Parker solar probe flies through powerful solar explosion, a first

NASA’s Parker Solar Probe has achieved remarkable milestones in its inaugural five years of operation. It boasts a series of extraordinary achievements: It holds the record as the closest spacecraft to the sun, the fastest human-made object, and the pioneering mission to “touch the sun.”

Adding another accolade to its remarkable journey, Parker Solar Probe has become the first spacecraft to venture through a potent solar explosion in the vicinity of the sun.

In a recent study published on September 5th, precisely one year after the event, in The Astrophysical Journal, it is revealed that the probe successfully navigated through a coronal mass ejection (CME).

These formidable outbursts can discharge magnetic fields and, at times, billions of tons of plasma, hurtling at speeds ranging from 60 to 1,900 miles (100 to 3,000 kilometers) per second. When directed towards Earth, these ejections can influence and shape our planet’s magnetic field, producing breathtaking auroras and, if particularly intense, pose a potential threat to satellite electronics and terrestrial power grids.

Parker Solar Probe was positioned on the far side of the sun, a mere 5.7 million miles (9.2 million kilometers) from the sun’s surface – remarkably closer than Mercury ever ventures to the sun, which is 22.9 million miles (36.8 million kilometers). The probe initially detected the CME from a distance before skirting along its side. Subsequently, the spacecraft penetrated the CME structure, traversing through the wake of its leading edge, and ultimately emerged on the opposite side.

A composite of images collected by Parker Solar Probe’s Wide-field Imager for Solar Probe (WISPR) instrument captures the moment the spacecraft passed through a coronal mass ejection (CME) on Sept. 5, 2022. The event becomes visible at 0:14 seconds. The sun, depicted on the left, comes closest on Sept. 6, when Parker reached its 13th perihelion. The sound in the background is magnetic field data converted into audio. Credit: NASA/Johns Hopkins APL/Naval Research Laboratory/Brendan Gallagher/Guillermo Stenborg/Emmanuel Masongsong/Lizet Casillas/Robert Alexander/David Malaspina

Over the course of nearly two days, the Parker Solar Probe, on its sunward journey, closely observed a significant solar event, granting physicists an unprecedented glimpse into these celestial occurrences during their early stages.

Nour Raouafi, the project scientist for the Parker Solar Probe at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, expressed, “This is the closest we’ve ever observed a CME to the sun. We’ve never witnessed an event of this magnitude at such proximity.”

The CME that occurred on September 5, 2022, was exceptionally potent. As the Parker probe traversed behind the shockwave, its Solar Wind Electrons, Alphas, and Protons (SWEAP) instrument suite recorded particles accelerating up to a staggering 840 miles (1,350 kilometers) per second. Had this event been directed towards Earth, Raouafi speculates it could have rivaled the Carrington Event of 1859, considered the most powerful solar storm on record to strike our planet.

“The potential consequences of such large and high-speed CMEs can be catastrophic,” Raouafi cautioned. Scientists believe that if a similar event were to occur today without timely detection, it could disrupt communication systems and trigger continent-wide power outages.

Remarkably, the Parker Solar Probe remained resilient in the face of this solar eruption. Its carefully designed heat shield, radiators, and thermal protection system ensured that the probe’s temperatures remained constant. Moreover, its autonomous system enacted mitigation plans, enabling the avionics suite to continue operating without disruption. The only noticeable effect of the CME was a minor torque, quickly compensated for by the spacecraft.

Jim Kinnison, the Parker Solar mission systems engineer at APL, emphasized, “We knew from the outset that Parker Solar Probe would encounter CMEs. It was part of the mission’s scientific objectives, so we engineered the spacecraft with the intention of not only surviving but also conducting scientific research within a CME. Overall, Parker proved its robustness and resilience, validating the meticulous design work.”

Scientists have long been intrigued by the mechanisms behind these solar explosions and the extraordinary acceleration of particles they entail. The only way to truly investigate this was to venture through one of these events near the sun.

The scientific team meticulously pieced together the sequence of events and the probe’s position during the CME by comparing data collected within the CME with data obtained outside it, including images captured by NASA’s STEREO spacecraft using the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument. While they constructed a basic model of the event, the extreme proximity to the sun introduced complexities that made some aspects challenging to explain.

Orlando Romeo, a space physicist at the University of California, Berkeley, and the lead author of the study, shared, “We attempt to use simplified models to elucidate certain facets of the event. However, when you are this close to the sun, none of these models can comprehensively account for everything.”

The team identified three key phases during the event, but reconciling them posed a unique challenge. Two segments, the shockwave near the event’s front and the subsequent CME plasma, were consistent with previous CME observations upon reaching Earth. However, the third segment, characterized by low density and slow-moving particles, was unfamiliar and perplexing.

“We are still working to fully understand this particular segment and its connection to the other two,” Romeo admitted.

Advanced models that incorporate additional spacecraft measurements are expected to shed more light on this puzzle. Nevertheless, the prospect of encountering more CMEs as the Parker Solar Probe continues its approach to the sun, with the sun nearing the peak of its activity cycle, offers hope that further insights will be gained through future encounters.

Source: Johns Hopkins University

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