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Home , Magnetosphere, Solar wind

From THEMIS to ELFIN: Exploring Near Professor Vassilis Angelopoulos Space

CREDIT: NASA GSFC/SVS FROM THEMIS TO ELFIN: EXPLORING NEAR EARTH SPACE

Dr Vassilis Angelopoulos and his colleagues at the UCLA Earth Planetary and Space Sciences Department in California study the interaction of solar radiation with the Earth’s using multiple NASA research satellites. Their aim is to protect our modern technology from being ravaged by solar storms while educating the next generation.

Too Much of a Good Thing This is exactly the scenario Dr Angelopoulos and his colleagues are interested in The is ultimately the engine of all life on forecasting and preventing from happening. Earth. The radiation from our Sun powers our He tells Scientia that he and his team have , provides our food and supports been ‘studying space , and in the Earth’s entire biosphere. Without energy particular one aspect in greater detail: how from the Sun, all life would end and the Earth does become converted into CREDIT: NASA GSFC/SVS would eventually become a cold, dark . the harmful radiation that zaps satellites, But on occasion, the Sun puts out a little too threatens astronauts and creates space much energy in the form of solar flares. electrical currents which can fry transformers of the power grid on the ground?’ This CREDIT: E. Masongsong, UCLA EPSS First described back in 1859 by the amateur energy conversion, which powers damaging astronomers Richard C. Carrington and magnetic storms, is not easy to figure out, Richard Hodgson, a is a sudden but by using advanced satellites orbiting the neighbourhood. These probes are the result the THEMIS mission to determine where and converted. One thing they noticed was and massive release of magnetic energy Earth and the , Dr Angelopoulos and his of a major effort by Dr Angelopoulos and when the energy exchange occurs between that the energy release was only in a small – on the order of millions of team are making some headway. his colleagues at UCLA. Under the mission the solar and the magnetosphere location in space, usually about 25 Earth bombs – that travels outward into the solar names of THEMIS and ARTEMIS, the probes relative to the ground. According to Dr radii away from Earth at the night side. But system, interacting with objects in its path. Probing Energies in Near Earth Space have been exploring the physical processes Angelopoulos, they did this by lining up the the Earth’s magnetosphere’s tail is very large, In particular, ionised particles and magnetic occurring between the and five THEMIS probes and tracking the flow of stretching much further than that. So why is released from solar flares, in the form As the energy released from the Sun – called , to understand the causes of the energy to determine its origin with sufficient this energy release so localised? of coronal mass ejections, interact with the solar wind – flows past the Earth, it aurorae and magnetic storms in the Earth’s time resolution. In other words, they mapped Earth’s magnetic field, and can cause huge interacts with the Earth’s magnetosphere. magnetosphere. Here we discuss the team’s the flow of energy as it moved from the solar To figure this out, Dr Angelopoulos and damage to electrically sensitive equipment. The solar wind is composed primarily of high- ground-breaking discoveries to date, along wind through the magnetosphere. his team tallied the total energy in the This is important for us on Earth, since energy plasma – matter that is so energised with their plans to launch a new mission Their findings were published in the system, measuring where that energy is our civilisation has become increasingly that it becomes ionised, with being – called ELFIN – which aims to investigate journal Science. converted and estimating whether that dependent upon complex electronics. ripped from atoms and molecules. Since electrons in the hazardous radiation belts energy conversion is sufficient to give the plasma is ionised and therefore magnetic, around earth. ‘We found that the trigger of the energy results they actually saw. But the total energy CREDIT: NASA GSFC/SVS Solar storms and solar flares can disable it interacts with magnetic fields, like the release is , a process coming from the solar wind was difficult to satellites, threaten orbiting astronauts and magnetic field of the Earth. The Earth, with THEMIS: Looking for Answers from whereby magnetic field lines – visualised as measure without a spacecraft far enough overload electric transformers on Earth. In its spinning metallic core, is after all a large and solar wind causes massive bursts of The Gods stretched rubber bands – are broken and from Earth where good estimates of the fact, former US President Obama warned that magnet, with a north pole and a south pole. energy that can often be seen from the Earth’s then re-connected to form two loops that magnetosphere tail size could be made, say such phenomena could ‘significantly degrade The resultant magnetic field surrounding the surface as aurorae – dramatic light shows Formally, the THEMIS project is entitled are allowed to contract,’ Dr Angelopoulos greater than 30 Earth radii. Since the radius of critical infrastructure – could disable large Earth – the magnetosphere – deforms the especially at higher latitudes. In the northern the ‘Time History of Events and Macroscale explains. ‘The field line contraction results in the Earth is about 6400 km, that means over portions of the electrical power grid, resulting solar wind and diverts its flow, while the solar hemisphere, aurorae are termed the Interactions during ’. But a double transferring energy released by reconnection 192000 km – about half way to the Moon. in cascading failures that would affect key wind deforms the magnetosphere as well. On borealis, while in the southern hemisphere, entendre points the name to Themis, the towards the Earth, which then accelerates The scientists realised that they could not services such as water supply, healthcare, the dayside of the Earth, which faces towards it’s the aurora australis. Up until a decade Greek goddess of justice, wisdom and good particles to high energies and creates coordinate the furthest THEMIS probes from and transportation.’ In other words, solar the Sun, the pressure of the solar wind ago, the mechanism by which aurorae and counsel. The daughter of the god the space currents.’ The energy is thus Earth well with the closest ones because their storms might cause system wide power compresses the magnetosphere closer to the other solar wind phenomena were generated and the Earth goddess Gaia, Themis is the transformed from magnetic flux to kinetic orbits were significantly interfered with by the failures that don’t just turn off the lights. They Earth. On the night side of the Earth facing were not well understood. However, since perfect patroness of scientists studying the energy, thermal energy and acceleration of moon. So, in Dr Angelopoulos’ words, ‘rather could also lead to a massive human toll when away from the Sun, the solar wind drags the 2007, satellite probes have been exploring the and other manifestations of the particles. This is how aurorae are formed than trying to beat the moon, we decided to food, water and other necessities cannot be magnetosphere out over great distances, regions of space where the solar wind and the Earth’s interaction with the solar wind in from the deformations of the magnetosphere join it.’ distributed, leading to disease, famine and forming a tail similar to that of a . Earth’s magnetosphere interact, sending back the sky. by the solar wind. But it was still not even death on a global scale. The interaction between the magnetosphere information to explain what’s going on in our Dr Angelopoulos’ group and NASA designed clear exactly how the energy was actually

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CREDIT: E. Masongsong, UCLA EPSS ARTEMIS: Getting the Most Out of What You’ve Got we would be using flotillas of space buoys,’ he explains. ‘There is a trend to capitalise on CubeSat technology to help advance space In a strategy that enabled NASA to extend the THEMIS probes’ mission instrumentation. We are looking to do that for energetic particle and save millions of dollars, the team used the remaining fuel on two detectors.’ of the THEMIS probes to raise their orbits and enter Moon orbit, about Meet the researcher 60 Earth radii from home. This new mission was called ARTEMIS – A CubeSat – also called a U-class spacecraft – is a miniaturised, cubic Professor Vassilis Angelopoulos ‘Acceleration, Reconnection, Turbulence and Electrodynamics of the satellite made primarily with off-the-shelf electronics. Relatively cheap Department of Earth, Planetary and Space Sciences Moon’s Interaction with the Sun’. The objectives of this new mission and small, are used extensively with the International Space were to study the lunar and to get into the Earth’s Station and its scientific projects. Dr Angelopoulos’ team are now in the University of California, Los Angeles magnetosphere’s tail and make estimates of the total magnetic process of building a CubeSat that can be used in fleets launched in energy content. The repurposed probes could also be better aligned the magnetosphere. Their proposed mission is called ELFIN – Los Angeles, California with the remaining three THEMIS probes to determine where the Losses and Fields Investigation. USA energy conversion was occurring. In a paper published in Science, Dr Angelopoulos and his group reported that the energy conversion occurs Designed and built by UCLA undergraduates, ELFIN’s goal is to within extremely thin sheets of electrical currents in space. At only investigate high-energy electrons that travel at relativistic in about 10 km thick, these current sheets or magnetic fronts can convert Earth’s radiation belt, and to understand how they become knocked Dr Vassilis Angelopoulos received his PhD from the University of FUNDING all the available energy from magnetic energy into particle energy. out of their cyclical orbits by low frequency electromagnetic . California at Los Angeles in 1993, for a thesis on Space Plasma . This process scatters the electrons that are then guided by the Earth’s After receiving his doctorate, he worked as a post-doctoral researcher NASA So first of all, the of the solar wind is converted into magnetic field and fall into the atmosphere. Then, at an altitude of at the Applied Physics Laboratory at Johns Hopkins University. After NSF magnetic energy in the Earth’s magnetospheric tail. This magnetic about 100 km above the poles, these electrons finally lose their harmful working as a research physicist at the University of California at US Air Force Research Laboratory energy is then converted back into particle energy when the magnetic energy, generating auroral displays in the process. This effective Berkeley, Dr Angelopoulos joined the faculty at UCLA in 2007 where he fields reconnect. It is the conversion of that energy back into particle emptying of the radiation belts moderates increases in electron fluxes is now Professor of . REFERENCES energy that ultimately powers the aurorae. This conversion also heats caused by solar events. ‘We need to understand these loss processes Dr Angelopoulos’ primary interest is the study of how particles are up the magnetospheric plasma and energises the Van Allen radiation to assemble the full picture of how space radiation is driven by solar accelerated by and in the Earth’s magnetosphere, and how the upper V Angelopoulos, et al., Electromagnetic Energy Conversion at belts – areas on the inner part of the magnetosphere that sequester particles,’ Dr Angelopoulos explains. atmosphere, the and the lunar environment respond Reconnection Fronts, Science, 2013, 341, 1478–1482. DOI: 10.1126/ energised particles. In other words, the ‘weather’ in space around our to space currents driven by the solar wind. Dr Angelopoulos is the science.1236992 Earth is in large part determined by the solar wind blasting away at But that’s not the only expected benefit of ELFIN. There is already Principal Investigator of the ELFIN Cubesat nanosatellite mission, the Earth’s magnetosphere. This causes storms, substorms and other a great reward being reaped at UCLA – ELFIN and its CubeSats are supported by grants from NASA and NSF. He is also Principal VA Sergeev, V Angelopoulos and R Nakamura, Recent advances in phenomena, and just like our terrestrial weather, we would like to be at the forefront of higher education. Dr Angelopoulos proudly tells Investigator of THEMIS – a five satellite and 20 ground based understanding dynamics, Geophysical Research Letters, 2012, able to predict our . Dr Angelopoulos and his team are Scientia that the project provides opportunities for students to work observatory mission proposed and managed by the UC-Berkeley’s 39, L05101. DOI: 10.1029/2012GL050859 up for that. in a professional environment and develop critical thinking and Space Science Laboratory – and Principal Investigator of the ARTEMIS problem solving abilities that are much needed in research and project – a two satellite lunar mission. Dr Angelopoulos has authored V Angelopoulos, The ARTEMIS Mission, Space Science Reviews, 2010. Into the Future – ELFIN industry. Dr Angelopoulos’ vision is that innovation and discovery or co-authored more than 500 articles published in peer-reviewed DOI: 10.1007/s11214-010-9687-2 come from transcending disciplinary boundaries and approaching journals and other professional proceedings. In order to develop quantitative models of space weather, you have problems holistically. His students are exposed to a fast-paced research V Angelopoulos, et al., Tail Reconnection Triggering Substorm Onset, to understand the correlation and self-organisation of the energy environment with realistic goals and obstacles. Furthermore, with CONTACT Science, 2008, 321, 931. conversion regions into one large magnetic storm. Dr Angelopoulos information readily available through Internet resources, teaching believes that this will require multiple small satellites that can make students how to critically and effectively process information towards T: (+1) 310 794 7090 V Angelopoulos, The THEMIS Mission, Space Science Reviews, 2008. multi-point measurements over broad areas in space with sufficient generating new knowledge or products becomes the new role of E: [email protected] DOI: 10.1007/s 11214-008-9336-1 spatial resolution. So, he and his team have now embarked on a academia. Dr Angelopoulos’ ELFIN project is more than just checking W: http://esp.epss.ucla.edu miniaturisation effort with the potential to radically change how space weather around the Earth. With ELFIN he’s trailblasing a new way they conduct . ‘Rather than using classical spacecraft, of teaching science at the university level.

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