VanRijn, I made no brown dwarf claim as you say.
I asked if a BD could be the source of these high energy electrons. I made a connection between BDs being pulsar-like and one of the given possible explanations - a nearby pulsar - for these findings.

The articles I referenced and the quotes given discuss high energy electrons, their acceleration, and what mechanisms might be the cause on the BD.

From another:

"A very similar process is believed to apply to brown dwarfs, albeit producing radio emission many orders of magnitude brighter than that detected from the planets. The resulting radiation, which is very strongly beamed perpendicular to the magnetic field of the brown dwarf, sweeps Earth once per rotation period of the dwarf to produce the bright pulses. However, it remains a mystery how the high energy electrons which produce the radio emission are continuously accelerated into the magnetic poles of the dwarf. What has been established is that this radio emission requires these brown dwarfs to possess very powerful, large-scale magnetic fields as strong as those detected from the most magnetically active main sequence stars."

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So, you never posted this:

This was after we'd already discussed the subject, repeatedly.

And still again: They do not discuss extremely high energy electrons that are the subject of the thread.

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The Leif Ericson Cruiser

Rubbish.

All 3 articles I linked discuss the NUI Centre for Astronomy's research on BDs.
The link above expounds on the other two.
The quote above, particularly the bold, using the same verbiage, should've made it clear.

"A very similar process is believed to apply to brown dwarfs, albeit producing radio emission many orders of magnitude brighter than that detected from the planets. The resulting radiation, which is very strongly beamed perpendicular to the magnetic field of the brown dwarf, sweeps Earth once per rotation period of the dwarf to produce the bright pulses. However, it remains a mystery how the high energy electrons which produce the radio emission are continuously accelerated into the magnetic poles of the dwarf."

So, high energy electrons produce radio emissions we see from BDs.

I'd say this answers a couple of your questions: how do you get from radio emissions to high energy electrons & what indication is there that BDs produce high energy electrons.
Although, the latter was more a claim than a question as you said, "there is no indication...."

I think we're finished here.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Then please show where they discuss brown dwarfs generating 300-800 GeV electrons (or positrons). If they don't, they aren't relevant to the subject of this thread.

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The Leif Ericson Cruiser

Interesting. Jupiter-like? I wonder if there is a correlation between size/mass and field strength.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

Jupiter-like, pulsar-like, ....

Anywhere that electrons are accelerated electromagnetic radiation will be emitted. In the case of acceleration at the magnetic poles of planets and stars (including compact objects) the emission is in the radio frequency band. One of the methods is "linear acceleration emission" which has been proposed for radio wave emission from electrostatic double layers. Mostly, all mechanisms are dependent on magnetic field strength and rotation rate of the object as the electric field doing the acceleration is basically the vxB electric field.

One of the first ones (I think) to do this for pulsars was Don Melrose (with a time varying electric field) and is described in his excellent book (if you are a math buff that is) Instabilities in Space and Laboratory Plasmas.

The size of the object will not have much influence, apart from maybe creating a larger generation area at the poles, but that would be dependent again on the magnetic field strength, yadayadayada ....

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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道德經, 二十七 (dào dé jīng, 27)

I disagree.
This is about the discovery of high energy electrons from an unknown nearby source. I asked if it might be a BD, citing research which shows some BDs to emit radio waves from high energy electrons, similar to pulsars and planets alike. And while the reference doesn't specify the high energy electrons as being 300-800Gev, it remains valid as a basis for my question, which was never answered.

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Hi tusenfem.

In your opinion, is it possible for this "mysterious" source to be a nearby BD, considering some have been found to be pulsar-like? And am I wrong thinking that were this the case, it'd have to be spinning fast to generate ~600+Gev electrons?

Thanks.

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A.DIM

I am not familiar with brown dwarfs, so I do not know the magnetic field strengths that they might achieve, but definitely not as strong as e.g. pulsars. So, let's see what we can try to figure out:

Here is a Nature paper on brown dwarfs and X-ray emission. A quote from that paper:

So I guess this sort of throws my idea into the waste basket.

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
He who is good at counting, uses no counting tools
“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

You think so?
Considering how we don't fully understand these pulsar-like BDs I wouldn't throw out your idea based on their expectations.

A more recent paper, here, discusses BDs as well as UCDs (ultra cool dwarfs) and their sporadic long term variability, favoring ecmaser emissions as the more likely mechanism. However, and as the authors say, much more data is needed before anything which regards their emission mechanism or long term variablility is certain.

What's your take on this "quiescent" aspect of BDs / UCDs and might it affect your idea?

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The problem is that that paper is discussing radio emission, which is much easier to generate than X-rays, a lot less energetic.

X-ray ~10¹⁷ Hz
Radio ~10⁷ Hz

The electron-cyclotron maser has difficulties, if I am not mistaken, when the emitted frequency gets too high. First of all the frequency is magnetic field dependent:
f = q B / 2 pi m, so zou need a heck of a magnetic field to get to X-ray, about 10⁶ Tesla, although you can win a bit with synchrotron-self-compton radiation, where the emitted photons are inverse-compton scattered at the energetic electrons that are creating the photons.

A pulsar has ~10¹² gauss magnetic field at the pole (1 Gauss = 10^-4 Tesla) and a radius of 12 km
A brown dwarf has a radius of Jupiter (~71000 km)
Conservation of magnetic flux then gives a dipole field of about (12-71000)² = 3 10^-8 smaller, waaaayyyyy below the needed value.



However, my gut feeling tells me that

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

Is there something more you were going to say?

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

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I guess there was

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

Don't know whether this is related specifically, though I think it *may* be? Assuming we're talking about excess / anomalous energetic electrons... Apologies if this paper has been mentioned already. Haven't had time to peruse the 4 pages of the thread yet.

(Heliosheath Synchrotron Radiation As A Possible Source For The Arcade 2 CMB Distortions)
http://xxx.lanl.gov/abs/0902.0181
http://xxx.lanl.gov/ftp/arxiv/papers/0902/0902.0181.pdf

If it's not directly related to the original thread's topical article(s), is it at least potentially applicable to the same issue?

Is it possible that our solar system (or rather the heliospheric boundary / heliosheath) *is* the source of some of the cosmic rays being detected by ATIC and/or Arcade 2 as suggested (lightly) by Sharpe?

Anyway, thought folks would find the article of interest re: the current topic. Discuss amongst yourselves.

Regards,
Michael

Just a brief thought. Hultqvist might have a *possible* / tentative explanation, derived from known / newly measured terrestrial auroral physics.

(On the importance of auroral processes in the Universe.)
http://dx.doi.org/10.1016/j.jastp.2008.03.023

Unfortunately, it requires like $30-35 to download. I wish science were actually available to John Q Public rather than sequestered in ivory towers, but c'est la vie, non?

It's an interesting article, if you've got access. Tentative, but interesting. Notes that the electron-cyclotron maser instability may give us a window into how auroras and other processes in the universe operate, since many seem to produce radio emissions similar to if not the same as that produced by the aforementioned plasma process.

See also:

(Sporadic Long-term Variability in Radio Activity from a Brown Dwarf)
http://arxiv.org/PS_cache/arxiv/pdf/...707.0634v1.pdf

and

(Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs)
http://adsabs.harvard.edu/abs/2008arXiv0805.4010H

Regards,
~Michael

I just asked a colleague to download the Hultqvist paper. Seems interesting and just in my street of work.

ETA: I now have said Hultqvist paper in pdf.

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

Yeah, I had a brief skim of it from a colleague as well. Seemed pretty good. I'm probably not qualified to assess the specific technical merits at this point (though I followed portions of it well enough), but I assume others in the forum should be able to pick it apart for technical plausibility and usefulness under other circumstances.

From what I can gather, Hultqvist seems to follow the Alfvén line of reasoning and investigation RE: the auroras. Not sure whether he's in any way a protége or studied under Alfvén, or is simply familiar with the work.

Either way he seems to have plenty of kind words for Alfvén in acknowledging that Alfvén made a lot of predictions and suggestions that weren't taken seriously at the time or were dismissed but later confirmed. *Shrug* Alfvén had a fair enough track record.

Regards,
~Michael

I have not read the paper yet, too busy writing my own paper at the moment, but will do it this weekend or this evening after the gym.

Well, you cannot be a Swedish space physicist and NOT be influenced by Alfvén (mm bet you can't be a plasma physicist in general and not be influenced by him). What Hultqvist is describing is basically the mainstream view of aurora's, when I look at it quickly, field aligned (Birkeland) currents, parallel electric fields, inverted V's etc.

Alfvén was a great plasma physicist, unfortunately at the end of his life he started moving into some strange stuff, like his "resonance theory" in the Saturnian rings (he even wanted me to start working on that when I was in Stockholm, but my PhD experiments were on double layers, so his "request" was a bit off topic). So, let's just remember him as the guy who created MHD, double layers and some other interesting stuff.

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

I'd like to read the paper by Hallinan et al which confirms the ec maser mechanism.
The final statement in the abstract intrigues me: "The implied size of the radius, together with the bolometric luminosity of the dwarf, suggests that either LSR J1835 is a young- or intermediate-age brown dwarf, or that current theoretical models underestimate the radii of ultracool dwarfs."

Tusenfem, if the above is the case would it account for the problem you mentioned in #71?

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There is a nice review article in the 28th Feb issue of Science News (on-line version here).

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Interesting; thanks guys.

The mystery remains...

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Geminga and MILAGRO observations linked to cosmic rays

Although this is an older thread, there has been some new research done on the mystery of the source of these cosmic rays.

From Physicsworld:

EXCESS POSITRONS LINKED TO GEMINGA PULSAR
http://physicsworld.com/cws/article/news/40065

Thanks for the update borman

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This could've been its own thread I suppose but it might be an alternative to borman's info(?):

Mystery Emissions Spotted at Edge of Solar System.

In the murky boundary between our solar system and the rest of the galaxy, scientists have spotted a bright band of surprising high-energy emissions.

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Also being discussed in this thread on the IBEX mission that discovered it, and by Fraser on UT.

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Ah, thanks.

Good that it's cross referenced!

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Here is a question. Let us say there was a pulsar that was orbited by a brown dwarf that was originally larger but lost a lot of gas, and that the brown dwarf was in an elliptical orbit. The Brown dwarf thus was between us and the pulsar it orbits for some time. It then nears, blows off some material which is eaten, then goes silent again.

Could such a binary system exist, explaining any sporadic spikes that might be detected, with a larger less dense body hiding a smaller, more energetic body for lengths of time?

IBEX measures energetic neutral atoms while the cosmic rays discussed in this thread are charged. One would not expect the two to be related as charged particles can be governed by magnetic fields whereas the neutral atoms would not.

However, IBEX sees the band at right angles to the magnetic field and there is fine structure suggesting more energetic neutral particles in the center of the band.

A speculation that might connect the two is that there is a rogue black hole and the ribbon represents its accretion disk seen edge-on by IBEX. Charged particles from the same source would suffer deflection from galactic and solar system magnetic fields. For there to be anything to this supposition, there should also be present microlensing and or Shapiro time delays associated with the gravity field of the black hole that should be monitored in the vicinity of ribbon.

After the finding of ring fragments around a certain ice giant, and the large ring around Saturn that was unseen previously, I wonder if Sol has a diffuse Vega style outer ring. The leading edge of such a ring fragment might 'ablate' gently in the interstellar medium, mixing with who knows what. Thus we see the linear path as a leading edge of some kind. IBEX might be blind to other parts segments of the ring that trail our system and are thus not excited by the ring and thus not as visible to it. Where the clumps are heavier, you might see an object. Ring Around the Heliosphere