Parker Solar Probe’s Confirmation Of Interchange Reconnection Being The Source Of Fast Solar Wind

Diagram of the Sun. (Credit: Kelvinsong)

Although experimental verification is at the heart of the scientific method, there is quite a difficulty range when it comes to setting up such an experiment. Testing what underlies the formation of the fast solar winds that are ejected from coronal holes in the Sun’s corona is one of these tricky experimental setups. Yet it would seem that we now have our answer, with a newly published paper in Nature by S. D. Bale and colleagues detailing what we learned courtesy of the Parker Solar Probe (PSP), which has been on its way to the Sun since it was launched in August of 2018 from Earth.

Artist rendition of the Parker Solar Probe. (Credit: NASA)
Artist rendition of the Parker Solar Probe. (Credit: NASA)

The Sun’s solar wind is the name for a stream of charged particles which are ejected from the Sun’s corona, with generally two types being distinguished: slow and fast solar winds. The former type appears to originate from the Sun’s equatorial belt and gently saunters away from the Sun at a mere 300 – 500 km/s with a balmy temperature of 100 MK.

The fast solar wind originates from coronal holes, which are temporary regions of cooler, less dense plasma within the corona. These coronal holes are notable for being regions where the Sun’s magnetic field extends into interplanetary space as an open field, along which the charged particles of the corona can escape the Sun’s gravitational field.

These properties of coronal holes allow the resulting stream to travel at speeds around 750 km/s and a blistering 800 MK. What was unclear up till this point was exactly what powers the acceleration of the plasma. It was postulated that the source could be wave heating, as well as interchange reconnection, but with the PSP now close enough to perform the relevant measurements, the evidence points to the latter.

Essentially, interchange reconnection is the reestablishing of a coronal hole’s field lines after interaction with convection cells on the Sun’s photosphere. These convection cells draw the magnetic field into a kind of funnel after which the field lines reestablish themselves, which results in the ejection of hotter plasma than with the slow solar wind. Courtesy of the PSP’s measurements, measured fast solar winds could be matched with coronal holes, along with the magnetic fields. This gives us the clearest picture yet of how this phenomenon works, and how we might be able to predict it.

(Heading image: Diagram of the Sun. (Credit: Kelvinsong) )

4 thoughts on “Parker Solar Probe’s Confirmation Of Interchange Reconnection Being The Source Of Fast Solar Wind

  1. There has to be better terms to describe interchange reconnect that unfortunatly invoke fictional field lines, (inventions of the human imagination to represent field direction and density to represent magnitude) and the equally fictional reconnection of them.

    The general public, and many armchair layman scientist is often ignorant to the nature of fields in part because, it’s often not stressed that field lines are fictional tools to visualize certain representations of fields characteristics, direction and magnitude.

  2. The whole thing vaguely resembles how neurons and their tunneling and interconnects work.
    So if someone would postulate a thinking sun with magnetic field neurons I expect it to be accepted by half the population in a week.
    It doesn’t matter if it’s silly nonsense anymore as you probably know.

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