At the Mercy and Fury of Our Parent Star
Nearly every organism that’s ever lived and died (certainly every person you’ve ever met) owes their continued existence to the steady flow of charged, particulate energy that originates from the thermonuclear fusion of our star. It is the most perfectly spherical object ever observed in nature. The Earth, by comparison is lumpy and bulging, not a sphere, but an oblate spheroid (flat at its poles, bulbous around its equatorial regions). Once thought of as average and relatively banal, scientists now know that our star is unique, brighter than 85% of the rest of the those in our Milky Way galaxy. It has become scientifically fashionable, as a clearer picture of the chaotic nature of our star has emerged, to regard the sun as a menace, a looming threat. However, while solar dynamics do occasionally put technology in their proverbial crosshairs, without our star, Earth would be little more than a cold, desolate rock. Watch ‘Unlocking the Secrets of Space Weather’
Auroral blooms and proton storms
Humanity is wholly subject to this basically unnamed star that we refer to as “the” Sun (why shouldn’t we name it?), and its gravitational and energetic forces that hold together our solar system and drive the biological processes that make up 99.9% of all life on Earth. Only chemosynthetic organisms can live without the power of our sun, deriving their life in darkness from remote volcanic vents in the deeps of our planet’s oceans.
It’s tempting to think of our sun as a steady part of daily life, rising each day on the eastern horizon and setting in the west with the accuracy of precision clockwork. In reality, the gentle grace of the sun’s habitable zone, where our humble planet resides, is actually a volatile, subtly interconnected system of charged particles, fiery prominences, coronal mass ejections, magnetospheric undulations, auroral blooms, proton storms, and a perpetual subatomic stream that changes constantly, sometimes chaotically with every single second of every passing day.
IN DEPTH | Solar Science Glossary
Carrington event – The largest solar storm in modern history was recorded by Richard Carrington an amateur astronomer at his estate in London in 1859. Two solar flares exploded from the sun, traveled 93 million miles, and arrived at the Earth’s magnetosphere in roughly 17 hours. The resulting aurorae were visible across the entire planet and early telegraph infrastructure in Europe and North American was severely damaged as a result.
Coronal Mass Ejection (CME) – outburst of solar wind following a solar flare, CMEs refer to the body of plasma, usually a solar prominence, that escapes the corona of the sun and travels away from the star. CMEs that travel in the direction of Earth are referred to as Earth-directed.
Geomagnetic storm – once a CME makes contact with the magnetosphere and sends ions toward the surface of the Earth, the resulting solar wind shock wave that begins at the poles and works toward the equator is known as a geomagnetic storm.
Oblate spheroid – a symmetrical object bulging at its equator and flat at its poles. M&M Candies are example of extreme oblate spheroids.
Magnetosphere – the area of space beyond Earth’s atmosphere whose physics are dictated by Earth’s magnetic field. The magnetic field of the Earth protects it from cosmic rays that originate from extreme distances as well as nearby solar radiation.
Solar Meridional flow – an axisymmetric flow of solar material that is generally directed from its equator toward its poles at the apparent visual surface.
Solar flare – energetic events in the corona of the sun that are classified as C, M or X according to the peak flux (in watts per square meter).
Getting into solar dynamics
This is an exciting time to catch the bug of solar science. Space weather, the study of the connected Earth-sun system, is a term in popular scientific usage only since the 1990s. Since that time, the various fields of solar science have pieced together a constellated image of our sun as a highly variable star. The solar cycle, long-understood to be fixed at 11 years, is now known to vary from cycle to cycle, in periods of nine to 12 years.
Solar science aims to quantify the variables of our star’s dynamic system, studying the energetic prominences that build up on the surface of the sun, which occasionally discharge as coronal mass ejections (CME’s); vast clouds of charged particles that break free during solar flares. As happens every decade or so, our current cycle, Solar Cycle 24 is nearing its peak of activity. Both 2012 and 2013 have not recorded a single day without sunspots. These spots, which appear visibly as dark spots, are in fact temporary fluctuations in temperature on the sun’s photosphere, caused by powerful surges in magnetic activity. Watch ‘Sunspot Animation’
Current theories hold that the sun’s magnetic potential is generated by a magnetic dynamo within the star, which varies appreciably over the course of the solar cycle. Its changes are cyclical, which seem to demonstrate that changes in surface activity are driven by the conveyor belt-like drift of the sun’s convection zone. This subsurface section of the sun then gradually pushes material slowly away from the equator, toward the poles at a virtual crawl (roughly 20 meters/second).
Escaping the sun’s gravity
2011 saw some of the most powerful flares in almost five years; so-called X Class flares, which can trigger radio blackouts around the whole world and long-lasting radiation storms in the upper atmosphere. It’s for this reason that solar flares are often associated with doom and gloom scenario’s – without power, our world as we know it would be in trouble. How would that work exactly? During low-level CMEs and the geomagnetic storms they can produce, high latitude auroral displays are fairly common (i.e. the Northern or Southern Lights).
Solar flares are classified as C Class, M Class and X Class; small, medium, and large. M and X Class flares cause radio interruptions pretty much at the moment they occur. If highly charged ejected matter is able to escape the sun’s gravity, they occasionally break free as Earth-directed CMEs. Earth’s magnetic field protects our planet from the direct impact of these events, but several Earth orbiting satellites have been destroyed or suffered massive failures due to CMEs, and any spacewalking astronauts are reeled in, before CME impacts with the Earth’s magnetosphere. Only after ions cause the magnetic field lines to warp, stretch, bend, and reconnect do these particles find their way into Earth’s atmosphere.
The largest modern CME-geomagnetic storm episode, known as the Carrington Event, occurred in 1859 and resulted in the failure of telegraph systems in both North America and Europe. On September 1st, 1859, two large solar flares occurred. The first was large and cleared the path for the second, which covered 1 AU (Astronomical Unit) in distance, which is nearly 150 million kilometers or 93 million miles, between the Sun and the Earth in a mere 17 hours. Reports of aurorae as far south as Hawaii and Cuba reported nighttime illumination brighter than a full moon that awakened sleeping gold miners in Colorado’s Rocky Mountains.
Dealing with what’s inevitable
Fortunately, the electrically dependent infrastructure of humankind was still in its infancy in 1859. There were no large-scale power distribution networks, no phone lines, no high-speed internet cables. A March 1989 geomagnetic storm tripped circuit breakers on Hydro-Quebec’s power grid, resulting in a black out that lasted for several hours and closed the Toronto Stock Exchange for a day. The risks associated with this type of event happening again cannot be overstated (a matter of when, not if). With information technology so completely dependent on electricity to run the financial, medical, and infrastructural nerve centers of the entirely globally integrated planet, a Carrington event would be disastrous for humans.
While coastal cities like Amsterdam and Singapore have devised unique infrastructure solutions to deal with rising oceans, there is little humanity can do to defend against potential threats from solar storms without investing billions of dollars. Following the Canadian 1989 geomagnetic storm, efforts were made to make the electrical grid more robust, increasing the level of throughput transmission lines are able to tolerate and putting in place backup systems, should sections of the grid fail. Unfortunately, the timeline of the sun is so gradual, that back on Earth, the threat seems banal. Only after a more serious event occurs are nations likely to recognize the need for preventative measures.
IN DEPTH | The Solar Dynamics Observatory
The Solar Dynamics Observatory (SDO) is the crown jewel of NASA’s heliophysics fleet. Positioned in Earth orbit and approximately the size of a school bus, SDO uses two instruments, its Atmospheric Imaging Assembly (AIA) and Helioseismic Magnetic Imager (HMI) to produce images that are roughly twice the size of even the most advanced and expensive Earth-bound 4K televisions can display. SDO records and returns roughly 1.5 terabytes of data per day and has been in space and operational since 2010. SDO returns the psychedelic looking multi-wavelength images that reveal enormous solar prominences, coronal loops, active regions, and coronal mass ejections in striking detail. Whoever warned you not to look at the sun as a child had absolutely no concept of the wonder and intrigue that SDO can generate.
Reaching Solar Maximum
Do we need to be worried? It’s hard to say. Solar Cycle 24 is nearing its peak, but a recent lull in flare and active region activity has some of the leading experts in the field of solar science questioning the consensus of the Solar Cycle Prediction Panel, which was assembled between 2006 and 2008 to analyze available data and predict the arrival of the Solar Maximum (the trough of solar activity is called, you guess it, Solar Minimum). Rather than a simple peak in May of 2013 as originally predicted, cycle 24 might have two distinct peaks of activity.
“ is solar maximum,” reports Dean Pesnell of NASA’s Goddard Spaceflight Center. “But it looks different from what we expected because it is double peaked… I am comfortable in saying that another peak will happen in 2013 and possibly last into 2014.”3 To back up his contention, Pesnell cites data from Solar Cycle 14, which also double peaked during the first decade of the last century. If this is true, the sun will likely begin a steadily increasing output of M and X class flares, sending powerful clouds of solar plasma in all directions, much like it did in 2011. Should any of these prove to be Earth-directed, the possibility of a large scale CME-geomagnetic storm event could spell trouble for satellites and electrical grids. Watch ‘Reaching Solar Maximum’
IN DEPTH | DIY Solar Science
Using an app created by NASA, called the Integrated Space Weather Analysis System, citizen scientists have access to a vast suite of tools and predictive models that track massive clouds of charged particles as they expand away from the sun, toward the four innermost rocky planets. Some satellites and most robotic spacecraft are designed to be radiation hardened and can withstand the intense bursts of energy associated with some of the larger, faster moving coronal mass ejections (CMEs).
Carving out a quantitative understanding of the sun
The far future of solar science must include the variability of other sun-like stars in order for the human body of scientific knowledge to assemble a complete picture of solar dynamics across our galaxy. Because science now understands our star to be unique, relative to others in our galaxy, the natural tendency of human curiosity is to compare and contrast. Is the output of our star responsible for the rise of advanced life? Do solar flares interact differently in other planet-star systems? Sending spacecraft at near-relativistic speeds to nearby star systems like Alpha Centauri (a mere four light years away), would allow scientific observations to be analyzed and compared, better informing predictive models. Does Alpha Centauri A have a solar cycle similar to our star? Is Proxima Centauri, the nearest star to our’s in the Alpha Centauri system, prone to coronal mass ejections of different sizes, speeds, and scales?
Already slated for launch in the near future are NASA’s Solar Probe Plus, a robotic spacecraft scheduled to deploy in 2018, that will approach less then four million miles from our sun to study solar wind and plasma, and ESA’s Solar Orbiter, scheduled for a 2017 launch, to study the sun’s internal dynamo.
NASA’s Living With a Star program, which includes the Solar Dynamics Observatory, the Van Allen Probes, and the upcoming launch of Solar Probe Plus, places the emerging understanding of the Earth-Sun relationship into an appropriate, accessible context. The program began in 2001 and has solicited several rounds of proposals from the world’s leading scientists to use the exquisite array of instruments within these spacecraft to help carve out a quantitative understanding of the sun, along with advanced predictive capabilities.
While it has become fashionable (to the point of yawning cliché) to fear the next coronal mass ejection and the havoc it may potentially bring to our technologically dependent civilization, there is a larger truth that this doomsday scenario fails to take into account: without our parent star, Earth would not be living at all.
Kuhn, J., Bush, R., Emilio, M., & Scholl, I. (2012). The Precise Solar Shape and Its Variability Science, 337 (6102), 1638-1640 DOI: 10.1126/science.1223231
Charles J. Lada (2006). Stellar Multiplicity and the IMF: Most Stars Are Single Astrophys.J. 640 (2006) L63-L66 arXiv: astro-ph/0601375v2
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