Carrington flare of 1859 as a prototypical worst-case solar energetic particle event

Abstract

Recent analyses of ice core samples indicate that the Carrington flare of 1859 was the largest event observed in the past 500 years. These ice core data yield estimates of the proton fluence for energies greater than 30 MeV, but provide no other spectrum information. Assuming that the proton energy distribution for such an event is similar to that measured for other recent, large events, total ionizing doses in deep space are estimated for these hypothetical worst-case spectra. These estimated doses, as large as 50 krad (Si), could be catastrophic for sensitive electronic devices unless substantial shielding is provided.

Recommendations to mitigate against human health risks incurred due to energetic particle irradiation beyond low earth orbit/BLEO

“…The latter curve was then multiplied by two to produce a further spectrum, referred to as SEPEM Extreme SEP (x2),. These simulated spectra are compared in the figure with three spectra recorded in space -on October 2003, August 1972 and July 2012 (aboard STEREO A) -as well as with an estimate of the spectrum of the 1 September, 1859 Carrington event published earlier in [49].…”

The Carrington event: Possible doses to crews in space from a comparable event

“…Analyses of possible doses from a solar energetic particle event similar to the Carrington Event of 1859 have been carried out for purposes of estimating doses in deep space for electronics (Townsend et al, 2003) and humans (Stephens et al, 2005); and for humans in low-Earth orbit (Townsend et al, 2004). In these analyses various spectral shapes were assumed.…”

“…Such doses might result in component failure, especially for many commercial off the shelf (COTS) parts, which have not been radiation-hardened. In Townsend et al (2003), doses in silicon materials shielded by aluminum shield thicknesses comparable to those found in manned and unmanned spacecraft were calculated for deep space. The values obtained indicated that a Carrington-type event could present a significant hazard to onboard electronics.…”

“…For parts shielded with less than $40 mils Al, doses exceeding 25 krads (Si) are possible. Hence, it is clear that significant shielding may be required to shield both Table 4 Doses in silicon for hypothetical worst case solar energetic particle events based on the Carrington event of 1859 (Townsend et al, 2003) Al shield thickness (g cm À2 ) components and human crews in deep space, and in near polar orbits since these events will have access into lower altitude polar regions.…”

“…Unfortunately, one fluence datum at a single energy does not constitute a spectrum. Hence, to generate plausible spectra, the Carrington flare fluence for >30 MeV protons, reported by McCracken et al (2001) has been used as an overall normalization in combination with the spectral shapes of several large solar particle events from the space era to create hypothetical worst-case solar particle event spectra, which have been used to assess possible doses in electronics (Townsend et al, 2003) and humans (Stephens et al, 2005;Townsend et al, 2004).…”