Solar wind is charged particles up to about 10 keV. That is not terribly penetrating radiation. Cosmic rays have much higher energies occasionally exceeding TeV.
The are very penetrating. Outside the atmosphere providing a shielding of (1kg mass per cm^2) there is about 100 times as much cosmic radiation than at sea level.
A cosmic ray shower can be captured as by the camera sensor with a result as shown in the linked image. But, cosmic rays can also do permanent damage to the sensor, hot pixels. We have not enough information from the single example image, whether it shows a cosmic ray detection or the hot pixels. The hot pixels will always show in sufficiently dark parts of the image. My standard procedure to identify hot pixels is, to do multiple black frames with exposure of 1/5s at ISO 1600. (exposure short enough to avoid Nikon's HPS suppression)
Some hot pixels can be healed by thermal cycling (very limited for a standard camera system). Some other hot pixels are permanent. They can only dealt with, by substituting OK image data from the neighborhood. This is sometimes termed remapping of hot pixels. Newer Nikon cameras have a user controllable feature (not mentioned in the manual) to remap hot pixels: just run sensor clean manually twice in immediate succession.
