Upper limit for solar flare energies · Karel Schrijver Hinode-7, Takayama, November 14, 2013 Solar-stellar ﬂaring Flare: • deﬁnition/stellar: a sudden, temporary brightening

Karel Schrijver Hinode-7, Takayama, November 14, 2013 1

Karel SchrijverLockheed Martin Advanced Technology Center

Karel SchrijverLockheed Martin Advanced Technology Center

Upper limit for solar flare energies

Wednesday, November 13, 2013

Karel Schrijver Hinode-7, Takayama, November 14, 2013

Chameleon behavior of solar storms

2

Aschwanden et al. (2013, SPh, subm.)

l GOES class provides a very uncertain measure of the energy in a solar coronal storm event.

l Example: large scatter in event peak brightness as function of wavelength.


http://www.lmsal.com/~aschwand/publications/publ.html

http://www.lmsal.com/~aschwand/publications/publ.html

http://www.lmsal.com/solarsites.html

http://www.lmsal.com/solarsites.html

Hinode-7, Takayama, November 14, 2013Karel Schrijver

Chameleon behavior of solar stormsl GOES class provides a

very uncertain measure of the energy in a solar coronal storm event.

l Example: GOES classes for an active-region flare and quiet-Sun filament eruption differ by factor of ~250 for comparable ‘bolometric’ energies in the X-ray/(E)UV domain.

3

Fe XVI Fe XVI

Fe IX Fe IX



From Kretzschmar (2011)

Superposed-epoch light curves for

solar flares

X rays

E/XU

Vvisible

The bulk of the energy is emitted where it is hardest to measure!



Flare energy: mostly WL and kinetic

From Emslie et al. (2012): values for X3, X3, X4, X7, X8, X10 flares.5



Flare energy: mostly WL and kinetic

From Emslie et al. (2012): values for X3, X3, X4, X7, X8, X10 flares.6



Solar flare statisticsCombining solar EUV to X-ray data for 39 years of GOES monitoring of solar activity, combined with ~2 decades of EUV observing.

7

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?

?


Hinode-7, Takayama, November 14, 2013Karel Schrijver

Observed spot group areas:no cutoff (yet)?

8

“On the size distribution of sunspot groups in the Greenwich sunspot record 1874-1976”, Baumann & Solanki (2005).



Powering superflares

9

Aulanier et al. (2013, A&A 549, 66)

The largest sunspot group ever reported since the end of the nineteenth century, as observed in April 5, 1947 in Ca ii K1v by the Meudon spectroheliograph.


http://adsabs.harvard.edu/abs/2013A%2526A...549A..66A



Solar flare statisticsCombining solar EUV to X-ray data for 39 years of GOES monitoring of solar activity, combined with ~2 decades of EUV observing.

10

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?

?

Aul

anie

r et

al.

(201

3)



Studying flares by proxies?

11



Lunar radionuclides

12



Lunar radionuclides

13



Solar-stellar flaring

Flare:

• definition/stellar: a sudden, temporary brightening

• conceptually/solar: a conversion of EM field energy into kinetic energy, resulting in photons + associated phenomena

Solar-stellar comparison possible for infrequent largest solar flares, generally with non-overlapping wavelength ranges.

14

Schrijver, C., "Driving major solar flares and eruptions: A review" ASR 43, 739 (2009).

Hugh Hudson’s cartoon archive: http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/


http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/

http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/


Courtesy: Rachel Osten15



Stellar flares: XUV

Audard et al. (2000)16



Visible-light flaring on stars

Walkowicz et al. (2011)

Kepler



Visible-light flaring on stars

Notsu et al. (2013)

Kepler



Notsu et al. (2013, ApJ 771, 127)

Sola

r ro

tatio

n pe

riod

Kepler dataVisible-light flaring on stars


http://arxiv.org/abs/1304.7361v1





Powering superflares

21

Notsu et al. (2013, ApJ 771, 127)

????????

Aulanier et al. (2013, A&A 549, 66)







Are ‘Kepler flares’ ‘flares’?Potential issues causing misinterpretation:

• Particle hits.

• Source misidentification: binary system, source confusion, period error (Notsu et al. (2013): “in some cases simply taking the highest peak can lead to choose spurious peaks at long timescales.”), ... (not likely comet impacts: C/2011 N3 ~1011g & W3 ~1012g at 600 km/s: 2 1026 - 2 1027 ergs)

• Calibration problem given unknown source spectrum

• Multiple events: percolation/sympathy

• Very strong dependence on rotation/age

• Low-statistics of solar events

• ...

22



Extreme solar flares

23

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?



Extreme solar flaresMaximum for cool stars in general: ~3 1036 ergs.

24

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?Stellarmax.




Kepler observations suggest continuation up to at least ~5 1035 ergs.

25

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?

Kepler: Prot>25d

Max. Sun-like stars Stellarmax.





But the frequency scaling with more active stars fails.

26

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?

Kepler: Prot>25d


EK Dra-3.60

k Cet, 1994-2.08k Cet, 1995-2.08





But the frequency scaling with more active stars fails.

Need to add more stellar observing time, improve understanding of energy distributions, and wait ...

27

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

10-5

100

105

1010

f(>E b

ol) (

per h

emis

pher

e pe

r yea

r)

1018 1020 1022 1024 1026 1028 1030Ebol (Joules)

Sun: EUV

Sun: SXR

Sun: X-rays

1024 1026 1028 1030 1032 1034 1036 1038

Ebol (ergs)

Sun?

Kepler: Prot>25d


EK Dra-3.60

k Cet, 1994-2.08k Cet, 1995-2.08



Lunar radionuclides

28





The worst space weatherStellar data reveal that some space weather can be much more severe than what we have recently experienced:

• Solar flares may reach energies up to 100 times above those observed in the past four decades.

Lunar and terrestrial radionuclide and geomagnetic storm theory suggest that different types of extreme space weather do not serve as mutual proxies:

• Energetic particle storm intensities likely saturate at a few times the space-age maximum.

• Geomagnetic storms may never exceed twice the strength of the powerful 1859 Carrington event.

All these potential extremes exceed the levels to which modern technologies, connected in a network of growing complexity, have been exposed.

30



The worst space weather

Stellar observations essential to establish largest possible flare from the Sun.

Radio-nuclide studies of lunar rocks and terrestrial ice and biosphere records need to be re-analyzed and extended in time and increased in S/N.

Models are needed to know the worst possible SEP and geomagnetic storm.

And, yes, it can get worse than we have seen to date ...

31




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Upper limit for solar flare energies · Karel Schrijver Hinode-7, Takayama, November 14, 2013 Solar-stellar ﬂaring Flare: • deﬁnition/stellar: a sudden, temporary brightening