5. What Is Light?

What Is Light?
2021-02-09. Ham Radio Forms a Planet-Sized Space Weather Sensor Network. By Kristina Collins, David Kazdan, and Nathaniel A. Frissell, Eos/AGU. Excerpt: For researchers who monitor the effects of solar activity on Earth’s atmosphere, telecommunications, and electrical utilities, amateur radio signals a golden age of crowdsourced science. Space weather events, triggered by solar emissions and their interactions with Earth’s atmosphere, can have significant effects on communications and navigation technology and on electric power systems. As with terrestrial weather events, the economic impacts of space weather–related disruptions can be substantial, affecting satellite systems as well as systems on the ground. A severe geomagnetic storm (on the order of the Carrington Event of 1859) could have a catastrophic effect on modern infrastructure. ...The Ham Radio Science Citizen Investigation (HamSCI) is a collective that unites amateur radio operators with the research community in the space and atmospheric sciences. This confederation of scientists, engineers, and hobbyists holds annual workshops during which ham radio operators and space scientists share findings. A new HamSCI effort, the Personal Space Weather Stationproject, aims to develop a robust and scalable network of amateur stations that will allow amateurs to collect useful data for space science researchers. The next HamSCI workshop will be held virtually 19–21 March 2021, and it will focus on midlatitude ionospheric measurements.... [https://eos.org/features/ham-radio-forms-a-planet-sized-space-weather-sensor-network]

2020-12-21.  Habitability and the Evolution of Life Under Our Magnetic Shield. By Manasvi Lingam, Eos/AGU. Excerpt: ...The existence of a global magnetic field raises questions about how it affects habitability and life. This is a question wide in scope, and the discussion here is limited to only a couple of salient effects. It is commonly thought that magnetic fields are necessary to protect planetary atmospheres from erosion by the solar wind, which hastens the acceleration and escape of atmospheric particles through electromagnetic interactions. But how valid is this premise? ...There is promising evidence that Earth’s geodynamo initiated as early as 4.2 billion years ago and that the crystallization of Earth’s inner core, which paved the way for the geodynamo of today, occurred more than half a billion years ago. Although the changes in Earth’s magnetic field wrought by these transitions were likely profound, the concomitant effects on our planet’s biosphere are much less clear. Earth’s organisms must have been affected to some degree, but fathoming the magnitude and nature of these repercussions necessitates further research synthesizing knowledge from geology, astronomy, plasma physics, microbiology, evolutionary biology, and other disciplines. By resolving the riddle of whether Earth’s magnetic field played a significant role in modulating the evolution of life, we will be better positioned to consider the related question of whether a magnetic field is necessary for a planet to be habitable in the first place.... [https://eos.org/science-updates/habitability-and-the-evolution-of-life-under-our-magnetic-shield]  See also The Herky-Jerky Weirdness of Earth’s Magnetic Field  and A Field Guide to the Magnetic Solar System 

2019-12-27. Ancient Assyrian Aurorae Help Astronomers Understand Solar Activity. By Mara Johnson-Groh, Eos/AGU.

2019-03-04. How Did We Miss This? An Upper Atmospheric Discovery Named STEVE. By Bea Gallardo-Lacourt, Gareth W. Perry, William E. Archer, and Eric Donovan, Eos/AGU. 

2018-04-04. An Aurora of a Different Color. By Kimberly M. S. Cartier, AGU-Eos. 

2008 Jul 24. NASA Satellites Discover What Powers Northern Lights. NASA RELEASE: 08-185. Excerpt: GREENBELT, Md. -- Researchers using a fleet of five NASA satellites have discovered that explosions of magnetic energy a third of the way to the moon power substorms that cause sudden brightenings and rapid movements of the aurora borealis, called the Northern Lights. The culprit turns out to be magnetic reconnection, a common process that occurs throughout the universe when stressed magnetic field lines suddenly snap to a new shape, like a rubber band that's been stretched too far. "We discovered what makes the Northern Lights dance," said Dr. Vassilis Angelopoulos of the University of California, Los Angeles. Angelopoulos is the principal investigator for the Time History of Events and Macroscale Interactions during Substorms mission, or THEMIS....

2008 Mar 20. SPRING IS AURORA SEASON. NASA Earth Observatory News. For reasons not fully understood by scientists, the weeks around the vernal equinox are prone to Northern Lights. In other words, spring is aurora season. Observations from NASA spacecraft are shedding new light on this old mystery.

2007 December 11. THEMIS Discoveries. A fleet of NASA spacecraft, launched less than eight months ago, has made three important discoveries about spectacular eruptions of Northern Lights called "substorms" and the source of their power. NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission observed the dynamics of a rapidly developing substorm, confirmed the existence of giant magnetic ropes and witnessed small explosions in the outskirts of Earth's magnetic field. The discoveries began on March 23, when a substorm erupted over Alaska and Canada, producing vivid auroras for more than two hours. A network of ground cameras organized to support THEMIS photographed the display from below while the satellites measured particles and fields from above. "The substorm behaved quite unexpectedly," says Vassilis Angelopoulos, the mission's principal investigator at the University of California, Los Angeles. "The auroras surged westward twice as fast as anyone thought possible, crossing 15 degrees of longitude in less than one minute. The storm traversed an entire polar time zone, or 400 miles, in 60 seconds flat." ...Angelopoulos was quite impressed with the substorm's power and he estimated the total energy of the two-hour event at five hundred thousand billion Joules. That's equivalent to the energy of one magnitude 5.5 earthquake . Where does all that energy come from? 
THEMIS may have found the answer. "The satellites have found evidence of magnetic ropes connecting Earth's upper atmosphere directly to the sun," said David Sibeck, 
project scientist for the mission at NASA's Goddard Space Flight Center, Greenbelt, Md. "We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras."
A magnetic rope is a twisted bundle of magnetic fields organized much like the twisted hemp of a mariner's rope. Spacecraft have detected hints of these ropes before, but a single spacecraft was insufficient to map their 3D structure. THEMIS' five identical micro-satellites 
were able to perform the feat. "THEMIS encountered its first magnetic rope on May 20," said Sibeck."It was very large, about as wide as Earth, and located approximately 
40,000 miles (70,000 km) above Earth's surface in a region called the magnetopause." The magnetopause is where the solar wind and Earth's magnetic field meet and push against one another like sumo wrestlers locked in combat. There, the rope formed and unraveled in just a few minutes, providing a brief but significant conduit for solar wind energy...

2004 July 13. Will Compasses Point South?. By WILLIAM J. BROAD -- The Earth's magnetic field is collapsing and may eventually reappear with opposite polarity. But what effect will that have on us?

2003 December 3. Cracks in the Earth's Magnetic Sheild - California-sized cracks in our planet's magnetic field can remain open for hours, allowing the solar wind to gush through and power stormy space weather--this according to new observations from Earth-orbiting satellites.


Articles from 2003–present

Electromagnetic Pasta. Using different types of pasta (spaghetti, linguini, cappellini, fettucini, lasagne, orzo, macaroni, rigatoni, manicotti, ziti, etc), create a combined model/display as analogies to explain the principal classification of the electromagnetic spectrum.

ForgeFX Interactive 3D simulation by Prentice Hall - OCEAN WAVES - demonstrates the connection between wind speed and ocean particle motion depth.

Introduction to the Electromagnetic Spectrum, NASA, a brief, rich illustrated primer to the electromagnetic spectrum.