But the probe also found that the stream of particles from the sun does not spike in response to solar flares. Instead, the solar wind is surprisingly steady and placid at the edge of the solar system, and no one knows why.
These observations raised another puzzle: when the team revised its estimate for how many X-rays should be seen around Pluto given that compact atmosphere, Chandra now saw too many.
“We know the gas exchange rate is lower than expected,” Lisse said. “Yet we see more X-rays than we expected in that situation. That doesn’t make sense.”
New Horizons discovery raises solar wind riddle around Pluto | New Scientist
Is it an AC, DC, AC/DC, or 'other' Electromagnetic Universe?
Or is it just the circuit of Pluto and the Sun's plasma wind?
Charge-exchange between SW CNO ions & escaping Pluto neutrals could produce this. Less likely is scattering of solar x-rays by haze particles in Pluto's atmosphere.
The puzzling detection of x-rays from Pluto by Chandra