Segmental interpolating spectra for solar particle events and in situ validation

Abstract

It is a delicate task to accurately assess the impact of solar particle events (SPEs) on future long‐duration human exploration missions. In the past, researchers have used several functional forms to fit satellite data for radiation exposure estimation. In this work we present a segmental power law interpolating algorithm to stream satellite data and get time series of proton spectra, which can be used to derive dosimetric quantities for any short period during which a single SPE or multiple SPEs occur. Directly using the corrected High Energy Proton and Alpha Detector fluxes of GOES, this method interpolates the intensity spectrum of a typical SPE to hundreds of MeV and extrapolates to the GeV level as long as sufficient particles are recorded in the high‐energy sensors. The high‐energy branch of the May 2012 SPE is consistent with the Band functional fitting, which is calibrated with ground level measurement. Modeling simulations indicate that the input spectrum of an SPE beyond 100 MeV is the major contributor for dose estimation behind the normal shielding thickness of spacecraft. Applying this method to the three SPEs that occurred in 2012 generates results consistent with two sets of in situ measurements, demonstrating that this approach could be a way to perform real‐time dose estimation. This work also indicates that the galactic cosmic ray dose rate is important for accurately modeling the temporal profile of radiation exposure during an SPE.

Calibration of the GOES 6–16 high-energy proton detectors based on modelling of ground level enhancement energy spectra

“…For each data gap, we simply used the average flux of the two ends to fill the missing points; for spikes, we followed the algorithm described in Raukunen et al (2020) to identify them and clean the data. After these processes, we applied a segmental spectrum approach (Hu et al, 2016) to get the hourly spectra of the selected data, and the event-integrated spectrum, with every data point subtracted by the calculated background 1 day or 7 days before the onset. Various effective energies for EPS and HEPAD channels can be applied to get the spectra.…”

“…Although the HEPAD channels only have uncorrected data, there is guidance to remove the high energy proton contamination from out-of-acceptance particles (especially rear-penetration effects) (Smart & Shea, 1999). Particularly, the integral channel P11 (>700 MeV) data can be processed as a differential channel with energy integrated geometrical factor R G(E)dE = 1565 cm 2 sr MeV and effective energy of 1000 MeV (Smart & Shea, 1999;Hu et al, 2016). In this work, we follow the procedure of Bruno (2017), use both the uncorrected and corrected EPS proton fluxes and uncorrected HEPAD fluxes directly to derive the eventintegrated spectra, and estimate the matching energies of each channel by comparing with the two sets of spectra of historical GLEs described in Section 2.…”

“…Even for the current state-of-the-art crew vehicles such as the orion multi-purpose crew vehicle (MPCV), particles with energies > 100 MeV are still of concern, as they can penetrate the thick shielding, induce energetic secondary particles, and deliver hazardous radiation doses to astronauts in a short time frame (Hu et al, 2020). To investigate the properties of these energetic particles and probe the possible mechanism of their origin, acceleration, and transport in interplanetary space, multiple instruments have been deployed at various locations in the heliosphere, among which the series of Geostationary Operational Environmental Satellites (GOES) are widely used for radiation exposure estimation (Atwell et al, 2009;Hu et al, 2016) and solar proton radiation environment modelling (Xapsos et al, 2000(Xapsos et al, , 2004Jiggens et al, 2014). These multidecade measurements provide a standard source of both realtime and historical information on the characteristics of SPEs (Sandberg et al, 2014).…”

ARRT Development for the Upcoming Human Exploration Missions

“…The historical data set in ARRT is generated by transport calculation with the SEPEM 2.0 data set (http://www.sepem.eu/), which is a cross‐calibrated uniform data set using the Geostationary Operational Environmental Satellite (GOES) measured solar proton fluxes during 1974–2015, with an energy range 5–289 MeV. With segmental spectra (Hu et al, 2016) of 15‐min cadence generated from the fluxes as a boundary condition and material and shielding thicknesses determined by ray tracing the computer‐aided design (CAD) model of the MPCV for Artemis II (with six HERA sensors), transport calculations through the vehicle are performed by a numerical solution of the one‐dimensional Boltzmann transport equation using the HZETRN2015 code (Slaba et al, 2016; Wilson et al, 2016). The resultant data set contains dose rates for the six dosimeters spanning uniformly from 1974 to 2015, with a 15‐min cadence.…”

Nowcast and forecast of galactic cosmic ray (GCR) and solar energetic particle (SEP) fluxes in magnetosphere and ionosphere – Extension of WASAVIES to Earth orbit

“…On the other hand, estimation of real-time SEP fluxes during SPE is beneficial for mission operation to take adequate actions, such as sheltering astronauts in well-shielded locations in their spacecraft (Townsend et al, 2018). A few studies (Hu et al, 2016;Matthiä et al, 2018) have been conducted to reproduce the SEP fluxes in spacecraft during certain SPEs, but these studies were mostly dedicated to post-exposure evaluation. Therefore, it is desirable to develop a system that can nowcast or forecast the SEP fluxes during a SPE.…”