Spectroscopic Signatures of Solar Flare Onset

太阳耀斑爆发的光谱特征

• 批准号: 2728026
• 金额: --
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2728026
• 关键词: Spectroscopic; Signatures; Solar; Flare; Onset

The Sun is our closest star, and with space now firmly established as part of our society's environment, its unique proximity has inescapable consequences for us. While solar radiation provides the energy source of our whole ecosystem, our understanding of how the variations in that radiation control, e.g. our climate, still contains huge gaps. As well as the long-term variations in the solar output, the Sun exhibits a cycle of activity the constituents of which are explosive events which release energy. This explosive energy release occurs on a myriad of scales, from nanoflares to huge eruptive flares, which are accompanied by the bulk eruption of plasma and magnetic field known as coronal mass ejections (CMEs) and whose impacts can be seen globally across the Sun and throughout the heliosphere. The most extreme of these events constitute the largest examples of explosive energy release within our solar system, during which upwards of 1026 J of energy is released. Solar flares comprise a key component of space weather, and yet despite their key importance and the extensive range of observations available from space and the ground, the precise mechanisms that lead to their onset remain an open question.Emission lines measured in the solar atmosphere routinely show widths in excess of both the thermal Doppler and instrumental line widths. Measurements of these so-called 'non-thermal' widths provide additional information on the state of the emitting plasma, including the possible existence of turbulence, or effects due to pressure and opacity broadening. X-ray non-thermal line widths have long been observed to show substantial enhancements during flaring activity, peaking early in the impulsive phase and increasing up to tens of minutes before the flare peak, a result that has been confirmed and refined with EUV observations from Hinode EIS (for which Sarah Matthews is the Principal Investigator). Such an early response to the flaring suggests that this parameter is potentially significant in the early trigger phase of flares. X-ray and EUV spectral lines are formed in plasmas with temperatures that represent conditions in the solar corona, where the standard model indicates energy is released. However, recent work exploring the profiles of spectral lines formed in the lower atmosphere suggests correlations between profile shape and flare energy deposition. These initial results have yet to be compared with coronal line profiles, however, which would enable the energy release and deposition process to be tracked throughout the entire solar atmosphere enabling new insights into flare onset and possibilities for future prediction techniques.The project will initially utilise spectroscopic data from Hinode EIS and IRIS, incorporating new data from Solar Orbiter as it becomes available from the EUI, SPICE and STIX instruments. The research undertaken will also form part of the solar group's preparatory work for the Solar C EUVST mission currently under development and scheduled for launch in 2028. The student undertaking this project would thus have the opportunity to participate both in the international Hinode EIS and Solar C EUVST teams, including attending team meetings and collaborative visits.

太阳是离我们最近的星星，随着太空已经牢固地成为我们社会环境的一部分，它独特的接近性对我们产生了不可避免的影响。虽然太阳辐射为我们整个生态系统提供了能源，但我们对辐射变化如何控制气候的理解仍然存在巨大差距。除了太阳输出的长期变化外，太阳还表现出一个活动周期，其组成部分是释放能量的爆炸事件。这种爆炸性的能量释放发生在无数的尺度上，从纳米耀斑到巨大的爆发性耀斑，伴随着被称为日冕物质抛射（CME）的等离子体和磁场的大量爆发，其影响可以在太阳和整个日光层中看到。这些事件中最极端的事件构成了我们太阳系内爆炸性能量释放的最大例子，在此期间释放了超过1026 J的能量。太阳耀斑是空间天气的一个关键组成部分，尽管其至关重要，而且空间和地面的观测范围也很广，但导致耀斑爆发的确切机制仍然是一个悬而未决的问题，在太阳大气中测量的发射谱线通常显示的宽度超过热多普勒谱线和仪器谱线的宽度。对这些所谓的“非热”宽度的测量提供了关于发射等离子体状态的额外信息，包括可能存在的湍流，或由于压力和不透明度加宽而产生的影响。长期以来，X射线非热谱线宽度被观察到在耀斑活动期间显示出实质性的增强，在脉冲阶段早期达到峰值，并在耀斑峰值之前增加数十分钟，这一结果已被Hinode EIS的EUV观测所证实和完善（Sarah马修斯是该项目的首席研究员）。这种早期反应的耀斑表明，这个参数是潜在的显着的早期触发阶段的耀斑。X射线和EUV光谱线是在等离子体中形成的，其温度代表了日冕中的条件，标准模型表明能量被释放。然而，最近的工作，探索在低层大气中形成的光谱线的轮廓表明轮廓形状和耀斑能量沉积之间的相关性。然而，这些初步结果还有待与日冕线轮廓进行比较，这将使能量释放和沉积过程能够在整个太阳大气中被跟踪，从而对耀斑爆发和未来预测技术的可能性产生新的见解。该项目最初将利用Hinode EIS和IRIS的光谱数据，并结合太阳轨道器的新数据，因为它可以从EUI获得，SPICE和STIX仪器。所进行的研究也将成为太阳能集团目前正在开发并计划于2028年发射的Solar C EUVST使命的准备工作的一部分。因此，承担该项目的学生将有机会参加国际Hinode EIS和Solar C EUVST团队，包括参加团队会议和合作访问。