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

Wed Jul 1 11:54:41 EDT 2020

Phil

Thanks. I'd not yet looked up PMSE/PMWE, but it's on my list. In my world
(this week; nucleation microphysics is a variable target) we don't think
there's much free water involved, but that molecular water, upon
nucleation, immediately freezes and accretion begins. This shouldn't affect
the dusty plasma theory, and should actually enhance the charge state
argument (ice crystal charge tends to be more intense than water droplet
charge due to size and shape). This doesn't mean regular droplets don't
have charge, shape maintenance is an electrostatic phenomenon especially in
a 1G field.

gerry

On Wed, Jul 1, 2020 at 9:35 AM Phil Erickson <phil.erickson at gmail.com>
wrote:

> Hi Gerry,
>
>   FYI, the PMSE/PMWE mechanisms inherently rely on highly charged
> nucleated water drops / dusty plasmas, because then they are directly
> affected by electrodynamics in addition to tides / wind patterns.  So yes,
> a charge density increase would be definitely expected IF the dust gets
> there and IF it's the right size, as you already mentioned.  (Comparing the
> dust size from below to that deposited by micrometeoroids would be
> illustrative if I had time, which alas I don't at the moment.)
>
> 73
> Phil
>
> On Wed, Jul 1, 2020 at 10:13 AM 'Gerry Creager - NOAA Affiliate' via
> HamSCI <hamsci at googlegroups.com> wrote:
>
>> I'll do some looking. I've been bogged down trying to spend end of year
>> money. That'll end today whether I'm successful in spending it or not!
>>
>> Right off the top, I can think of two things. First, ice nucleation (or
>> water droplet nucleation; I subscribe to the former, at least today)
>> generally requires relatively sparse and extremely fine particles. If a
>> significant portion of the Saharan dust were to erupt into the stratosphere
>> rather than increasing nucleation I'd expect it to virtually sweep the
>> region clear of molecular water as the dust is hydrophilic. On the other
>> hand, if a significant eruption of dust into the stratosphere were
>> observed, since it'd be relatively unimpeded by the sparse water, I'd also
>> expect to see an increase in charge density. The dipole moment of different
>> size dust particles is pretty significant and charge differential would see
>> some significant charge potential.
>>
>> This is right off the top of my head, and before the coffee has really
>> circulated; I'll go check for real references.
>>
>> gerry
>>
>> On Wed, Jul 1, 2020 at 9:02 AM Phil Erickson <phil.erickson at gmail.com>
>> wrote:
>>
>>> 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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>>>>> .
>>>>>
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>>>> .
>>>>
>>>
>>>
>>> --
>>> ----
>>> Phil Erickson
>>> phil.erickson at gmail.com
>>>
>>> --
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>>> .
>>>
>>
>>
>> --
>> Gerry Creager
>> NSSL/CIMMS
>> (C) 979.229.5301 <--- NOTE THAT MY OFFICE NUMBER HAS CHANGED
>> ++++++++++++++++++++++
>> *The way to get started is to quit talking and begin doing.*
>>
>> *   Walt Disney*
>>
>> --
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>> .
>>
>
>
> --
> ----
> Phil Erickson
> phil.erickson at gmail.com
>
> --
> Please follow the HamSCI Community Participation Guidelines at
> http://hamsci.org/hamsci-community-participation-guidelines.
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> .
>

-- 
Gerry Creager
NSSL/CIMMS
(C) 979.229.5301 <--- NOTE THAT MY OFFICE NUMBER HAS CHANGED
++++++++++++++++++++++
*The way to get started is to quit talking and begin doing.*

*   Walt Disney*
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