(meteorobs) Significant fireball over New Mexico - Sep 21, 2010 2101 MDT

[Thomas Ashcraft]

  On 9/22/10 9:07 AM, Matthew Earnshaw wrote:
>> Forward scatter:  Interestingly, large slow fireballs often do not make
>> strong radio scatter reflections. This fireball can be heard at its
>> onset and throughout its path but you will have to listen closely as it
>> is subtle, but clearly evident.
> Hm, interesting. Why should this be? Is it that slow moving objects just don't have the same ionizing power as fast meteoroids or is it more subtle than that?
>
> Regards,
> Matthew Earnshaw
>
Hi Matthew,

I was able to find some previously posted information on this complex 
subject of  "radio stealth fireballs" so here you go:  -  Thomas

The following was excerpted from :
http://www.amsmeteors.org/radio/ams203.txt

::::::::::

Fast meteors have a tendency to ionize higher than the optimum
altitude band, causing the forward-scatter system to discriminate
against the lower magnitude, fast meteors.  Only the brighter fast
meteors will penetrate deep enough into the atmosphere to get below
the "height ceiling" and cause reflections.
     On the other hand, slow meteors have a tendency to ionize
below the optimum altitude band, causing the system to discriminate
against the higher magnitude, slow meteors.  Only the fainter slow
meteors will ionize fully in the correct region to cause full
reflections.  Bright, slow meteors may begin their ionization in
the proper region, but then pass under the "height floor," causing
only a partial, low duration reflection.

******* Along these same lines, very bright, slow fireballs which have
the potential for dropping meteorites will generally also not cause
noticeable reflections.  These fireballs often do not produce
visible light and ionization until they are below about 70 km,
making them rather "stealth" to radio detection. *********

     Meteors of medium velocities tend to have the best forward
scatter capability throughout their magnitude range.