When Earth’s magnetic field is struck by violent geomagnetic storms, narrow streams of fast-moving ions can form, which pose serious threats to vital satellite systems. Through her research, Dr Amy Keesee at the University of New Hampshire is shedding new light on how these streams originate, by picking up the energetic neutral atoms they occasionally generate. Her team’s work has proved that these atoms can be used to build reliable temperature maps of the magnetosphere – the region around Earth dominated by the planet’s magnetic field. Such temperature maps can help us to better predict when satellite systems may be under threat.

Earth’s Protective Shield

The magnetic field which surrounds our planet provides a vital barrier against the streams of energetic ions which constantly hurtle towards us. Under the laws of electromagnetism, the paths of these charged particles are deflected by magnetic field lines, so that when they interact with Earth’s magnetosphere, particles that were previously on a collision course with Earth are repelled into space, protecting the planet’s surface from dangerous radiation.

Most of the time, these particles come in the form of electrons, protons, and helium nuclei originating in the Sun’s upper atmosphere, which permeate the solar system in a steady stream named the solar wind. In more extreme cases, particles can be ejected through violent eruptions of plasma on the Sun’s surface, named coronal mass ejections.

Triggering Storms

These dramatic events send energetic blobs of plasma out into space, which carry significant magnetic fields of their own. As they clash with Earth’s magnetosphere, the magnetic forces induced by these blobs can generate shockwaves which reverberate throughout the entire system, in events named geomagnetic storms.

In turn, these shockwaves can generate violent and unpredictable movements in the ionosphere: a region in Earth’s upper atmosphere that is mostly unshielded from the Sun’s radiation. Here, atoms have been stripped of their outer electrons, leaving behind positively-charged atomic nuclei whose motions are directly influenced by surrounding magnetic fields. As these particles interact with the reverberating magnetosphere, the energy they gain can allow them to penetrate far deeper into Earth’s atmosphere.

This phenomenon can have destructive consequences for the satellite systems we now rely on for many vital applications: including communication, navigation, financial transactions, and national security. During geomagnetic storms, energetic ions and electrons can more readily cross paths with these orbiting satellites – damaging and potentially even destroying their electronics if they are still powered on. This makes it particularly crucial for researchers to understand the coupled dynamics that play out in the magnetosphere and ionosphere when geomagnetic storms strike.

Heated Ion Slingshots

Dr Amy Keesee and her colleagues at the University of New Hampshire explore one particularly important aspect of this process, which stems from the unique geometry of Earth’s magnetic field on its night-time side. While the field lines facing the Sun are continually compressed by the solar wind, those on the opposite side form an elongated ‘magnetotail’ – which points away from the Sun, and extends far out into interplanetary space.

As the energy deposited during a geomagnetic storm reverberates around the magnetosphere, it will eventually be dumped in the magnetotail. This causes the tail’s elongated magnetic field lines to act like a slingshot – capturing particles within small sections of the magnetosphere, heating them up, and sending them hurtling towards Earth.

These channels of fast-moving ions are a major part of the threat faced by orbiting satellites during geomagnetic storms, but so far, they have proven notoriously difficult to study. The problem is that these channels don’t emit secondary particles of their own – like how a star can be analysed by the photons it emits, for example.

Ultimately, the only way to study them is to place observational instruments directly in their path. This is particularly challenging, since the events are both unpredictable and short-lived, making it increasingly difficult for researchers to observe them directly. So far, these challenges have prevented researchers from making accurate predictions of when and where heated channels of ions will arise; and subsequently, how satellite systems can be better protected from them.

Searching for Energetic Neutral Atoms

Dr Keesee and her colleagues have been developing a way around this barrier, which could make the process far easier to study. Their approach is based on searching for particles named energetic neutral atoms (ENAs) – which only emerge in rare circumstances, but may offer vital clues as to what is happening in the magnetotail during geomagnetic storms.

ENAs are generated when fast-moving atomic nuclei steal orbiting electrons from the neutral atoms they interact with, while barely losing any of their original energy. As ordinary atoms, the paths taken by these new particles are no longer influenced by the shape of Earth’s magnetic field, leaving them free to travel unabated towards the planet’s surface.

By detecting the ENAs that make it to the inner magnetosphere, some researchers have proposed that the particles could be used to study localised bursts of charged particles in the magnetotail. So far, however, it has remained unclear whether this link can really be made.

For example, while ENAs have been observed at around the same time as geomagnetic storms in the past, similar observations have also been made without any concurrent evidence of energy being injected into the magnetosphere – placing doubt on whether ENAs could really be used to study the magnetosphere’s deeply complex dynamics.

Measurements with TWINS

To shed new light on the problem, Dr Keesee’s team analysed the ENA observations made by NASA’s Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) mission, which ran from 2008 until 2020. On top of this, they aimed to recreate narrow streams of ions within simulations of real geomagnetic storms – incorporating the coupled interactions between charged particles and moving magnetic fields.

In one recent study, the team used their simulations to create a temperature map of the magnetosphere, in which higher ion temperatures are associated with local-scale accelerations within the magnetotail. ‘We used a novel technique to observe these ions by calculating ion temperature maps of the magnetosphere using data from energetic neutral atom imagers,’ says Dr Keesee.

As they had hoped, the maps produced by their simulations largely agreed with the temperature maps generated by TWINS through its ENA measurements. This was a particularly welcome surprise – providing robust evidence that ENAs are indeed a reliable indicator of where ions are being heated and accelerated.

The researchers did find that the ion channels observed by TWINS were hotter than those that appeared in their simulations. All the same, they hope that these differences could be ironed out through further improvements to their simulation techniques, which consider the many different factors involved in the accelerations in greater detail.

Mapping the Magnetosphere

In an additional study, Dr Keesee and her colleagues combined ENA observations from TWINS with direct observations of energetic streams of ions made by orbiting satellites. They also included ground-based measurements of Earth’s magnetic field, and observations of the aurora: the famous light display commonly seen in Earth’s polar regions, where ions can penetrate far enough through the magnetosphere to interact with the atmosphere.

While this phenomenon usually occurs since Earth’s magnetic field lines dip below its surface above its poles, leaving the atmosphere exposed to outer space, the disruption unleashed by geomagnetic storms can make the aurora visible at lower latitudes.

With these combined measurements, the researchers examined the changes that unfolded within the ionosphere and magnetotail during a real geomagnetic storm, triggered by a coronal mass ejection in 2012. They discovered that the ENAs picked up by TWINS both prior to and during the storm were closely associated with streams of charged particles being heated and accelerated in the magnetotail – but only after a reconfiguration of the Earth’s magnetic field were enhancements picked up by the magnetic field and aurora-measuring instruments.

Early Warning Systems

The team’s results are already incredibly promising – proving definitively that the ENA measurements provided by the TWINS mission could realistically be used to create temperature maps of the magnetotail. Crucially, they also show that the same instrument could be used to examine how local-scale temperatures in the magnetotail vary over time, without any need to send spacecraft to monitor its unpredictable dynamics directly.

These maps could be particularly crucial when geomagnetic storms are imminent. If coupled with observations of coronal mass ejections on the Sun, they could provide a more accurate weather forecast for the magnetosphere – allowing researchers to better predict when bursts of energetic ions are more likely to penetrate closer to Earth’s surface.

In turn, the techniques developed by the team could provide more effective early warning systems for satellite systems. By paying close attention to these warnings, satellite operators could assess when their instruments may be vulnerable to incoming streams of ions – signalling an urgent need to power their systems down.

Although this would incur financial and operational costs in the short term, it could also save satellites from potentially irreparable damage – allowing them to remain fully operational during future solar storms.

In her current research, Dr Keesee is working with colleagues that are designing a new generation of imaging instruments. If achieved, these designs could ultimately produce maps of the magnetotail’s constantly varying temperature in unprecedented detail, based on ENA measurements alone.

Recent studies suggest that South Africa’s youth are less engaged in formal politics than earlier generations. Professor Elirea Bornman and her students at University of South Africa have recently investigated the opinions of youth on democratic institutions and the state of democracy in post-Apartheid South Africa. Their findings suggest that the apparent political disengagement and withdrawal from voting among young people is not necessarily associated with apathy or a lack of political opinions, but can reflect their lack of confidence in political processes and older generations of leaders.

Politics in Post-Apartheid South Africa 

The disengagement of youth in politics is a major issue facing democracies worldwide. When young people are not engaged with political processes, this means that they have no influence in important decisions that affect their daily lives. By including the voices of youth and responding to their needs, countries across the globe can build more equitable, stable and peaceful societies.

The involvement of young people in African politics is more controversial than that of youth in other parts of the world. Over the past few decades, African youth have been associated with very different political events, such as the ‘Arab spring’ in North Africa, where youth were at the forefront of political change, and – on the other hand –  the suppression of youth during the 1970s Red Terror in Ethiopia. In addition, African culture highly values age as a cultural symbol. Thus, it often only views young people as citizens of the future.

Because of its unique history, the political situation in South Africa is particularly complex. During apartheid, voting rights were restricted to white people only. These rights were extended to all citizens in 1994, enabling newer generations to vote irrespective of their ethnic or racial background.

Investigating Political Opinions

People born in South Africa after 1994 are often referred to as the ‘Born Frees’, as they have grown up in a society where equal rights to vote and to participate in society are guaranteed. Professor Elirea Bornman and her students wanted to understand how ‘Born Frees’ view their role in South African politics, as well as to gain insight into their opinions about elections, political parties, and party membership.

Recently, analysts suggested that many young people who do not vote might be voicing their opinions in other ways, such as on social media or through political protests. To determine whether this is the case, the researchers gathered the opinions of South African youth residing in the Pretoria area, by conducting six focus groups conducted between 2014 and 2018.

The participants were between 18 and 34 years old. As past studies suggested that white people in South Africa are sometimes hesitant to voice their opinions in the presence of other cultural groups, the researchers conducted separate focus groups for white and black participants.

Reasons for Voting

During the focus groups, the young people voiced a wide range of opinions. Overall, the findings gathered by the team suggest that South African youth form a very diverse group, as different participants had very different views on politics, voting, and political processes.

While some participants reported that they regularly voted, others said that they had no intention of participating in elections. The researchers tried to understand the reasons behind these differences and what encouraged South African youth to vote or to abstain from voting.

‘Some participants viewed voting as an expression of their love and dedication to the country,’ says Professor Bornman. Many saw it as a rite of passage into adulthood, through which they could influence decision-making and bring about change. Others, particularly some of the black participants, viewed voting as a responsibility, feeling that they should take full advantage of the rights that were unjustly denied to their ancestors.

Reasons for Not Voting

While some of the participants were politically active and deeply valued the democratic process, others said that they had no interest in voting or participating in political conversations. This lack of interest, however, did not always appear to be associated with ignorance or with what theorists have described as ‘political apathy’.

Instead, many people who did not vote expressed a general lack of confidence in the older generation of leaders and existing political parties, as they believed that these leaders were too old and did not reflect the needs of younger generations. For instance, some pointed out that current politicians did not understand problems of the modern era and did not communicate using contemporary technological tools, such as social media and the internet.

Others also believed that voting did not bring any real change, as the ANC party, the most supported party in South Africa, would likely win irrespective of their vote. Government corruption and poor performance were also two major reasons why some participants preferred not to vote.

‘In their case, withdrawal from elections cannot be regarded as political apathy, but represents a conscious act of opposition and an alternative form of political participation,’ says Professor Bornman. ‘However, whether they intended to participate in elections or not, most of the participants expressed dissatisfaction with the current political leadership in the country.’

Interestingly, regardless of whether they voted or not, most participants appeared dissatisfied with the current government in South Africa, as they felt that it did not prioritise the interests of the country and its citizens. As one of the participants put it: ‘I really think the ANC has been in power too long and we need some sort of a change. The politics are becoming… stagnated… the fat cats are getting fatter.’

Another participant added: ‘I feel like they should really start realising our education, our children, our healthcare, our poverty, jobs… they really, really have to start doing something about that, which I don’t feel our government does.’

Preventing Alienation

Overall, the recent study carried out by Professor Bornman and her team shows that South African youth range from young people who are engaged in politics to those who are largely disengaged. However, their findings suggest that those who do not actively participate in politics do not always desist due to apathy. Instead, some are untrusting of existing politicians and parties.

‘Our findings are important not only to achieve a better understanding of youth in post-apartheid South Africa, but also to get a glimpse of the disillusionment and frustration of youth in Africa where they no longer share the revolutionary ideals of their political leaders,’ says Professor Bornman. ‘They have also become tired of gerontocratic African leaders. Instead, the Arab Spring as well as the influence of the media – and social media in particular – have raised awareness among African youth of what good and accountable democratic governance entails.’

In the future, Professor Bornman’s study could encourage South African leaders and political parties to devise alternative communication strategies and initiatives that address the doubts and concerns of younger generations. Such initiatives could ultimately bring youth back into the political dialogue, ensuring that their voice is heard during important decision-making processes.

‘Youth alienation could, in the end, have far-reaching negative implications for the stabilisation of democracy in South Africa, but also in other post-colonial societies,’ says Professor Bornman. ‘In order to consolidate democracy and to prevent destabilising youth uprisings, political leaders should govern in transparent and accountable ways. The youth should furthermore not be perceived as citizens of the future. Their voice in the current political situation should be taken seriously.’

A key step towards a carbon-neutral future could be reached through dispersed power grids, featuring networks of local-scale renewable energy and battery storage plants. To prevent these power grids from damaging themselves and their surroundings when electrical faults arise, they must be integrated with ‘circuit breakers’, which temporarily interrupt the current flowing through them. However, currently available circuit breakers cannot handle the medium-voltage direct currents best suited for these grids. Through an innovative new circuit breaker design, Steve Schmalz and his colleagues at Eaton Corporation, the Illinois Institute of Technology (IIT), Virginia Tech and the National Energy Technology Laboratory (NETL), hope that this challenge will soon be overcome.

AC vs DC

Currents in electrical circuits can flow in two distinct ways: either periodically changing direction in alternating current (AC), or maintaining a constant direction in direct current (DC). Each of these types has its own advantages. Owing to its high efficiency and low maintenance costs, AC has dominated the US power grid for over a century. However, through the latest advances in semiconductor electronics, DC is now becoming increasingly popular.

With its ability to transmit large amounts of power with very little energy loss, DC is now the current of choice in a wide array of applications, which vary depending on voltage. While low-voltage DC is commonly used in consumer electronics, LED lighting and electric vehicles, high-voltage DC can reliably transmit power across large distances – making it key to the performance of undersea and underground cables.

While the technology required to implement DC at low and high voltages is now maturing, there remains a gap in the middle, spanning voltages ranging from 1 to 100 kilovolts. Such ‘medium-voltage DC’ is still in the early stages of technological development.

Dispersed Power Grids

Steve Schmalz and his colleagues at Eaton Corporation, alongside partners at IIT, Virginia Tech and NETL, recognise two key advantages of medium-voltage DC: it is both the most practical voltage range for converting AC into DC, and is well suited to transmitting power across local-scale regions. Because of these advantages, progress in medium-voltage DC technology could bring immense benefits to the development of dispersed power grids. Rather than being generated on industrial scales in single locations, such as coal or nuclear power plants, energy in these grids is produced, stored and distributed on local scales.

In a dispersed power grid, the excess energy produced by networks of smaller renewable energy plants, including wind and solar farms, can easily be stored in local battery facilities, and then released when required. For example, a solar farm may produce more energy than demand requires during the day – and so this excess can be used to charge a battery. This energy can then be used to power homes and businesses after sunset, when no solar power is being generated.

On top of this, the use of medium-voltage DC would mean that these new systems could easily plug into existing AC power grids, without major changes to infrastructure. ‘For example, a medium-voltage DC system could serve as a bi-directional link between separate AC grids that are unsynchronised and could otherwise not be connected without massive reconfiguration or replanning,’ explains Schmalz. ‘This could provide added grid resilience allowing one AC grid with excess capacity to share with an adjacent grid that is being overtaxed. Depending on the geography, retrofit medium-voltage power converters between the AC and DC systems could control the power flow between grids with less added infrastructure, and minimizing the need to clear rights-of-way for completely new AC power lines.’

Altogether, the efficiency and flexibility offered by dispersed, small-scale power grids could make them central to the widespread rollout of renewable energy. As such, dispersed power grids could be essential in drastically reducing greenhouse gas emissions. However, before this can be achieved, new innovations in the technology required to support medium-voltage DC will be essential.

Interrupting Faulty Circuits

Currently, one of the biggest roadblocks in this development is the need for an essential safety component, named a ‘circuit breaker’. These devices come in a wide array of designs, but all operate by the same general principles. During electrical faults, which can produce damaging or even dangerous surges in current, powered sensing devices detect any excess flows of current by picking up the heating or magnetic effects they generate.

Once the fault is detected, the device opens a switch to break the circuit, temporarily interrupting the path of its flowing current, thus stopping the surge. In mechanical circuit breakers, this involves using transducers in response to the excess current to trigger switch mechanisms such as springs or levers – physically separating two contacts in the circuit in a controlled way. This separation generates an arc of electricity where the current jumps between the contacts, which must be cooled, contained, and extinguished as quickly as possible.

The main advantage of mechanical circuit breakers is that they allow currents to flow with very little conduction loss in normal circumstances. However, since their contact separation mechanisms can take a long time to trigger, the level of safety they offer can be limited. In addition, the emergence of an arc can damage the device, limiting its operational lifetime. More fundamentally, quenching an arc between parting contacts is more difficult to accomplish in DC, as the current does not periodically reach zero like in AC, allowing the arc to extinguish. So far, these drawbacks have meant the use of mechanical circuit breakers has largely been limited to AC and low-voltage DC systems. These challenges make upscaling to medium-voltage DC more difficult.

Alternatively, solid-state circuit breakers involve the use of semiconductor-based transistors, which interrupt flowing currents within the semiconductor material itself. These switches don’t generate arcs, and can be switched to block current far more quickly when electrical faults arise. This makes them ideal for applications where circuit breakers are placed close to the equipment being protected, such as battery packs in electric vehicles.

However, solid-state circuit breakers also induce high energy losses. This means that much of the current flowing through them is lost as heat – creating the need for separate cooling systems. Currently, it would be incredibly difficult to scale this setup to medium-voltage levels, without sacrificing their cost and efficiency.

Hybrid Circuit Breakers

One further design, named a ‘hybrid’ circuit breaker combines the advantages of mechanical and solid-state circuit breakers – rapidly interrupting circuits when faults arise, while keeping power losses comparatively low.

Hybrid circuit breakers can have different configurations, but each one employs four basic functional elements: a mechanical switch, at least one semiconductor-based switch which ultimately interrupts the current flow, a means of transferring or ‘commutating’ current flow from the mechanical switch to the semiconductor interrupter, and a system of surge arrestors that limit the peak voltage and dissipate any excess electrical energy as heat.

When a fault occurs, the commutator transfers the current to the semiconductor switch. The mechanical switch then opens, but only once the current has been completely diverted – preventing an arc from forming. Afterwards, the semiconductor is turned off, and any remaining current is dissipated by the surge arresters.

Roadblocks to Commercial Rollout

In principle, this combination of circuit breaking mechanisms makes hybrid circuit breakers ideal for integrating with medium-voltage DC systems. However, there are still challenges to overcome. While existing hybrid circuit breaker designs provide lower energy losses than solid-state circuit breakers, they don’t typically provide the same rapid response times because they are limited by the speed of the mechanical switches. Meanwhile, the method of commutation may compromise the overall efficiency that the hybrid circuit breaker can truly achieve.

Prototypes for medium-voltage DC circuit breakers are now in development by several research teams around the world, and are now capable of handling voltages ranging from 7 to 12 kilovolts. However, these challenges mean that they have only been demonstrated in lab settings and aren’t yet considered commercially-viable products.

Designing an Improved Hybrid Topology

Through their research, Schmalz and his colleagues have made promising steps towards overcoming this barrier, through the development of a modular, scalable device, specifically designed for interrupting medium-voltage DC current, with key improvements to the essential hybrid breaker elements.

Some previous hybrid designs employ methods to transfer current from the mechanical switch to the semiconductor interrupter. Such designs require the insertion of another semiconductor in the conduction path with the mechanical switch, which compromises overall efficiency. In the team’s new design, current flows only through a closed mechanical switch under normal circumstances, minimising energy loss. This switch is connected in parallel to a second conduction path, containing a novel power electronic circuit that can carefully track the current flowing through it, and subsequently inject current in the opposite direction.

When a fault occurs, this injector transfers the current from the mechanical switch to its own conduction path – which also contains the semiconductor interrupting switch. When the current passing through the mechanical switch reaches zero, it opens with no arcing or damage to the contacts.

Other key improvements in the design reside in the mechanical switch, which employs contacts enclosed in a vacuum and a Thomson coil-based actuator capable of forcing the contacts open 20 times faster than traditional mechanisms. The vacuum provides higher-voltage insulating properties at shorter contact separation distances. These traits combine to dramatically improve the response time to be comparable to that of pure solid-state circuit breakers, because the semiconductor interrupting switch can be switched off soon after the contacts part, completing the fault interruption process.

Another key advantage of this design is that the semiconductor interrupting switch is completely modular – meaning any number of them could be connected in series to scale to higher voltage systems. In turn, this means that the surging current can be shared between as many interrupters as required.

Such an easily scalable setup allowed Schmalz’s team to optimise their system over a wide range of voltages. In their setup, they used their hybrid circuit breaker to handle up to 6 kilovolts. Compared with previous designs, this setup offered both comparatively fast response times, improved efficiency and far higher power density. This allowed it to be compacted into far smaller volumes, removing any need for bulky and expensive cooling apparatus.

Bringing Medium-Voltage DC to Maturity

Schmalz and his colleagues hope that their novel hybrid circuit breaker design could help to overcome many of the challenges currently faced by medium-voltage DC technology. By integrating their device into power grids, operators could confidently safeguard their systems against damage when electrical faults arise.

If the device becomes commercially available in the near future, it will enable easier integration of renewable energy and battery storage into existing power grids, in addition to more efficient powering of native DC loads that connect to power grids, such as railways and data centres. By implementing dispersed power grids, capable of generating and delivering energy on local scales, Schmalz and his colleagues hope that an important step towards a carbon-neutral future may finally be achieved.