I Effects of hydrogen anions in the solar atmosphere

AI Thread Summary
Hydrogen anions (H^-) exist in the solar atmosphere and are significant due to their role as the dominant source of opacity in radiative transfer at visible and near-infrared wavelengths. They form when a hydrogen atom captures a free electron, releasing a photon, but can be stripped of this second electron through photodissociation. The stability of H^- anions is limited by heat, which ionizes them back to protons. Their population density in relation to neutral hydrogen atoms remains unclear, as available research does not provide specific figures. Understanding the abundance of H^- is crucial for comprehending their impact on stellar atmospheres.
sciFax
Messages
21
Reaction score
7
TL;DR Summary
I have some questions concerning ##H^-## hydrogen anions in the Sun's atmosphere.
What is the population density of ##H^-## hydrogen anions in the Sun's atmosphere, how stable are they, what limits their numbers, and since they are the dominant source of opacity in radiative transfer in stellar atmospheres, what do they effectively "hide"?
 
Astronomy news on Phys.org
My guess - very rare. Heat would ionize to protons.
 
mathman said:
My guess - very rare. Heat would ionize to protons.
Before I heard about the ##H^-## anion (a hydrogen atom with TWO electrons), I would have guessed they would not even exist. Apparently they do in fact exist in the solar atmosphere, and in sufficient numbers/abundance that they are "the dominant bound-free opacity source at visible and near-infrared wavelengths in the atmospheres of stars like the Sun and cooler ".

Having done a little more reading on the subject, it would appear the these anions are formed by the acceptance of a free electron, which becomes bound to the H atom, but not so strongly as the original electron in the atom. This is accompanied by the release of a photon. The process of stripping the second electron is known as photodissociation, since that electron is knocked out the anion by another, higher energy photon (and since this leads to a neutral H atom, it's not termed ionization). So this is where the opacity comes from, since a wide range of photon energies can lead to this photodissociation.

So, my one remaining question is: how many of these ##H^-## anions exist in the Sun's atmosphere at anyone time as a proportion to, say, neutral hydrogen atoms?
 
Sorry - google search didn't turn up anything.
 
@mathman - yes, it's frustrating. Thanks for trying though :)
 
This thread is dedicated to the beauty and awesomeness of our Universe. If you feel like it, please share video clips and photos (or nice animations) of space and objects in space in this thread. Your posts, clips and photos may by all means include scientific information; that does not make it less beautiful to me (n.b. the posts must of course comply with the PF guidelines, i.e. regarding science, only mainstream science is allowed, fringe/pseudoscience is not allowed). n.b. I start this...
Asteroid, Data - 1.2% risk of an impact on December 22, 2032. The estimated diameter is 55 m and an impact would likely release an energy of 8 megatons of TNT equivalent, although these numbers have a large uncertainty - it could also be 1 or 100 megatons. Currently the object has level 3 on the Torino scale, the second-highest ever (after Apophis) and only the third object to exceed level 1. Most likely it will miss, and if it hits then most likely it'll hit an ocean and be harmless, but...

Similar threads

Back
Top