The Sun and geospace Resource GS1 K. Endo/Nikkei Science BAS The aurora over the BAS Halley Research Station. Inset: Artist’s impression of the Sun and geospace (not to scale) illustrating how particles flowing radially from the Sun are deflected by the Earth’s magnetic field which forms a cavity in the particle stream, known as the magnetosphere. Solar wind – magnetosphere interaction Resource GS2

An illustration of the inter- action between the solar wind and magnetosphere. Solar wind streamlines are deflected by a shock wave to flow around the magnetosphere in a turbulent layer known as the magnetosheath. Some solar wind plasma leaks inside the magnetosphere. In the magnetosphere particles are guided in spiral helical trajectories along magnetic field lines. Some of these precipitate into the atmosphere to create the aurora. SUN BAS The aurora over Antarctica Resource GS3 Professor L.A. Frank (University of Iowa) A satellite view of Antarctica showing the aurora encircling it The effects of space weather on human activity Resource GS4

Effects on satellites radiation belts. Similarly, the continuous Satellites often operate in the space bombardment by atoms in the thin upper environment for many years. As a result, atmosphere can alter orbits and wear the Hubble Space Telescope. These boosts they can sustain long-term exposure surfaces away. Some materials become Effects on power systems again add to costs. effects in addition to special ‘space storm’ brittle from long-term exposure to solar Electric power systems on the ground problems. Depending upon their orbit, ultraviolet light above the protective can be affected by the enhanced satellite electronic components, solar absorbing atmosphere of Earth. Single currents that flow in the magnetosphere- cells, and materials degrade from the penetrating energetic particles (from ionosphere system during geospace accumulated radiation dose caused by the Van Allen belts or cosmic rays) can storms. These currents cause magnetic repeated traversals of the Van Allen change the information stored in elec- field perturbations on the ground that in tronics components such as spacecraft turn induce other currents in long memory chips by flipping binary values EPRI transmission lines, especially those that encode the information. Map of power disruption in North America, located at high latitudes. The slowly A particular ‘danger zone’ for duelow- to a space weather storm in March 1989 varying DC part of the currents can be altitude spacecraft is in the region of large enough to cause overheating and the South Atlantic, where the energetic damage to systems designed for AC. particle populations in the radiation propulsionbelts systems. This appeared to Disruption of power distribution systems can reach unusually low altitudes duehappen to with the Canadian ANIK E1 and can adversely affect many aspects of our a local weakness in the Earth’s magneticE2 satellites. They experienced a loss of daily lives should a blackout result. field. Space weather ‘storms’ add systemsnew during an interval of elevated intensity of high-energy electrons in the Earth’s outer magnetosphere. The upper atmosphere becomes inflated problems while exacerbating the cumul- Effects on pipelines if it is heated by extra energy sources ative effects. Some satellites charge up Space weather-induced currents similarly such as auroral particles and enhanced when they are suddenly immersed in flow in long conductors on the ground resistive ionospheric currents. The enhanced radiation environments in the such as oil pipelines. These currents resulting increased atmospheric particle Van Allen belts, the auroral zone, or create galvanic effects that lead to rapid inter- densities at 300–500 km altitude signific- corrosion at the pipeline joints if they are planetary space. Component surfaces can antly increase the number of microscopic not properly grounded. Such corrosion charge to very high potentials compared collisions between the satellite and the requires expensive repairs or can lead to to the metallic surfaces of the satellite, surrounding gas particles. This increased permanent damage. leading to discharges between the two. ‘satellite drag’ can alter an orbit enough Such discharges cause both material so that the satellite is temporarily ‘lost’ to damage and electrical currents on the communications links. It also causes the Effects on communications systems spacecraft. The latter can masquerade premature decay of the orbit. This can as ‘phantom commands’ to spacecraft lead to early loss of the system withShort wave radio communication at HF systems. These events can cause a loss of associated financial implications orfrequencies (3–30 megaHertz), which is elesat, Canada controlT of instruments and power or necessitate shuttle ‘boosts’ for some, likestill extensively used by the military and Anik E1 satellite for overseas broadcasting in various

Page 1 of 2 The effects of space weather on human activity Resource GS4

countries, depends upon the reflection of signals from the Earth’s ionosphere. The signals are attenuated when the electron number density in the lower ionosphere increases. This affects the usable radio solar events likely to produce a geospace communication frequencies and can storm (such as a coronal mass ejection) cause a total communications blackout. are less apparent. Solar flare ultraviolet and x-ray bursts, Astronaut radiation exposure is a solar energetic particles, or intense major concern for manned space flight. aurora during geospace storms can all Most manned missions occur in orbits bring on this condition. that are below the regions where the Van The changes in ionospheric attenuation Allen belt radiation is most intense. and reflection of electromagnetic waves Spacewalks in the region of anomalously also affect the use of ‘over-the-horizon’ high radiation over the South Atlantic HF radars used to detect and monitor need to be avoided. However, the Mir aircraft and sea conditions. Ionospheric space station and the International Space Station (ISS) have orbits sufficiently inclined from the equator to bring them electron density irregularities also produce into the expanded auroral zones that noise or ‘clutter’ in the radar signals. occur during geospace storms. The likelihood of a frequently disturbed Effects on navigation systems magnetosphere and presence of solar The same disturbance-related changes energetic particles is considerable given in the Earth’s ionosphere that affect NASA the phasing of the ISS construction with communications introduce changes inView of Earth across the cargo bay of the Space Shuttle the next solar maximum. the time it takes signals to traverse the For missions that leave low-Earth orbit, ionosphere. The abnormal time delays like the Apollo missions to the Moon, the introduce position errors and decrease survey data that can be mistakenprotection from cosmic rays and solar ability to rapidly traverse the radiation the accuracy and reliability of the Global for signatures of subsurface resources.energetic particles, there is still concern belts and to predict the occurrence Positioning System (GPS), which is used Survey schedules or operations mustfor flights on polar routes during major of solar energetic particle events is for many range-finding and navigational be modified, often suddenly and withsolar particle events. The primary means essential. While proposed manned space- purposes. significant costs, to avoid errors in theof reducing this hazard is to modify craft for future missions to Mars will survey data. flight paths as necessary and to limit the generally be equipped with shielded flight time of personnel on high-altitude astronaut shelters, adequate warning is Hazards to humans in space aircraft such as Concorde. It is clear necessary for these to be useful. Effects on geomagnetic surveys The principal space weather hazard to that in this case early warnings of An astronaut on the lunar surface humans is radiation exposure to astro- Geomagnetic surveys are important tools solar energetic particles are extremely would be in danger of a lethal dose of nauts and passengers in high-altitude in the commercial exploration of natural desirable. While some sources (solar radiation from solar energetic particles resources. However, space weather-relatedaircraft. Although the residual atmosphere flares) can be monitored at least on the were a major coronal mass ejection to perturbations can create signals inabove an aircraft provides a measure of visible disk of the Sun, indications of occur unnoticed.

This article is drawn from the views of the US National Academy of Sciences as expressed on their World Wide Website (http://nas.edu/ssb/spwptSnw.html) Page 2 of 2 Why study geospace in Antarctica? Resource GS5

Nightlights of the world as viewed by satellites in space, illustrating the lack of light pollution in Antarctica and its remoteness from industrialised areas. NOAA/USAF

There are six compelling reasons for conducting frontier the solar wind energy transferred into the magnetosphere between the energy input to the upper atmosphere from experimental research on geospace physics in the and ionosphere is deposited in the high latitude regions, below, due to the different topography and albedo of the Antarctic: owing to the configuration of the Earth’s magnetic field. two hemispheres. One manifestation of this is the aurora. • The effects of the separation of the geographic and • The ionosphere above the Antarctic provides a viewing • The geospace environment deposits energy into both geomagnetic poles is most apparent in the Antarctic window through which to remotely sense nearly all regions north and south polar regions, but often in different Peninsula region compared to anywhere else on Earth. of geospace. A small region of the high latitude amounts. Simultaneous observations in both polar regions For this reason, solar and geomagnetic effects on the polar ionosphere senses large volumes of geospace via provide critical data to study this. Comprehensive upper atmosphere can be distinguished more readily geomagnetic field lines that diverge from the Earth’s instrumentation in Antarctica complements the similarly here. surface. extensive instrumentation in the geomagnetically • Antarctica is relatively free from radio and light • The Antarctic is a preferred region for energetic conjugate region of Greenland, eastern USA and Canada. pollution and is therefore ideal for operating sensitive electron precipitation into the upper atmosphere. Most of • There are also significant north-south differences instruments. Geospace Worksheet 10

Many of you will be unfamiliar with the concept Resource GS1 contains an inset showing an artist’s magnetic field is very disorganised. Magnetic structures in of geospace. This is not surprising, as its study is a impression of geospace illustrating the flow of particles the corona can spontaneously erupt to throw out plasma relatively new science. Although in earlier centuries from the Sun and what happens to them when they at high speed in a ‘coronal mass ejection’. These cause there was an awareness of geospace phenomena such encounter the Earth’s magnetic field. magnetic storms in geospace. There was a solar maximum as the aurorae, it is only with the arrival of radio in 1989. In March of that year a magnetic storm knocked communications and the development of space travel out the power supply to six million people in the Canadian Task 1 and satellite systems that the significance of geospace What shape does the stream of particles from province of Quebec. has emerged. This worksheet examines the nature the Sun form around the Earth? Suggest reasons for this pattern. of geospace, its influence on human activity and the The interaction of the solar wind with the Earth’s reasons why Antarctica is an ideal location from which magnetic field to study it. The solar wind Just as the solar wind is initially influenced by the solar The particles involved in the interactions with the Earth’s magnetic field so it is also affected as it approaches the What is geospace? magnetic field are known as the solar wind. They originate Earth’s magnetic field. The Earth can be regarded as a Geospace is where the atmospheres of the Sun and Earth in the outer atmosphere of the Sun, the corona, where the dipolar bar magnet with North and South magnetic poles meet. It is a comet-like area of space around the Earth high temperatures (over 1,000,000°K) generate an outward close to the geographic poles but moving from year to which includes the magnetosphere, a region of space flow of ionised, coronal gas. Such a gas is known as a plasma. year. What happens to the solar wind when it approaches above the atmosphere dominated by the Earth’s magnetic The gas comprises charged ions and an equal number of the Earth is shown in the diagram in Resource GS2. field. Geospace extends for over a million kilometres electrons so that the overall electrical charge is neutral. although it is only populated by particles at a very low The plasma ions are largely hydrogen though there is Task 3 With reference to Resource GS2 create your density. If all the particles were brought down to the some helium and heavier elements. A million tonnes of own annotated diagram to explain the key characteristics Earth’s surface they would occupy no more space than that this solar wind plasma flows out from the Sun every second of the magnetosphere. in a typical supermarket. at speeds ranging from 300 to 800 km/second. By the time the plasma reaches the Earth every cubic centimetre contains an average of eight ions and eight electrons. The aurorae While most of the solar wind plasma is diverted around the magnetosphere, some of it ‘leaks’ inside. Particles are Task 2 Given a distance between the Sun and Earth of trapped on magnetic field lines in doughnut shaped layers 150 million km and an average speed of 600 km/second calculate the time taken for the solar wind to flow from the around the Earth called radiation belts. Some particles are Sun to the Earth. ‘precipitated’ into the Earth’s atmosphere, along magnetic field lines. As they collide with neutral atoms of oxygen and nitrogen, light is emitted. This is known as the aurora. The solar wind is not constant. Its outflow is strongly It is concentrated in the polar regions. influenced by the solar magnetic field which varies with Analysis in the 19th century of the Northern Lights the so-called ‘sunspot cycle’ of 11 years. When there are revealed an early insight into geospace. Measurements

BAS few sunspots (solar minimum) the solar magnetic field is were taken of the frequency of sightings of the aurora at High frequency radar aerials at the BAS Halley Research Station like that of a bar magnet with a north and south pole. various locations and a map compiled to show isolines used for investigating geospace When there are many sunspots (solar maximum) the solar of equal numbers of sightings. These turned out to be Geospace Worksheet 10 aligned with lines of magnetic rather than geographical latitude. Current magnetic co-ordinates can be seen in Task 6 Using the information provided in Resource GS4 Task 7 Refer back to your calculations regarding the the diagram on this page. It was thus assumed that the create a space weather impact table. In the first column solar wind. How much warning could be given of an phenomena were related to the Earth’s magnetic field. identify the systems under threat (e.g. power supplies). approaching magnetic storm to an astronaut if he or she Nowadays we can see the whole auroral ‘oval’ with the In the second briefly describe the nature of the hazards was on a space walk in Earth orbit? If you were ‘Mission aid of satellites, as can be seen in the image shown in (e.g. geomagnetically induced electrical currents). The third Control’ what would you tell the astronaut to do? Resource GS3. column should outline the impact of the hazard (e.g. How might military strategists make use of space weather failure of transformers at power stations and substations). forecasts? The fourth column should indicate any costs attaching Task 4 Compare the image in Resource GS3 with the to the impacts (e.g. replacement of the iron core of a map of geomagnetic latitude and comment on the relation- transformer). A final column could suggest preventative or Task 8 Working in small groups use your imagination, ships between them. Explain with reference to Resource other measures that might be implemented to minimise knowledge of current weather forecasting and the GS2 why aurora are found mainly in the polar regions. impacts (e.g. new electrical monitoring equipment to warn information provided in this worksheet to prepare an Earth operators). In some cases such measures may not be space weather forecast for broadcast on TV in the late 21st possible. Auroral colours are determined by the neutral atoms that century. You should assume that by then space flight is the precipitating particles are interacting with, green for common and includes shallow space flight to distant nitrogen and red for oxygen. A photograph of an aurora Space weather forecasts parts of the world (e.g. UK to Australia), tourist flights on over Halley Research Station is shown in Resource GS1. It is possible to provide both long and short-term space the space shuttle and short holidays on the Moon. You A typical aurora involves 1026 plasma particles per second weather forecasts. The sunspot cycle is well known but should outline a ‘storyboard’ for the broadcast, which yet it can generate from 108 to 1013 watts of electricity, other fluctuations can also be anticipated. should not exceed two minutes. You should indicate what making it possible to read by its light. maps or other graphics you might use to support your forecast.

Task 5 Compare this output to the generating capacity of a power station. For example, Didcot ‘A’ Why is Antarctica so important to geospace science? power station near Abingdon has a generating capacity You may have already guessed some of the reasons why of 2000 megawatts. How many such stations would be Antarctica is a highly suitable place to study geospace. needed to produce the electricity found in a 1013 watt Resource GS5 lists the key reasons. aurora?

Task 9 In what fundamental ways does the use What is the significance of space weather? of Antarctica by geospace scientists differ from those of You may be wondering if the solar wind has any relevance other scientists such as biologists, geologists? to everyday life. In centuries past it would not have. Now, In your view does geospace science have a significant however, an understanding of space weather is extremely impact on the environment? important not only to manned space flight but also to In what ways does the Antarctic Treaty System (see the satellite and other telecommunications, power grids, Worksheet 5 on the Antarctic Treaty System) in particular pipeline networks, geomagnetic surveys and complex Redrawn from NASA/GSFC the Environmental Protocol, provide protection for navigation systems. Resource GS4 summarises some of A map of Antarctica showing lines of geomagnetic latitude and geospace science? these potential impacts and their financial and other longitude (solid) compared to lines of geographical latitude implications. and longitude (dotted).