skip to main content

SciTech ConnectSciTech Connect

Title: On a solar origin for the cosmogenic nuclide event of 775 A.D

We explore requirements for a solar particle event (SPE) and flare capable of producing the cosmogenic nuclide event of 775 A.D., and review solar circumstances at that time. A solar source for 775 would require a >1 GV spectrum ∼45 times stronger than that of the intense high-energy SPE of 1956 February 23. This implies a >30 MeV proton fluence (F {sub 30}) of ∼8 × 10{sup 10} proton cm{sup –2}, ∼10 times larger than that of the strongest 3 month interval of SPE activity in the modern era. This inferred F {sub 30} value for the 775 SPE is inconsistent with the occurrence probability distribution for >30 MeV solar proton events. The best guess value for the soft X-ray classification (total energy) of an associated flare is ∼X230 (∼9 × 10{sup 33} erg). For comparison, the flares on 2003 November 4 and 1859 September 1 had observed/inferred values of ∼X35 (∼10{sup 33} erg) and ∼X45 (∼2 × 10{sup 33} erg), respectively. The estimated size of the source active region for a ∼10{sup 34} erg flare is ∼2.5 times that of the largest region yet recorded. The 775 event occurred during a period of relatively low solar activity, with amore » peak smoothed amplitude about half that of the second half of the 20th century. The ∼1945-1995 interval, the most active of the last ∼2000 yr, failed to witness a SPE comparable to that required for the proposed solar event in 775. These considerations challenge a recent suggestion that the 775 event is likely of solar origin.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Space Vehicles Directorate, Air Force Research Laboratory, Sunspot, NM 88349 (United States)
  2. Code 672, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  3. Praxis, Inc., Alexandria, VA 22303 (United States)
  4. Atmospheric Environmental Research, 3550 Aberdeen Ave., Kirtland AFB, NM 87117 (United States)
Publication Date:
OSTI Identifier:
22348170
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; CLASSIFICATION; COMPARATIVE EVALUATIONS; DATA; DISTRIBUTION; EMISSION; MEV RANGE; SOFT X RADIATION; SOLAR ACTIVITY; SOLAR PROTONS; SPECTRA; SUN