The HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service) project focuses on ‘Coronal mass ejections’ (CMEs) — enormous plasma/magnetic field structures that are expelled from the Sun and propagate through interplanetary space — and ‘Co-rotating interaction regions’ (CIRs) — extensive swathes of compressed plasma/magnetic field that form in regions where fast solar wind catches up with slow wind.
HELCATS combines heliospheric imaging of these features with observations of their source regions on the Sun, their detailed signatures measured by spacecraft at different points throughout the solar system — including near Earth — and complementary observations using, for example, radio techniques, to provide a unique set of coordinated catalogues.
Prof. Richard Harrison, coordinator of the project and chief scientist at STFC’s Rutherford Appleton laboratory, discusses the project outcomes and expected legacy.
Why did you choose to focus your research on CMEs and CIRs?
Members of our consortium recognised that combining our areas of expertise was critical for understanding the complex behaviour of the solar wind including CMEs and CIRs. Moreover, CMEs are the principal drivers of potentially damaging effects on Earth (so-called Space Weather), especially if they act in concert with other CMEs or indeed CIRs. Hence, as well as being scientifically interesting, there is societal importance to the work.
In parallel, our group at the Rutherford Appleton Laboratory manages the Heliospheric Imager (HI) instruments aboard the NASA STEREO spacecraft. Visible-light signatures of both CMEs and CIRs can be detected by heliospheric imaging as they travel outwards from the Sun, potentially towards Earth. HELCATS was designed, not least, to maximise the awareness and usage of the HI data and the results of a variety of modelling techniques that had been developed for its exploitation. An excellent way to achieve this is by providing a coordinated set of catalogues that combine the HI data with other complementary datasets.
Why are the catalogues developed under HELCATS so important? What kind of advances could they potentially lead to?
The HELCATS catalogues are unique. They provide the first long-term record of CMEs and CIRs in the heliosphere — covering an entire solar cycle — coupled with catalogues of associated in situ events recorded near Earth and elsewhere, as well as catalogues of associated activity near and on the Sun. These catalogues will enable us to develop a holistic understanding of the evolution of solar events as they travel all the way from Sun to Earth, or to other planets.
This facility will underpin scientific research activities for many years to come. As mentioned before, the catalogues will enable novel modelling techniques to be validated, which is key to improving both our understanding of the science of the solar wind and our ability to prepare for and mitigate against potential space weather effects.
What would you say are the most important lessons learned from the project?
One of the most valuable aspects of the HELCATS projects is that it brings together, under a single and unique umbrella, catalogues based on widely differing datasets — including both physical observations and modelling results — over a number of different disciplines. Careful and thorough comparison of the catalogues provides the basis for linking events generated on the Sun to their effects on Earth and on other planets. It is this holistic view that provides the most powerful impact of the project, and is the most important achievement, in my view, in terms of enabling potential scientific advances.
What do you hope will be the impact of HELCATS on the scientific community?
HELCATS will leave behind a tangible legacy in terms of its provision of extensive facilities that will be mined by the scientific community for many years to come. Moreover, it will provide key pointers to the most useful tools by which the potential space weather impact of CMEs and CIRs can be predicted.
What has been the community’s feedback so far?
The wider research community is already aware that HELCATS is providing the official catalogues of solar wind structures observed by the STEREO/HI instruments; our post-project legacy planning ensures that this will continue beyond the end of the project and that the facilities will continue to be available. The wider scientific community is already exploiting HELCATS’ results to produce research publications.
The space weather community is also providing very positive feedback on the project. For example the UK Met Office, which provides a space weather forecasting facility funded by the UK Government, has been closely associated with the project throughout and its members are engaged in discussions of the project outcomes. Again, a number of research papers are being published, based on the HELCATS’ results, that specifically address space weather issues.
Do you have any plans to pursue this research after the end of the project?
The HELCATS team will ensure that the catalogues will remain available long after the project has ended, notably through their ingestion into a number of formal data centres. Moreover, upon completion of the project, a set of definitive publications has been planned and will ensure that details of the project itself and its results are widely available. These will form the ‘shop window’ that the wider community will use to exploit the results of the HELCATS project, in addition to the future research that will undoubtedly be conducted by the eight groups within the HELCATS consortium itself over the years to come.
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