Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted November 24, 1997)

I am a freshman at the University of Arizona. I am writing a paper on solar flares for astronomy and was wondering if there in any chance that a solar flare could be large enough to wipe out all communication and bring mass destruction to our planet. Thanks.

The Answer

Dear freshman at the U. of Arizona

You can sleep soundly tonight--all we know about solar flares suggests they can never pose a life hazard at the Earth's surface*. And as far as I know, no one ever suggested that one of them caused the demise of dinosaurs. Asteroid impacts, giant volcanoes--yes; flares--no.

Very few flares produce charged particles, and the energies involved are generally too low to penetrate the entire atmosphere, which is equivalent to about 10 feet of concrete. In such a thick layer, both ions and electrons dissipate their energy among a growing number of secondary fragments, whose number grows but the energy of each one drops, until it is so low that other processes stop them.

The Earth's magnetic field also helps deflect particles, especially near the equator. I don't remember numbers, but I would guess that in the last 40 years, the most flare particles did was double for a few hours the cosmic ray intensity to which all life is exposed continually, day in and day out.

For your project on flares, you may want to look up on the web:

and other files reachable from those.

Dr. David P. Stern
for 'Ask an Astrophysicist'

*note added:

However, you may be interested that in August 72 (between the missions of Apollo 16 and 17) there was a solar flare intense enough to have delivered a fatal radiation dose to any crew caught in an Apollo capsule in Earth-moon transit!

Dr. Paul Butterworth

Addendum (Dec 29, 2009): Although the above answer remains appropriate to the original question, which appears to envision a Hollywood disater movie like scenario, solar flares can disrupt satellite based communications and cause some damages on the ground. For more, see:

Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See for help on other astronomy Q&A services.

Previous question
Main topic
Next question

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

DVD Table of Contents
Educator's Index