Questions for PAMELA

[Hasanuddin]

Data is starting to come in from the PAMELA project.

 

Before we start forming conclusions based on this data is it extremely important to fully understand the conditions under which this data was collected. I have read several Arxiv papers on the subject and have not found two vital pieces of information. I am hoping that there are those w/in this community who have had better luck, or who know 1st hand.

Where was the data collected? Inside the magnetosphere, just outside, very far away from, at S2, between planets—if so which ones, etc?? Perhaps this obvious question is clearly answered, but I just haven’t seen it.

Could PAMELA detect the direction of particles? The studies I have read reported counts and energies of particles counted, but I saw no mention of the direction of the origin of particles counted. Using modern detector technology making counts and determining energy is one layer, its unclear if PAMELA was equipped with the 2nd layer that would have detected particle trajectory.

 

If possible, and you know the answers to either of these two questions, please link the references. Thanks.

[freeztar]

The project website has lots of good info, particularly this page, which I believe answers your two questions.

 

Welcome to PAMELA MISSION Official Website - PAMELA PROJECT - Mission

[Hasanuddin]

Hi freeztar,

 

The site you list only narrows the first question down (w/out fully answering) and doesn't address the 2nd question at all.

 

Yes, the mission's cover does say that PAMELA is in an eliptical orbit, but does it fully clear the magnetosphere? That home page does mention that a mission goal is to count particles in the upper layers of the magnetosphere, which is helpful.

 

Probably the most important question to me has to do with establishing the trajectories of the particles counted. I know that extra layer of precision would have required more weight, thus increasing expense of the project, and could have easily been cut (as unfortunately occurs to many projects that are cut short by the accountants/politicians.)

[freeztar]

Hi freeztar,

 

The site you list only narrows the first question down (w/out fully answering) and doesn't address the 2nd question at all.

 

Yes, the mission's cover does say that PAMELA is in an eliptical orbit, but does it fully clear the magnetosphere?

 

From wiki:

 

The magnetosphere of Earth is a region in space whose shape is determined by the extent of Earth's internal magnetic field, the solar wind plasma, and the interplanetary magnetic field (IMF).

 

Since the magnetosphere is non-spherical and determined by the above, it seems like the best answer would be "it depends". Digging a little deeper...

 

On the side facing the Sun, the distance to its boundary (which varies with solar wind intensity) is about 144455522222 football fields (10-12 Earth radii or RE, where 1 RE=6371 km; unless otherwise noted, all distances here are from the Earth's center). The boundary of the magnetosphere ("magnetopause") is roughly bullet shaped, about 15 RE abreast of Earth and on the night side (in the "magnetotail" or "geotail") approaching a cylinder with a radius 20-25 RE. The tail region stretches well past 200 RE, and the way it ends is not well-known.

 

So it extends (towards the sun) about 10-12 R_E. From the PAMELA page:

 

The satellite is travelling around the Earth along an elliptical orbit with an upward orientation, at an altitude ranging between 350 - 610 Km with an inclination of 70.0 °.

 

We can now answer, "not even close (couple orders of magnitude) to clearing it".

 

Probably the most important question to me has to do with establishing the trajectories of the particles counted. I know that extra layer of precision would have required more weight, thus increasing expense of the project, and could have easily been cut (as unfortunately occurs to many projects that are cut short by the accountants/politicians.)

 

From this page (poor quality graphic) it appears it does track trajectory (at least for positrons).

 

Welcome to PAMELA MISSION Official Website - Positrons

[Hasanuddin]

Hi freezter,

 

Good and thorough deduction to arrive at an answer: PAMELA does not ever clear the magnetosphere.

 

I found out a little more since the last time posting by having a conversation with one of the folks working on this project. Without directly answering the question, he firmly asserted that the magnetosphere would not significantly affect the behavior of the positrons and electrons being detected by PAMELA because of the extremely high energies in these positrons/electrons... up to 2 TeV http://arxiv.org/pdf/0903.2794v1

 

As far as the directional capabilities of PAMELA are concerned, again without directly answering the question, he asserted that they are isotropic, because they travelled through the interstellar magnetic field becoming diffuse--as is known to occur with charged cosmic rays. Honestly, I'm not 100% satisfied with his answer on this matter because it is unclear whether the isotropic nature of the measured particles is actually confirmed by PAMELA's instrumentation or simply assumed because of past understanding of cosmic ray behavior.

 

I bring up these issues because they are of high interest to the Dominium model being discussed on the "Alternate theories" board. The fact that PAMELA has conclusively recorded an excess of positrons over electrons is also very interesting as a fact unto itself.

[Hasanuddin]

Can someone answer this question: the Blasi paper mentioned earlier on this thread states that electrons (and/or positrons) were measured with energies of 2TeV... but how is that possible give the mass of an electron and the understanding that it can't move faster that 3e8?

 

I realize the answer must be simple/obvious, but I am not making the connection

[CraigD]

Can someone answer this question: the Blasi paper mentioned earlier on this thread states that electrons (and/or positrons) were measured with energies of 2TeV... but how is that possible give the mass of an electron and the understanding that it can't move faster that 3e8?

 

I realize the answer must be simple/obvious, but I am not making the connection

I’ve not read the paper mentioned, but as Hasanuddin realizes, the question “how can an electron have an energy of 2 T2V?” has a simple/obvious answer, as follows.

 

The invariant (rest) mass [math]M_0[/math] of an electron is about [math]0.5110 \,\mbox{MeV/c}^2[/math].

To have an energy of 2 TeV ([math]2 \times 10^6 \,\mbox{MeV}[/math], its relativistic mass [math]M[/math] must be increased so that

 

[math]2 \times 10^6 \,\mbox{MeV}= E = M c^2 = \frac{M_0 c^2}{\sqrt{1 - \left( \frac{v}{c} \right)^2}} [/math]

 

where [math]v[/math] is its velocity relative to what detects its energy.

 

Solving for [math]v[/math], then, gives:

 

[math]v = \sqrt{1 - \left( \frac{M_0 c^2}{E} \right)^2} \dot= 0.9999999999999674 \,\mbox{c}[/math]

 

The electron is traveling very fast.

 

If the 2 TeV energy is for a pair of colliding electron/positrons, you’d do the calculation for [math]E = 1 \,\mbox{TeV}[/math], which would give [math]v \dot= .999999999999869 \,\mbox{c}[/math] for each of the particles.