕克螺线长30- 50%，比弯曲磁力线长20%。随后，SEP分布变宽，与SEP在场线上的扩散扩散一致。我们的研究结果表明，SEP可以快速传播通过平均帕克螺旋场，以达到广泛的范围内，即使没有一个广泛的粒子源。模拟的SEP发作时间，峰值强度和随后的日长演变复制几个观察到的SEP事件的功能。需要进一步研究行星际传输和源大小在不同湍流环境中的相对重要性。
Solar energetic particles (SEPs), accelerated during solar eruptions, are observed to rapidly reach a wide heliolongitudinal range in the interplanetary space. To access these locations, the SEPs must have either been accelerated at a wide particle source, or propagated across the mean Parker spiral magnetic field. We study the propagation of SEPs in a new model of heliospheric turbulence which takes the spiral geometry of the average magnetic field into account, to evaluate how this improved description affects the SEP path lengths and the overall evolution of SEP intensities at 1~au. We use full-orbit test particle simulations of 100-MeV protons in a turbulence model dominated by modes that are transverse and 2D with respect to the Parker spiral. We find that the SEPs spread along the meandering field lines to arrive at a 60$^\circ$ heliolongitudinal range at 1~au within an hour of their injection at the Sun, consistent with the extent of the meandering field lines. The SEP onset times are asymmetric with respect to the location connected to the source along the Parker spiral, with westward locations seeing earlier arrival and higher peak intensity. The inferred path length of the first-arriving SEPs is 1.5-1.7~au, 30-50\% longer than the Parker spiral, and 20\% longer than the length of the meandering field lines. Subsequently, the SEP distribution broadens, consistent with diffusive spreading of SEPs across the field lines. Our results indicate that SEPs can propagate rapidly across the mean Parker Spiral field to arrive at wide range of longitudes, even without a wide particle source. The modelled SEP onset times, the peak intensity and subsequent heliolongitudinal evolution replicate several observed SEP event features. Further studies are be required to investigate the relative importance of interplanetary transport and source size in different turbulence environments.