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Solar Flare Forecasting
Solar
flares are very hard to predict because they depend
on what the sun's magnetic field is doing, and scientists
don't fully understand what triggers a flare. the most
common things we look for as clues to future flaring
activity are sunspots and the shapes of their magnetic
fields. The bigger they are and the more complex they
look, the greater the chance for a flare.
Here is a summary of the links you will need to investigate solar flares:
Here is a four-step introduction to solar flare forecasting:
Step
1: Are there any sunspots?
The basic rule of thumb is that, if there are no sunspots,
or if the sunspots are very small, it is unlikely that
the conditions are present for solar storms that could
trigger bad space weather here at Earth. Visit the National
Solar Observatory or the Big
Bear Solar Observatory links to get the latest image
of the sun, and check for sunspots. Also visit the NOAA
archive of solar data which summarizes the last
30 days of flares, sunspots and sunspot area. Class
3 spots are very good candidates for powerful solar
flares. Class 1 spots are not very good candidates for
big flares, but could produce some minor flaring activity.
Here is a suggested scale from archived Mees
Observatory images:
Class
1: A few spots but not very large
Class
2: A medium-sized spot, or large group
Class
3: One or more very large spots
Step
2: How magnetically complex are the spots?
The more tangles the magnetic field, the greater is
the likelyhood that it will try to unravel itself and
release bursts of energy. Have a look at the Solar
Monitor at NASA. It shows full-sun views that highlight
the most active regions and sunspots. By selecting each
image you can also find the assigned numbers for each
active region. You should use these to track an active
region as it evolves with time. The two images you should
look at are the x-ray image and the magnetogram image
which look like the ones below:
X-ray
image showing active regions.
 Magnetogram
image
Look
for the brightest and largest regions like the three
shownb in the above images. These are good candidates
for flares. At the Solar Monitor, you can click on the
magnetogram image to open an enlarged image. Then, click
on the active region and an enlargement of that area
will open as shown below:
Black
denotes a North-type polarity .White denotes a South-type
polarity. The above image of Active regions 10885 and
10884 show that they are close together, but the white
and black regions are mostly far apart. When large distinct
white regions become close together, they can form flaring
regions. Visit the Rabin
Systems solar activity summary to read the latest
report about the complexity of each active region. The
above active regions had magnetic fields classified
as 'Beta', and had produced two B-class solar flares.
Sunspot
magnetic fields are classified by the Greek letters
Alpha through Gamma, with mixtures like 'Beta-Gamma'
also possible for the more complex sunspot groups:
alpha:
A
unipolar sunspot group. It seems to have only one polarity
(all black or all white)
beta:
A sunspot group having both North and South magnetic
polarities (bipolar), with a simple and distinct division
between the polarities. (See the magnetogram above)
gamma:
A complex active region in which the North and South
polarities are so irregularly distributed as to prevent
classification as a bipolar group.
delta:
A
qualifier to magnetic classes indicating that the dark
sunspot regions (the Umbra) are very close together
and share a common penumbra and have opposite polarity.
Step
3: Is there any X-ray activity from the sunspot region?
Usually an active region produces several flares over
its lifetime, which can last from a few days up to two
weeks. Many satellites monitor the sun's X-ray output.
Visit the NOAA
X-ray monitior to see the last few days of activity,
which you will see in plots like the one below. The
vertical 'spikes' show x-ray flares. The letters A,
B, C, M and X on the far-left edge of the plot are the
classes for the flares .The flares seen on May 22 was
a Class-B flare. the most powerful, and rare, flares
are Class-X.
Visit
the NOAA
log of solar activity to see which flares have happened
during the last 30 day, and which active regions were
involved. Our two examples above, AR10884 and AR10885
are show in the sample listing below:
6520 + 1333 1338 1344 G12 5 XRA 1-8A B1.8 9.3E-05
0884
6520 1339 1341 1343 G12 5 XFL S12E03 1.3E+02 2.2E+02
0884
6530 + 1348 //// 1349 SVI C RSP 025-072 III/1
6540 + 1523 1528 1533 G12 5 XRA 1-8A B2.2 1.1E-04
0885
6540 1528 1532 1532 G12 5 XFL S10E08 3.3E+02 6.2E+02
0885
6550 + 1635 1641 1646 G12 5 XRA 1-8A B5.0 2.2E-04
0884
6550 1639 1645 1645 G12 5 XFL S12E01 7.8E+02 1.9E+03
0884
6560 + 1809 1815 1824 G12 5 XRA 1-8A B1.4 1.1E-04
On
May 23, 2006 AR10884 had two solar flares of class
B1.8 and B5.0. The region AR10885 had one solar flare
of class B2.2.
Step
4: Now make your forecast!
After looking through the above information for today,
try to predict if there will be a solar flare tomorrow,
and whether it will be a small flare (Class A, B, C)
a medium-sized flare (Class M) or a very powerful flare
(Class-X). Keep track of your predictions and what the
actual flares were that were seen by NOAA satellites.
Can you create a strategy for improving your accuracy
for a 24-hour flare forecast? A 3-day forecast? A one-week
forecast? Most professional forecasts have about a 50/50
chance of predicting the next flare strength (C, M or
X) correctly. How close can you get to this success
rate?
Additional Resources:IMAGE
Tracking a solar storm. A PDF file that introduces
more advanced approaches to solar storm tracking, developed
by the IMAGE satellite program. See also their illustrated
guide with more details.
NASA
Student Observation Network. Developed by NASA educators,
this is a comprehensive introduction to solar storm
tracking in which students may network across the world
to make and log their own forecasts using an extensive
collection of satellite and ground-based data from online
sources ,as well as student-built instruments.
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