Confused about Solar Flares & CMEs

[GeeKay]

I am trying to understand the composition of solar flares: whether they are purely electromagnetic, for example, which to say they ALL propagate through space at the speed of light, or else composed of (or include) high-energy particles. The reason for the 'ALL' is because I keep coming across conflicting descriptions of solar flares, with many accounts actually referring to CMEs, or else discussing solar flares and CMEs as if they were merely two terms for the same phenomena. For example, did Richard Carrington (and most of the world) witness in 1859 a solar flare or a CME? I've come across both explanations. Finally, it seems that solar flares cause aurorae, and at the same time they most definitely do not cause aurorae. . .

 

Help!

[Acme]

CME Week: The Difference Between Flares and CMEs @NASA

 

There are many kinds of eruptions on the sun. Solar flares and coronal mass ejections both involve gigantic explosions of energy, but are otherwise quite different. The two phenomena do sometimes occur at the same time indeed the strongest flares are almost always correlated with coronal mass ejections but they emit different things, they look and travel differently, and they have different effects near planets.

 

Both eruptions are created when the motion of the suns interior contorts its own magnetic fields. Like the sudden release of a twisted rubber band, the magnetic fields explosively realign, driving vast amounts of energy into space. This phenomenon can create a sudden flash of light -- a solar flare. Flares can last minutes to hours and they contain tremendous amounts of energy. Traveling at the speed of light, it takes eight minutes for the light from a solar flare to reach Earth. Some of the energy released in the flare also accelerates very high energy particles that can reach Earth in tens of minutes.

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[GeeKay]

Ah, yes, I understand now. Thank you, Acme. One thing that hadn't been clear to me until reading this NASA article was the propensity solar flares have for charging up and accelerating particles that lie in their path. I think it was this more than anything else that created the confusion in the first place.

 

On a related issue: I heard that aurora had recently been detected on Mars. I don't know how extensive this was, but given that Mars doesn't have a global magnetic field, I'm a bit puzzled how solar activity, such as CMEs, are able to generate aurora on Mars in the first place.

 

Many thanks.

[Acme]

Ah, yes, I understand now. Thank you, Acme. One thing that hadn't been clear to me until reading this NASA article was the propensity solar flares have for charging up and accelerating particles that lie in their path. I think it was this more than anything else that created the confusion in the first place.

De nada. Glad to help.

 

On a related issue: I heard that aurora had recently been detected on Mars. I don't know how extensive this was, but given that Mars doesn't have a global magnetic field, I'm a bit puzzled how solar activity, such as CMEs, are able to generate aurora on Mars in the first place.

 

Many thanks.

It appears to be a consequence of areas of high magnetism in the crust; remnants of a once geodynamic magnetic field.

Mars Express discovers aurorae on Mars

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Like Venus, Mars is a planet with no intrinsic magnetic field. A few years ago it was suggested that auroral phenomena could exist on Mars too. This hypothesis was reinforced by the recent Mars Global Surveyor discovery of crustal magnetic anomalies, most likely the remnants of an old planetary magnetic field.

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SPICAM observations provide for the first time a key insight into the role of the Martian crustal magnetic field in producing original cusp-like magnetic structures. Such structures concentrate fluxes of electrons into small regions of the Martian atmosphere. Eventually, they induce the formation of highly concentrated aurorae whose formation mechanism a localised emission controlled by anomalies in the crusts magnetic field is unique in the Solar System.

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[GeeKay]

Thanks again! I gather then that aurorae on Mars are strictly localised, occurring only in those parts of the regolith with crustal magnetism. All this leaves me wondering about the long-term risks of trying to establish a planet-wide colony on Mars. I would imagine that a major CME impacting upon those unprotected parts of Mars - which is to say most of the planet's surface - would have a devastating effect upon anyone foolish enough to be caught in the open. Then there are the solar flares themselves, which could in theory strike the Martian surface without any advance warning whatsoever. Our Sun might not be a flare star, but it might as well be one, seen from a potential colonist's point of view.

[Acme]

Thanks again! I gather then that aurorae on Mars are strictly localised, occurring only in those parts of the regolith with crustal magnetism. All this leaves me wondering about the long-term risks of trying to establish a planet-wide colony on Mars. I would imagine that a major CME impacting upon those unprotected parts of Mars - which is to say most of the planet's surface - would have a devastating effect upon anyone foolish enough to be caught in the open. Then there are the solar flares themselves, which could in theory strike the Martian surface without any advance warning whatsoever. Our Sun might not be a flare star, but it might as well be one, seen from a potential colonist's point of view.

You're welcome again. Because of the satellites we have observing the Sun we would have the same notice of flares and CMEs for Mars as we have for Earth. (Because of its distance, Mars warnings would have greater lead time than Earth of course.) I don't get the 'our Sun might not be a flare star' since the Sun has flares all the time. I agree that the minimal atmosphere of Mars presents a considerable problem for colonists.

[GeeKay]

Sorry for the confusion: I was referring to those variable stars (e.g. UV Ceti), certain red/brown dwarf stars and their ilk that are classed as flare stars.

 

On a related point (this has been proposed by others, and it's worth mentioning again) I wonder if generating an artificial magnetic field around Mars might one day offer some global protection for any future colonies against inclement solar weather?