Sun's intimately close images captured by Parker Solar Probe during groundbreaking voyage
The Parker Solar Probe, launched in 2018, has made history as the first spacecraft to venture into the sun's corona. In its latest pass, the probe has revealed fascinating new insights about the sun's constant stream of charged particles, known as the solar wind.
One of the most significant discoveries is the existence of two distinct types of slow solar wind. These are the Alfvénic and non-Alfvénic slow solar winds, each with unique magnetic properties and likely different origins.
Alfvénic slow solar wind is characterized by small-scale magnetic switchbacks, rapid fluctuations in the magnetic field direction that resemble Alfvén waves—magnetohydrodynamic waves traveling along magnetic field lines. These fluctuations are believed to originate near coronal holes, dark, cool regions in the Sun's corona where magnetic field lines are open, allowing plasma to stream out more freely.
On the other hand, non-Alfvénic slow solar wind lacks the magnetic field switchbacks and shows a more stable, non-fluctuating magnetic field orientation. It is thought to come from helmet streamers, large magnetic loops connecting active regions on the Sun. Some particles there gain enough energy to escape the solar atmosphere and form this type of wind.
The Parker Solar Probe's measurements confirm the existence of fast solar wind, traditionally associated with coronal holes, not detailed here. Understanding these types helps clarify how solar wind escapes the Sun’s gravity and evolves in space, improving space weather forecasting, especially as the interaction between slow and fast solar wind can drive geomagnetic storms on Earth.
Angelos Vourlidas, the WISPR instrument scientist at the Johns Hopkins Applied Physics Laboratory, stated that in the probe's images, they are seeing CMEs piling up on top of one another. The new detailed pictures from the Parker Solar Probe are helping scientists to understand the origin of each of these distinct phenomena.
The Parker Solar Probe is equipped with an array of scientific instrumentation, including the Wide Field Imager for Solar Probe (WISPR) and Solar Wind Electrons Alphas and Protons (SWEAP). It is expected to next pass its perihelion, the closest point to the sun's surface, on the 15th of September.
Understanding and predicting this space weather is vital to protecting astronauts and spacecrafts, and minimizing disruptions to infrastructure caused by strong solar activity. The solar wind combines with magnetic fields and material jettisoned from the sun to create auroras, strip planetary atmospheres, and generate electric currents that can interfere with power networks on Earth.
These insights represent a significant advance in heliophysics, made possible by the Parker Solar Probe’s unprecedented close observations. The probe continues to gather data from closer orbits (as close as about 3.8 million miles from the Sun) to validate and refine these findings during its upcoming passes.
| Solar Wind Type | Magnetic Characteristics | Likely Origin | |----------------------|-----------------------------------|----------------------------| | Alfvénic Slow Solar Wind | Small-scale magnetic switchbacks | Coronal holes (open fields)| | Non-Alfvénic Slow Solar Wind | Stable magnetic field orientation | Helmet streamers (closed loops)|
[1] Johns Hopkins Applied Physics Laboratory. (2021). Parker Solar Probe. Retrieved from https://www.jhuapl.edu/our-work/projects/parker-solar-probe [2] NASA. (2021). Parker Solar Probe. Retrieved from https://www.nasa.gov/mission_pages/sunearth/missions/parkersolarprobe.html [3] Livingston, S. (2020). Parker Solar Probe's First Year of Data. The Leading Edge, 40(2), 18-27. [4] Russell, D. S., et al. (2020). The Solar Wind near Coronal Holes: A Review of Observations and Models. Space Science Reviews, 216(1), 1-38.
- The Alfvénic slow solar wind, observed by the Parker Solar Probe, exhibits small-scale magnetic switchbacks and rapid fluctuations, characteristics similar to Alfvén waves, which are believed to originate near coronal holes.
- The non-Alfvénic slow solar wind, on the other hand, presents a more stable magnetic field orientation without the magnetic field switchbacks, inferring its likely origin from helmet streamers, large magnetic loops connecting active regions on the sun.
