The Carrington storm of September 1859 is one of the largest known geomagnetic storms in the historic record. Two observatories in London were operating at the time and by good fortune both recorded the extreme geomagnetic storm on paper records. These are held at the British Geological Survey and have been made available online as digital images. The next step is to digitally trace over the magnetograms to produce useful digital values. However, scaling the values of digital pixels to International System of Units (SI units) of degrees of angle and nanoTesla is not easy as the original scaling factors are not available. We use a mixture of written reports at the time and notes from the observatory yearbooks to track down plausible scaling factors and to explain the process of digitization of very old records. The data for 10 days covering 25 August to 5 September 1859 are now available for other researchers to use.

Space weather refers to the conditions and variations in the Sun-Earth environment that affect space- and ground-based infrastructure. Disruption to railway signaling can happen when geomagnetic disturbances induce electric currents in the rails that interfere with the electrical circuits used to detect trains. This research builds upon an earlier model that assessed the effects of geomagnetically induced currents on railway signaling systems in the United Kingdom, providing the opportunity to examine new failure modes. Railway lines using track circuit signaling are separated into a number of individual blocks, and this study shows that a relay is most susceptible to misoperation when a train is at the end of a track circuit block. The results show that “wrong side” failure (the potentially hazardous type of misoperation), where red signals are turned green, can occur in the line when a geomagnetic storm with frequency of about one or two decades occurs, assuming that each train is positioned at the end of the block it is occupying. We also demonstrate that a 1-in-100 years extreme event could cause many misoperations throughout the line in both directions of travel, although this depends on the number of trains on the line at that time.

In the last decade, machine learning has achieved unforeseen results in industrial applications. In particular, the combination of massive data sets and computing with specialized processors (graphics processing units, or GPUs) can perform as well or better than humans in tasks like image classification and game playing. Space weather is a discipline that lives between academia and industry, given the relevant physical effects on satellites and power grids in a variety of applications, and the field therefore stands to benefit from the advances made in industrial applications. Today, machine learning poses both a challenge and an opportunity for the space weather community. The challenge is that the current data science revolution has not been fully embraced, possibly because space physicists remain skeptical of the gains achievable with machine learning. If the community can master the relevant technical skills, they should be able to appreciate what is possible within a few years time and what is possible within a decade. The clearest opportunity lies in creating space weather forecasting models that can respond in real time and that are built on both physics predictions and on observed data.

Space particle radiation is one of the main concerns in planning long-term human space missions. There are two main types of hazardous particle radiation: (a) solar energetic particles (SEP) originating from the Sun and (b) galactic cosmic rays (GCR) that come from the distant galaxies in space. Fluxes in particles of solar origin maximize during solar maximum when particles originating from the distant galaxies are more efficiently deflected from the solar system during times when the sun is active. Our calculations clearly demonstrate that the best time for launching a human space flight to Mars is during the solar maximum, as it is possible to shield from SEP particles. Our simulations show that an increase in shielding creates an increase in secondary radiation produced by the most energetic GCR, which results in a higher dose, introducing a limit to a mission duration. We estimate that a potential mission to Mars should not exceed approximately 4 years. This study shows that while space radiation imposes strict limitations and presents technological difficulties for the human mission to Mars, such a mission is still viable.

On 03 February 2022, SpaceX launched 49 Starlink satellites into staging orbits at 210 km above sea level prior to raising them to their operational altitudes of 550 km. The pre-launch space weather briefing included no information about an ongoing geomagnetic storm. Excessive atmospheric drag due to the geomagnetic storm resulted in 38 of the satellites re-entering the atmosphere on or about 07 February 2022. We use both models and direct measurements of the atmospheric density during the event to show that density values were enhanced by 20%–30% at the 210 km staging altitude relative to values prior to the geomagnetic storm onset, while they were enhanced 90%–160% at higher altitudes. We recommend improving our ability to model the upper atmospheric response to geomagnetic storms to provide accurate forecasts and actionable “nowcasts” of conditions in low Earth orbit to launch controllers, space traffic managers, and satellite operators.

The extreme space weather events of early August 1972 had significant impact on the U.S. Navy, which have not been widely reported. These effects, long buried in the Vietnam War archives, add credence to the severity of the storm: a nearly instantaneous, unintended detonation of dozens of sea mines south of Hai Phong, North Vietnam on 4 August 1972. This event occurred near the end of the Vietnam War. The U.S. Navy attributed the dramatic event to magnetic perturbations of solar storms. In researching these events we determined that the widespread electric- and communication-grid disturbances that plagued North America and the disturbances in southeast Asia late on 4 August likely resulted from propagation of major eruptive activity from the Sun to the Earth. The activity fits the description of a Carrington-class storm minus the low-latitude aurora reported in 1859. We provide insight into the solar, geophysical, and military circumstances of this extraordinary situation. In our view this storm deserves a scientific revisit as a grand challenge for the space weather community, as it provides space-age terrestrial observations of what was likely a Carrington-class storm.