Energetic Radiation from Lightning Leaders: Effects and Origins

闪电领导者的能量辐射：影响和起源

• 批准号: 1106779
• 负责人: Victor Pasko
• 金额: $ 40.47万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1106779&HistoricalAwards=false
• 关键词: Energetic; Radiation; Lightning; Leaders; Effects

Neither the exact mechanisms through which lighting is initially triggered and propagates through the free atmosphere nor the relationship of these processes to recently emerging observations of high-energy emissions associated with active thunderstorms are well understood. This research will apply state-of-the-art numerical simulation methods to investigate the emission of energetic electrons from lightning-related charge-streamer and stepped-leader discharges and the propagation of the associated energetic radiation (from X-rays to hard X-rays and terrestrial gamma-ray flashes) through the Earth's atmosphere. The only known mechanism capable of explaining generation of associated high-energy electrons is the "runaway process" by which energy gained from an imposed electric field exceeds that lost to collisions, thus accelerating electrons to very high energies (1 MeV). To-date, two scenarios for initially "seeding" this runaway breakdown process have been proposed: (1) cosmic rays, and (2) "thermal" runaway induced by extremely high electric fields. Theoretical and experimental studies have shown the paramount importance of the coupling of streamer and leader discharge dynamics to the thermal runaway process, which is in-turn now thought to be inseparable from emission of X-rays by lightning or production of terrestrial gamma-ray flashes. Targeted observations of high-energy radiative emissions by thunderstorms and associated electrical activity have recently been obtained from ground-based, airborne and satellite platforms, but the detailed nature of relationships among these previously uncorrelated phenomena have not previously been quantified as this project sets out to do.The Intellectual Merit of this activity is defined by efforts to develop a unifying theoretically-sound explanation for the location, timing and specific nature of observed high-energy radiation originating in the Earth's atmosphere. The importance of related questions is emphasized by the need to quantify the intensity of radiation emitted from lightning and to understand its relationship to the formation and propagation of lightning channels, and extends to the possibility of adverse health impacts for crewmembers and passengers of aircraft transiting regions of strong thunderstorm activity. Broader impacts of this effort will come through development of an interdisciplinary research program, via graduate and undergraduate student education and training, and through dissemination of results using illuminating graphical methods.

无论是通过最初的照明触发和传播通过自由大气的确切机制，也没有这些过程的关系，最近出现的观测活动雷暴相关的高能量发射很好地理解。 这项研究将采用最先进的数值模拟方法，调查与闪电有关的电荷流和步进先导放电产生的高能电子发射以及相关高能辐射（从X射线到硬X射线和地面伽马射线闪光）通过地球大气层的传播。 唯一已知的能够解释相关高能电子产生的机制是“失控过程”，通过该过程，从施加的电场中获得的能量超过碰撞损失的能量，从而将电子加速到非常高的能量（1 MeV）。 到目前为止，已经提出了两种最初“播种”这种失控击穿过程的方案：（1）宇宙射线，和（2）极高电场引起的“热”失控。 理论和实验研究表明，流光和先导放电动力学的耦合对热失控过程至关重要，而热失控过程现在又被认为与闪电发射X射线或产生地面伽马射线闪光密不可分。 最近，人们通过地面、空中和卫星平台对雷暴和相关电活动产生的高能辐射进行了有针对性的观测，但这些以前不相关的现象之间的关系的详细性质以前并没有像本项目所做的那样被量化。观测到的源自地球大气层的高能辐射的时间和具体性质。 强调了相关问题的重要性，因为需要量化闪电发射的辐射强度，并了解其与闪电通道形成和传播的关系，并扩展到对经过强雷暴活动区域的飞机机组人员和乘客的不利健康影响的可能性。 这一努力的更广泛的影响将通过跨学科研究计划的发展，通过研究生和本科生的教育和培训，并通过使用启发性的图形方法传播结果来实现。