14 c increase 775 and 993 ad: aurora observations in ancient times. m. a. shea
TRANSCRIPT
14C increase 775 and 993 AD:
Aurora observations in ancient times.
M. A. Shea
Jull et al., 2014
Possible explanations:
Extreme Solar Proton EventComet Collision - January 773Gamma-ray Burst – Super Nova
HOW CAN OUR MODERN KNOWLEDGE
HELP IN THE UNDERSTANDING OF HISTORICAL PHENOMENA?
COMMONLY USED GEOPHYSICAL DATABASES
Satellite data – IMF, solar wind, proton events (1965-present)
Cosmic radiation data (1935 – present)Solar flare reports (1932 - present)Geomagnetic indices (1864 - present)Geomagnetic data (~1828-present)Sunspot Number (~1700 - present)Auroral lists (1000 – present)
(some earlier records from ~210 BC to 1000)
SOLAR AND GEOMAGNETIC DATA-SELECTED EVENTS
EVENT SOLAR GLE GMS AA* RANK ACTIVITY INDEX
22 Mar 91 28 E No Yes 176 7410 Mar 89 22 E No Yes 441 125 Jul 46 15 E Yes Yes 329 1128 Feb 42 4 E Yes Yes 168 8021 May 90 37 W Yes No19 Nov 49 72 W Yes No23 Feb 56 80 W Yes Yes 131 1667 Mar 42 90 W Yes No29 Sep 89 105 W Yes No
5 Oct 60 N/A No Yes 253 28
AA* Index: 1868-2010
THINGS WE HAVE LEARNED:
MAJOR SPEs FROM CENTRAL MERIDIAN ACTIVITYGENERALLY 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.
CAN IDENTIFICATION OF LOW LATITUDE AURORA HELP TO RESOLVE UNUSUAL GEOPHYSICAL RECORDS SUCH AS 14C INCREASES IN TREE RINGS?
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
CHANGE IN MAGNITUDE OF THE G(1,0) TERM OF THE EARTH’S MAGNETIC FIELD, 1600-2010
(18% decrease in 400 years)
CHANGES IN THE POSITION OF THE EARTH’S DIPOLE1000 AD – 2000 AD
CHANGES IN THE POSITION OF THE EARTH’S DIPOLE
0 AD TO 1990 AD
EXAMPLES OF GEOMAGNETIC LATITUDE CHANGES
LOCATION 1000 2000 CHANGE
S. SPAIN 35° N 40° N 5° NSAN DIEGO 25° N 40° N 15° NCHICAGO 36° N 51° N 15° NEGYPT 34° N 28° N 6° STASMANIA 38° S 50° S 12° S
(VALUES ARE APPROXIMATE)
HISTORIC MID AND LOW LATITUDE AURORA
• Oct 817 Iraq• 816/817 Yemen• Oct 879 Morocco• 939-940 Syria• May 941 Spain• Aug 977 Egypt• Sept 979 Morocco• 991-992 Egypt*• Apr 1050 Egypt*• 1059-1060 Egypt
• 1176 Syria*• May 1179 Syria• Nov 1203 Yemen• 1223 Syria*• 1264 Syria*• 1321/1322 Yemen• Nov 1370 Syria• 1422-23 Egypt• Aug 1449 Yemen• 1570-71 Spain
• * Suspected aurora
Ref: Basurah, Sol. Phys, 225,2005; JASTP, 68, 2006
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.
14C INCREASES – 774/775 AND 992/993
IF THESE INCREASES ARE THE RESULT OFA 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.
