Parker Solar Probe recorded unexpected details of an explosion near the Sun: protons and heavy ions do not accelerate equally
Magnetic reconnection – the sudden “rewiring” of magnetic field lines in plasma – is one of the key triggers of the processes that power solar eruptions and can grow into space weather hazardous for technology on Earth. In such moments, magnetic energy turns into kinetic energy: particles accelerate, jets and high-speed flows form, and the whole system becomes more unpredictable than models sometimes assume. The latest insight into this mechanism was provided by NASA’s Parker Solar Probe, which during a 2022 flyby passed through a position that enabled scientists to carry out a rare direct “inside measurement” of a reconnection event in the solar wind.
Why reconnection matters before a storm reaches Earth
Space weather is not an abstract concept reserved for astronomers: its most visible signature is the aurora, but the consequences can be very practical. During periods of heightened solar activity, ejections of material and energetic particles can disrupt radio communications, affect satellite electronics, and geomagnetic storms can induce currents in power systems. NOAA’s Space Weather Prediction Center notes that X-ray radiation from solar flares can temporarily degrade or block high-frequency radio communications, while solar energetic particles can penetrate satellite electronics and cause malfunctions; such effects are especially emphasized in the context of critical infrastructure and navigation systems. The European Space Agency (ESA) additionally warns that space weather can affect economically critical systems – from satellites and communications networks to power grids – because changes in plasma, magnetic fields, and particle flows alter the environment around Earth.
Magnetic reconnection lies at the very start of many such episodes. In a simplified picture, magnetic field lines in plasma approach, break, and reconnect into a new configuration. In that “reconnection,” energy is released, fast flows form, and particles gain an extra push. But the real system is complex: plasma is a mixture of electrons, protons, and heavier ions, and local conditions – density, temperature, the orientation of magnetic fields, and waves – determine how energy will be distributed.
A rare opportunity: reconnection in the solar wind as a “laboratory within spacecraft reach”
The most dramatic reconnection events that drive strong storms often occur in the hard-to-reach solar atmosphere, in the corona. Parker Solar Probe was designed precisely to dive ever deeper into that region, but even then, “hitting” an event at the right moment and in the right place remains a challenge. Scientists therefore particularly value situations in which reconnection takes place in the solar wind – the continuous stream of particles and magnetic fields that the Sun releases into interplanetary space – because such events can be observed with direct measurements of particles and fields as the spacecraft passes through the region.
According to a press release from the Southwest Research Institute (SwRI), during one pass Parker Solar Probe collected data showing that protons and heavy ions behave differently in reconnection, suggesting that the Sun’s “magnetic engine” is more complex than earlier assumptions. The study was published on March 31, 2026, in The Astrophysical Journal, under the title
Proton and Heavy Ion Acceleration by Magnetic Reconnection at the Near-Sun Heliospheric Current Sheet (DOI: 10.3847/1538-4357/ae48f2).
What Parker Solar Probe actually “saw”: a jet toward the Sun, but with two different signatures
In the observed event, the spacecraft recorded a jet of particles directed toward the Sun. It contained protons and heavy ions – atoms that are missing or have extra electrons, so they are electrically charged and therefore sensitive to magnetic and electric fields. In reconnection theories, one often starts from the assumption that different ion species, once they enter the acceleration zone, will acquire a similar “signature” in the velocity distribution. But here the opposite happened: heavy ions “shot” straight like a laser beam, while protons formed a more stretched-out, diffuse beam – more like a flashlight beam.
SwRI describes the key difference: under such conditions, protons can generate waves that then scatter particles more efficiently, while heavy ions remain “beam-like” and retain the spectral shape they acquired through acceleration. The lead author, Dr. Mihir Desai of SwRI, emphasizes that the new data “rewrite” the understanding of reconnection precisely because they show different spectra of protons and heavy ions that do not fit simplified models.
Why the difference between a “flashlight” and a “laser” is more than a vivid comparison
At first glance, it might seem like a nuance in a laboratory detail, but in plasma physics such differences change the entire story of how energy moves through a system. A more diffuse proton beam means that part of the energy is transferred into waves and turbulence, which then affects further acceleration, heating, and spreading of particles. A more collimated heavy-ion beam suggests that they pass through the acceleration zone with fewer “losses” to scattering, so they can preserve a clearer trace of the original mechanism.
In practice, this matters for two reasons. First, space weather models often have to estimate how particle populations evolve on the way from the Sun to Earth: how fast they will arrive, what energies they will have, and how long the “shower” of energetic particles will last. Second, reconnection is a universal process: it occurs in Earth’s magnetosphere (e.g., during geomagnetic storms), around other stars, and even in extreme environments around black holes and supernovae. If it turns out that different ion species systematically behave differently, theory must explain when and why such a “division of roles” occurs.
The role of the heliospheric current sheet and why 2022 was suitable for such a catch
The published paper focuses on reconnection associated with the near-Sun heliospheric current sheet (Heliospheric Current Sheet – HCS), a vast structure in the solar wind that separates regions of oppositely directed magnetic fields. It is precisely at such “boundaries” that magnetic fields naturally come into contact and create conditions for reconnection. Because of its trajectory, Parker Solar Probe crosses such structures multiple times as it approaches the Sun, giving it opportunities to observe how magnetic configurations change and how particles behave in the real, turbulent environment of the corona and inner heliosphere.
NASA’s mission page states that Parker Solar Probe is designed to approach to about 6.5 million kilometers from the Sun’s surface and to investigate how the corona is heated, how the solar wind is generated, and what accelerates particles to high energies. Such proximity is crucial because in that region magnetic energy and particle flows have not yet “mixed” and diluted as they do at greater distances; measurements are therefore more sensitive to the original processes.
How the spacecraft measures the invisible: instruments that capture particles and fields
To detect the difference between protons and heavier ions at all, a combination of measurements of electric and magnetic fields and measurements of particle composition and speeds is needed. NASA’s instrument page highlights, among other things, WISPR – the only imaging instrument on the spacecraft – which observes structures in the corona and solar wind before the spacecraft “flies through” them and measures them in situ. Such linking of large-scale imagery and local measurements helps scientists understand the context in which an event occurs: whether it is a jet, the remnant of a mass ejection, or a structure associated with the HCS.
In this case, measurements of the distribution of particle speeds and directions were decisive. Precisely that “beam geometry” – the diffuseness of protons and the collimation of heavy ions – raised the question about the role of waves and turbulence, that is, about who in reconnection “carries” energy and who merely receives it.
What changes in theory and what is still unclear
In classical descriptions of reconnection, especially under idealized conditions, energy is expected to be shared among different particles in a relatively similar way, with corrections due to mass and charge. The new data suggest that “one formula for all” is not sufficient. If protons create waves that feed back on the plasma and scatter the beam, then acceleration cannot be viewed as a one-off “hit” of energy, but as a process with feedback in which particles change the medium through which they pass.
At the same time, it is not certain how universal this behavior is. This is a detailed measurement of a single event under specific conditions near the Sun. Scientists will therefore look for similar signatures in other passes and compare them with models, including computer simulations of plasma. According to SwRI, the goal is precisely to refine theoretical models to better understand how solar storms are powered and how energy is transferred into particles that can pose a risk to technology.
The bigger picture: why investing in “space weather” pays off through system safety
Society’s growing dependence on satellites, precise navigation, communications, and stable power grids makes space weather forecasting increasingly important. NOAA warns that different types of space weather have different technical consequences – from radio blackouts to damage to satellite systems – and ESA emphasizes that such disruptions are also relevant for economic activity. That is why science that at first glance seems “distant” turns into a very concrete need: to better understand the physics behind eruptions, so that it can be recognized earlier when conditions on the Sun are developing toward a more dangerous scenario.
In that sense, Parker Solar Probe is one of the key sources of data because it approaches the place where processes originate, instead of observing consequences only when they reach Earth. SwRI notes in its press release that the spacecraft passes through the corona three times a year and collects unique measurements, and the mission for NASA is led by the Johns Hopkins University Applied Physics Laboratory. The more such measurements are collected, the clearer picture plasma physicists will have of when reconnection produces “laser-like” beams, when “flashlights,” and what kind of space scenario can develop from that.
Sources:- Southwest Research Institute (SwRI) – press release about the study published on March 31, 2026, and the explanation of differences between protons and heavy ions ( link )- The Astrophysical Journal – reference to the paper and DOI 10.3847/1538-4357/ae48f2 ( link )- NASA Science – mission description of Parker Solar Probe and key goals ( link )- NASA Science – overview of instruments, including WISPR and how it links images and measurements in the solar wind ( link )- NOAA / Space Weather Prediction Center – overview of space weather impacts on technologies, including radio, satellites, and grids ( link )- ESA – explanation of space weather risks and impacts on satellites, communications, and power systems ( link )
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Creation time: 18 April, 2026