Space Debris and Other Threats From Outer Space (6 page)

 

Solar energetic particles (SEPs) and coronal mass ejections (CMEs) pose a significant threat to in-orbit satellites as well as to Earth’s infrastructure in terms of extensive damage that could be caused to the modern electronic grid, computer processes, telecommunications networks, all types of electronic devices (even pipelines) and essentially everything that can conduct electricity. In light of the pervasiveness of electronic devices and electrical systems throughout modern society the risks grow larger each year on an almost exponential basis. A massive solar flare or intensive forms of solar wind can have a devastating effect across the world in terms of automobiles, appliances, computer and telecommunications networks. It is a serious potential problem indeed. The threat extends to aircraft in the skies, electronic grids on the ground and even subterranean networks due to a phenomenon called ground-induced currents (GICs). This chapter discusses the current global monitoring and response systems that address global flares and coronal mass ejections. Today the protective response systems include powering down of spacecraft and switching off their electrical currents when the massive surges come from the Sun, but also Earth-based protective actions to help forestall massive energy failures such as occurred in March 1989 as a result of a large coronal mass ejection (Fig. 
6.1
).

Coronal mass ejections and super intense space weather have the potential to zap and disable operational satellites. Solar monitoring systems on the ground and now in space constantly monitor the Sun to detect such eruptions so that orbiting satellites can power down and achieve maximum protection against such events, but there is more at risk than just spacecraft. A sufficiently powerful blast from the Sun can also adversely affect electric power grids, computer networks, and more. Figure 
6.2
shows a transformer before and after being hit by a major ejection on March13, 1989 [23].

One of the consequences of a coronal mass ejection is a ground-induced current or geo-magnetically induced current (often expressed simply as a GIC). In the case of a very large coronal mass ejection GICs can flow as deep as 20–25 km (12.5–16 miles) within Earth. One such solar event occurred on March 13, 1989. As a result of the CME a number of transformers failed or were rendered useless, including the one shown in Fig. 
6.2
. The March 1989 coronal mass ejection created a massive power failure from Chicago to Quebec. Overall this event affected many millions of people and lasted for many hours. A strong enough CME can affect power grids at all latitudes, but the ground-induced currents and the most severe impacts on grid systems are most likely to have their strongest impact farther to the south or north [24]. This is because the Van Allen belts tend to divert these incoming surges off to the polar regions. A strong ground-induced current can enter and destroy electrical grids and transformers, but it can also adversely affect pipelines, telecommunications networks, other electrical devices and even hydrocarbon production. Trying to protect critical infrastructure or key aircraft or vehicles from a massive CME would not only involve putting these key assets in underground structures but also ones that are sealed with protective insulation coatings.

The truth is that the highest southern and northern latitudes are almost daily affected by ground-induced currents that are driven by modest levels of auroral activity. Fortunately the Van Allen belts generally tend to divert incoming alpha and beta particles and gamma rays to the polar regions and protect all forms of life, which are largely concentrated at the low to moderate latitudes. In short Earth is constantly bombarded by solar and cosmic radiation that includes photons and high energy super X-rays (i.e., gamma rays), alpha and beta particles, and other elements of space weather on a 24/7 basis.

In 1997 the Solar and Heliospheric Observatory (SOHO), a joint undertaking of NASA and the European Space Agency (ESA) was launched in order to study the Sun. The mission was designed with a particular focus on a better understanding of the concept of space weather and the powerful coronal mass ejections that occur during the course of the Sun’s 11-year cycle that ranges from its lowest to its highest level of activity. This monitoring of the complete cycle is important because of the great variation in solar activity. During solar max, the Sun can have as many as three coronal mass ejections in one day, while during the solar minimum CMEs can be as few as once every four or five days. The reason of this cycle and why the activity can be fifteen times more frequent from solar max to solar minimum is still not understood [25].

Although this mission with joint funding by NASA and ESA was initially scheduled for only a two-year life time, it has now been extended six times. The lifetime of the SOHO extended from 1997 through 2012 and has thus been able to accumulate data over the entire 11-year solar activity cycle. Although this space mission cost a total of about $1.5 billion the costs were divided between the two space agencies to spread the cost of this expensive undertaking, and this mission has produced a great wealth of data.

Some of the key results that have come from SOHO observations include:

More recently in 2006 NASA launched two satellites—one ahead of Earth in solar orbit and one behind Earth so as to be able to witness the characteristics, speed, dimensions and intensity of coronal mass ejections of the Sun. These solar observing satellites are aptly know as Stereo. On July 23, 2012, the Stereo satellites captured images of one of the most rapid CME events ever recorded with this X-type event spewing mass out from the Sun at a super fast speed of over 2,000 mile/second (3,200 km/second) or 7.2 million miles/hour (11.5 million km/hour.)

NASA and NOAA have set up a system to measure in "real time" the data related to solar wind in a series of “dials” that display the speed, pressure density, plasma heat, and magnetic fields associated with solar wind and CME events. Typically the speed level is in the range of 1–1,000 miles per second, but the July 23, 2012, event was clearly off the charts of the normal velocity data that NOAA’s website (using data from the NASA Advanced Composition Explorer, ACE, satellite, launched in 1997) normally displays every 15 min. This ACE satellite, located in the L-1 Lagrangian point about 1.5 million km (just under a million miles) from Earth is equipped with six sensors and three monitoring devices that allow a wide range of data to be collected and relayed back to Earth so that solar weather and particularly CME events can be characterized in terms of velocity, pressure, magnetic force, and heat. Figure 
6.3
shows an artist’s representation of a solar storm with Earth being the small blue circle from which the magnetosphere originates.

Today one can contrast and compare the images taken by SOHO and the two Stereo satellites as well as collect the data from the ACE satellite to understand more precisely why and how space weather events occur and also to witness CME (coronal mass ejections) representations in three dimensions, since the Stereo satellite and SOHO shows these events from all angles (Fig. 
6.4
) [27].

The combined capabilities of SOHO and the stereo satellites have now revealed the workings of the Sun to the greatest level yet attained. The power and the impact of CME events on Earth seem to depend on a variety of functions that include the mass of the solar flare, its rate of acceleration, and its direction in relationship to Earth and Earth’s orbital speed.

Despite all of the new knowledge that has been acquired and the greater ability to predict when solar coronal mass ejections will occur there is still a great deal more to be learned. There is likewise a great deal more to be learned about how to protect satellites from these massive solar flares both by designing greater protection and improving operational procedures for when warnings of solar flares are received. The precise nature of how solar storms affect satellites and creates failures is still an evolving field of study. Although satellite operators claim that few total satellite failures are directly related to coronal mass ejections, the statistics show that nearly half of all satellite failures that have occurred in the last twenty years transpired during the years of maximum solar activity in the 11-year cycle seems to be more than a coincidence.