Opened 7 years ago

Closed 7 years ago

Last modified 5 years ago

#160 closed physics (fixed)

secondary excitation for species lines are not evaluated correctly

Reported by: gary / robin Owned by:
Priority: major Milestone: c13 release
Component: atomic/molecular data base Version: trunk
Keywords: Cc:

Description (last modified by Ryan Porter)

On Jul 17, 2010, at 3:58 PM, Robin Williams wrote:

In species2.cpp, at line 365, is it just me or is

(dBaseTrans[ipSpecies][ipHi][ipLo].Emis->gf/ dBaseTrans[ipSpecies][ipHi][ipLo].EnergyWN) / (dBaseTrans[ipSpecies][ipHi][ipLo].Emis->gf/ dBaseTrans[ipSpecies][ipHi][ipLo].EnergyWN);

just an expensive way of calculating 1?


it is going to take some study to understand what to do. here is my recollection.

there are simple relations between collision cross section and the transition probability at high collision energies - these underlie the g-bar approximation. we know the HI Lya suprathermal collisional excitation rate and want to find the collisional excitation rate for other lines by scaling with quantities related to the transition f, energy, and statistical weight.

x21_tot is the Lya secondary excitation rate, which is dominated by 50 - 100 eV non-thermal electrons, as in Spitzer & Tomasko.

Ryan and I worked on this at the IoA - we had found a paper in the physics literature, from the 1970's, which gave a simple scaling. The correct scaling should use the chianti line parameters relative to the HI Lya parameters.

we use this in other places - see the same term at mole_h2.cpp:1750 - for electronic transitions in H2. We stored the ratio in the collision strength variable since there are no known collision rates for H2 electronic transitions. This is already a design error - we should have made yet another variable, the suprathermal scaling factor. The ratio is saved one time at startup at mole_h2_create.cpp:774. we should probably define a new variable to save this, then do a one-time caching for the species as we already do for H2.

But the scaling does not agree. The H2 scaling has different dependencies from the line Robin pasted above. '

Change History (3)

comment:1 Changed 7 years ago by rjrw

Description: modified (diff)
Milestone: C12 branchC10 branch

Does this need to be fixed if Lamda & parts of Chianti are in the C10 release?

comment:2 Changed 7 years ago by Ryan Porter

Description: modified (diff)
Resolution: fixed
Status: newclosed

Fixed in r4428.

comment:3 Changed 5 years ago by Ryan Porter

Milestone: C10 branchc13 release

Milestone C10 branch deleted

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