Balloon Observations of MeV Electron Precipitation

MeV 电子沉淀的气球观测

• 批准号: 0230441
• 负责人: George Parks
• 金额: --
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230441&HistoricalAwards=false
• 关键词: Balloon; Observations; MeV; Electron; Precipitation

The proposed project is the preparation and flight of a series of balloon payloads to study energetic electrons precipitated from the outer zone of the Earth's radiation belts into the atmosphere, and the subsequent data analysis. The electrons under consideration are relativistic (kinetic energy greater than the electron rest mass of 511 keV). These electrons can be responsible for damage to satellites in geosynchronous orbit. They are trapped in the Earth's magnetosphere between roughly 4 and 6 Earth radii at the equator, which means they hit the Earth near the Arctic and Antarctic circles when they come down. The precipitation can be triggered by a number of causes, some associ-ated with magnetic storms and some which can occur under all conditions. The balloons study not the electrons themselves, but rather x-rays emitted by the bremsstrahlung process when they hit the atmosphere. A balloon can therefore watch all the precipitation, taking place within a hundred kilometers of its location or more, and can track the variability of the emission with time. Most satellites only observe electrons at their own position, and move too quickly through the precipitation zone to observe the evolution of the precipitation events. Balloons were used ex-tensively until the 1970s to study precipitation of non-relativistic electrons (roughly 20-200 keV). When relativistic electrons hit the atmosphere, they can produce enough ionization to create chemically important amounts of "odd nitrogen" (e.g. NO2 and other compounds). Depending on the circumstances, these compounds can either destroy stratospheric ozone or else bind up and deactivate chlorine atoms which destroy ozone even more efficiently, and thus perhaps partially protect the ozone layer. Although their role in either case is widely understood to be small compared to that of increases and decreases in chlorine introduced by human activity, that role is not well studied and may represent an important perturbation on the main chemistry. The campaign proposed for December 2004/January 2005will address the physics of the various relativistic electron precipitation processes, their patterns of occurrence in space and time, and the energy and number of electrons precipitated. The last point is relevant to the overall balance of relativistic electrons in the radiation belts and also to their impact on atmospheric chemistry.

拟议的项目是准备和飞行一系列气球有效载荷，以研究从地球辐射带外层沉淀到大气中的高能电子，以及随后的数据分析。所考虑的电子是相对论性的（动能大于电子静止质量 511 keV）。这些电子可能会损坏地球同步轨道上的卫星。它们被困在赤道大约 4 到 6 个地球半径之间的地球磁层中，这意味着它们降落时会在北极圈和南极圈附近撞击地球。引发降水的原因有很多，有些与磁暴有关，有些则可能在所有条件下发生。气球研究的不是电子本身，而是它们撞击大气层时由轫致辐射过程发出的 X 射线。因此，气球可以观察其位置一百公里或更远范围内发生的所有降水，并可以跟踪排放随时间的变化。大多数卫星仅观察其自身位置的电子，并且在降水区中移动过快，无法观察降水事件的演变。直到 20 世纪 70 年代，气球才被广泛用于研究非相对论性电子（大约 20-200 keV）的沉淀。当相对论性电子撞击大气时，它们可以产生足够的电离，从而产生化学上重要数量的“奇数氮”（例如二氧化氮和其他化合物）。根据具体情况，这些化合物可以破坏平流层臭氧，或者结合氯原子并使氯原子失活，从而更有效地破坏臭氧，从而可能部分保护臭氧层。尽管人们普遍认为，与人类活动引起的氯的增加和减少相比，它们在这两种情况下的作用都很小，但这种作用尚未得到充分研究，并且可能代表对主要化学的重要扰动。提议于 2004 年 12 月/2005 年 1 月开展的活动将讨论各种相对论电子沉淀过程的物理学、它们在空间和时间上的发生模式以及沉淀电子的能量和数量。最后一点与辐射带中相对论电子的总体平衡及其对大气化学的影响有关。