Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features?
Variations of the geomagnetic field prior to direct observations are inferred from archeo- and paleomagnetic experiments. Seemingly unusual variations not seen in the present-day and historical field are of particular interest to constrain the full range of core dynamics. Recently, archeomagnetic in...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2018-03-01
|
| Series: | Frontiers in Earth Science |
| Subjects: | |
| Online Access: | http://journal.frontiersin.org/article/10.3389/feart.2018.00017/full |
| _version_ | 1819229172599357440 |
|---|---|
| author | Monika Korte Catherine G. Constable |
| author_facet | Monika Korte Catherine G. Constable |
| author_sort | Monika Korte |
| collection | DOAJ |
| description | Variations of the geomagnetic field prior to direct observations are inferred from archeo- and paleomagnetic experiments. Seemingly unusual variations not seen in the present-day and historical field are of particular interest to constrain the full range of core dynamics. Recently, archeomagnetic intensity spikes, characterized by very high field values that appear to be associated with rapid secular variation rates, have been reported from several parts of the world. They were first noted in data from the Levant at around 900 BCE. A recent re-assessment of previous and new Levantine data, involving a rigorous quality assessment, interprets the observations as an extreme local geomagnetic high with at least two intensity spikes between the 11th and 8th centuries BCE. Subsequent reports of similar features from Asia, the Canary Islands and Texas raise the question of whether such features might be common occurrences, or whether they might even be part of a global magnetic field feature. Here we use spherical harmonic modeling to test two hypotheses: firstly, whether the Levantine and other potential spikes might be associated with higher dipole field intensity than shown by existing global field models around 1,000 BCE, and secondly, whether the observations from different parts of the world are compatible with a westward drifting intense flux patch. Our results suggest that the spikes originate from intense flux patches growing and decaying mostly in situ, combined with stronger and more variable dipole moment than shown by previous global field models. Axial dipole variations no more than 60% higher than observed in the present field, probably within the range of normal geodynamo behavior, seem sufficient to explain the observations. |
| first_indexed | 2024-12-23T11:08:57Z |
| format | Article |
| id | doaj.art-217bef019d8644b6a60e3122334cd7da |
| institution | Directory Open Access Journal |
| issn | 2296-6463 |
| language | English |
| last_indexed | 2024-12-23T11:08:57Z |
| publishDate | 2018-03-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Earth Science |
| spelling | doaj.art-217bef019d8644b6a60e3122334cd7da2022-12-21T17:49:24ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632018-03-01610.3389/feart.2018.00017324519Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features?Monika Korte0Catherine G. Constable1GFZ German Research Center for Geosciences, Potsdam, GermanyScripps Institution of Oceanography, University of California, San Diego, San Diego, CA, United StatesVariations of the geomagnetic field prior to direct observations are inferred from archeo- and paleomagnetic experiments. Seemingly unusual variations not seen in the present-day and historical field are of particular interest to constrain the full range of core dynamics. Recently, archeomagnetic intensity spikes, characterized by very high field values that appear to be associated with rapid secular variation rates, have been reported from several parts of the world. They were first noted in data from the Levant at around 900 BCE. A recent re-assessment of previous and new Levantine data, involving a rigorous quality assessment, interprets the observations as an extreme local geomagnetic high with at least two intensity spikes between the 11th and 8th centuries BCE. Subsequent reports of similar features from Asia, the Canary Islands and Texas raise the question of whether such features might be common occurrences, or whether they might even be part of a global magnetic field feature. Here we use spherical harmonic modeling to test two hypotheses: firstly, whether the Levantine and other potential spikes might be associated with higher dipole field intensity than shown by existing global field models around 1,000 BCE, and secondly, whether the observations from different parts of the world are compatible with a westward drifting intense flux patch. Our results suggest that the spikes originate from intense flux patches growing and decaying mostly in situ, combined with stronger and more variable dipole moment than shown by previous global field models. Axial dipole variations no more than 60% higher than observed in the present field, probably within the range of normal geodynamo behavior, seem sufficient to explain the observations.http://journal.frontiersin.org/article/10.3389/feart.2018.00017/fullarcheomagnetismpaleomagnetismintensity spikesecular variationglobal magnetic field models |
| spellingShingle | Monika Korte Catherine G. Constable Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features? Frontiers in Earth Science archeomagnetism paleomagnetism intensity spike secular variation global magnetic field models |
| title | Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features? |
| title_full | Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features? |
| title_fullStr | Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features? |
| title_full_unstemmed | Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features? |
| title_short | Archeomagnetic Intensity Spikes: Global or Regional Geomagnetic Field Features? |
| title_sort | archeomagnetic intensity spikes global or regional geomagnetic field features |
| topic | archeomagnetism paleomagnetism intensity spike secular variation global magnetic field models |
| url | http://journal.frontiersin.org/article/10.3389/feart.2018.00017/full |
| work_keys_str_mv | AT monikakorte archeomagneticintensityspikesglobalorregionalgeomagneticfieldfeatures AT catherinegconstable archeomagneticintensityspikesglobalorregionalgeomagneticfieldfeatures |