Earth Science: Geology, the Environment, and the Universe

Chapter 30: Stars

Problem of the Week

Cyclic Nature of Solar Events

Traveling at speeds of approximately 900 km/s, solar wind streams toward Earth. The wind is composed of particles, mainly electrons and protons, that have escaped the Sun’s gravity. Earth is protected by its magnetosphere, so the solar wind does not usually impact Earth. However, particles of the solar wind can leak into Earth’s magnetosphere. The particles are channeled to a portion of the magnetosphere called the Van Allen radiation belts. The Van Allen radiation belts form large rings above each of Earth’s poles.

Solar activity affects Earth in several ways. One way is the formation of the aurorae, in both the northern and southern hemispheres. Here, the solar wind excites atoms and molecules in Earth’s atmosphere, causing them to emit light. At other times, storm events on the Sun send strong surges of particles, causing geomagnetic storms on Earth. These geomagnetic storms can disrupt electronic activities such as communications and electrical systems.

The largest of these storms are often related to events called coronal mass ejections (CMEs); huge bubbles of plasma ejected from the Sun over the course of several hours. In turn, CMEs are often related to solar prominences. During one of these events, particles can be hurled toward Earth at speeds of up to 2000 km/s, which is much faster than the normal solar wind. These massive storms often result in major disruptions of communications and other electronic activity on Earth.

Problem:

As you may know, solar flares, sunspots, and other solar events are cyclical occurrences. At the following Web site address, you will see a graph that shows the cyclical nature of both sunspots and CMEs. Analyze the graph in order to answer the following questions. (The CMEs are labeled as SSC on the graph, which stands for Sudden Storm Commencements).

http://www.oulu.fi/~spaceweb/textbook/fig/SSC_and_R.gif

1. What is the relationship between these two phenomena as shown on the graph?
2. Notice that there are peaks for both events and troughs for both events. What is the average number of years between peak years?
3. Notice that there is a portion of the graph, between 1850 and about 1875, where CMEs are not shown. What might be a reason for the absence of data during this time period?
4. What other information does this graph give you?

Web References and Resources:

1. Geomagnetic Storms
2. Coronal Mass Ejections
3. Sudden Impulse/Storm Sudden Commencement (SI/SSC)
4. Graph Showing Sunspots and CME events