NASA’s TRACERS First Results Offers Peek into Violent Magnetic Process

NASA's TRACERS (Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites) mission has gathered its first clues to how space weather affects Earth's magnetic field. In a new paper, researchers break down how these interactions work after analyzing initial observations from the first year of the mission.

The two TRACERS spacecraft launched last year to explore how the Sun's solar wind interacts with Earth's magnetic shield in an explosive process known as magnetic reconnection. While scientists are familiar with the process of magnetic reconnection, questions remain on how energy is transferred during the process and how the edge of Earth's magnetic field - the magnetopause - reacts.

"Analyzing the data TRACERS collected gave our team a clearer view of solar wind particle behavior and how it connects to reconnection events," said Stephen Fuselier, TRACERS deputy principal investigator and instrument lead at the Southwest Research Institute in San Antonio. "This is an important first step in understanding how magnetic reconnection works and how these processes can affect Earth."

Magnetic reconnection occurs when the Sun's magnetic field, embedded in a continuous outpouring of electrically charged particles called the solar wind, collides with Earth's magnetic shield, known as the magnetosphere. At the magnetosphere's boundary with space, called the magnetopause, these collisions cause energy to build up and can cause the magnetic field lines to snap and explosively fling away nearby particles at high speeds directly into our atmosphere.

Understanding what primarily drives the reconnection process - specifically whether the location of reconnection events influences the magnetopause reaction more than the rate of reconnection - is a critical initial step. The TRACERS mission was designed to explore these dynamics by having twin satellites fly one behind the other, locked in a Sun-synchronous orbit, passing through areas where Earth's magnetic field converges like funnels over the north and south magnetic poles. These areas, called polar cusps, funnel solar wind particles, concentrating the solar wind particles in a small region of our upper atmosphere. The repeated orbits through this concentrated region give TRACERS the opportunity to collect measurements on reconnection events at the southern cusp, allowing scientists to compare the data between the two satellites and observe how quickly reconnection changes and evolves.

Now, a year after launch, TRACERS researchers have analyzed the initial data collected and outlined the results in a new paper published in the Journal of Geophysical Research. The paper discusses how data taken by the Analyzers for Cusp Ions instruments on the TRACERS satellites show that magnetic reconnection is largely a spatial process, meaning where reconnection is occurring is moving, rather than changing in time. Future measurements will help confirm these results.

According to TRACERS Principal Investigator David Miles of the University of Iowa, publishing these findings and exploring the mysteries of magnetic reconnection in the magnetopause is deeply meaningful to the team. "The TRACERS team has demonstrated exceptional collaboration and resolve to gather and evaluate this data," Miles said. "I am excited to see what is revealed by future measurements."

After a setback with one of the satellites after launch, the TRACERS team worked determinedly to re-establish contact with the satellite and establish routine data collection. The TRACERS spacecraft now observe the southern cusp routinely several times a day. In September, NASA approved a prime mission extension for the spacecraft to continue studying reconnection events into spring 2027.

Understanding how magnetic reconnection varies helps scientists better understand space weather, since reconnection provides the fundamental linkage between solar wind and Earth's space environment. Studying space weather also helps scientists better predict geomagnetic storms that can affect the safety of astronauts near Earth, as well as the power grids and communication systems that we rely on.

The TRACERS mission is led by David Miles at the University of Iowa with support from the Southwest Research Institute in San Antonio. NASA's Heliophysics Explorers Program Office at the agency's Goddard Space Flight Center in Greenbelt, Maryland, manages the mission for the agency's Heliophysics Division at NASA Headquarters in Washington. The University of Iowa, Southwest Research Institute, University of California, Los Angeles, and University of California, Berkeley, all lead instruments on TRACERS that study changes in Earth's magnetic field and electric field.