Topband: Recent Conditions

[BobK8IA at aol.com]

In a message dated 12/5/07 2:55:16 A.M. US Mountain Standard Time,  
nhp at ieee.org writes:

At 01:29  05/12/2007, you wrote:



>W2PM Responds:
>...  BUT
>how is the SFI still in the low 70's when there have been no  sunspots?
>I recall the last minima has SFIs in the low 50's, maybe  lower.


I'm not sure that 50's are valid numbers for the SFI, at  least for 
the values we see reported on a daily basis; I don't recall  seeing it 
lower than 65.  I'm sure that others on the list could  clarify further.


The SFI hardly got down into the high  60's during the the last 
solar minimum, 1996-1997; see  
http://www.drao-ofr.hia-iha.nrc-cnrc.gc.ca/icarus/www/daily.html for  
daily values

This past summer, we had a number of runs of mid to  high 60's for 
SFI, so it seems that this minimum might have been a little  quieter 
than the last one.

As for conditions seeming poorer as one  approaches midwinter in spite 
of low solar and geomagnetic indices, medium  wave DXers (listeners) 
have noticed this for years, but no-one seems to  have come up with an 
explanation.   At one time, it was  suggested that stratwarms were 
associated with periods of higher  absorption in the winter months, 
but K9LA was not able to find any  correlation when he looked at it.

best  wishes,

Nick
VE7DXR



****************************************************************************
Nick  Hall-Patch
Victoria,  B.C.
Canada

****************************************************************************  

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Nick et al;
 
>From VOACAP site:
 
 
SFI =  63.7 + 0.727 SSN + 8.95x10-4  SSN2 
where SSN  refers to the F10.7-derived SSN using the Penticton Radio 
Observatory noon  

Thus, the  lowest mathematical SFI is 63.7. 

73, Bob  K8IA




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