[OpenMadrigal-developers] F10.7 Multiday average proposal

[John Holt]

Phil's suggestion seems reasonable. In the context of a model, the
definition of F10.7bar as a centered average is an absurdity,
obviously. In the "old" days we always used the 81 days ending with the
day of interest, but at some point it apparently became more common to
forget causality and use a centered average (I have seen 27 days, 54
days, 81 days 90 days and one year) and a variety of filter functions
causal and not.  Unfortunately, in my view, causal filters fell out of
favor.  Had they not, we would not have had this problem and would have
been consistent with the laws of physics as well, which is no small
thing. I suspect, by the way, that using the 81 days ending with the
day of interest will tend to give a somewhat better prediction than
using a centered average, even though the model was computed using a
centered average.

John

________________________________________________________________________
|                                                                      |
| John M. Holt                         tel:   781-981-5625             |
| Principal Research Scientist         fax:   781-981-5766             |
| MIT Haystack Observatory             email: jmh at haystack.mit.edu     |
| Route 40                             WWW:   http://www.haystack.edu/ |
| Westford, MA 01886                                                   |
| USA                                                                  |
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> Date: Fri, 20 Oct 2006 11:53:15 -0400
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> Phil Erickson has suggested we modify out definition of the F10.7 
> Multiday average (FBAR).  Right now this is an 81 day average, where the 
> 81 days the center day, 40 days in the past, and 40 days in the future.  
> The problem with this definition is that this parameter is never 
> available for any day less than 40 days in the past.  For example, since 
> MSIS uses FBAR as an input, this means that MSIS also cannot be run for 
> any day less than 40 days in the past. 
> 
> Phil has suggested that for any day less than 40 days in the past, we 
> calculate FBAR as an average over the most recent 81 days.  From the 
> Madrigal point-of-view, this means that every time we reload geophysical 
> data, the FBAR values for the latest 40 days might change slightly.  At 
> present, FBAR is not loaded into Madrigal for days less than 40 days ago.
> 
> We would document this FBAR definition on the Madrigal help pages.  Any 
> thoughts?
> 
> Bill Rideout
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