[Aavso-sid-list] VLF and Decametric SID comparisons

[Thomas Ashcraft]

( I am forwarding this message to the SID list from Jerry Fishman)  -  
Thomas Ashcraft




Thomas-

Apparently my message to you and to others on the AAVSO SID server list 
did not get forwarded, probably because I am a valid receiver but not 
sender?

Could you please forward my note below to the membership?

Thanks,

Jerry Fishman

NASA-Marshall Space Flight Center

Huntsville, Alabama

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Regarding Thomas Ashcraft's question on the correlation between 
decametric solar radiation and VLF observations:

 

The decametric through cm solar flare radiation is produced by a process 
known as synchrotron radiation from high-energy electrons accelerated at 
the sun during a flare and radiating in the magnetic field in the flare 
region.  The VLF disturbances, on the other hand, are a result of X-rays 
from a flare temporarily depressing the lowest regions of the Earth's 
ionosphere.  These X-rays are produced at the sun by a different 
process, thermal bremsstrahlung radiation from high-energy electrons, as 
these electrons interact with the material (plasma) near the flare.

Since both types of radiation are initiated by the same electron 
populations, they are highly correlated.

However, there are important, subtitle differences (due to the quite 
different emission processes), that solar scientists have used to infer 
the magnetic field, electron spectrum and other physical characteristics 
of the flare region.  They usually use GHz microwave data and direct 
solar x-ray observations from a number of satellites for their data 
comparisons.

If you are interested in pursuing the subject, most of the scientific 
literature on these comparisons, as well as solar flares in general, is 
contained in the two journals: "Solar Physics" and "The Astrophysical 
Journal".

 

Jerry Fishman

NASA-Marshall Space Flight Center

Huntsville, Alabama

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