Astronomers have been trying to understand the source of the solar wind ever since the first direct observations of it in 1959. Now, researchers utilizing the ESA/NASA Solar Orbiter spacecraft believe they have a solution: microscopic eruptions known as “picoflares.” At a speed of 100 kilometers per second, they emerge into the corona.
The discovery is the result of in-depth research in the extreme ultraviolet of a coronal hole at the south pole of the Sun. The observations identified a number of transient, weak characteristics linked to tiny plasma jets released from the Sun. According to Lakshmi Pradeep Chitta of the Max Planck Institute for Solar System Research in Germany, “We could only detect these tiny jets because of the unprecedented high-resolution, high-cadence images produced by EUI.” Chitta and associates list the facts and conclusions in a paper summarizing the observations.
Creating the Solar Wind
Numerous events in the Solar System are caused by the solar wind. It affects the magnetic fields of many planets, including Earth, and contributes to space weather phenomena like aurorae. As these frozen bodies circle the Sun, it also has an impact on comets, sculpting their plasma tails.
Despite the fact that this wind is a fundamental characteristic of the Sun, solar physicists haven’t always had a clear understanding of how it is produced. They’ve known for a while that coronal holes are mostly responsible for it. On the solar surface, these black areas represent magnetic structures in the corona. They are essentially regions of the solar atmosphere where the magnetic field does not revert to the Sun. Instead, through the Solar System and out from the Sun, their magnetic field lines stretch. The solar wind is simply plasma escaping from the Sun along those “exit lines,” as is only natural for plasma to do. However, the crucial query is still, “What launches it in the first place?”
On the Sun, coronal holes can emerge almost anywhere, though they are more common around the poles. During the quieter period of the solar cycle (the solar minimum), they appear to occur more frequently and last longer. They do, however, also appear during solar maximum.
Jets and the Solar Wind
Solar physicists have long observed a variety of the Sun’s jets and outbursts, which are not a novel concept. Coronal mass ejections are the biggest. These send out through space vast quantities of energetic particles. Additionally, there are things known as X-class solar flares. The solar nanoflares are another factor. Although less active, these are nonetheless powerful. Despite having a billion times less energy than the powerful solar flares, they occur almost continuously. They might be to blame for raising the corona’s temperature to its astonishingly high 2-million-degree level.
Compared to nanoflares, picoflares are less powerful. Solar Orbiter’s small jets have a thousand times lower energy output than a nanoflare. They do, however, appear to have a lot of punch. They focus the majority of their energy on ejecting plasma away from the Sun. This contributes to the solar wind’s almost continuous flow. They are so common that they undoubtedly emit a higher proportion of solar wind than anticipated.
Although there is still a lot to understand about this process, ongoing Solar Orbiter investigations should assist clarify the mechanism. “One of the results here is that to a large extent, this flow is not actually uniform, the ubiquity of the jets suggests that the solar wind from coronal holes might originate as a highly intermittent outflow,” said Andrei Zhukov, Royal Observatory of Belgium, a collaborator on the work and the man in charge of the Solar Orbiter observational campaign.
These persistent little ejections are still being measured by Solar Orbiter. In fact, it is currently revolving around the Sun in the equatorial regions. Its orbit will eventually include the polar regions. Fortunately, the spacecraft will be able to observe changes in the Sun as the current solar cycle develops thanks to that adjustment in orbit. This implies that it will be able to investigate these minute features in coronal holes that appear at various solar latitudes.
More info:
Solar Orbiter Discovers Tiny Jets that Could Power the Solar Wind
Picoflare Jets Power the Solar Wind Emerging from a Coronal Hole on the Sun
arXiv Article
