Talk by Michael Hesse from the Space Weather Lab at NASA GSFC
Last week Dr. Hesse gave a presentation to the science community at Goddard about space weather and it’s importance. Dr. Hesse has a Phd in theoretical physics, and did a post doc in Los Alamos. Now he is Chief of the space weather lab, CCMC , and works on improving space weather forecasts.
Summary:
- Space weather is the interaction between the sun, solar wind, and the earth.
- Coronal mass ejections (CMEs) are large eruptions from the sun that move very quickly and contain a lot of mass.
- They affect things on earth like spacecraft, electrical grids, commercial flight, GPS, and more.
- NASA is using state of the art technology to study the sun, and improve our ability to predict these events.
What is space weather?
“Conditions on the sun and in the space environment that can do bad things to us… like influence the performance and reliability of space borne and ground based technology.” (from the nspa.gov definition.)
The sun can at times produce eruptions that propagate through space and hit earth’s magnetic field. Among other things they cause the beautiful aurora. The sun is a magnetized star. Below the surface there is convection, which makes the magnetic field move through the surface. Sometimes the fields are bunched up, and if there is enough energy stored there it can be released explosively. The magnetic field of the sun is constantly active, but sometimes it can create large explosions. These transient events drive space weather.
A typical CME releases 10^14 kg of mass up to 3000 km per sec. Hard to picture? Imagine 1 million Nimitz class air craft carriers coming at you at 1-6.5 million mph.
Now that is intense!
During periods of high solar activity, CME’s are ejected typically a few times a day. Energetic particles also are released, often consisting of hundreds of millions of volts. When the particles are accelerated, and released from the sun they create solar wind, which gives the earth’s magnetic field it’s tear drop shape.
Energetic particles are released from the sun in a spiral because the sun is rotating. Imagine holding a hose and spinning around. The water would make a spiral shape around you. The sun does the same thing. Why is this important? Because energetic particles will travel along the spiral shaped magnetic field lines and hit the earth. Eruptions don’t have to be exactly earth facing to have an influence on the earth.
As these particles hit the atmosphere, it can cause it to heat and expand, affecting LEO spacecraft by causing more drag, which changes their orbit.
Also, when you are communicating with a spacecraft, your signals go through this layer of ionized atmosphere to the spacecraft. When an event happens it can increase the total electron content of the atmosphere (electron density) and it can prevent you from talking to your spacecraft.
What does space weather do, and why should we care about it?
Lanzerotti image NJIT
The graphic shows some of the most important influences of space weather on earth:
Perhaps the most important effect is the influence on the electricity grid. When the atmosphere is excessively charged, it can transfer to the ground and the electrical grids that are attached to it, causing DC currents to build in the system.
Planes flying polar routes need to maintain communication with geosynchronous GPS satellites. During an event the structure of the atmosphere changes and can absorb those signals. Result is planes having to fly less than optimal routes, with stops for more gas, time delays, and cargo changes.
On space crafts, some areas will be unevenly charged. Negative and positive areas will discharge to even out and the discharge can burn out systems. It can cause damage to solar cells, and memory, and false sensor readings.
GPS precision can be affected. Think about guided missiles. You need three GPS satellites to get accuracy within about a meter or so. During a solar event the currents cause changes in the ionized atmosphere, making the signal from the GPS satellite less reliable. Financial transactions are also timed by GPS because it is very accurate. This is important when doing international trading, where time zones can confuse transactions.
GPS is also essential to precision farming, oceanic drilling, snow plowing in Alaska, (in whiteout conditions, along mountain roads, it’s important not to accidentally plow off the road!)
So what are we doing to learn about space weather?
There are several sun-observing spacecrafts, including the new Solar Dynamics Observatory, that take data and send it to us 24/7. Next, we create models that will help us predict impacts and their effects. The space weather lab at Goddard has an unprecedented suite of models running, serving national and international needs. Take a look at the CCMC, where you can run any model we have, and go through archives of data. Our goals are to become faster and more accurate in our predictions, mitigating damage in space and here on earth.
