Hi Arthur,
Persistent high speed solar wind speed contains significantly more
kinetic energy than transient high density solar wind.
High density solar wind is a transient event of solar wind origin often
occurring during the rising phase of the solar cycle as fast coronal
mass ejections interact with the much slower background solar wind ,
causing compression regions in the solar wind.
Low density solar wind is a more persistent event of solar origin,
typically caused by coronal hole high speed streams during the declining
and solar minimum phases of the solar cycle. Low density solar wind
can recur during one or more 27 day solar rotations and can
have persistent extremely low density during solar minimum.
Solar flares, coronal mass ejections and persistent southward oriented
interplanetary magnetic field (IMF) often cause moderately to severely
degraded propagation while transient high density solar wind usually
causes only unsettled to active geomagnetic disturbances unless it
coincides with persistent southward oriented IMF.
73
Frank
W3LPL
----- Original Message -----
From: "Arthur Delibert" <radio75a3@msn.com>
To: donovanf@erols.com, topband@contesting.com
Sent: Saturday, November 7, 2020 2:31:36 AM
Subject: Re: Topband: Solar Flux Question
Thanks. Very helpful. One question: The attachment says: " The coloured dot
within the black square, is an indicator of solar wind density, and is yellow
when density exceeds 10 particles per cubic cm, red when density exceeds 15
particles per cubic cm, otherwise green." It wasn't clear to me whether the
solar wind density has any significance for propagation. Do you know?
My observation of NOAA data has been that when solar wind speed is down,
particle density increases and vice-versa. So I don't see how a decline in
solar wind speed, accompanied by a proportionate increase in particle density,
would necessarily lead to a decrease of disturbances, since kinetic energy
would remain the same (although momentum would decrease). Maybe the increase in
density isn't actually proportional to the decrease in wind speed?
Thanks.
KB3FJO
From: Topband <topband-bounces+radio75a3=msn.com@contesting.com> on behalf of
donovanf@erols.com <donovanf@erols.com>
Sent: Friday, November 6, 2020 5:58 PM
To: topband@contesting.com <topband@contesting.com>
Subject: Re: Topband: Solar Flux Question
Hello Henk,
Most of the kinetic energy released from solar wind into the Earth's
magnetosphere and then its ionosphere is in contained in the velocity
of the solar wind. Much less energy is in the extreme high temperature
of the solar wind's magnetized charged particles and in its embedded
interplanetary magnetic field.
Fortunately the Earth's magnetic field shields the magnetosphere and
ionosphere from vast majority of the solar wind's kinetic energy
unless the Bz component of interplanetary magnetic field vector is
oriented southward, opposite to the Earth's magnetic field.
The worst case combination of conditions for disturbed propagation is
500 km/second or greater solar wind velocity and southward oriented
IMF with magnetic field intensity greater than 10 nanoTeslas.
This web site proves a basic explanation of the relationships between disturbed
propagation conditions and the solar wind's speed, density, and the magnetic
field orientation of the its embedded interplanetary magnetic field.
www.sws.bom.gov.au/Solar/1/4
73
Frank
W3LPL
----- Original Message -----
From: "Henk Remijn PA5KT via Topband" <topband@contesting.com>
To: topband@contesting.com
Sent: Friday, November 6, 2020 9:54:51 PM
Subject: Re: Topband: Solar Flux Question
This one has a larger span and you can see the 27 day periods.
https://www.solen.info/solar/images/swind.png
73 Henk
Op 6-11-2020 om 22:52 schreef Henk Remijn PA5KT via Topband:
> My experience is that 160 conditions are also influenced by the solar
> wind.
>
> https://solen.info/solar/indices.html .
>
> This graph shows SFI and solar wind. When solar winds are up to 300
> km/s the conditions are usually good on 160.
>
> This happened in the beginning of october. Conditions in the week
> before the Stew Perry TBDC were good, During the contest it was less.
>
> Due to the rotation of the Sun in approx 27 days you can a bit predict
> if it is useful to be on the band.
>
> Other might have other experiences.
>
> 73 Henk PA5KT
>
>
> Op 6-11-2020 om 21:55 schreef Artek Manuals:
>> Bill
>>
>> Last night ON 160 I worked 32 European and SA stations with the
>> reported SFI of 88. earlier in the week with a similar SFI number I
>> heard nothing from EU on 160. Conclusion : At these levels SFI is not
>> the factor
>>
>> Conditions on 15 and 12 have been for the last week or so been great
>> . Lots of long path on 40 through 15 depending on the time of day &
>> band. certainly far better than a year ago at SFI of 68-72 on the
>> upper bands, on 160 and 80 hasn't been much of factor so far
>>
>> DAVE
>> nr1dx
>>
>>
>> On 11/6/2020 3:23 PM, Bill Stewart wrote:
>>> Per WWV, the solar flux is at 91. What, if any, affect does this
>>> have on propagation in HF or other
>>> frequency bands....and of course 160 meters. I have seen these
>>> geophysical numbers often, but
>>> never really understood what they meant. The flux has been running
>>> in the high 60s/low 70s until
>>> a few weeks ago when I saw it in the 80s.
>>> Tnx de Bill K4JYS
>>> _________________
>>> Searchable Archives: http://www.contesting.com/_topband - Topband
>>> Reflector
>>
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> Searchable Archives: http://www.contesting.com/_topband - Topband
> Reflector
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