[TangerineSDR] [HamSCI] The University of Scranton ARC now W3USR

[Phil Erickson]

Hi Ward,

  I don't know about the dust plume access to the lower stratosphere -
haven't gone to enough AMS meetings and my copy of Holton's The Dynamic
Atmosphere is inaccessible at the moment.  I suppose if the dust accessed
the mesopause - coldest place in the atmosphere at 140 K - it could provide
seeds for large ice crystal nucleation that would cause enhanced VHF
scatter (look up Polar Mesospheric Summer Echoes / Polar Mesospheric Winter
Echoes; lots of studies with both low and high power radars showing 40+ dB
enhanced echoes due to Bragg scatter from highly reflective coherent
structures at few meter scales).  This sort of dusty ice crystal formation
has been measured with sounding rocket flights, and normally is thought to
be triggered by meteoric dust input.

  However, the trouble is that PMSE/PMWE occurs at lower altitudes - 80 to
90 km - and is distinct from sporadic E up at 110 km or so.  Connections
between the two are not a settled matter at all.  This Kirkwood and Nilssen
(2000) paper extensively reviews information on PMSE/PMWE at high latitudes
and sporadic E at mid-latitudes.  In essence, these two have similar
seasonal behavior, but are likely driven by different things (tides or high
latitude electric fields):

"Observations of high-latitude sporadic-E (Es) layers and theories of their
formation are reviewed. The layers are found to be composed of metallic
ions, they are at times formed by tidal wind shear, and they are more
common in summer than in winter. All of these properties are common to Es
layers at mid-latitudes. However, the high-latitude layers are rather often
formed, modified or transported by the action of magnetospheric electric
fields. Taking into account the action of both tides and electric fields
leads to an understanding of the daily variation of Es occurrence, the
daily variation of Es heights and the occasional appearance of upward
migrating Es layers. Correlations between Es and neutral metallic layers at
low altitudes can be explained by neutralisation of the metallic ions in
the Es layers, but joint Es and neutral layers at higher altitudes are
still unexplained."

Kirkwood, S., Nilsson, H. High-latitude Sporadic-E and other Thin Layers –
the Role of Magnetospheric Electric Fields. Space Science Reviews 91,
579–613 (2000).
https://doi.org/10.1023/A:1005241931650

  Gerry might know about stratosphere / mesosphere circulation cells for
the original dust question and could comment more.  I'm not going to
comment though on the causal chain needed to connect those effects all the
way to sporadic E.

73
Phil

On Wed, Jul 1, 2020 at 9:24 AM Ward Silver <hwardsil at gmail.com> wrote:

> Test drive in the IARU HF Championship on the 11th?  Great opportunity to
> observe summer-time, world-wide HF propagation.  Only partially
> tongue-in-cheek since there are few world-wide contests in the Northern
> Hemisphere summer.
>
> General question for the Real Scientists inhabiting this list - although
> most of the Sahara dust plume is in the lower troposphere, how much makes
> into the lower stratosphere and could that be affecting sporadic E
> propagation?  This summer has simply been extraordinary (even if I'm not on
> the East Coast and can't work Europe on 6 meters like falling out of bed)
> and I'm wondering what kind of events could contribute to that?
>
> 73, Ward N0AX
>
> On Wed, Jul 1, 2020 at 8:20 AM Dr. Nathaniel A. Frissell Ph.D. <
> nathaniel.frissell at scranton.edu> wrote:
>
>> Hi, everyone!
>>
>>
>>
>> A little bit of a personal note, but I am happy to announce that The
>> University of Scranton Amateur Radio Club is now officially W3USR!
>>
>>
>>
>> See you on the air!
>>
>>
>>
>> 73 de Nathaniel W2NAF
>>
>>
>>
>>
>>
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-- 
----
Phil Erickson
phil.erickson at gmail.com
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