Solving the Bz problem in heliospheric weather forecasting

Project Information

HELIO4CAST

Grant agreement ID: 101042188

DOI

10.3030/101042188

EC signature date 23 June 2022

Start date 1 September 2022

End date 29 February 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 999 417,50

EU contribution

€ 1 999 417,50

Coordinated by

GEOSPHERE AUSTRIA - BUNDESANSTALT FUR GEOLOGIE, GEOPHYSIK, KLIMATOLOGIE UND METEOROLOGIE
Austria

Periodic Reporting for period 1 - HELIO4CAST (Solving the Bz problem in heliospheric weather forecasting)

Reporting period: 2022-09-01 to 2025-02-28

Summary of the context and overall objectives of the project

Space weather forecasting is not as sophisticated and advanced as terrestrial weather forecasting. Solar storms lead to the strongest geomagnetic disturbances in the Earth's magnetic field, but their magnitude is impossible to predict longer than ten minutes to one hour in advance. Solving the problem of predicting the solar storm parameters in near-Earth space would improve the forecasts for surges of currents in power grids on the ground, for errors in global navigation systems, or predictions of the radiation environment for astronauts and flight crews. On the bright side, it would also enable much improved forecasts for the aurora, which is appreciated by millions of people around the world.

This project deals with possible solutions to the so-called "Bz problem", which is the key unsolved issue in space weather forecasting, due to the nature of how the interplanetary magnetic field interacts with the Earth's magnetosphere. When the solar wind magnetic field points southward, a geomagnetic storm is intensified, but it is attenuated for a northward-directed field. So not only the speed of a solar storm, but mainly its magnetic field direction, matters for forecasting. Solar storms consist of magnetic structures with higher total magnetic fields that sweep up the solar wind ahead. But these magnetic fields also often rotate smoothly. It is nothing short of amazing that the Sun creates these magnetic cores with a structure that has a clear order. Nature has given us this ordered field as a key to unlock a better way to forecast these storms.

It is not yet understood how these ordered fields in the solar storm magnetic core are created, and thus they cannot be forecasted using images of the Sun or the solar wind. Our approach to prolong the lead time thus focuses on in situ data, which are observations that are taken directly at the position of the spacecraft in the solar wind. These data are continuously available in the solar wind close to Earth. In this case, we simulate the storm's magnetic fields to predict how it looks a few hours from now, based on the current data. If data is taken by a spacecraft that is further ahead between the Sun and the Earth, we combine these observations with knowledge of solar storm physics to produce a forecast at Earth. The latter has been achieved during the project for the first time in real-time with the spacecraft Solar Orbiter and STEREO-A.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We are developing the semi-empirical model 3DCORE for the solar storm magnetic core. An interactive software has been built as a front end, which allows, for the first time, to receive immediate feedback on changing parameters of the model manually. Automatically, 3DCORE can produce ensemble runs, checking many outcomes of the model by making a large number of runs with slightly varying parameters. Our model can make those runs in such a short time that it can compute forecasts in real-time as the solar storm is sweeping over the Earth.

However, we need to figure out if the model represents well how a solar storm magnetic field looks in 3D in the heliosphere. For using the simulation for forecasting solar storms at Earth, we need to know how to set its parameters in the best way possible. We have applied the simulation to solar storms that have been observed by both the Parker Solar Probe and Solar Orbiter, or both at STEREO-A and the Wind spacecraft near Earth. The main result is that a newly developed deformable model version describes the data better than a more rigid shape. We have also made simulations for probing the structure of the 3DCORE model, with synthetic spacecraft that fly through the model at different positions. We found that flank encounters that often show constant components of the magnetic field can be explained by a very low twist of this field, which is a major result for improving both solar storm forecasting.

Due to high solar activity and the fortunate placement of spacecraft orbits with respect to Earth, we have used STEREO-A and Solar Orbiter for analyses of how to use in situ data from closer to the Sun to improve the forecast accuracy and lead time. We have made the first real-time prediction of the geomagnetic effects of a solar storm with Solar Orbiter in March 2024. With STEREO-A we are testing the feasibility of a possible future spacecraft mission on a distant retrograde orbit, in which one of several spacecraft would always be in between the Sun and Earth to provide in situ data for warnings with longer lead time. On 10 May 2024, STEREO-A saw a solar superstorm arrive 2.5 hours before its arrival at Earth, and we informed the public worldwide through social media, and through classical media in central Europe, that a strong solar storm is imminent, which turned out to be the strongest geomagnetic storm in 20 years. An analysis of the interaction of the five solar storms involved in this event is ongoing.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The combination of a magnetically active Sun, producing more solar storms, with the new fleet of active spacecraft (Parker Solar Probe, Solar Orbiter) makes it possible to see much higher numbers of solar storms that were detected by more than one spacecraft, exactly as anticipated in the project proposal. We have produced by far the most extensive catalogue for the research community for these types of solar storm observations at multiple spacecraft. Results beyond the state of the art include the analysis of these multipoint events in various contexts for model development and improved solar storm forecasting.

A major highlight of these new observations includes the impact of a solar storm at Parker Solar Probe, when the spacecraft was in the solar corona at 0.07 astronomical units, in September 2022. We have published the first study to combine modelling of the solar storm observations at Parker Solar Probe with those made by the Solar Orbiter spacecraft, which was impacted by the same storm further out in the heliosphere. We used the version of 3DCORE which has a rigid circular global shape with an elliptical cross-section, and it turns out that the data at the two locations are difficult to interpret with this model. Together with a team at NASA Goddard, a 3DCORE version was developed that has a much more deformable shape, and this model very well explained the observations of a solar storm magnetic field both at Wind and STEREO-A in April 2023.

Another breakthrough concerns the potential usage of upstream solar wind monitors. We have achieved the first prediction of the geomagnetic effects of a solar storm with a spacecraft positioned far ahead of the Earth and near the Sun-Earth line. We invented a new technique based on solar storm physics and applied it in real-time to predict the 23-24 March 2024 solar storm using real-time Solar Orbiter data, provided by Imperial College London. The forecast turned out to be largely correct. On 10 May 2024, the NASA STEREO-A spacecraft made the first observation of a solar superstorm with an upstream solar wind monitor. We are analysing how well a spacecraft at such a position performs for predicting the geomagnetic effects of such events. STEREO-A makes it possible for the first time to systematically study how solar storms can be forecasted with in situ data ahead of the L1 point, which forms the basis for future mission concepts for studying the 3D structure of CMEs and operational forecasting.

Simulation of solar storm magnetic fields with 3DCORE

Magnetic field forecast based on Solar Orbiter data of the March 2024 solar storm

The HELIO4CAST catalog of observed magnetic fields in solar storms up to 0.07 au.

Solar storm arrival time modeling and in situ observations of the 2024 May 10 solar superstorm