To Tame the Solar Wind

by Paul Gilster on December 10, 2007

Some day we may be using solar sails to take payloads into an increasingly busy Solar System. Let’s hope that day isn’t far off, because the technology looks practical. But as we study solar sail methods, in which the sail is pushed by the momentum of photons, we also want to keep magnetic sail possibilities firmly in mind. A magsail could theoretically ride the ‘solar wind,’ that stream of charged particles pushing out from the Sun at speeds approaching 1.5 million kilometers per hour.

Dana Andrews (Andrew Space) considered the problem of drag posed by interstellar ramjet concepts back in the 1980s, and along with fellow engineer Robert Zubrin went on to ponder how enormous magnetic sails could take advantage of the solar wind. The beauty of the concept is that you do away with a material structure of the sort so tricky to deploy in large solar sail designs. Instead, you generate the magsail from within the spacecraft. Couple this with a particle beam and you may have an interstellar vehicle on your hands.

Burst seen by Hinode

Robert Winglee (University of Washington) has been working with his own version of such a sail under a methodology called Mini-Magnetospheric Plasma Propulsion, or M2P2, for some time. A magsail to the heliopause would really move out, continuously gaining momentum from the flux of protons and electrons flowing outward from the Sun. Launched today, such a vehicle might cross the heliopause before either of our Voyagers. But of course it won’t be launched today, for we have much to learn not only about how magsails might function, but also about the nature of the solar wind itself.

Image: An X-ray jet launching plasma out into the solar system from the Sun’s north polar coronal hole. This image was taken Jan. 10, 2007, by Hinode’s X-ray telescope. Credit: Hinode/SAO/NASA/JAXA

Japan’s Hinode mission is helpful on that score. It’s clear from Hinode data recently reported in Science that magnetic waves are critical in driving the solar wind outward. So-called Alfvén waves, magnetic waves that transfer energy from the Sun up through its atmosphere, have been theorized as the cause of the solar wind, but it took Hinode to clarify the role they play. Thus Alexei Pevtsov, a Hinode program scientist:

“Until now, Alfvén waves have been impossible to observe because of limited resolution of available instruments. With the help of Hinode, we are now able to see direct evidence of Alfvén waves, which will help us unravel the mystery of how the solar wind is powered.”

Hinode carries a high resolution x-ray telescope, allowing researchers to observe x-ray jets low in the corona at the Sun’s poles. The upshot: Whereas before we only saw a few of these jets of hot plasma a day, Hinode saw an average of 240 a day. Alfvén waves and the plasma bursts of these jets are both formed when oppositely charged magnetic fields collide and release energy, a process called magnetic reconnection. The x-ray jets and the Alfvén waves within them are thus identified as major factors in the creation of the solar wind, a theory born out by another team’s findings that the solar chromosphere is riddled with Alfvén waves.

The more we learn about the power of the solar wind, the more interesting it becomes not only as a natural phenomenon but as a propulsion concept. The European Space Agency offers an overview of the recent Hinode findings, and the December 7 issue of Science carries ten papers on Hinode, among them Cirtain et al., “Evidence for Alfvén Waves in Solar X-ray Jets,” Science Vol. 318, No. 5856, pp. 1580-1582 (abstract).

{ 8 comments }

ljk December 10, 2007 at 10:46

The Solar Optical Telescope for the Hinode Mission: An Overview

Authors: S. Tsuneta, et al

(Submitted on 12 Nov 2007 (v1), last revised 7 Dec 2007 (this version, v2))

Abstract: The Solar Optical Telescope (SOT) aboard the Hinode satellite (formerly called Solar-B) consists of the Optical Telescope Assembly (OTA) and the Focal Plane Package (FPP). The OTA is a 50 cm diffraction-limited Gregorian telescope, and the FPP includes the narrow-band (NFI) and wide-band (BFI) filtergraphs, plus the Stokes spectro-polarimeter (SP). SOT provides unprecedented high resolution photometric and vector magnetic images of the photosphere and chromosphere with a very stable point spread function, and is equipped with an image stabilization system that reduces the error to less than 0.01 arcsec rms.

Together with the other two instruments on Hinode (the X-Ray Telescope (XRT) and EUV Imaging Spectrometer (EIS)), SOT is poised to address many fundamental questions about solar magneto-hydrodynamics. Note that this is an overview, and the details of the instrument are presented in a series of companion papers.

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0711.1715v2 [astro-ph]

Submission history

From: Saku Tsuneta [view email]

[v1] Mon, 12 Nov 2007 06:33:36 GMT (865kb)

[v2] Fri, 7 Dec 2007 15:07:28 GMT (872kb)

http://arxiv.org/abs/0711.1715

occam's comic December 10, 2007 at 22:32

“Not everything is plasma currents – in fact very little is.” = Adam
As long as you don’t pay attention to the Sun or the Solar wind. ;-)

Hans Bausewein December 11, 2007 at 18:12

Nice about using solar winds is that it can also be used to slowdown when arriving at another star. I don’t see how you can reduce the speed with beamed propulsion. (or have I missed something?)

Getting enough information about the ‘brake’ solar wind might be a problem, though.

Administrator December 11, 2007 at 19:10

Hans, Robert Forward had a neat trick he proposed for slowing an incoming lightsail by dividing the sail and using one part to reflect the Earth-based laser beam back onto the other part. But that was using lasers, not particle beams. As you point out, though, the same magsail concept that could harness beamed propulsion to get to another system could be converted to a brake upon arrival.

ljk December 12, 2007 at 11:25

The Sun in Time: Activity and Environment

Authors: M. Guedel

(Submitted on 11 Dec 2007)

Abstract: (abridged) The Sun’s magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analog stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system.

The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun. At those stages, interactions of high-energy radiation and particles with the circumsolar disk in which planets eventually formed were important. Traces left in meteorites by energetic particles and anomalous isotopic abundance ratios in meteoritic inclusions may provide evidence for a highly active pre-main sequence Sun.

The present article reviews these various issues related to the magnetic activity of the young Sun and the consequent interactions with its environment.

Comments: accepted by The Living Reviews in Solar Physics, 121 pages, 44 figures; many figures have been degraded; for a version with full-quality figures, see this http URL

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0712.1763v1 [astro-ph]

Submission history

From: Manuel Guedel [view email]

[v1] Tue, 11 Dec 2007 17:37:06 GMT (905kb)

http://arxiv.org/abs/0712.1763

Tokr December 26, 2007 at 16:41

Reading the insightful comments here about particle beam propulsion, I thought this might be a good place to ask a question about “hybrid mass driver” propulsion systems. This is a system where two mass drivers, one stationary and fixed to a large mass, and one on the vehicle which serves to catch and “reflect” back the packages of mass that the first one shoots at it. In this way the ship doesn’t need to carry any propellant, like the laser sail propulsion but with a lot more “push”.
I am surprised that I’ve heard so little about this system, so I assume that there must be some severe disadvantage which I do not see. Can anyone explain this to me?

Adam December 26, 2007 at 17:56

Hi Tokr

The mass-beam system you describe is used extensively in the short stories of Gerald Nordley, who has published several technical papers on the mass-beam concept.

http://www.gdnordley.com/

…mass-beams would need immense amounts of power and need a mature space-based industrial society to construct. In the early days of the first interstellar probes simpler, lower power, systems will be preferred – like Jordin Kare’s sail-beam concept.

The reflected mass-package idea would be used by well developed interstellar trade routes, to minimise total energy expended. The first mass-beams would use masses blasted into plasma by the starship, which would then push against the ship’s magnetic fields.

ljk April 2, 2008 at 6:43

Hinode: source of the slow solar wind and superhot flares

A plethora of latest results from the Hinode solar observatory
contains a wealth of new discoveries. This includes the discovery
of a source of the slow solar wind and the observation of a
superhot micro flare.

More at:

http://www.esa.int/esaSC/SEMJQK5QGEF_index_0.html

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