When giant blobs of solar wind collide with the magnetosphere, they can trigger disturbances there that interfere with satellites and everyday communications signals. Di Matteo found dotted trails of blobs that oozed from the Sun every 90 minutes or so. Whatever process sends the solar wind out from the Sun must leave signatures on the blobs themselves.
Samantha Wallace, one of the study collaborators and a physics Ph.D. student at the University of New Mexico in Albuquerque, used an advanced solar wind model to link magnetic maps of the solar surface to Helios' observations, a tricky task since computer languages and data conventions have changed greatly since Helios' days. Now, the researchers could see what sorts of regions on the Sun were likely to bud into blobs of solar wind.
Then, Di Matteo searched the data for specific wave patterns. The team expected conditions to alternate -- hot and dense, then cold and tenuous -- as individual blobs engulfed the spacecraft and moved on, in a long line. After they removed segments of the old data they found five instances that Helios happened to catch trains of blobs. While scientists have spotted these blobs from Earth before, this is the first time they've studied them this close to the Sun, and with this level of detail. They outline the first conclusive evidence that the blobs are hotter and denser than the typical solar wind.
Whether blob trains bubble in 90-minute intervals continuously or in spurts, and how much they vary between themselves, is still a mystery. But the study is perfect for Parker Solar Probe, which aims to study the Sun up close, seeking answers to basic questions about the solar wind. Parker Solar Probe performed its second solar flyby in April, which brings it 15 million miles from the Sun -- already cutting Helios 2's record distance in half. The researchers are eager to see if blobs show up in Parker's observations. Eventually, the spacecraft will get so close it could catch blobs right after they've formed, fresh out of the Sun.