Proba-3 sees slow solar wind speeding close to the Sun
This graph shows how gusts of solar wind move through the Sun’s inner corona, right above the Sun’s surface. Each arrow in the graph shows how a single blob of plasma – a clump of charged gas making up solar wind – changes its speed as it moves away from (right-pointing arrow) or towards (left-pointing arrow) the Sun.
Arrows pointing up show plasma blobs speeding up as they move, while down-pointing arrows show blobs slowing down. The shaded regions indicate uncertainties in the measured speeds and directions.
The grey curve shows how solar wind speeds are expected to change with the distance to the Sun, based on older data published in 2009. While this curve suggests that a typical wind speed close to the Sun would be around 100 km/s, the new data (arrows) show plasma blobs moving at speeds 3–5 times higher.
The colours of the arrows in the graph indicate which side of the Sun each plasma blob was moving on. Red (blue) arrows show solar wind moving within 45 degrees of the Sun’s north (south) pole, while green and yellow arrows show wind moving to the left and right of the Sun.
Because the Sun is near its most active part of the 11-year solar cycle, called solar maximum, streamers carrying ‘slow’ solar wind are pointing in all directions.
As the Sun’s activity slows down over the next few years and the Sun’s magnetic field becomes less chaotic, it is expected that streamers and slow solar wind will originate mostly near the solar equator. The regions around the Sun’s poles will have more coronal holes producing fast solar wind.
This graph is adapted from Figure 4 in ‘Ubiquitous Small-scale Dynamics in the Slow Solar Wind Formation Region Observed by Proba-3/ASPIICS’, A. N. Zhukov et al., 2026 ApJL 999 L41.
[Image description: A graph with 'Distance from the Sun's centre in solar radii' on the x-axis and 'Plasma blob speed (km/s)' on the y-axis. Arrows in four different colours and of different lengths point in various directions between 1.5 and 3.0 solar radii on the x-axis, and between 0 and above 500 km/s on the y-axis. Each arrow represents one plasma blob's movement as it changes speed and moves away from or towards the Sun, with the colours indicating the four cardinal directions (north, east, south, west). A grey curve based on older data arcs from around 1.5 solar radii and 100 km/s to 3.1 solar radii and 250 km/s. A cluster of right-pointing arrows stand out by lying high above this grey curve, particularly between 1.5 and 2.0 solar radii from the Sun's centre, having speeds between 250 and 500 km/s. On the right of the graph there is a legend explaining what the arrows, their colours and the grey curve represent.]
