Solar Cycle 24

Carl Luetzelschwab K9LAk9la@arrl.net

QCWA Chap 36 April 2012 K9LA

What We’re Going to Cover

• Recent solar minimum• Predictions for Cycle 24• Cycle 24 status• Four FAQs

QCWA Chap 36 April 2012 K9LA

Recent Solar Minimum

QCWA Chap 36 April 2012 K9LA

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

2 2

1 6 1 1 1 6 2 1 2 6 3 1 3 6 4 1 4 6 5 1 5 6

m o n th s fr o m d e s c e n t b e lo w a s m o o th e d s u n s p o t n u m b e r o f 2 0

smo

oth

ed s

un

spo

t n

um

ber

b e tw e e n C y c le s 1 8 a n d 1 9(m in A p r 1 9 5 4 )

b e tw e e n C y c le s 1 9 a n d 2 0(m in N o v 1 9 6 4 )

b e tw e e n C y c le s 2 0 a n d 2 1(m in Ju n 1 9 7 6 )

b e tw e e n C y c le s 2 1 a n d 2 2(m in S e p 1 9 8 6 )

b e tw e e n C y c le s 2 2 a n d 2 3(m in O c t 1 9 9 6 )

b e tw e e n C y c le s 2 3 a n d 2 4(m in D e c 2 0 0 8 )

Minimum between Cycle 23 and 24 very unusual for our lifetimes

All Solar Minimum Periods

QCWA Chap 36 April 2012 K9LA

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1-2

2-3

3-4

4-5

5-6

6-7

7-8

8-9

9-10

10-1

111

-12

12-1

313

-14

14-1

515

-16

16-1

717

-18

18-1

919

-20

20-2

121

-22

22-2

323

-24

s o l a r m i n i m u m b e tw e e n i n d i c a te d c y c l e s

nu

mb

er o

f m

on

ths

bel

ow

a

smo

oth

ed s

un

spo

t n

um

ber

of

20

• But not all that unusual for all 23 solar minimum periods• Note cyclic nature of data

All Solar Maximums

• Note cyclic nature of this data, too• Is there a correlation between duration of solar min and next max?

QCWA Chap 36 April 2012 K9LA

0

5 0

1 0 0

1 5 0

2 0 0

2 5 0

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3

so la r c y c le n u m b e r

max

imu

m s

mo

oth

ed

sun

spo

t n

um

berAverage ~ 115

Next Max vs Previous Min

• Suggests Cycle 24 will be below average– 56 months (from previous slide) = 85

• And maybe the next couple cycles, too

QCWA Chap 36 April 2012 K9LA

N e x t S o la r M a x v s D u ra tio n o f P re v io u s S o la r M in

R 2 = 0 .5 8 1 5

0

5 0

1 0 0

1 5 0

2 0 0

2 5 0

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

m o n th s a t so la r m in im u m (sm o o th e d su n sp o t n u m b e r < 2 0 )

max

imu

m

smo

oth

ed s

un

spo

t n

um

ber

of

nex

t so

lar

cycl

e

Latest Prediction from MSFC

• Nominal max of 61• Uncertainty in

prediction puts high side at 87

QCWA Chap 36 April 2012 K9LA

MSFC is the Marshall Space Flight Center in Huntsville, AL

[ http://solarscience.msfc.nasa.gov/predict.shtml ]

Latest Predictions from ISES

QCWA Chap 36 April 2012 K9LA

in terms of sunspot number in terms of 10.7 cm solar flux

ISES is the International Space Environment Service – a service used by the Space Weather Prediction Center of NOAA [http://www.swpc.noaa.gov/SolarCycle/ ]

Don’t forget that the sunspot number and 10.7 cm solar flux are proxies for the true ionizing radiation

Latest Data for Cycle 24

• The recent slowdown in the smoothed sunspot number may just be a normal “leveling off” as seen in other cycles

• April monthly mean is likely to be higher than March monthly mean• Expect the smoothed sunspot number to again increase

QCWA Chap 36 April 2012 K9LA

When Are The Higher Bands Open?

• 15-Meters: F2 when the smoothed sunspot number > 25– We’re already there

• 12-Meters: F2 when the smoothed sunspot number > 35– We’re already there

• 10-Meters: F2 when the smoothed sunspot number > 50– We’re right on the border for consistent worldwide openings

QCWA Chap 36 April 2012 K9LA

Four FAQs

• Is Cycle 24 going to have two peaks?• Is Cycle 24 going to offer any 6-Meter F2

propagation?• Are sunspots disappearing?• Are we headed for another Maunder

Minimum?

QCWA Chap 36 April 2012 K9LA

Two Peaks?• Cycle 19, 20, and 21

didn’t show much of a second peak

• Cycle 22 and 23 did show a definite second peak– Cycle 23’s second peak

made 6-Meter DXers very happy in the Winter of 2001

QCWA Chap 36 April 2012 K9LA

Cycle 24 has a decent chance of a second peak

Any 6-Meter F2 Propagation?

• Not very likely (extremely low probability) with the current Cycle 24 prediction

• If F2 does happen, it would be most likely during the Spring, Fall, and Winter of 2013

• To reiterate, Sporadic E should still be there– Late morning and early evening in the Summer– Early evening in December

QCWA Chap 36 April 2012 K9LA

Are Sunspots Disappearing?• W. Livingston and M. Penn

measured the maximum strength of magnetic fields of sunspots

• Strength has been declining since 1992

• Need about 1500 gauss for sunspots to be visible

• Extrapolating their data says sunspots will disappear by 2015

• 2012 update – declining trend continues thru 2011

QCWA Chap 36 April 2012 K9LA

Remember that sunspots are a proxy for the true ionizing radiation (EUV), which still appears to be alive and well

Another Maunder Minimum?• Maunder Minimum was a lack of sunspots from 1645-1715 • Cycles -11, -10, and -9 showed a smooth decrease in group

sunspot number leading up to the Maunder Minimum– 125, 40, 20

• It’s generally agreed that the Sun is “slowing down”• Cycles 22, 23, and 24 exhibit a smooth decrease, too

– 158, 121, around 60 to 90

• Where Cycle 24 ends up and the solar minimum between Cycle 24 and 25 will be interesting, and may suggest where we’re headed

QCWA Chap 36 April 2012 K9LA

Summary

• Cycle 24 maximum expected in early or mid 2013

• Cycle 24 expected to be below average• 15-Meters, 12-Meters, and 10-Meters are

good now, so take advantage of them• Have fun!

QCWA Chap 36 April 2012 K9LA