Tiny magnetic episodes may have large consequences on the sun

ESA’s Photo voltaic Orbiter could have taken one other step in direction of fixing the eighty-year-old thriller of why the sun’s outer ambiance is so sizzling.

On March 3, 2022, only a few months into Photo voltaic Orbiter’s nominal mission, the spacecraft’s Excessive Ultraviolet Imager (EUI) returned information displaying for the primary time {that a} magnetic phenomenon known as reconnection was happening persistently on tiny scales.

At the moment, the spacecraft was about midway between the Earth and the sun. This enabled coordinated observations with NASA’s Photo voltaic Dynamics Observatory (SDO) and Interface Area Imaging Spectrograph (IRIS) missions. The information from the three missions was then mixed through the evaluation.

Magnetic reconnection happens when a magnetic field adjustments itself right into a extra steady configuration. It’s a elementary power launch mechanism in superheated gasses referred to as plasmas and is believed to be the main mechanism for powering large-scale solar eruptions. This makes it the direct explanation for space climate, and a prime candidate for the mysterious heating of the sun’s outer atmosphere.

It has been recognized because the Nineteen Forties that the sun’s outer ambiance, known as the corona, is far hotter than the sun’s floor. Whereas the floor glows at round 5,500°C, the corona is a rarified fuel of round 2 million °C. How the sun injects power into its ambiance to warmth it to this super temperature has been a serious puzzle ever since.

Up to now, magnetic reconnection has normally been seen throughout large-scale, explosive phenomena. Nevertheless, the brand new end result presents ultra-high-resolution observations of persistent small-scale (round 390 km throughout) reconnection within the corona. These are revealed to be a long-lived ‘light’ sequence in comparison with sudden explosive releases of power that reconnection is normally related to.

The March 3, 2022 occasion came about over the interval of 1 hour. The temperatures across the level of the magnetic discipline the place the magnetic discipline depth drops to zero, referred to as the null-point, sustained itself at round 10 million °C, and generated an outflow of fabric that got here within the type of discrete “blobs” touring away from the null level with a velocity of round 80 km/s.

Along with this steady outflow, an explosive episode additionally came about round this null level, and lasted for 4 minutes.

Photo voltaic Orbiter’s outcomes counsel that magnetic reconnection, at scales that had been beforehand too small to be resolved, proceeds regularly in each light and explosive methods. That is importantly as a result of it signifies that reconnection can subsequently persistently switch mass and power to the overlying corona, contributing to heating it. These outcomes are printed in Nature Communications in a paper titled “Extremely-high-resolution Observations of Persistent Null-point Reconnection within the Photo voltaic Corona.”

These observations additionally counsel that even smaller and extra frequent magnetic reconnections await discovery. The objective is now to watch these with EUI at even increased spatio-temporal decision sooner or later round Photo voltaic Orbiter’s closest approaches to estimate what fraction of the corona’s warmth could also be transferred on this method.

Photo voltaic Orbiter’s most up-to-date closest passage to the sun came about on 10 April 2023. At the moment, the spacecraft was simply 29% the Earth’s distance from the sun.

Photo voltaic Orbiter is a space mission of worldwide collaboration between ESA and NASA, operated by ESA.