# Is it possible to surf a solar flare?

I was rereading The Restaurant at the End of the Universe, the sequel to The Hitchhiker's Guide to the Galaxy, and I came across an interesting passage:

Flare riding is one of the most exotic and exhilarating sports in existence, and those who can dare and afford to do it are among the most lionized men in the Galaxy.

. . .

This sport is made possible by the star ship's heat-sink, a mass of some two thousand billion tons and is contained within a black hole mounted in an electromagnetic field situated halfway along the length of the ship. This heat-sink enables the craft to be maneuvered to within a few miles of a yellow sun, there to catch and ride the solar flares that burst out from its surface.

Okay, so I'm calling Douglas Adams out on that one, but then again, nobody ever said that the books are scientifically plausible. I, however, would like to know if it's possible for us humans to do something similar, i.e. "surfing" solar flares, with our current technology or realistic technology that could be developed in the near future, or about 50 years from now.

Can we "surf" the Sun by using some sort of craft (perhaps modeled on a solar sail) to "ride" solar flares, coronal mass ejections, or something similar? If not, what are the major obstacles to doing so.

• If you're a silver guy on a silver surf-board, anything is possible.... – Snow Mar 23 '17 at 13:33
• So, my theory was that I wanted to use the x-ray reflector as a 'lightweight', 1m radius radiation shield, and stand on it, surfing up and away away from the sun, riding a stream of charged particles using a sort of (magnetic?) solar sail. The reason this might not work would be if the charged particles are too energetic and destroy the sail, or the force is too weak to overcome gravity and I get sucked into the sun. – kingledion Mar 31 '17 at 18:48
• Unfortunately, I can't find anywhere even estimates of charged particle flux at the point of the flare and for all types of particles. The data I found was just too spotty and specific to generalize to reasonable estimates. So, without being able to calculate the force on our sail, I can't make any estimates about force on the sail, and can't answer this any better than I already have. Alas! No one likes giving up. – kingledion Mar 31 '17 at 18:49
• The heat sink is a black hole and you're calling shenanigans on the surfing? – The Nate Apr 1 '17 at 16:10

# Sounds awesome, let's try it

First off, let's talk about what a solar flare is putting out. According to Wikipedia, you are getting somewhere in the 1e20 to 1e25 J of EM radiation followed by charged particles moving at near the speed of light. Since either of these things would be deadly to you, let's assume that we want to surf the EM radiation, leaving the charged particles behind us.

# What are we riding?

First, here is the worst graphic I've ever pirated from a NASA website:

Despite being nearly illegible, we can see that we get peak flux in the ~1kEv X-ray range, which corresponds to about 1nm radiation. Conveniently, 0.1 to 0.8 nm X-rays are used to classify solar flares. The biggest (and therefore the best, and don't I deserve the best?) flares would give us over 1e-4 watts per square meter. This is measured at Earth orbit, 1.50e11 meters. We'd start surfing at the Sun's corona at maybe 5e9 m from the sun. Multiply this ratio squared to get our observed power flux: $$1\times10^{-4} \text{W/m}^2\left(\frac{1.5\times10^{11} \text{ m}}{5.0\times10^{9} \text{ m}}\right)^2 = 0.09 \text{W/m}^2$$ So let's say our max solar flare flux is an even $0.1 \text{W/m}^2$ while minimum is 1e-4.

# How to ride an X-ray

The best way to catch X-rays is to use a mirror, like the one on Suzaku, a former X-ray telescope satellite. The heavy metal coated foil mirrors work by deflecting x-rays at shallow angles of incidence. The Suzaku satellite mirrors are each about 40 cm in diameter and weight 19 kg.

# Stop right there

We've already discovered a problem. The area of a circle 40cm in diameter is 1.2 m$^2$. The ratio between energy of a photon, and its momentum is $c$, the speed of light: a photon as $c$ times more energy than it does momentum. So if we have an incident Type X solar flare, with 0.1 watts per meter squared, and every last shred of photon momentum is delivered to reflector, then we are delivering about 3e-10 kg m/s of momentum every second. Multiply by our area of 1.2 m$^2$ and divide that by 19kg of mass for the reflector, we can see that we are accelerating at about 1e-11 m/s$^2$. That's not going to get us anywhere.

# Ok, skip the X-rays, let's ride the charge particles

Well we've got another problem. Those 0.1 W/m$^2$ of x-rays aren't going to give you much momentum, but they sure will give you some cancer. Based on the radiation calculation parts from this answer, we can assume that the human body is an excellent absorbent for nanometer/keV X-rays. Using the assumptions there, a 100kg person will absorb all the incident energy of about .5 m$^2$ of exposed surface, or about 0.05 J per 100 kg per second. This is equivalent to about 5 rem. That's not bad if that is your only dose, but that is per second.

In about 20 seconds, you will hit 100 rem for acute radiation poisoning; and the 1000 rem surely fatal dose will take about 3 minutes.

# What a downer

Looks like we're trapped between a rock and hard place. If we try to surf the x-rays, we won't get anywhere, and if we try to surf the charged particles, we'll get killed by x-rays. Looks like we'll have to settle for more Earthly surfing pleasures.

• What about a surfing mechanism that does both -- x-rays and charged particles? If solar flare surfing is as dangerous as that, no wonder solar flare riders are so lionized. Most likely, they'd be ionized instead in doing so. – a4android Mar 24 '17 at 1:02
• Nice, but thin film mirror sails are already considered, maybe you could also consider them? – Mołot Mar 24 '17 at 5:52
• @Molot The link to 'foil mirrors' is the thin film. The really thin solar sails are for catching charged particles, not x-rays. X-rays have too much penetrating power for anything less dense than electron degenerate matter to absorb in a thin film. If you surfed the charged particles with a solar sail, however, you would likely die of X-ray radiation. – kingledion Mar 24 '17 at 12:08
• Oh, OK. My bad, I guess. – Mołot Mar 24 '17 at 12:11
• Even with that acceleration, overall you'll still be much more attracted to the star, no? – wleightond Mar 28 '17 at 22:48

FIRST OF ALL, WHAT WE NEED IS POWER!!

The reaction force that we require to surf is much higher than what the normal surfboard shape can get from the flares.

What I suggest is having large spherical shell at the bottom of surfboard fulfilling following aspects:

1. Much less mass for obvious reasons (Newton's third law).
2. Made up of Ferromagnetic material as we will be using magnetism.
3. Durable, after all it's solar flares we are riding.

WORKING PRINCIPLE

When solar flares hit earth, the charged particles accumulate at the poles giving rise to what we call AURORA BOREALIS. The reason behind it is the magnetic field of Earth. Similarly, our sphere is going to collect charged particles from surrounding, thus providing the required thrust.

For rest details consider Kingledion's answer (right up there).

Not in any way that at all resembles "surfing", definitely not in the near-future.

The big challenge of doing anything near the Sun is thermal management. Right now it's a major achievement to just to get a probe within the orbit of Mercury. Making a probe that could directly interact with a flare in a meaningful way would need to get much closer and deal with far more heat even before you consider the flare itself.

Since large flares are the energy equivalent of 1 billion megatons of TNT I don't think we'll construct anything can survive it anytime soon.

• -1 for lack of science and imagination – kingledion Mar 23 '17 at 14:32
• @kingledion OP tagged the question reality-check, so scientific citations are not required. – a CVn Mar 29 '17 at 11:08