A Statistical Study of Coronal Holes and Active Regions Producing Intense Geomagnetic Storms over Four Solar Cycles

Smithsonian Institution Astrophysical Observatory, Cambridge MA

Investigators

Abstract

One of the most fundamental properties controlling activity on the Sun is its magnetic field. The Sun’s magnetic field consists of closed and open field lines that interact, snap, and reconnect, affecting the motion of plasma leaving the Sun in coronal mass ejections (CMEs) and through the solar wind. The solar wind can be accelerated to high speed through coronal holes (CHs), or regions with open field lines. Active regions (ARs) are regions of strong closed magnetic field lines that launch eruptive events such as CMEs and solar flares. Understanding these phenomena are crucial to predicting and preparing for harmful space weather effects on Earth. This project will perform a statistical study over four full solar cycles. Two early-career female scientists will be supported and three undergraduate students will be mentored through this research. The project is a detailed study of the role of coronal hole – active region interactions in the generation of intense geomagnetic storms (IGS). Two science questions will be addressed: (1) Can the evolution of CH location and size be used as a proxy to understand IGS occurrence and timing? (2) How does the interaction between HSSs and CMEs affect the strength of geomagnetic storms? In the past, limited studies have hinted at the possibility that the number of geomagnetic storms in even cycles increases with increasing number of close CH-AR pairs and decreases with increasing number of close CH-AR pairs in odd cycles. It is still not well understood how location, size and CH-AR interactions could influence the potential for an eruption to be geo-effective. Therefore, this project will make a statistical observational study covering four complete solar cycles (21-24). They will provide an overview of the solar wind conditions related to all IGS events (265) and a detailed list of their characteristics (mean values of speed, magnetic field, density, temperature, flow and magnetic pressures, components of the magnetic field, minimum Dst index values) including their association with active regions, coronal holes, high speed streams, and CMEs. 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.