August 21, 2006
AM Location: Slope off Saglek Bank (60° 02' 12.43" N, 57° 58' 40.34" W)
The skies cleared after my late shift in the seismic lab last night so I ventured out onto the bow of the CCGS Hudson in search of a phenomenon known scientifically as "aurora borealis." Most people refer to them as the "northern lights" because they tend to occur in the northern sky on clear starlit nights. So, what are northern lights and why do you have to travel to the far north to see them?
Northern lights are caused by the interaction between radiation particles from the Sun and the Earth's atmosphere. And, since radiation is a form of energy, it stands to reason that waves of varying lengths and frequencies would be emitted with this energy. The wavelengths and frequencies associated with northern lights fall within the visible light spectrum of the electromagnet spectrum we looked at in the August 18th journal entry. (Refer back to the August 18th entry for a reference point on these wavelengths.) Charged particles from the Sun interact with the outer regions of Earth's atmosphere and create a cascading display of lights above the horizon. Sometimes the lights are extremely vivid and colorful, as shown in the example photograph below. The lights may even appear to be dancing across the sky. (See Example Photo below.)
Auroras also occur in the southern hemisphere where they are known as "aurora australis" or "southern lights." The light shows are most often seen in the higher polar latitudes because of the concentration of Earth's magnetism. The Earth contains many properties of a magnet: it has a magnetic core containing iron and, as the earth spins, it generates a magnetic field which protects us from much of the Sun's radiation. As with any magnet, the alignment of magnetized particles is strongest at the poles. The Earth is no different. The North and South Polar regions harbor the strongest concentrations of magnetism, thereby attracting the charged particles from the Sun toward the Poles. Occasionally, during events known as "solar maximums," auroras can be viewed as far south of the Carolinas. These solar events occur on a cycle of about every 11 years. The next solar maximum is scheduled for the year 2012.
Today's Activity: Sprinkle iron shavings onto a paper plate. Place a bar magnet beneath the plate. Slowly move the bar magnet around the underside of the plate and observe the changes in the concentration of the iron shavings in relation to the ends of the magnet. Describe how your observations mimic the concentrations of magnetism within the Earth's magnetic field.
Word of the Day: Vivid
REMINDER: Record today's Sea Surface Temperature (SST) and the Air Temperature on the data table you created from the August 05 journal entry.