SGS March 26, 2013 Curdt 1

A discussion on the AD 774/775 event

SGS March 26, 2013 Curdt 2

T1/2 = 5730 a

Miyake et al., Nature 486, 240 (2012)

“A signature of cosmic-ray increase in AD 774-775 from tree rings in Japan”

Melott & Thomas, Nature 491,1 (2012)Thomas et al., GRL (2013, in press)Schrijver et al., 117, JGR A08103 (2012)Aulanier et al., A&A 549, 66 (2013)Shibata et al., PASJ 65, 3 (2013)Hambaryan & Neuhäuser, MNRAS (2013, in press)

SGS March 26, 2013 Curdt 3

SGS March 26, 2013 Curdt 4

Miyake et al. 2012

- a nearby supernova- a violent solar eruption

SGS March 26, 2013 Curdt 5

Nearby supernova:

no historical record

no remnants

AD1054 SN remnant (NASA-HST)

SGS March 26, 2013 Curdt 6

Could a violent solar eruption be responsible?

If so: could it be that the AD774 event happens again as a Black Swan event?

typical SEP energy release 1025 J2 1028 J needed

(1) How much energy would be needed?

(2) Can the Sun release this amount of energy?

Miyake conclusion: neither supernova nor solar SEP event

SGS March 26, 2013 Curdt 7

Hambaryan & Neuhäuser, MNRAS 2013 (in press):

-ray burst fits the scenario, no visible effect seen at Earth

However:

jet is narrow and short-lived extremely unlikelyozone layer depletion not observed

SGS March 26, 2013 Curdt 8

Kepler data: One 1027 J flare per millenium may be possible

Dynamo models: 2 1023 Mx from an entire solar cycle

Shibata 2013Maehara et al., 2012

SGS March 26, 2013 Curdt 9

younger stars: more dynamicfast rotators: accumulate energy in shorter timebinaries: tidal effects

Melott & Thomas, 2012

credit: Berdyugina

Thomas et al., 2013Schrijver et al., 2012

Miyake scaling incorrect (24° cone angle)1027 J flare monster spot / 12% of the disk

Can the Sun store this amount of energy?

SGS March 26, 2013 Curdt 10

Sunspot area – flare energy relationship(Aulanier et al. 2013)

Emax ≤ 1026 J 150“ diameter spot

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The largest sunspot recorded since 1900, observed April 5,1947 from Meudon.(Aulanier et al. 2013)

Ca II K H

SGS March 26, 2013 Curdt 12

Willis & Stephenson

AD 1128, Dec 8sunspotsChronicle of John of Worcester

- 0.8% disk area- independent records- no C-14 excursion

SGS March 26, 2013 Curdt 13

Usoskin et al. (2013), A&A 552, L3 “The AD775 cosmic event revisited: the Sun is to blame”

- measurement confirmed with data from German oak trees- data compatible with Be-10 measurements- overestimated event strength by incorrect use of carbon cycle- historical records of aurora sightings in Chinese, Irish, English German chronicles- candidates for similar events- „The Sun can do such things“

How would such an event look like today?

SGS March 26, 2013 Curdt 14

- 1.3% per year continously- individual proton events dominant, 4% in a single year- the imprint of a series of violent events comparable to 11 y cosmic ray effects

SGS March 26, 2013Curdt

15

- SEU rate modulated by solar cycle- SEU 100 - spikes during solar events- handful of spikes comparable to 11 y cosmic rays