Fire in the sky

 (From New Scientist, 27 February 1999)

 

Illustration: Charlie Ward

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If the Sun spits, the Earth fries. Humankind is ill-prepared for the furious climax of the next solar cycle.

David Appell reports

       BATTEN down  the hatches, there's a  storm coming.Some time in 
       the next 18 months, the Sun will turn from a relatively placid 
       ball of  hot ionised  gases into  a raging  tempest of plasma, 
       spitting fireballs  out into  the Solar  System like  an angry 
       god. Woe betide any planet that gets in its way. 

       Should one of those  plasma storms hit Earth, the impact could 
       be  devastating.  Each   fireball--known  as  a  coronal  mass 
       ejection--is   a   giant  maelstrom   of   ionised   gases  at 
       temperatures  of   well  over  a   million  degrees.  But  the 
       temperature is  the least of Earth's  worries. The plasma will 
       tear  through the  Earth's  magnetic field  like  wind through 
       grass. These  wildly  fluctuating fields  can knock  out power 
       supplies, and  charged particles from  the plasma  can fry the 
       electronic  components  inside telecommunications  satellites, 
       bringing down  communications networks over  vast areas. A few 
       scientists and  engineers  are preparing  for the  worst while 
       others, strangely, have chosen to ignore the problem. The wary 
       few are racing to put in place measures to protect power grids 
       and telecommunications  networks, and  have launched sentinels 
       that sit in  space between the Earth  and the Sun watching for 
       storm signs. In addition, they are developing complex computer 
       models to predict which  parts of the Earth might be affected. 
       Others, fearing the worst,  are waiting to see what happens to 
       the giant communications networks that have grown up since the 
       last big solar storm 10 years ago. 

       Scientists have  been watching the changing  nature of the Sun 
       for over 200 years  and have witnessed these solar rages every 
       eleven years or so. This will  be the 23rd cycle on record and 
       researchers believe it  will be every bit  as bad as the last. 
       Six million  people  in the  Canadian  province of  Quebec can 
       testify to its effects. 

       The storm struck  in the early hours  of 13 March 1989. It was 
       not a good night to lose power. The temperature had dropped to 
       -15 °C and  furnaces went quiet as  six million Canadians lost 
       heat and  light. After the  winter sunrise,  subways sat still 
       for lack of  power, traffic lights hung  dark and petrol pumps 
       refused to deliver. 

       Later  in  the  day,  when  public  officials  called  for  an 
       explanation,  engineers at  Hydro-Quebec,  the  region's power 
       generating company,  had begun to  suspect an unusual culprit. 
       Four days earlier, a giant bubble of plasma had burst from the 
       surface of  Sun. That morning  it had hit  the Earth, wreaking 
       havoc. 

       Rapidly  changing  magnetic fields  generate  currents  in any 
       conductors within  reach. This  is how  a dynamo works--except 
       that the  magnetic field remains still  in these devices while 
       the conducting  wires move through  it. When  a magnetic storm 
       hits the  Earth, any networks of  conductors that stretch over 
       the same  scale as  the magnetic  fluctuations act  like giant 
       dynamos. Hydro-Quebec's  transmission  lines stretch  for over 
       1000 kilometres. Power lines, telephone lines and even railway 
       lines are all  potential conduits for "geomagnetically induced 
       currents" (GICs) of hundreds of amperes. 

       Power companies are vulnerable because their power lines guide 
       the GICs towards  sensitive components such as transformers at 
       power stations  and substations. A  transformer changes a high 
       voltage  supply  of alternating  current  into  a  low voltage 
       supply or vice versa. It  consists of a giant doughnut of iron 
       with two sets  of windings on each  side of the structure. The 
       voltage in one set of windings induces a magnetic field in the 
       iron core, which  in turn induces a  voltage in the second set 
       of windings.  The ratio of  the number of  windings in the two 
       coils determines the change in voltage. 

       High-performance transformers are  delicate machines. They are 
       designed to  cope  with voltages  within  a specific  range of 
       amplitudes  and   frequencies.   Outside  these   bounds,  the 
       transformer behaves unpredictably. 

       The trouble  with GICs  is that  the voltages  associated with 
       them change this  delicate balance. In particular, they set up 
       voltages at  harmonic frequencies to  the ordinary load. These 
       frequencies are  transformed  but in  a  way that  can rapidly 
       spiral  out  of  control.  The  result  is wildly  fluctuating 
       voltages called voltage  asymmetries. If the power is not shut 
       down, these  can create  enough heat  to damage  the iron core 
       beyond repair. Worse,  these fluctuations pass rapidly through 
       the  network  so that  neighbouring  transformers  also become 
       affected. Within seconds an entire network can collapse as one 
       transformer after another fails. 

       Exactly  this  happened to  Hydro-Quebec's  power  system that 
       fateful morning.  "Voltage regulations need to  be within 5 to 
       10 per cent of a nominal  value. If you fall outside that, you 
       generally see  a  system collapse  and the  start of  a domino 
       effect," says  John  Kappenman, an  expert  in the  effects of 
       geomagnetic  storms  at  the  Metatech  Corporation, based  in 
       Goleta, California. 

       Many  other  electricity   utilities  around  the  world  also 
       suffered the effects  of GICs that morning. Further south, the 
       iron core of a transformer at a New Jersey power station burnt 
       out  and had  to  be  replaced at  a cost  of  several million 
       dollars.  Later,   researchers  at  the   Oak  Ridge  National 
       Laboratory in  Tennessee predicted the  potential effects of a 
       geomagnetic storm  only slightly more  severe than  the one in 
       1989.  They concluded  that  the ensuing  blackouts  and chaos 
       could cost  the US  economy up to  $6 billion  dollars in lost 
       business. 

       Astronomers are  forecasting storms  just as  big as  those in 
       1989 for  the next  solar maximum, if  not bigger.  As the Sun 
       passes through  its 11-year  cycle, solar  astronomers measure 
       the activity on its surface by counting the number of sunspots 
       and the  number of  groups of sunspots  they can  see during a 
       predetermined period,  usually  a month  or a  year. Together, 
       these  numbers  allow them  to  calculate  an  index  of solar 
       activity known as the International Sunspot Number. During the 
       solar minimum, the sunspot number can be as low as 10. In July 
       1989, during the last solar  maximum, it peaked at 159. And in 
       March 1958,  it reached 201,  the highest  level ever recorded 
       (see Figure). 

       Cycle 23 "will be one of the largest on record, and comparable 
       to the last  two solar cycles", says  a panel of international 
       experts chaired by  Jo Ann Joselyn of  the US National Oceanic 
       and Atmospheric  Administration's Space  Environment Center in 
       Boulder, Colorado.  They  warn that  the sunspot  number could 
       reach 190, peaking sometime between June this year and January 
       2001. 

       Can anything  be  done to  avert  disaster? Leonard  Bolduc, a 
       researcher  at   Hydro-Quebec's   Institute  of   Research  in 
       Electricity of  Quebec, who  was working  on the  night of the 
       failure, has studied  the network's breakdown. There is little 
       that Hydro-Quebec can do to prevent GICs. Instead, Bolduc says 
       the  company's strategy  is  to  design grids  that  can cope. 
       "Hydro-Quebec has  spent a lot  of money  trying to understand 
       the phenomena and  to evaluate all its  equipment during a GIC 
       storm," he says. 

       Its solution has been  to fit its power lines with capacitors, 
       known as transmission line series capacitors, that prevent the 
       flow of direct  current without affecting alternating current. 
       The company has spent  more than C$1.2 billion fitting the new 
       capacitors. It has also set up monitoring equipment that spots 
       voltage asymmetries  and warns  operators to  redistribute the 
       load to other  parts of the network,  by bringing online other 
       generators  in different  areas.  "We are  confident  that our 
       network could now support such a big storm," says Bolduc. 

       Currents and electrojets 

       Another approach  is  to predict  the severity  of geomagnetic 
       storms before they hit the Earth so that preventive action can 
       be taken.  But this  isn't easy.  The interaction  between the 
       Earth's magnetic field and  the particles in the hot plasma is 
       extremely  complex.  Ari Viljanen  and  Risto  Pirjola  of the 
       Finnish  Meteorological  Institute  have  been  studying  this 
       process.  They  began  by  modelling  the interaction  between 
       plasma from  the Sun and  the Earth's magnetic  field, and the 
       way this generates  currents in ionised regions of the Earth's 
       upper   atmosphere.   These   currents--called   the   auroral 
       electrojet--have an  electric field associated  with them. The 
       horizontal  component of  this  field at  the  Earth's surface 
       together with  the conductance of the  surface are the crucial 
       factors that  determine the strength of  GICs. So Viljanen and 
       Pirjola have had to model the conductivity too. 

       By combining  their models of  the auroral  electrojet and the 
       conductivity  of  the Earth's  surface,  they  have  created a 
       formidable tool.  Their overall model  produces data that come 
       within 20  per  cent of  the  values of  GICs measured  in the 
       Finnish power system. 

       The Finnish  researchers  now want  to turn  the model  on its 
       head. They say that by  using data from GICs in Finland, their 
       model can  throw light on  the processes at  work in the upper 
       atmosphere. In  effect, they hope  to turn  the entire Finnish 
       power grid  system into  a giant  instrument for  studying the 
       interaction between the magnetosphere and the solar wind. 

       Kappenman also has ambitious plans. He is division manager for 
       Metatech's Applied Power Solutions Division, and the architect 
       of a  new computer model called  PowerCast designed to predict 
       the effects of  GICs before they occur.  His first customer is 
       National  Grid--the  company  that  operates  Britain's  power 
       transmission  network--which  is  installing  his system  this 
       month. 

       PowerCast  uses  a  model  of  the  interaction between  solar 
       plasma,  the  magnetosphere and  the  geology  of  the Earth's 
       surface.  But it  links  this  to a  model of  the  power grid 
       itself.  The National  Grid  uses about  900  transformers and 
       PowerCast takes  into account all of  them when deciding which 
       might be damaged by impending magnetic storms. 

       The data that PowerCast uses to make its predictions come from 
       a small  observatory called the  Advanced Composition Explorer 
       (ACE), a spacecraft  that sits in the solar wind approximately 
       1.5 million  kilometres upstream of  Earth at  the point where 
       the gravitational  forces from the  Earth and  the Sun balance 
       one another.  ACE measures the  composition of  the solar wind 
       and gives  roughly one  hour's warning  of an  impending solar 
       storm. 

       Using these  data,  PowerCast will  give  the National  Grid a 
       minute-by-minute update  of the threat  that GICs  pose to the 
       network. Operators can then take appropriate steps to mitigate 
       the  effects  of any  impending  storm  while  maintaining the 
       supply. It's a difficult job, says Kappenman. "Power companies 
       are not like phone companies  where, if it gets too busy, they 
       can give you  a busy signal." Metatech  claims that the system 
       works with "reasonable  accuracy". Just how it it will perform 
       during the forthcoming solar maximum remains to be seen. 

       Satellites  are  also at  risk  during  solar  storms.  The US 
       Department  of  Defense  has  estimated  that  disruptions  to 
       government  satellites  from  space  weather  cost about  $100 
       million  a year,  and  that even  when the  Sun  is relatively 
       placid, as  it was  in 1994  and 1995,  about 150 malfunctions 
       occur annually. 

       When the  communications satellite Galaxy  IV failed last May, 
       it brought  down  communications networks  and put  45 million 
       pagers  out of  action. The  satellite's  manufacturer, Hughes 
       Electronics Corporation, says  an on-board processor failed as 
       a  result of  a  random event.  Others believe  a  more likely 
       culprit is the Sun. 

       Killer electrons 

       Dan  Baker, director  of  the Laboratory  for  Atmospheric and 
       Space Physics  at the University  of Colorado  in Boulder, and 
       his colleagues have  studied the solar weather conditions that 
       existed at  the time of  the failure. They  found that a large 
       number  of high-energy  electrons  had become  trapped  in the 
       Earth's  magnetosphere  in  the  two-week  period  before  the 
       satellite failed,  as a  result of  exceptionally stormy solar 
       weather. According to  Baker, it was "one  of the most intense 
       periods that we've seen for the last two or three years". 

       Electrons  with  kinetic   energies  greater  than  a  million 
       electronvolts have been  dubbed "killer electrons". They smash 
       through the  skin  of spacecraft  and lodge  inside dielectric 
       materials such as thermal blankets, electronic boards, coaxial 
       cables  and electrical  insulation. If  more  electrons arrive 
       than can  leak away, the  buildup of charge  can create strong 
       electric fields  inside the spacecraft,  a process called deep 
       dielectric  charging. Eventally,  arcing  occurs  as electrons 
       jump between  areas at different potentials.  It is these tiny 
       bolts of lightning  that destroy spacecrafts' electronics. "We 
       don't know  for sure  if this  caused the  Galaxy IV failure," 
       says Baker,  but  he says  several  other spacecraft  also had 
       problems during the same period. 

       And nobody  knows whether networks that  have been designed in 
       the  10 years  since  the last  solar maximum  will  cope. "As 
       technologies change, new  vulnerabilities to solar events crop 
       up," says Lou Lanzerotti, a geophysicist at Bell Labs, the R&D 
       arm   of  Lucent   Technologies.   He  points   to   the  huge 
       proliferation of wireless  networks. "We find that there are a 
       few solar radio bursts  every solar maximum that are larger in 
       amplitude at Earth than the noise level in a cellular system." 

       Could these bursts drown  wireless networks in a sea of noise, 
       putting  millions  of cellphones  and  other  wireless devices 
       around  the  world out  of  action?  "It's  something  that we 
       haven't  thought  about  before  because  we  didn't have  the 
       technology  and   didn't  need   to  think   about  it,"  says 
       Lanzerotti. With  the solar maximum  approaching, time is fast 
       running out. 

         David Appell is a science journalist based in Gilford, New Hampshire 

       Further reading: 

          * The Space Weather Bureau at Marshall Space Sciences 
            Laboratory, Huntsville, Alabama 

                   --------------------------------------- 
                    From New Scientist, 27 February 1999 
 
  

                 © Copyright New Scientist, RBI Limited 1999 
 
 

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