Is the Solar Wind Electron Strahl a Seed Population for the Earth's Electron Radiation Belt?

太阳风电子斯特拉尔是地球电子辐射带的种子种群吗？

• 批准号: 2149822
• 负责人: Joseph Borovsky
• 金额: $ 68.23万
• 依托单位: SPACE SCIENCE INSTITUTE
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-15 至 2027-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2149822&HistoricalAwards=false
• 关键词: Solar; Wind; Electron; Strahl; Seed

The near-Earth space is filled with charged particles from the solar wind and the Earth's upper atmosphere. However, how these particles are accelerated and transported into the radiation belt remains a mystery. This Magnetospheric project will explore a possible pathway to discern the ultimate source population of the Earth's electron radiation belt and discern the controlling factors for that source population. The reasoning is as follows. (1) Because the electron radiation belt is lost on occasion, a seed population of energetic electrons is required to replace the belt. (2) It is commonly accepted that the radiation-belt seed population is the population of energetic electrons injected into the dipole by substorms. (3) These substorm-injected electrons are suprathermal electrons in the Earth's magnetotail plasma sheet that are adiabatically delivered from the magnetotail into the dipole by substorms. (4) A resulting question is: where do the magnetotail suprathermal electrons come from, and what factors control them? This project argues that the magnetotail suprathermal electrons come from the energetic electron strahl in the solar wind.The objectives of this NSF project are: (1) To determine whether (and by how much) the solar-wind electron strahl acts as a seed population for the Earth's electron radiation belt, (2) To determine the controlling factors for this process, (3) To trace the electron strahl from the solar wind, into the Earth's magnetotail plasma sheet, into substorm injections, and evolving into the electron radiation belt, and (4) To discern whether there are other sources of the suprathermal electrons in the magnetotail plasma sheet that become energetic substorm- injected electrons. In the diverse data analysis of this project, the strahl electron population in the solar wind at Earth will be statistically followed into the magnetotail plasma sheet, into substorm electron injections, and into the electron radiation belt. The data analysis will be guided by computer simulations to answer questions about the evolution of the strahl electron population as it enters into and traverses through the magnetosphere-ionosphere system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

近地空间充满了来自太阳风和地球上层大气的带电粒子。然而，这些粒子如何被加速并输送到辐射带仍然是一个谜。这一磁层项目将探索一种可能的途径，以查明地球电子辐射带的最终源种群，并找出该源种群的控制因素。理由如下。(1)由于电子辐射带有时会丢失，因此需要一个高能电子的种子群来替换该带。(2)人们普遍认为，辐射带种子群是亚暴注入偶极子的高能电子群。(3)这些亚暴注入的电子是地球磁尾等离子体片中的超热电子，它们被亚暴绝热地从磁尾送入偶极子。(4)由此产生的问题是：磁尾超热电子来自哪里，控制它们的因素是什么？这个项目认为磁尾超热电子来自太阳风中的高能电子Strahl。NSF项目的目标是：(1)确定太阳风电子Strahl是否(以及有多少)作为地球电子辐射带的种子种群，(2)确定这一过程的控制因素，(3)追踪来自太阳风的电子Strahl，进入地球磁尾等离子体片，进入亚暴注入，并演化成电子辐射带，以及(4)辨别磁尾等离子体片中是否有其他来源的超热电子成为高能亚暴注入的电子。在这个项目的各种数据分析中，地球太阳风中的Strahl电子总数将被统计地跟踪到磁尾等离子体片、亚暴电子注入和电子辐射带。数据分析将由计算机模拟指导，以回答有关Strahl电子群体进入和穿越磁层-电离层系统时的演化问题。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。