Solar Explosions Spark Controversy

by Mark Thompson on November 8, 2010

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A solar prominence is observed using photons at wavelength 304 Å. Credit: European Space Agency (ESA) and NASA

Nowhere in the Solar System are conditions more extreme than the Sun. Every second it converts millions of tons of matter into energy to create the intense levels of heat and light we expect of our local star. Study the Sun in different wavelengths and its violent nature can really become apparent. The STEREO satellite has been studying the Sun at a wavelength of 304Å and the results support a controversial solar theory.

Coronal Mass Ejections (or CMEs) are common on the Sun and they have a very real impact to us here on Earth. The solar explosions expel trillions of trillions of tons of super hot hydrogen gas into space, sometimes in the direction of the Earth. Traveling at speeds up to 2,000 kilometers per second it takes just a day for the magnetized gas to reach us and on arrival it can induce strong electric currents in the Earth’s atmosphere leading not only to the beautiful auroral displays but also to telecommunication outages, GPS system failures and even disturbances to power grids.

Solar flares, to use their other name, were first observed back in 1859 and since then, scientists have been studying them to try to understand the mechanism that causes the eruption. It has been known for some time that the magnetically charged gas or plasma is interacting with the magnetic field of the Sun but the detail has been at best, elusive.

In 2006, the international satellite STEREO was launched with the objective of continuously monitoring and studying the CMEs as they head toward the Earth and its data has helped scientists at the Naval Research Laboratory (NRL) in Washington, D.C., start to understand the phenomenon.

Using this new data, scientists at the NRL compared the observed activity with a controversial theory that was first proposed by Dr James Chen (also from the NRL) in 1989. His theory suggested that the erupting clouds of plasma are giant ‘magnetic flux ropes’, effectively a twisted up magnetic field line shaped like a donut. The Sun being a vast sphere of gas suffers from differential rotation where the polar regions of the Sun and the equatorial regions all rotate at different speeds. As a direct result of this, the plasma ‘drags’ the magnetic field lines around and the Sun and it gets more and more twisted up . Eventually, it bursts through the surface, taking some plasma with it giving us one of the most dramatic yet potentially destructive events in the Universe.

Dr Chen and a Valbona Kunkel, a doctorate student at George Mason University, applied Dr. Chen’s model to the new data from STEREO and found that the theory agrees with the measured trajectories of the ejected material. It therefore looks like his theory, whilst controversial may have been right all along.

Its strange to think that our nearest star, the Sun, still has secrets. Yet thanks to the work of Dr. Chen and his team, this one seems to have been unraveled and understanding the strange solar explosions will perhaps help us to minimise impact to Earth based technologies in years to come.

Mark Thompson is a writer and the astronomy presenter on the BBC One Show. See his website, The People’s Astronomer, and you can follow him on Twitter, @PeoplesAstro

DrFlimmer November 11, 2010 at 8:13 AM

@ JimHenson

The idea of EU is that the sun is on a potential relative to the heliosphere and/or the ISM. Thus, there should be a radially extending electric field between the sun and the heliosphere. That’s the idea.
Concerning the solar wind: It contains equal amounts of charges. It does not only contain protons or heavier nuclei, it also contains electrons and is overall neutral. If there would be a large scale electric field from the sun to the heliosphere we would see the effect. Because it would accelerate one species and decelerate the other. This is NOT observed. Hence, there is no large scale electric field from the sun to the heliosphere.

DrFlimmer November 11, 2010 at 9:53 AM

As I see it, what you describe is the ExB drift.

And btw: My first answer was to Lars, who gave the speculative idea (of the charged sun). All I did was refuting it for good reasons. I know that there are electric fields in space. But they are on small scales compared to the whole solar system. That’s it, I don’t see why we even need to discuss this.

iantresman November 12, 2010 at 8:59 AM

>The heliospheric current sheet is primarily caused by a polarity change in the interplanetary magnetic field.

Indeed, but why is the associated electric field not “large scale”?

1. Israelevich et al write “The existence of the radial component of the electric current flowing toward the Sun is revealed in numerical simulation. The total strength of the radial current is 3x10E9 Amps” (ref)

2. The heliospheric current sheet has also been described as”the biggest thing in the heliosphere”. That seems quiet large scale to me.

I’m not interested in whether the Sun is charged.

iantresman November 12, 2010 at 11:45 AM

>You can have a current without an electric field

You are quite right. I assumed, mistakenly, that the radial current in the heliospheric current sheet, must have an associated electric field. It doesn’t. As Dr. David P. Stern writes on “Particle Drifts in Space“.

“.. electric currents often flow in space without any voltage driving them. No electric field is involved–the magnetic field is doing it all, when it has the appropriate structure”.

DrFlimmer November 12, 2010 at 8:09 AM

The heliospheric current sheet is primarily caused by a polarity change in the interplanetary magnetic field. This sheet is similar to the sheet that surrounds the earth. I don’t know if those sheets contain electric fields. There is no need for them in the first place.

Btw: Your link concerning the “interplanetary electric field” states a noteworthy fact: The electric field is only observable for an observer at rest relative to the solar wind. If you fly with the solar wind, there is no electric field. This is an effect of the Lorentz transformation.

But / And still:

This is no hint for a charged sun. (Just emphasizing again, what this is all about. I don’t see the point of bringing up topics that just lead sideways, and do not directly support the points made originally by Lars and/or myself.)

jimhenson November 12, 2010 at 4:50 PM

the sun is not charged because the solar wind plasma undergoes charge exchange at the heliosphere ribbon, which I believe is a large plasma sheath ~100AU that surrounds the solar system in a DL double layer. The sheath seperates the solar systems plasma from the intersteller and intergalactic plasma, because the density & temp of plasmas are scalable in 14 known sizes! the electrical neutral atoms ENAs that are produced by charge exchange fly off into interstellar or intergalactic space, and the solar wind is deflected by either the ISM or IGM magnetic fields back to the solar system in a U-turn style. This is my original idea of a new solar system model and it does not change the likelyhood that gravity fuses elements in the sun. The sun may have had an EM source, because huge charged molecular clouds and protostars condense over vast distances, because plasmas attractive force increments increase with distance practically exponential compared to gravit. EM attracts/repels proportional to the distance, but weaker gravity only attracts the SQAURE of the distance. Gravity holds stars together, but is the weaker force to Em responsible for forming huge cosmological structures.

DrFlimmer November 12, 2010 at 10:03 AM

1.) I’ve searched through the paper and found no hit for “electric field”. The connection between an electric current and an electric field is not necessarily given. You can have a current without an electric field. All you need is a changing magnetic field (changing with respect to position) — that is to say: the curl of B should not vanish. Then you get an electric current, but not necessarily an electric field (dE/dt in Maxwell’s equation can still be zero!). Since the magnetic field does not a have a curl that is zero, we gain an electric current in the current sheet. But not necessarily an electric field. If there is one (that follows the entire structure!), it might be considered “large scale”. However, it does not necessarily exist, and I don’t think it does.
But I am not an expert here, and I could be wrong with the last statement.

conradwar November 14, 2010 at 1:37 AM

Is this the end of this world…?
Extamax

jimhenson November 14, 2010 at 6:05 AM

could stars like the sun not be colliding and remain very far apart in the galaxy despite gravity between stars, because the electric current flowing in the 10,000 km thick current sheet extending beyond the orbit of pluto, is a large scale current sheet that repels other stars?

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