The Solar Particle Event on 10 September 2017 as observed onboard the International Space Station (ISS)

Abstract

The nominal radiation environment in low Earth orbit, especially for the International Space Station (ISS), is dominated by two sources. The first is galactic cosmic radiation, which is modulated by the interplanetary and the Earth's magnetic fields, and the second is trapped radiation in the form of the Van Allen belts. The trapped radiation inside the ISS is mostly due to protons of the inner radiation belt. In addition to these sources sporadic solar particle events (SPEs) can produce high doses inside and outside the ISS, depending on the intensity and energy spectrum of the event. Before 2017, the last SPE observed inside the ISS with relevant radiation detectors occurred in May 2012. Even though we are currently approaching the next solar minimum, an SPE was observed in September 2017, which was (a) a ground‐level enhancement, (b) measured with various radiation detector systems onboard the ISS, and (c) observed on the surface of Mars. This paper gives an overview of the 10 September 2017 SPE measured with the DOSIS 3D‐DOSTEL and the ISS‐RAD (Radiation Assessment Detector) instruments, both located at this time in close proximity to each other in the Columbus Laboratory of the ISS. The additional dose received during the SPE was 146.2 μGy in Si as measured by ISS‐RAD and 67.8 μGy in Si as measured by the DOSIS 3D‐DOSTEL instruments. In comparison, the dose measured on the surface of Mars with the Mars Science Laboratory‐RAD instrument accounted to 418 μGy in Si.

The Solar Particle Event on 10–13 September 2017: Spectral Reconstruction and Calculation of the Radiation Exposure in Aviation and Space

“…Even so, the exposure to the incoming solar particles is restricted to relatively short passages at high latitudes. The total dose in silicon within the Columbus module numerically estimated in this work was 110 μGy compared to measurements which ranged between 68 and 146 μGy (Berger et al, ). This corresponds to about 1‐day exposure to GCR or about half a day exposure to GCR and trapped particles within Columbus on a regular day. In interplanetary space, where no atmospheric or magnetic shielding exists, the astronaut is protected from the radiation only by the spacecraft or, in case of an extravehicular activity, by the space suit.…”

“…Only during certain orbits, it enters areas where the magnetic shielding is low and energetic protons of a few hundred MeV can reach the station. This behavior was clearly observed for the 10 September event (Berger et al, ). The event started at 16:04 UTC on 10 September, but relevant ISS orbits with lower geomagnetic cut‐offs allowing the lower energy protons to reach ISS were only passed at around 04:00 on 11 September 2017 with an observed main peak of the event following at 07:30 UTC on 11 September.…”

“…The additional dose due to the event measured with relevant silicon detector systems (DOSIS‐3D DOSTEL and ISS‐RAD) accounted for 68 to 146 μGy. In Berger et al () the primary spectra of the protons derived within this work have been used in combination with a model of the Earth's magnetic field and a shielding model of the Columbus module to derive the dose rates along the ISS orbit and the event integrated doses for the 10 September event. Calculated results for this event amount to 110 μGy in Si which is within the range of the values measured with the silicon detector systems inside the Columbus Laboratory.…”

“…Jadrníčková et al () give average values between 30 and 50 g/cm 2 for different modules. The average shielding for the COLUMBUS module estimated from a CAD model and used in Berger et al () is 50 g/cm 2 . In interplanetary space, spacecraft and space suits are the only protection for astronauts providing mass shielding. Mars has only an insignificant localized magnetic field but a thin atmosphere that provides mass shielding for astronauts on the surface in future exploration missions.…”

Forbush Decreases and Geomagnetic Storms During a Highly Disturbed Solar and Interplanetary Period, 4–10 September 2017

“…Recovery of CRI was not smooth due to disturbed interplanetary conditions and different at different energies (profile Oulu and LS: at Oulu another depression of ~1.5% recorded on 9 September). Before reaching prerecovery level, a relatively small ground level enhancement (GLE # 72; ~4% at Oulu NM; https://gle.oulu.fi) occurred on 10 September at around 16:00 hr (e.g., Kurt et al, ) with impact on radiation dose level inside the International Space Station (Berger et al, ). On 11 September at ~08 UT the CRI recovered to its initial undisturbed level.…”