Physics of the Sun and astronaut safety in the new era of space exploration

As Associate Professor at the University of Hawai‘i, Dr Veronica Bindi and her team are analysing data from a unique instrument on the International Space Station to investigate high-energy particles originating from the galaxy and the Sun itself. A comprehensive understanding of these particles, their origin and transport processes will increase our understanding of the universe, solar physics and help to protect instruments and astronauts on future space missions.

Space exploration is currently entering a new and exciting era of discovery. With Voyager 1 making a historic journey beyond the heliosphere (the region of space influenced by the Sun), we are now, for the first time, able to explore interstellar space. At the same time, technological advancements are allowing instruments to measure particles from space at unprecedented precision. At the forefront of this research is Dr Veronica Bindi who, together with her team, is analysing new data to better understand our place in the universe and protect both technology and astronauts in space.

A quest for answers
Looking up at the night sky, few among us won’t have been struck by questions of overwhelming proportions. What is space made of? How old is the universe? To answer these questions, Dr Bindi’s research focuses on Galactic Cosmic Rays (GCRs), accelerated particles that originate from outside the solar system, and Solar Energetic Particles (SEPs), high-energy particles originating from the Sun. By collecting precise measurements of these particles, Dr Bindi hopes to better understand their origin and behaviour and shed light on the nature of matter in space.

New data: filling the void
Associated with solar flares and coronal mass ejection, SEPs are a key focus of heliophysics (the study of the Sun and its effects on space) research. SEPs are a type of Cosmic Ray that are accelerated by the Sun and its activity. The study of their composition and charge can allow us to better understand the mechanisms involved in producing solar flares and coronal mass ejection. The energy range of SEPs can vary over five orders of magnitude. Whilst low-energy (up to a few hundred MeV/nucleon) SEPs have been well observed, there is a lack of high-energy (near 1 GeV) measurements, and thus SEP characteristics at high energies are poorly understood. As a result, SEP models are currently unconstrained at higher energies. The dearth of high-energy measurements has also fuelled controversy within the heliophysics community regarding the source regions and processes responsible for accelerating particles up to high (GeV/nucleon) energies.

To build an accurate model of the radiation environment in space, it is crucial to obtain particle measurements across a broad range of energies and locations.

In addition, both SEPs and GCRs pose significant radiation risks for technology and people in space. To build an accurate model of the radiation environment in space, it is crucial to obtain particle measurements across a broad range of energies and locations. With the current push for long-duration manned space missions, accurate modelling of the radiation environment in space is increasingly important to ensure the safety of astronauts.

Working for ten years at CERN, Dr Bindi was involved in the construction, characterisation and optimisation of the Alpha Magnetic Spectrometer (AMS), a state-of-the-art magnetic spectrometer installed on the International Space Station (ISS). Now Associate Professor in the Department of Physics and Astronomy at the University of Hawai‘i, and the Principle Investigator of a long-term NASA grant and an NSF Career award, Dr Bindi and her team are analysing data collected by AMS.

AMS: a unique tool
AMS, the largest magnetic spectrometer ever built for space application, is capable of measuring particles with energies ranging between 400MeV/nucleon to a few TeV/nucleon and provides measurements with unprecedented precision. With five different detectors, the charge, energy, trajectory and velocity of particles can be measured accurately and continuously. Installed on the ISS in May 2011, it will collect data for the duration of the station (currently extended to 2024), allowing for the observation of particle behaviour across multiple solar cycles. These characteristics make AMS a unique and powerful instrument for heliophysics research.

New insights
By analysing the data already collected by AMS, Dr Bindi and her team have proved that it is possible to measure high-energy solar particles with a precision instrument, with 27 high-energy SEP events observed by AMS to date. Of these 27 events, only one of them has been measured by the ground instruments that are normally used to detect these type of high energy SEP events. This demonstrates unprecedented high sensitivity of this instrument. Data from AMS is also challenging previous theories relating to particle acceleration. Where previous observations have only recorded particles being accelerated for short time periods, AMS has detected particles up to 1GeV/nucleon persisting for hours and even days. The team are also analysing SEP measurements to get a better understanding of the mechanisms producing SEP events, with the aim of generating a baseline for SEP event modelling. In addition, new AMS data at high particle energies has identified several new behaviours and is challenging current thinking on dark matter and GCR propagation.

AMS, the largest magnetic spectrometer in space, is capable of measuring particles with unprecedented precision.

Furthermore, AMS is providing measurements of how GCR flux is changing over an entire solar cycle. This data will provide important insight into long-term solar modulation: how GCRs vary in intensity and energy when they encounter the heliospheric magnetic field. Two papers about the time variation of proton and helium and electrons and positrons in GCRs will be published before the end of the year in Physical Review Letters.

Research and Beyond
In addition to her main research work, Dr Bindi also dedicates significant time to outreach and education. Working with schools in Hawai‘i, Dr Bindi and her team are developing high- and middle school curricula and providing opportunities for students to engage with science through real-world applications. Current projects include incorporating physics, engineering, mathematics, astronomy, biology and arts to plan a mission to send astronauts to Mars, and a practical project constructing a particle detector from everyday objects such as webcams.

Into the Unknown
Dr Bindi’s work with AMS occupies an exciting position at the frontier of heliophysics research. The unique capability of AMS and its location above the atmosphere is providing new, detailed information to the research community. The data collected throughout the lifetime of AMS will greatly increase our understanding of SEPs and GCRs and will contribute significantly to heliophysics research, greatly increasing the safety of astronauts on future manned space missions. Dr Bindi’s work has the potential to not only contribute to scientific advancements by achieving their current objectives but also to contribute to science in unanticipated ways, as is often the case with new discoveries.

Contrary to the popular saying — for Dr Bindi and her team, the sky, and indeed the atmosphere, is definitely not the limit.