In article , "starman"
wrote:

Great report. Are these events more likely to happen during the decline
of a solar cycle?

Yes. In the declining part of the cycle flares are generally less frequent
but more energetic.

--
| John Doty "You can't confuse me, that's my job."
| Home:
| Work:

Folks:

What an exciting time for radio enthusiasts! This past weekend's media
hype about a major geomagnetic and solar storm was unfortunate and
unwarranted. But, today, solar events have occurred that has the whole
propagation science community buzzing.

I just finished talking with Mike Weaver from the National Ocean and
Atmospheric Administration Space and Environment Center (NOAA SEC). He is
the Solar Forecaster that has been on duty for the last four days. Last
week, I also spoke with Bill Murtagh, who is beginning a shift to cover the
next few days. Our discussion focused on today's events, and what will
transpire over the next few days. The following is my perspective of
current solar and geophysical conditions and the forecast for the next 48
hours or so.

On 28 October 2003 UTC, an X17.2-class flare from NOAA Region 486 occurred
at 0951Z, peaking at 1110Z. This caused severe radio blackouts (R4 is the
reported level, see http://www.sec.noaa.gov/NOAAscales/ for details on the
scales used) on the sunlit side of the Earth (which would have been
morning, on the eastern coast of North America). It also created an S3
(strong) solar radiation storm. Associated with this flare are a proton
event and a full-halo coronal mass ejection (CME). This flare is the
second most intense of the current solar cycle. It is not historical. We
expect several of these large flares during any given solar cycle.

The proton event started at about 1330Z, and has exceeded all threshold
levels, causing a Polar Cap Absorption event (PCA). It is expected that
this proton event will be prolonged and last for the next 36 hours, to some
degree. This will cause transpolar path degradation (don't expect any DX
over the poles nor over any high-latitude paths) for the next few days.

The CME was a full-halo, and is directed squarely at the Earth. Based on
the speed and recordings, so far, Mike expects it to impact the
Magnetosphere at about 1500Z 29 October 2003. When it hits, the shock
alone will produce at least G3-level geomagnetic activity. This would
translate to a Kp index of about 8, even if the IMF (Interplanetary
Magnetic Field) is not pointed south when the CME arrives. After the
initial shock wave, if the Bz is negative, indicating that the IMF has
turned south, the Kp index will remain high, with a possible Kp of 9 during
the passage of the CME. This will cause between a level G4 and a G5
(severe to extreme) geomagnetic storm. This will severely degrade HF and
MW radio communications (while possibly enhancing VHF/UHF propagation).

The timing of the arrival of the CME shock will occur after sunrise for
those in North America. Therefore, I do not expect to see any Aurora
tonight, local time on 28 October 2003. However, I do expect radio auroral
mode propagation during the day of 29 October 2003, and continuing into the
night of the same day. If the IMF remains negative, there is a strong
chance of a prolonged severe geomagnetic storm, with associated Aurora
viewable as far south as southern California and Florida.

Continued radio blackouts are likely from new flare activity. As I write
this, we are in the decline of a new M-class flare. There are eight main
regions on the visible solar disk, three of which are actively producing
flares. One of these is about to rotate out of view. One of the new
regions just rotating into view is active, and has already produced some
M-class flares.

Overall conditions:

In the next 12 to 20 hours, expect great conditions on frequencies above 15
MHz, while in general, all HF will have periods of radio blackouts during
the flare events, if they occur. (And, they will occur). Sometime around
1500Z, tomorrow (29 Oct 2003), expect all HF communications to become
severely degraded with the arrival of the CME shock, and for a severe to
extreme geomagnetic storm to commence and last for a prolonged period.
S3-level (severe) solar radiation storm conditions will last for the next
24 to 48 hours.

I expect a lot more activity during this week, but I don't view this as a
"third" peak in this current solar cycle, number 23. Several past cycles
have had such bursts during the decline of those cycles.

I'll post more about this soon.


73 de Tomas, NW7US (AAR0JA/AAM0EWA)
--
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Tomas wrote:

Folks:

What an exciting time for radio enthusiasts! This past weekend's media
hype about a major geomagnetic and solar storm was unfortunate and
unwarranted. But, today, solar events have occurred that has the whole
propagation science community buzzing.

I just finished talking with Mike Weaver from the National Ocean and
Atmospheric Administration Space and Environment Center (NOAA SEC). He is
the Solar Forecaster that has been on duty for the last four days. Last
week, I also spoke with Bill Murtagh, who is beginning a shift to cover the
next few days. Our discussion focused on today's events, and what will
transpire over the next few days. The following is my perspective of
current solar and geophysical conditions and the forecast for the next 48
hours or so.

On 28 October 2003 UTC, an X17.2-class flare from NOAA Region 486 occurred
at 0951Z, peaking at 1110Z. This caused severe radio blackouts (R4 is the
reported level, see http://www.sec.noaa.gov/NOAAscales/ for details on the
scales used) on the sunlit side of the Earth (which would have been
morning, on the eastern coast of North America). It also created an S3
(strong) solar radiation storm. Associated with this flare are a proton
event and a full-halo coronal mass ejection (CME). This flare is the
second most intense of the current solar cycle. It is not historical. We
expect several of these large flares during any given solar cycle.

The proton event started at about 1330Z, and has exceeded all threshold
levels, causing a Polar Cap Absorption event (PCA). It is expected that
this proton event will be prolonged and last for the next 36 hours, to some
degree. This will cause transpolar path degradation (don't expect any DX
over the poles nor over any high-latitude paths) for the next few days.

The CME was a full-halo, and is directed squarely at the Earth. Based on
the speed and recordings, so far, Mike expects it to impact the
Magnetosphere at about 1500Z 29 October 2003. When it hits, the shock
alone will produce at least G3-level geomagnetic activity. This would
translate to a Kp index of about 8, even if the IMF (Interplanetary
Magnetic Field) is not pointed south when the CME arrives. After the
initial shock wave, if the Bz is negative, indicating that the IMF has
turned south, the Kp index will remain high, with a possible Kp of 9 during
the passage of the CME. This will cause between a level G4 and a G5
(severe to extreme) geomagnetic storm. This will severely degrade HF and
MW radio communications (while possibly enhancing VHF/UHF propagation).

The timing of the arrival of the CME shock will occur after sunrise for
those in North America. Therefore, I do not expect to see any Aurora
tonight, local time on 28 October 2003. However, I do expect radio auroral
mode propagation during the day of 29 October 2003, and continuing into the
night of the same day. If the IMF remains negative, there is a strong
chance of a prolonged severe geomagnetic storm, with associated Aurora
viewable as far south as southern California and Florida.

Continued radio blackouts are likely from new flare activity. As I write
this, we are in the decline of a new M-class flare. There are eight main
regions on the visible solar disk, three of which are actively producing
flares. One of these is about to rotate out of view. One of the new
regions just rotating into view is active, and has already produced some
M-class flares.

Overall conditions:

In the next 12 to 20 hours, expect great conditions on frequencies above 15
MHz, while in general, all HF will have periods of radio blackouts during
the flare events, if they occur. (And, they will occur). Sometime around
1500Z, tomorrow (29 Oct 2003), expect all HF communications to become
severely degraded with the arrival of the CME shock, and for a severe to
extreme geomagnetic storm to commence and last for a prolonged period.
S3-level (severe) solar radiation storm conditions will last for the next
24 to 48 hours.

I expect a lot more activity during this week, but I don't view this as a
"third" peak in this current solar cycle, number 23. Several past cycles
have had such bursts during the decline of those cycles.

I'll post more about this soon.

73 de Tomas, NW7US (AAR0JA/AAM0EWA)

Great report. Are these events more likely to happen during the decline
of a solar cycle?


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John Doty wrote:

In article , "starman"
wrote:

Great report. Are these events more likely to happen during the decline
of a solar cycle?

Yes. In the declining part of the cycle flares are generally less frequent
but more energetic.

Is that because the magnetic field lines become more 'twisted' (for lack
of a better word) during the declining phase of the cycle?


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In article , "starman"
wrote:

John Doty wrote:

In article , "starman"
wrote:

Great report. Are these events more likely to happen during the
decline of a solar cycle?

Yes. In the declining part of the cycle flares are generally less
frequent but more energetic.

Is that because the magnetic field lines become more 'twisted' (for lack
of a better word) during the declining phase of the cycle?
---

Other way around. The field is less tangled, so there are fewer
opportunities for reconnection. However, this also means that if
reconnection occurs, it can rearrange the field on a large scale,
releasing a lot of energy.

--
John Doty "You can't confuse me, that's my job."
Home:
Work:

John Doty wrote:

In article , "starman"
wrote:

John Doty wrote:

In article , "starman"
wrote:

Great report. Are these events more likely to happen during the
decline of a solar cycle?

Yes. In the declining part of the cycle flares are generally less
frequent but more energetic.

Is that because the magnetic field lines become more 'twisted' (for lack
of a better word) during the declining phase of the cycle?
---

Other way around. The field is less tangled, so there are fewer
opportunities for reconnection. However, this also means that if
reconnection occurs, it can rearrange the field on a large scale,
releasing a lot of energy.

--
John Doty

I thought the solar cycle is primarily driven by the effect of the sun's
differential rotation on it's magnetic field. If this is correct, how
does it relate to what you say (above) about the field lines becoming
less 'twisted' during the declining phase of the cycle?


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-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

In article , "starman"
wrote:

I thought the solar cycle is primarily driven by the effect of the sun's
differential rotation on it's magnetic field. If this is correct, how
does it relate to what you say (above) about the field lines becoming
less 'twisted' during the declining phase of the cycle?

Differential rotation winds the field up. When the fields get really wound
up and tangled, reconnection becomes more frequent, breaking long tangled
field lines into shorter loops. Solar flares are the result of
reconnection events. If you see them, the field is untangling.

--
| John Doty "You can't confuse me, that's my job."
| Home:
| Work:

John Doty wrote:
Differential rotation winds the field up. When the fields get really wound
up and tangled, reconnection becomes more frequent, breaking long tangled
field lines into shorter loops. Solar flares are the result of
reconnection events. If you see them, the field is untangling.

Reconnection comes from resistance, which produces heating. Without dissipation
charged particles cannot cross field lines (actually reversing cause and effect
here; the field lines take into account charged particles not crossing them; their
motion is a current. The prohibition of crossing field lines disappears if the
particle velocities can be interrupted by something other than electrical effects,
like collisions. This produces heating. The sharp turns in the field lines then
can ``drag'' through the particles and become less sharp.)
--
Ron Hardin


On the internet, nobody knows you're a jerk.

In article , "Ron Hardin"
wrote:

John Doty wrote:
Differential rotation winds the field up. When the fields get really
wound up and tangled, reconnection becomes more frequent, breaking long
tangled field lines into shorter loops. Solar flares are the result of
reconnection events. If you see them, the field is untangling.

Reconnection comes from resistance, which produces heating.

That's the magnetohydrodynamic story. The trouble is that MHD is a poor
model for real plasmas. Also, the resistivity of astrophysical plasmas is
much too low to produce the reconnection phenomena we see.

Without
dissipation charged particles cannot cross field lines (actually
reversing cause and effect here; the field lines take into account
charged particles not crossing them; their motion is a current.

On the scale of the cyclotron radius they cross field lines all the time.
In a uniform magnetic field, with no electric field, the motion is helical
with the axis parallel to the field, so a particle must stay *near* a
particular field line. This is the sense in which "particles don't cross
field lines". However, if the field isn't uniform on the scale of the
cyclotron radius a particle can readily move away from a particular field
line.

The
prohibition of crossing field lines disappears if the particle
velocities can be interrupted by something other than electrical
effects, like collisions. This produces heating.

In astrophysical plasmas particle collisions are generally too infrequent
to have an effect. Wave-particle interactions are much more important.
These tend not to be very effective at entropy generation, but they can
exchange free energy between the particles and waves in the plasma.
Laser-like phenomena can occur: the presence of waves stimulates the
emission of more wave energy. Wave amplitudes can grow until the helical
motion of the particles is severely disturbed. The macroscopic effect is
similar to collisions (look up "Bohm diffusion" in your favorite plasma
physics text). There's not as much heat as collisions would produce,
however: the energy tends to wind up in waves and accelerated particles.

--
| John Doty "You can't confuse me, that's my job."
| Home:
| Work: