11/06/2026
By Lynne Schaufenbil

Please join the Lowell Center for Space Science and Technology (LoCSST) for the talk “Solar Wind Heavy Ions Within Earth’s Magnetosphere and Controls on Solar Wind Entry Identified Through Wind–ACE Heavy-Ion Diagnostics" by graduate student Stephanie Colón-Rodríguez, Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor.

  • Date: Thursday, Nov. 19
  • Time: 11 a.m.

Abstract

Solar wind (SW) entry into Earth’s magnetosphere occurs through several mechanisms, but whether this entry depends on the properties of different ion species is unknown. During 1995–2004, Wind frequently crossed Earth’s magnetosphere, where its SupraThermal Ion Composition Spectrometer (STICS) measured ion species up to 226 keV/e. In addition to H+, Wind-STICS provides measurements of He2+, C5+, O6+, and Fe10+ (of SW origin). These singly and multiply charged, heavy-ion data products from Wind-STICS in the magnetosphere were recently made available in 2022, making it timely to conduct a statistical analysis of these observations. While the science objectives of the STICS sensor were to measure the abundance of suprathermal ion species in the SW, its measurements taken during its time passing through Earth’s magnetosphere can be used to reveal the ion composition of the hot magnetospheric plasma.

The first part of our study statistically analyzes how the density ratio between SW heavy ions and alpha particles ([O6+ + C5+ + Fe10+] / He2+) varies for different upstream conditions and locations within the magnetosphere: Interplanetary Magnetic Field (IMF) orientation, low vs. high SW density (NSW), low vs. high SW dynamic pressure (PDyn), slow vs. fast SW (VSW), and dawn vs. dusk. Our results indicate that the SW heavies enter the magnetosphere more efficiently than He2+ during northward IMF. In addition, these ratios exhibit a dawn–dusk asymmetry, highly skewed towards the dawn side for most upstream cases, likely due to charge-exchange processes.

The second part of our study statistically analyzes how these SW-origin ions within Earth’s magnetosphere differ from their abundance in interplanetary space. Because the SW composition change is slower than what it takes for it to travel from L1 to Earth, this creates a steady boundary condition of its entry into the magnetosphere. Thus, we take a scaling factor between upstream and magnetospheric measurements of SW species. We therefore combine Wind observations in the magnetosphere with ACE L1 measurements, which allows us to study how the SW heavies-to-alpha ratio changes as species cross Earth’s magnetopause. With this, we can determine if there is a preferential entry between He2+ and SW heavies, if such preferential entry varies under different upstream conditions, and what factors control their entry. Our results show that entry is comparable during strong driving, but during weak driving (i.e., +Bz, low PDyn, slow VSW) heavier ions enter the magnetosphere more efficiently than He2+. We suggest this is due to a combination of Kelvin-Helmholtz instabilities and differences in gyroradii between species.

In this presentation, we will show how the SW heavy ions in the magnetosphere further our understanding of the mass-per-charge-dependent entry and flow during geomagnetic quiet times.

About Stephanie Colón-Rodríguez

I was born and raised in Puerto Rico, where I also earned my undergraduate degree in physics from the University of Puerto Rico, Río Piedras Campus. Currently, I am a Ph.D. candidate at the University of Michigan, Department of Climate and Space Sciences and Engineering. I am interested in understanding the plasma physics of the heliosphere, including the solar wind dynamics and its coupling with Earth’s magnetosphere. Therefore, I analyze spacecraft measurements to study the ion composition of Earth’s plasma sheet. I am also passionate and have been part of numerous initiatives in public, K-12, and undergraduate outreach. Some of these include volunteer and mentoring work with the Arecibo Observatory, the Simons Foundation, and the University of Michigan’s Rackham Graduate School.

If you are interested in attending, please contact Lynne_SchaufenbiL@uml.edu.