charge exchange raises H O ionization of high Z gas (trac #250)

[cloudy-bot]

reported by: @CloudyLex

four sims are attached. Only H and O are included, and it is a collisionally ionized gas at log T 4.1

There is a mysterious increase in the ionization of both species when CX is included in the high Z case. I cannot think of a physical reason for this.

There are four sims. All have a high density, log n=10. at solar O/H the gas is mostly neutral and CX does not change the solution greatly.

When O/H is increased by 30x the solution becomes more highly ionized, by a large factor, when CX is included. The ionization is similar to the low O/H case when CX is not included.

CX is simultaneously raising the ionization of both H and O by a large factor. Here is a table:

|| default || 0.894 || 0.106 || 0.912 || 0.088 || || default no cx || 0.931 || 0.0692 || 0.928 || 0.072 || || Z30 no cx || 0.931 || 0.0693 || 0.928 || 0.0719 || || Z30 || 0.403 || 0.597 || 0.455 || 0.545 ||

Migrated from https://www.nublado.org/ticket/250

{
    "status": "closed",
    "changetime": "2012-12-11T21:53:17Z",
    "_ts": "1355262797000000",
    "description": "four sims are attached.  Only H and O are included, and it is a collisionally ionized gas at log T 4.1\n\nThere is a mysterious increase in the ionization of both species when CX is included in the high Z case.  I cannot think of a physical reason for this.\n\nThere are four sims.  All have a high density, log n=10.  at solar O/H the gas is mostly neutral and CX does not change the solution greatly.\n\nWhen O/H is increased by 30x the solution becomes more highly ionized, by a large factor, when CX is included.  The ionization is similar to the low O/H case when CX is not included.\n\nCX is simultaneously raising the ionization of both H and O by a large factor.  Here is a table:\n\n || default || 0.894 || 0.106 || 0.912 || 0.088 || \n || default no cx || 0.931 || 0.0692 || 0.928 || 0.072 || \n || Z30 no cx || 0.931 || 0.0693 || 0.928 || 0.0719 || \n || Z30 || 0.403 || 0.597 || 0.455 || 0.545 || ",
    "reporter": "gary",
    "cc": "",
    "resolution": "fixed",
    "time": "2012-12-07T19:35:54Z",
    "component": "ionization convergence",
    "summary": "charge exchange raises H O ionization of high Z gas",
    "priority": "major",
    "keywords": "O H charge exchange",
    "version": "trunk",
    "milestone": "",
    "owner": "nobody",
    "type": "defect - convergence"
}

[cloudy-bot]

four sims used to create table in ticket Attachment: d10.tar.gz

[cloudy-bot]

@CloudyLex commented:

output generated with trunk r6922 on os x gcc 4.2.1.

But result was first noted by Wang Ye on dlx using icc / mpi at r6920 on WangYe branch

[cloudy-bot]

electron density's change via hden and metallicity Attachment: eden.pdf

[cloudy-bot]

@wangye0206 commented:

Figure 'eden.pdf' may help to locate where the bug is.

[cloudy-bot]

• @rjrw commented:

The problem was due to overpopulation of high levels by non-state-specific CX allowing collisional ionization, not by CX imbalance.

Fixed by r6948:6956

• @rjrw changed resolution from "" to "fixed"
• @rjrw changed status from "new" to "closed"