3He Enhancements in Large Solar Energetic Particle Events
3He Enhancements in Large Solar Energetic Particle Events
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DOI：
10.1086/312349
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发表时间：
1999-10
期刊：
影响因子：
--
通讯作者：
G. Mason;J. Mazur;J. Dwyer
中科院分区：
文献类型：
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作者：
G. Mason;J. Mazur;J. Dwyer
在1997年11月至1999年6月期间，我们测量了12个大型太阳高能粒子（SEP）事件中~0.5 ~ 2 MeV核子-1的3He丰度。在其中5个事件中，3He时间强度曲线与4He时间强度曲线相似，表明这两个物种具有共同的加速和输运起源。这些事件的平均3He/4He比值为（1.9±0.2）× 10-3，比太阳风值增大了5倍。在同一调查期间，我们还测量了大粒子事件之间较安静时期的低能离子强度。我们发现脉冲事件的3He和Fe残留物在大多数日子里都存在，这意味着它们在我们的调查中占据了黄道内行星际介质的相当大的体积（约50%）。因此，我们认为这些超高温离子可能是一个源群，可用于伴随大SEP事件的行星际冲击进一步加速，从而导致3He在很大一部分大SEP事件中增强。这种脉冲SEP事件材料也可以解释最近观测到的具有高能粒子电离态的大型太阳粒子事件，这些事件具有广泛的电离态，包括渐进和脉冲太阳SEP事件的预期值。
We have measured the 3He abundance from ~0.5 to 2 MeV nucleon-1 in 12 large solar energetic particle (SEP) events during the period 1997 November-1999 June. In five of the events, the 3He time-intensity profile is similar to the 4He time-intensity profile, indicating a common acceleration and transport origin for the two species. The average 3He/4He ratio during these events is (1.9 ± 0.2) × 10-3, a factor of ~5 enhancement over the solar wind value. During this same survey period, we have also measured the low-energy ion intensities during quieter periods in between the large-particle events. We find 3He and Fe remnants from impulsive events present on a majority of the days, implying that they fill a substantial volume (>50%) of the in-ecliptic interplanetary medium during our survey. We suggest that these suprathermal ions may therefore be a source population that is available for further acceleration by interplanetary shocks that accompany large SEP events, thereby leading to the 3He enhancements in a significant fraction of large SEP events. This impulsive SEP event material might also account for recent observations of large solar particle events with energetic particle ionization states that have a wide range of ionization states that encompass values expected for both gradual and impulsive solar SEP events.