[PPRAANet] Solar Tutorial From NA5N

[W0rw at aol.com]

Gang,

When I was at Dayton, several guys asked if I would fully explain

one of the NOAA RSGA (Solar & Geomagnetic Activity) reports 

someday.  Well, today's M4 solar flare produced all sorts of neat and

nifty solar activity and physics, making it a very good report to

dissect.  Hopefully it will help some of you understand the terminology

and "what it means" from these useful reports. 


72, Paul NA5N 


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> Joint USAF/NOAA Report of Solar and Geophysical Activity

> SDF Number 167 Issued at 2200Z on 16 Jun 2005


> IA.  Analysis of Solar Active Regions and Activity from  15/2100Z

> to 16/2100Z:  Solar activity was moderate.  Region 775 (N10W86)

> produced an M4.0 flare at 16/2022 UTC


If you look at the SOLAR X-RAY PLOT from the GOES satellites at:

http://www.sec.noaa.gov/today 


... you will clearly see today's M4 flare occuring on 16Jun at 2200 UTC.

Note how the scale on the right hand of the chart indicates the approximate 

intensity of the flare, i.e. M4.  Also note how this flare produced x-ray

energy for over an hour.  This makes it a "long duration flare."  Often,

long duration flares can be very energetic, ejecting copious amounts of

electrons and protons.  Look at the 2nd chart on the webpage entitled

SATELLITE ENVIRONMENT PLOT and the PROTON FLUX.  Note the sudden increase

in protons arriving at earth very shortly after the M4 flare.  This is

somewhat unusual.  Usually, the electrons and protons travel towards

earth along with the solar wind, taking 2+ days to get here.  In this

case, the protons arrived almost immediately.  These are protons traveling

at the SPEED OF LIGHT, or nearly so.  They leave the sun at the speed of

light, then get trapped in the sun's magnetic field, spiraling around

the field lines.  While traveling at the speed of light, their forward

motion, due to the spiraling, is a bit less.  Still, they travel from the

sun to the earth in tens of minutes, not days. 


These protons are now hitting the earth, traveling along our own magnetic

field lines, and dumping into the polar regions, where the earth's field

lines are the weakest.  This means our QRP buddies up north are now

experiencing a Polar Cap Absorption event, a near total absorption of HF

energy.  They are in a virtual blackout right now.  These protons can

also enhance the auroral activity. 


The arrival of this ionizing radiation ionizes the E and F layers slightly

above normal.  20M may remain open tonight a little longer than usual.

It also means the D-layer is extra ionized, attenuating HF signals more

than normal.  Fortunately, this ceases almost immediately at sundown.

(If you can't see the sun, there ain't no ionizing radiation hitting ya!)

If you were on HF this afternoon and the bands seemed kinda sluggish and

weak, now you know why. 


Region 775, that produced the flare, is located on the western limb of

the sun and will rotate out of view by tomorrow.  THIS IS IMPORTANT.

With the active region near the limb, there is no way the shockwave from the

flare and CME will strike the earth.  Inspite of the hysteria you will

probably hear on Art Bell tonight, this flare will NOT effect earth with

a geomagnetic storm.  The solar flare has to occur near the center of

the sun for the shockwave to be propelled towards earth to trigger a

geomagnetic storm.  Only the speed of light stuff is effecting us out of

this flare. 


> with associated Type II (989 km/s) and Type IV radio sweeps. 


The massive explosion of a solar flare produces a huge shockwave that 

travels outward from the sun.  As mentioned above, this shockwave is near 

the limb of the sun and not headed towards the earth.  However, as this 

shockwave travels outward, it "punches" through the sun's strong magnetic 

fields.  As it does so, it produces bursts of radio energy from around 

300MHz down to around 30MHz.  These bursts are called a TYPE II storm, as 

mentioned in today's RSGA report.  The farther away from the sun the 

shockwave travels, the LOWER in frequency the bursts occur.  Usually, the 

bursts are first noticed in the 150-300MHz range.  As they travel outward, 

they "sweep" downward in frequency to around 30 MHz ... even down to 10MHz 

or below in the case of very energetic flares.  Solar scientists measure the 

time it takes for the burst to appear at one frequency, then appearing at a 

lower frequency.  This is a measure of how fast the shockwave is traveling 

through the sun's magnetic field lines as they escape out into space.  This 

is how they estimate the speed of the shockwave, and when it will impact the 

earth (if it is headed our way, which this one isn't). 


Repeating the RSGA report:

> with associated Type II (989 km/s) and Type IV radio sweeps. 


In this case, the shockwave indeed produced a Type II storm (sounding

like ignition noise for 20 minutes or so following the flare) and it was

measured at nearly 1000 km/sec. ... or a fairly respectable shockwave.

Were this to hit earth, it would arrive at around 800-859 km/sec., more

than sufficient to trigger a major geomagnetic storm. 


If this shockwave/CME were headed for the earth (which it isn't), when

would it arrive? 


989 km/sec. = 625 miles per sec. x 3600 = 2,250,000 mph.  The shockwave

looses looses about 20% of it's velocity by the time it hits earth, or

80% x 2,250,000 mph = 1.8 million miles per hour when it reaches earth!

The sun is about 93 million miles away.  Therefore the shockwave would

take about 51-52 hours to get here.  From 16 June at 2200 UTC, that means

an impact time of 19 June about 0100 UTC (which it won't). 


> A 170 sfu Tenflare and a CME were also associated with this event. 


The solar flux is measured at a frequency of 2880 MHz, or 10cm wavelength. 

This frequency was chosen as a solar flare seldom effects the solar output 

power much above around 2 GHz.  However, once in a while it does, and when 

it does, it is called a TENFLARE.  This means that this solar flare caused 

increased radiation at TEN cm. (2880 MHz).  This is informing you that 

today's solar flux value has been contaminated by the flare, and may be

artifically high. 


But ... for QRPers, this *IS* indicating planet earth received additional 

ionization.  This is a hint the E/F layers may be more reflective to check 

the higher bands (like 15M) and 20M may be open longer than usual.  When the 

E/F layers are more reflective, particularly at night when the D-layer 

absorption is gone, QRP signals *can* have better than normal 

signal-to-noise ratios.  In other words, right after a solar flare, 

particularly a TENFLARE, is a great opportunity for QRPers to work DX. 



> Region 775 also produced a long duration C1.7 flare at 16/0905 UTC.

> Region 779 (S17W05) continues to show growth, but is developing more

> slowly.


This is referring to the smaller long-duration C-class flare occuring 

earlier in the UTC day.  Since this also came from region 775 on the limb, 

it also will not effect the earth with a geomagnetic storm.  Region 779 is 

the region currently near the center of the sun, and continues to grow. 

Should this region produce a fairly large flare over the next two days, it's 

shockwave *WILL* impact the earth.  Watch this region for a high C-class (C5 

or greater) or M class flare over the next 2-3 days.  If so, it will trigger 

a geomagnetic storm 2+ days later. 


> IB.  Solar Activity Forecast:  Solar activity is expected to be low.

> There is a slight chance for another M-class flare from Region 775

> as it rotates around the west limb.


But again, being on the limb of the sun, it posses no threat to earth except 

for the short-duration speed of light stuff immediately following a solar 

flare. 


> IIA.  Geophysical Activity Summary 15/2100Z to 16/2100Z:

> The geomagnetic field ranged from quiet to major storm levels.

> Transient material associated with the CME activity on 14 June

> impacted the ACE spacecraft at approximately 16/0830 UTC.


Look again at the SATELLITE ENVIRONMENT PLOT on the sec.noaa website.

Notice the K-index went RED (K=6) around 0900.  This has NOTHING to do with 

today's M-class flare, but is the shockwave arriving at earth from a flare 

earlier in the week, on 14 June.  This was when active region 775 was near 

the center of the sun, and it's shockwave belched out towards earth.  The 

arriving shockwave triggered today's major geomagnetic storm.  It was not a 

very strong shockwave, which is why the geomagnetic storm did not last very 

long, and has since returned to normal. 


The ACE spacecraft detects the arrival of the shockwave about 15 minutes 

before it impacts earth's magnetic field, giving us a little bit of warning. 


> A short-lived period of southward IMF Bz to near -16 nT resulted in a

> major storm from 0900 to 1200 UTC. 


The IMF, the Interplanetary Magnetic Field, is how the shockwave/CME travels 

from the sun outward to the planets.  When the shockwave hits earth, it 

triggers a geomagnetic storm.  If the magnetic vector is southward pointing, 

a -Bz, or opposite to the magnetic vector of the earth, it can greatly 

disturb our magnetic field, causing a strong geomagnetic storm.  Looking at 

the "Goes HP" chart on sec.noaa.gov, SATELLITE ENVIRONMENT PLOT, notice how 

the magnetic field (Hp) took a negative, or southward dip, and immediately 

following the K=6 geomagnetic storm was triggered. 


A -Bz shockwave also triggers strong auroral activity. 


> A greater than 10 and greater than 100 MeV proton enhancement began

> following today's M4 flare. 


The 10 and 100 Mev (Million Electron Volts) are different energy levels of 

the protons.  The "enhancement" began shortly after today's M4 flare as 

discussed above because they are arriving at nearly the speed of light.  A 

100 million volt electron smacking into your forehead at the speed of light 

can definitely be considered "energetic." :-)  In fact, this is ionizing 

radiation.  In some cases, these energetic electrons and protons can reach 

the earth's surface.  This is kinda bad, since this is ionizing radiation 

reaching the earth's surface, slow cooking your lawn to mankind.  This can 

also be especially threatening to astronauts in space and airline passengers 

if it persists for long periods. 


One more reason to hide in your shack, put on your lead hat, and work some 

QRP DX. 


> At the time of issue, the protons were slowly rising, but had not yet

> reached event thresholds. The greater than 2 MeV electrons at

> geosynchronous orbit reached high levels today.


The event thresholds are where the ionizing radiation effects from these 

electrons and protons can be a biological threat, as just discussed.  While 

at high levels, they have not (yet) reached levels to be a concern.  The 

2MeV electrons will not penetrate far into our atmosphere, but can cause 

problems or damage to satellites by building up a large voltage potentials 

across the surfaces.  This "alert" is intended mostly for the operators of 

satellites.  For the QRPers, with high MeV proton activity, it simply tells 

you why ESPN just went dead or your ATM quit working.  The satellites just 

got zapped or temporarily impaired. 


> IIB.  Geophysical Activity Forecast:  The geomagnetic field is

> expected to be active with isolated minor storming on 17 June due to

> the CME activity on 14 June. 


Again, this is due to the shockwave from the flare on 14 June, NOT today's 

M4 flare. 


> Conditions should decrease to predominantly unsettled on 18 June, with

> quiet to unsettled conditions expected on 19 June. 


This is because there is nothing heading our way at the moment, not even 

from todays M4 flare on the limb.  (See, I told you). 


> The greater than 10 and greater than 100 MeV protons are expected to 

> exceed event thresholds early in the period.


This just means better wear your radiation proof hardhat to work tomorrow! 

Seriously, this will not be a "ground level event" (GLE) causing problems on 

the earth's surface.  It is, however, an alert to people dealing with things 

farther up in our atmosphere, such as airline pilots (and passengers), 

operators of satellites, and indicating these energetic particles will 

continue dumping into our poles, causing continued poor HF conditions (or 

blackout) to enhanced auroras.  Auroral activity, of course, means an 

elevation to HF noise levels. 


> III.  Event Probabilities 17 Jun-19 Jun

> Class M    10/05/05

> Class X    01/01/01

> Proton     90/20/05

> PCAF       Green


There is a 10% chance of an M-class flare tomorrow, and a 5% chance for the 

two days after that.  Pretty small.  The proton event is not expected to 

last much after tomorrow.  The PCAF (Polar Cap Absorption Factor) is green, 

meaning no increased absorption in the polar regions YET.  But, if the 

particle radiation increases to "event thresholds" tomorrow as predicted, 

the PCAF may change to YELLOW (meaning minor polar region absorption) or RED 

(meaning severe absorption is being experienced).  This is particularly 

important to QRPers living in the northern latitudes, >60 degrees N/S. 


> IV.  Penticton 10.7 cm Flux

> Observed           16 Jun 098

> Predicted   17 Jun-19 Jun  095/095/090

> 90 Day Mean        16 Jun 093


Today's OBSERVED solar flux was 98.  Actually, in today's case, this is not 

strictly true.  Today's ACTUAL measured solar flux was about 120, due to the 

TENFLARE discussed above.  The 98 value above is NOAA's best guess as to 

what today's solar flux was, had it not been contaminated by the solar 

flare. 


As can be seen from the 3-day PREDICTED values, solar flux is dropping from 

95 to 90, heading into the 28-day minimum.  We'll be out of the minimum and 

heading towards the 28-day maximum shortly, which is why a solar flux around 

95 is predicted for Field Day.  It might be a little higher. 


> V.  Geomagnetic A Indices

> Observed Afr/Ap 15 Jun  014/021

> Estimated Afr/Ap 16 Jun  018/025

> Predicted Afr/Ap 17 Jun-19 Jun  018/025-010/015-005/010


This part of the RSGA report seems to give many some confusion.  Note the 

OBSERVED Ap (planetary A index) was 21 (stormy).  But, also note the date 

... 15 June.  Today, NOAA released the A-index for YESTERDAY.  The A-index 

is the 24-hour average of our magnetic field for the PAST UTC day.  It tells 

us what happened YESTERDAY, not today.  TODAY's A-index is estimated to be 

25 (due to today's geomagnetic storm) and 25, 15, and 10 over the next 3 

days.  You'll have to wait until tomorrow's NOAA RSGA report to find out 

what TODAY's A-index really ended up being with the geomagnetic storm. 


If you are operating, check the K-index to see what conditions are like 

RIGHT NOW.  Yesterday's A-Index means nothing about right now.  However, the 

PREDICTED Ap-Index does give you a general idea of what conditions will be 

like over the next three days. 


> VI.  Geomagnetic Activity Probabilities 17 Jun-19 Jun

> A.  Middle Latitudes

> Active                35/25/20

> Minor storm           25/10/10

> Major-severe storm    10/05/05


For middle latitudes, there is a 35% chance of active conditions tomorrow, 

and only a 10% chance of a major storm.  If NOAA is expecting something to 

arrive, such as a CME, a coronal hole stream or IMF boundry crossing, it 

will predict a higher percentage.  For example, earth may be passing through 

a coronal hole stream around June 24-25, *IF* the coronal hole is still 

there when that part of the sun rotates into view next week.  This is why 

the long range forecast for the A-Index is 20 for Field Day.  It is in 

anticipation of a minor storm due to a reoccuring coronal hole.  And, 

several days before FD, you'll see the above Probabilities show a higher 

percentage for a Minor storm ... again, purely in anticipation of the 

reoccuring coronal hole.  If the coronal hole does not reappear, then 

conditions for FD could be quite nice, the A index well below 20. 


> B.  High Latitudes

> Active                40/30/25

> Minor storm           30/15/10

> Major-severe storm    15/05/05


Ditto for the higher latitudes.  The higher latitudes are always much more 

sensitive and vulnerable to geomagnetic activitiy, and the percentages of 

storms are always higher than us folks in the middle latitudes.  And if you 

live above the Arctic Circle, it gets even worse. 


Hopefully, this helped take out some of the mystery of these daily reports. 

To keep this post from getting giagantic, I know I glossed over a couple of 

things.  But if I did omit to explain something you're still curious about, 

feel free to email privately or pose the question on qrp-l.  I'll answer it 

sometime tomorrow when I get a chance. 


72, Paul NA5N