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14 C increase 775 and 993 AD: Aurora observations in ancient times. M. A. Shea.

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Presentation on theme: "14 C increase 775 and 993 AD: Aurora observations in ancient times. M. A. Shea."— Presentation transcript:

1 14 C increase 775 and 993 AD: Aurora observations in ancient times. M. A. Shea

2 Jull et al., 2014

3 Possible explanations: Extreme Solar Proton Event Comet Collision - January 773 Gamma-ray Burst – Super Nova

4 HOW CAN OUR MODERN KNOWLEDGE HELP IN THE UNDERSTANDING OF HISTORICAL PHENOMENA?

5 COMMONLY USED GEOPHYSICAL DATABASES Satellite data – IMF, solar wind, proton events (1965-present) Cosmic radiation data (1935 – present) Solar flare reports ( present) Geomagnetic indices ( present) Geomagnetic data (~1828-present) Sunspot Number (~ present) Auroral lists (1000 – present) (some earlier records from ~210 BC to 1000)

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7 SOLAR AND GEOMAGNETIC DATA-SELECTED EVENTS EVENT SOLARGLEGMS AA* RANK ACTIVITYINDEX 22 Mar 9128 ENoYes Mar 8922 ENoYes Jul 4615 EYesYes Feb 424 EYesYes May 9037 W YesNo 19 Nov 4972 WYesNo 23 Feb 5680 WYesYes Mar 4290 WYesNo 29 Sep WYesNo 5 Oct 60N/ANoYes AA* Index:

8 THINGS WE HAVE LEARNED : MAJOR SPEs FROM CENTRAL MERIDIAN ACTIVITY GENERALLY HAVE SOFTER SPECTRA THAN EVENTS FROM THE WEST LIMB. MAJOR HIGH ENERGY ( 4 GeV) SPEs FROM CENTRAL MERIDIAN ACTIVITY ARE RARE. MAJOR HIGH ENERGY SPEs ARE NOT ALWAYS ASSOCIATED WITH A SUBSEQUENT GEOMAGNETIC STORM. MAJOR GEOMAGNETIC STORMS CAN OCCUR WITHOUT A LARGE SPE.

9 CAN IDENTIFICATION OF LOW LATITUDE AURORA HELP TO RESOLVE UNUSUAL GEOPHYSICAL RECORDS SUCH AS 14 C INCREASES IN TREE RINGS?

10 EARTH'S GEOMAGNETIC FIELD IS RAPIDLY EVOLVING IN GEOPHYSICAL TIME THE GEOMAGNETIC LATITUDE OF AURORAL OBSERVATIONS SHOULD BE CALCULATED FOR THE EPOCH OF THE OBSERVATION

11 CHANGE IN MAGNITUDE OF THE G(1,0) TERM OF THE EARTH’S MAGNETIC FIELD, (18% decrease in 400 years)

12 CHANGES IN THE POSITION OF THE EARTH’S DIPOLE 1000 AD – 2000 AD

13 CHANGES IN THE POSITION OF THE EARTH’S DIPOLE 0 AD TO 1990 AD

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16 EXAMPLES OF GEOMAGNETIC LATITUDE CHANGES LOCATION CHANGE S. SPAIN35° N40° N5° N SAN DIEGO25° N40° N15° N CHICAGO36° N51° N15° N EGYPT34° N28° N6° S TASMANIA38° S50° S12° S (VALUES ARE APPROXIMATE)

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19 HISTORIC MID AND LOW LATITUDE AURORA Oct 817Iraq 816/817Yemen Oct 879Morocco Syria May 941Spain Aug 977Egypt Sept 979Morocco Egypt* Apr 1050Egypt* Egypt 1176Syria* May 1179Syria Nov 1203Yemen 1223Syria* 1264Syria* 1321/1322Yemen Nov 1370Syria Egypt Aug 1449Yemen Spain * Suspected aurora Ref: Basurah, Sol. Phys, 225,2005; JASTP, 68, 2006

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21 ITEMS NEEDED FOR COMPREHENSIVE STUDY OF HISTORIC EXTREME SOLAR-TERRESTRIAL EVENTS ● CONSOLIDATED MID AND LOW LATITUDE AURORA LIST THESE DATA ARE CURRENTLY SCATTERED ALL OVER THE LITERATURE – IN BOOKS, ARCHIVES AND INDIVIDUAL PUBLICATIONS ● NAKED EYE SUNSPOT SIGHTINGS PRE 1700 ● INDIVIDUAL MAGNETIC DISTURBANCE RECORDS SHIP’S LOGS MAY PROVIDE SOME INSIGHT CARE MUST BE TAKEN WITH THE DATES CITED IN THE ORIGINAL RECORDS.

22 14 C INCREASES – 774/775 AND 992/993 IF THESE INCREASES ARE THE RESULT OF A MASSIVE SOLAR PROTON EVENT, THERE MIGHT NOT HAVE BEEN A MAJOR GEOMAGNETIC DISTURBANCE OR LOW LATITUDE AURORA, ESPECIALLY IF THE SOLAR ACTIVITY WAS ON THE WEST LIMB OF THE SUN.

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