[K6BW] Continuing Solar Flare discussion - purloined from QRP-L

[Bill Smith]

Gang,
Below is today's solar activity report from NOAA regarding yesterday's X3.
It is updated daily towards the end of the UTC day and found at:
http://www.sec.noaa.gov/today.html

I am adding commentary to help explain "how to read" the reports I hope some
of you find helpful.

>Joint USAF/NOAA Report of Solar and Geophysical Activity
>SDF Number 347 Issued at 2200Z on 13 Dec 2006

>IA.  Analysis of Solar Active Regions and Activity from  12/2100Z
>to 13/2100Z:  Solar activity was high. Region 930 (S05W33) produced
>an X3.4/4B flare with a 44000 sfu 10 cm radio burst at 13/0240 UTC.

Normally, a solar flare causes radio emissions to begin in the 300-1000MHz
range, then sweeps downward into HF.  On especially strong flares, emissions
can occur higher, at 10cm or 2880MHz where the Canadian Pentictin
Observatory measures the hourly solar flux.  The solar flux is the
normalized energy output of the sun - thus, when a flare causes radio
emissions at that frequency, it contaminates the daily flux reading.
Pentictin removes the flare effect, such that the daily solar flux does NOT
include the radio energy due to the flare.

The 44000 sfu (solar flux units) is a large value and likely highly
contaminated the flux readings.  This statement is basically telling you the
flare was a very energetic event to extend all the way to 10cm/2880 MHz, and
informing you the daily solar flux reading is the "best guestimate" after
removing the effects of the solar flare.

What's important for QRPers to understand is this extra dose of solar flux,
while meaningless to most people, means the E and F layers also got an extra
dose to make them more reflective and elevated the MUF.  Unfortunately,
there are no "numbers" to tell you this, since the effect is removed from
the daily solar flux readings.  So, just remember that when a fairly large
solar flare occurs, an hour or so afterwards until sundown is a good time to
expect an improvement in the higher bands due to the MUF and E/F
reflectivity.

Normally, this enhancement ends when the sun goes down.  The higher bands
remained in good shape today (unexpected 10M openings) due to the
persistence of the energetic proton event.

>Type II (1534 km/s) and Type IV radio sweeps were associated with
>this event,

As the coronal mass ejection (CME) is blown away from the surface of the
sun, it punches through the magnetic field lines of the disturbance causing
radio bursts.  Very near to the sun, these bursts will be in the above
mentioned 300-1000MHz region.  As the shockwave travels farther away from
the sun, the radio bursts occur at lower and lower frequencies (due to the
electron density of the sun's atmosphere getting less).  These radio bursts,
starting at high frequencies and "sweeping" to lower frequencies are the
Type II bursts.

Of particular importance is by measuring the time the bursts occur at one
frequency vs. a lower frequency, one can calculate the velocity of the
shockwave.  In this case, the Type II sweeps indicated the CME was leaving
the sun at 1534 km/s.  It is interesting to note that with all the neat
fancy satellites and ground based solar instruments, the shockwave is still
measured by following the radio bursts from VHF to HF at various
observatories.

Once the CME is far out into space, the SOHO satellite can often see the
movement of the plasma wave, and hence calculate the velocity of the CME.
Unfortunately, these SOHO instruments are currently not operational to do
this.  So, good old radio is the only indication that this CME is a fairly
fast one.

> as well as a fast moving CME (estimated plane of sky speed of 1500 km/s).

To be honest, with SOHO down, I don't know how they estimated the CME unless
through mathmatical manipulation of the radio Type II sweep (like the 85%
rule I used last night to estimate arrival time).  The "sky speed" means the
speed of the CME once it has escaped the sun's influence and traveling along
the plane of the solar wind (or, the ecliptic).

> Region 930 has a strong delta configuration in the southern penumbral area
> of the leader spot.

Large sun spots develop magnetic field lines between them called a beta
configuration.  When these magnetic field lines get very strong and complex,
they are called a delta configuration.  The majority of major flares occur
from a delta region, though not all delta groups produce flares.  This is
basically telling you the delta group in region 0930 still has the
capability of producing another major flare.  NOAA's prediction below of a
60% chance of an M-class flare, and a 35% chance for another X is simply
based on this "strong delta configuration" that still remains.  Therefore,
the fun may not be over yet.

The penumbra are the small hair-like structures that extend outward from a
sunspot.  One belief is the darker "hairs" are painting a picture of the
magnetic field lines around that particular sunspot.  Sunspots in a delta
group, with strong magnetic fields, tend to have a pronounced penumbra.

>IB.  Solar Activity Forecast:  Solar activity is expected to reach
>moderate to high levels. Isolated X-class flares are possible from
>Region 930.

Again, just based on the persistence of the strong magnetic delta group.

>IIA.  Geophysical Activity Summary 12/2100Z to 13/2100Z:
>The geomagnetic field was at quiet to active levels for the last 24
>hours. A greater than 100 MeV proton event started at 13/0245 UTC,
>and reached a maximum of 88.7 pfu at 13/0525 UTC.

The proton event is due to the X-class flare.  The higher the energy level
(MeV), the higher the ionizing radiation.  PFU=proton flux units, a measure
of the ionizing radiation due to the protons.

>A greater than 10 MeV proton event started at 13/0250 UTC, and reached a
>maximum of 698 pfu at 13/0925 UTC.

Ditto for the 10MeV protons (less ionization than the 100MeV)

>The greater than 2 MeV electron flux at geosynchronous orbit reached high
>levels again today.

This is a warning to those who operate satellites that the ELECTRON flux
(not proton) is high, which can cause various problems to satellites.  One
effect is when the stream of electrons flows past the satellite, it can
cause a large voltage differential to occur from one side of the satellite
to the other (usually only a few feet).  This can cause damage to the
internal electronics.  Some satellite operators will bring in their solar
arrays, initiate an intentional spin, etc. to reduce the hazards.

>IIB.  Geophysical Activity Forecast:  The geomagnetic field is
>expected to reach major to severe storm levels. Activity from the
>CME observed early on 13 December is expected to impact the
>geomagnetic field by mid to late UTC on day 1 (14 December) of the
>forecast period.

In last night's post, a purely mathematical approach based on the Type II
sweep speed was used to predict impact of the CME with Earth about 1000UTC
on 14DEC (early morning EST).  NOAA's prediction seems to be about two hours
later than this.  It is comforting to know they, too, are now predicting a
severe geomagnetic storm.

The point of that exercise, of course, was to demonstrate the methodology
QRPers can use to estimate when a geomagnetic storm may occur following a
major solar flare when you don't have your own personal SOHO satellite.  Of
course with this flare, neither does NOAA!

Sometime tomorrow morning, we'll find out who's right ...
NOAA or the QRPers :-)  (tounge in cheek)

>Major to severe storm conditions are expected to continue early into 15
>December.

This is based primarily on the fact that a severe geomagnetic storm usually
persists from 18-24 hours.

>The greater than 100 MeV and 10 MeV proton events now in progress are
>expected to continue for the next 24 to 48 hours.

For QRPers, this is telling us a couple of things.
First, the ionizing radiation from the proton event will continue to ionize
our upper atmosphere, that is, the E/F layers.  This means tomorrow will
also have a higher MUF and good skip propagation not normally there.

Second, the influx of protons will continue to fuel the Polar Cap Absorption
event, keeping our QRP friends in the higher latitudes in a state of
perpetual HF blackout for a few more days.

>III.  Event Probabilities 14 Dec-16 Dec
>Class M    60/60/60
>Class X    35/35/35
>Proton     99/99/75
>PCAF       in progress

The delta configuration suggests further M or X class flare activity.
The proton event at 99% due to it's expected continuance for 48 more hours.
PCAF is the polar cap absorption event discussed above - still in progress
due to the proton event.

>IV.  Penticton 10.7 cm Flux
>Observed           13 Dec 094
>Predicted   14 Dec-16 Dec  095/095/095
>90 Day Mean        13 Dec 081

The observed 10.7cm flux, again, is with the flare effects removed to show a
normalized day-to-day change.

>V.  Geomagnetic A Indices
>Observed Afr/Ap 12 Dec  015/026
>Estimated Afr/Ap 13 Dec  008/010
>Predicted Afr/Ap 14 Dec-16 Dec  065/130-050/100-012/020

Yikes! An estimated A-index of >100!  That is definitely a severe
geomagnetic storm, translating to a K-index of 7 to 8, and noise levels in
the S8-S9 range.  Of course, there is no precise correlation between these
"numbers," just a general indicator.  Also, on HF, the effects of a
geomagnetic storm get worse the lower in frequency you go.  If 40M is
totally wiped out, noise levels on 20M may be manageable.

>VI.  Geomagnetic Activity Probabilities 14 Dec-16 Dec
>A.  Middle Latitudes
>Major-severe storm    55/45/05
>B.  High Latitudes
>Major-severe storm    65/55/15

A greater than 50% chance of a major-severe geomagnetic storm.  Also note
the chances are greater in the higher latitudes, as is always the case, as
the closer you are to the poles, the solar electrons and protons trapped in
the Earth's magnetic field lines will be closer to the Earth's surface, and
because our magnetic field, being disturbed, is weaker at the poles.

For those interested in some illustrations on the beta and delta groups, or
a table estimating K vs. A indices, etc., the handout I used at Rochdale is
now online at:
http://www.gqrp.com
under the SPRAT button, "Handiman's Guide to Solar Activity"
(Thanks Tony)

Sorry to be so long winded, but this may be the last opportunity to study a
major flare event for many moons to come.  Three X-class flares from the
same region at the bottom of the solar cycle is indeed quite rare.

72, Paul NA5N

PS -- For those who might be in the shack when the shockwave hits, it would
be very interesting to monitor WWV at 5MHz or a shortwave station 5-6MHz
with a tape recorder running.  The onset of a high velocity CME can be very
astounding.  I'm sure thousands of QRPers would love to hear it if you are
lucky enough to catch it.  I'll bet a handful of those PhD type astronomers
would love it too.