Temperature Measurement Of Interstellar Matter

Question

Have read many articles about the temperature of interstellar gas/dust/plasma. Recently, Voyage2 departed the heliosphere. According to a paper this article below, "In one of the papers, the researchers suggest that the interstellar medium near the heliopause — the boundary at the edge of the heliosphere — is hotter than expected, with a temperature of around 30,000–50,000°K"

How are they measuring such a hot, but yet, extremely diffuse gas? What is the tech behind the instrument?

Thank you so much for your time.

https://www.dailymail.co.uk/sciencetech/article-7647729/NASAs-Voyager-2-space-probe-sends-discoveries-interstellar-space.html

Answer 1

In section 4 of this paper, the autors claim that "[...] the temperature in the VLISM is not directly measured"; from what I understood, they measure a total effetctive pressure with a nominal value of $P_{Total} = 267 \pm 55$ fPa. The instrument that measures this pressure is the Plasma Science (PLS). From this, they use some equation of state to determine a temperature of $ T_{VLISM} = 20,000$ K. Notice that this temperature is simply a measure of the kinetic energy of the particles composing the plasma: you wouldn't necessarily experience such hot temperatures if transported there.