Archive for May, 2010

04
May
10

see, you do need us!

Out-of-control satellite threatens spacecraft

“The satellite’s manufacturer, Orbital Sciences Corp. of Virginia, says an intense solar storm in early April may be to blame.”

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03
May
10

An Introduction to Solar Physics

Last week both Phillip and I spent a significant amount of time with children. I was leading the ‘bring your child to work day’ for my branch at the Naval Research Laboratory. And, Phillip spent the day as the Education and Public Outreach scientist at the first light press conference for his recently launched satellite, SDO, Solar Dynamics Observatory.

In honor of this experience, I wanted to take a few minutes to explain the basic what and why of Heliophysics. For reference, NASA’s Science Directorate has four sub-categories: the Earth, the Planets, Astrophysics and Heliophysics. So, to start, we know that Heliophysics is not the study of the Earth, the Planets or the Stars.

WHAT: NASA defines Heliophysics (a word which NASA scientists created) as the study of the Sun and its effect on the Earth and our Solar system. Let’s start with the Sun. Basically, you can think of the sun as a pot of boiling spaghetti. The burner is like the Sun’s core which generates its energy by nuclear fusion of hydrogen into helium, the spaghetti represents the turbulent magnetic field of the sun, and the steam represents the solar wind that is ejected from the Sun’s outer layers and is composed of charged particles and plasma.

Solar Wind: Taken from SDO Imager

Next we have the Earth. During quiet times, our magnetosphere protects us from the solar wind. However, solar storms (often referred to as coronal mass eruptions) alter the makeup of solar wind. The more powerful storms are able to disturb our Earth’s magnetosphere and inject energetic particles into the lower levels of the Earth’s atmosphere.

WHY: NASA, as well as most of the Defense Agencies, are interested in Heliophysics and fund the continued research in this field. Most funding agencies look to scientists to establish a method to predict space weather. The solar wind carries a massive amount of energy as it travels through space. Space Weather (No, JP, I didn’t make this up!) defines the changes that the plasma and particles of the solar wind create in the Earth’s atmosphere.

The aurora are an example of a positive outcome of these storms. No doubt you have all seen a picture of an aurora in your lives, and few would refer to these events as less than spectacular to witness. However, many of the effects of solar storms are not so highly regarded. Many storms are so massive that they disturb our protective magnetosphere. Any disturbance of the magnetosphere could lead to highly energetic particles impairing satellites, impacting astronauts or causing power disturbances on the Earth’s surface.

I’m going to use Phillip’s PhD thesis as an example of what a heliophysics scientist may study. Phillip created an empirical model of the solar irradiance spectrum FISM His model uses the scarce, intermittent data available from satellites above the Earth’s atmosphere as an input and calculates a full, expanded spectrum of irradiance over all wavelengths. I know this may be a lot to understand – irradiance is still a hard concept for me and I’ve been studying the Sun for 5 years! For another way to understand this problem, imagine you create a focus group to find out the percentage of people who like the color red and you divide your participants by age. But, no one in your group is of the ages 5, 10 or 15. When you plot the results, you will have data gaps in your plot. Phillip’s model works with irradiance data that isn’t complete, just like your focus group was incomplete. He uses his knowledge of physics and his experience working with other solar data sets to calculate the missing pieces of data. Why is it so important that we have a complete plot? The irradiance spectrum allows scientists to track the changes in the Sun’s energy output. Changes in the Sun’s energy output effect the Earth’s atmosphere. His model focuses on tracking changes that occur during storms, as these events are most likely to cause an impact at Earth.

FISM Example

For my current project at work, I investigate the changes of the magnetic field (the boiling spaghetti). Specifically, I am looking at the magnetic field configuration and dynamics after solar coronal mass ejections occur. I’ll be sure to include another post when I have more results!

Again, the long term goal, for both of our projects, focus on predictive capabilities. The million dollar question for a Heliophysics scientist asks “when will each storm hit the Earth and how much energy will it carry with it?” To answer this question, we need to understand why and under what conditions each storm develops.

PS. I won’t have time to post next week. My finals are on Monday, May 10th. Wish me luck!




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