Astronomy

What does the Sun look like from the heliopause?

What does the Sun look like from the heliopause?


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I calculated the angular diameter of the Sun at the heliopause to be 0.004°. If that is correct, would the Sun appear as a disk, or like the pinpoint of light from a star?

How bright would the light from the Sun appear? I understand at Pluto the Sun appears as bright as the full moon at night on Earth. Assuming the heliopause is 3x distant from the Sun as Pluto, does that mean there would be 1/9th as bright at the heliopause. What would that brightness translate to an everyday measure?


0.004° converts to about 14.4 arc-seconds. That's within the range typical for Mars; 5-25 arc-seconds. You'll see the sun as a point with the naked eye. Heliopause is about 14 billion miles out. Absolute magnitude of sun is 4.83. 14 billion miles = 0.0007297pc. Apparent magnitude will be -15.8543. Magnitude of the full moon, from earth, is about −12.74 So you'll see a point source of light, brighter than the full moon.


The Heliosphere

The heliosphere is the immense magnetic bubble containing our solar system, solar wind, and the entire solar magnetic field. It extends well beyond the orbit of Pluto. While the density of particles in the heliosphere is very low (it's a much better vacuum than is created in a laboratory), it is full of particles of interest to heliospheric scientists. Check out the image below for a diagram of the heliosphere.

The solar wind near our Sun's surface contains alternating streams of high and low speed. These streams corotate with the Sun, that is, they rotate along with it. The high-speed streams originate in coronal holes and extend toward the solar poles the low-speed streams come from near the Sun's equator. There are compositional differences between the high and low speed streams of the solar wind.

With increasing distance from the Sun, the high-speed streams overtake the slower plasma, producing corotating interaction regions (CIRs) on their leading edges. CIRs are bounded by two shocks at the front and rear edges called the forward and reverse shocks . At these shocks, the density, pressure, and magnetic field strength are all higher. These regions are quite effective as energetic particle accelerators. When ions that have been accelerated at a CIR are observed, they are called corotating ion events .

Energetic storm particles (ESPs) , accelerated by shocks associated with solar flares and CMEs, are another example of interplanetary acceleration.

The heliopause is the name for the blurred boundary between the heliosphere and the interstellar gas outside the solar system. As the solar wind approaches the heliopause, it slows suddenly, forming a shock wave. This solar wind termination shock is exceptionally good at accelerating particles.


How would we know when we’ve arrived in interstellar space?

When it comes to the Sun it’s all about detecting the concentration and temperature of the particles around you.

Inside the heliosphere, the solar particles are hot but less concentrated. Outside of the bubble, they are very much colder but more concentrated.

Once you arrive in interstellar space, there would be an increase of “cold” particles around you. There would also be a magnetic field that does not originate from our Sun. Welcome to interstellar space!


Voyager 1 Reaches Interstellar Space. But Has It Left the Solar System? Wellllll…

Yesterday, NASA announced with some fanfare that after 36 years in space, the probe Voyager 1 has entered interstellar space.

I have two things to say here, and I want to be careful. First, this is an amazing event, and well worth celebrating. Second, a lot of people are saying Voyager 1 has left the solar system, and that’s not really accurate.

More Bad Astronomy

First things first. What scientists discovered is that in mid-to-late 2012, Voyager entered a new region of space. This all has to do with the solar wind, a stream of subatomic particles blown outward by the Sun. This wind expands outward, and far beyond the orbit of Neptune it encounters the particles that exist between the stars. It pushes those aside, and loses momentum as it does so. At some point, the pressure from the wind is no longer strong enough to expand against the pressure of those external particles, and it slows to a stop. This region is called the heliopause. For years, we’ve known that Voyager is in the fuzzy volume of space where the heliopause lies, but it’s been maddeningly difficult to know if it had punched through.

Diagram showing the positions of Voyager 1 (upper left) and Voyager 2 (middle left). The inner blue region is the expanding solar wind, the lighter blue the interaction of the solar wind and interstellar material. Note that Voyager 1 is outside both regions. Credit: NASA/JPL-Caltech

The Sun then gave us a gift: a coronal mass ejection. These vast explosions of material sweep outward, and one went off in March 2012. After more than a year of travel, this blast reached the heliopause. When it did so, it interacted with the material there, causing it to vibrate. This type of interaction is detectable by Voyager, and when scientists analyzed the data, they realized the density of the material was far higher than expected. This is just what would happen if Voyager had in fact flown through the heliopause.

So. It looks like, after traveling 19 billion kilometers (12 billion miles), one of our spacecraft has entered what can reasonably be considered interstellar space.

But does this mean it has left the solar system? Well, no. That might seem odd, since I just said it’s in interstellar space, but that’s only when you look at the Sun’s influence on the particles out there.

However, there’s more to our solar system’s far-flung suburbs than errant electrons and protons. Even out there, over 120 times farther from the Sun than the Earth’s orbit, there are more substantive objects: huge, frozen chunks of ice that are essentially giant comets. The Sun is surrounded by trillions of these iceballs, a countless swarm of them called the Oort Cloud. They take thousands of years to orbit the Sun even once, but enthralled to its gravity they are.

This makes them bona fide solar system objects, and that’s why we can’t really say Voyager 1 has left the solar system. There’s still more solar system beyond it!

It’s like walking outside the front door of your house and saying you’ve left your property. While you’ve left your house, there’s still the yard all around you. You have a ways to go yet.

I make this point because the claim that Voyager has left the solar system has been made before. Many times. Many, many times. The latest was in March of this year, when some scientists announced they had detected a change in the environment Voyager was in, marking the boundary to interstellar space. That announcement was quickly contradicted by the Voyager team at JPL, including Voyager team leader Ed Stone. Full disclosure and mea culpa: I said at the time that Voyager had left the solar system, but then quickly backed off that claim when the Voyager team chimed in.

However, with these new results, Stone has given his blessing. So while Voyager still has a ways to go (many thousands of years, actually) before it actually leaves what we can think of as our solar system, I think it’s fair to say it’s now in interstellar space.

And this is an astonishing achievement for humanity. It was inevitable we knew this would happen even before Voyager (and its twin Voyager 2) was even launched, in 1977. But still, after all these years, and so much terribly empty space traveled, this point has now been reached. Humanity is now an interstellar species.

I think the words I wrote back in March, premature as they were, finally can ring even more truly today:


Voyager 2 Illuminates Boundary of Interstellar Space

Five new research papers detail Voyager 2's observations since it exited the heliosphere, or the protective bubble of particles and magnetic fields created by our Sun.

One year ago, on Nov. 5, 2018, NASA's Voyager 2 became only the second spacecraft in history to leave the heliosphere - the protective bubble of particles and magnetic fields created by our Sun. At a distance of about 11 billion miles (18 billion kilometers) from Earth - well beyond the orbit of Pluto - Voyager 2 had entered interstellar space, or the region between stars. Today, five new research papers in the journal Nature Astronomy describe what scientists observed during and since Voyager 2's historic crossing.

Each paper details the findings from one of Voyager 2's five operating science instruments: a magnetic field sensor, two instruments to detect energetic particles in different energy ranges and two instruments for studying plasma (a gas composed of charged particles). Taken together, the findings help paint a picture of this cosmic shoreline, where the environment created by our Sun ends and the vast ocean of interstellar space begins.

The Sun's heliosphere is like a ship sailing through interstellar space. Both the heliosphere and interstellar space are filled with plasma, a gas that has had some of its atoms stripped of their electrons. The plasma inside the heliosphere is hot and sparse, while the plasma in interstellar space is colder and denser. The space between stars also contains cosmic rays, or particles accelerated by exploding stars. Voyager 1 discovered that the heliosphere protects Earth and the other planets from more than 70% of that radiation.

When Voyager 2 exited the heliosphere last year, scientists announced that its two energetic particle detectors noticed dramatic changes: The rate of heliospheric particles detected by the instruments plummeted, while the rate of cosmic rays (which typically have higher energies than the heliospheric particles) increased dramatically and remained high. The changes confirmed that the probe had entered a new region of space.

Before Voyager 1 reached the edge of the heliosphere in 2012, scientists didn't know exactly how far this boundary was from the Sun. The two probes exited the heliosphere at different locations and also at different times in the constantly repeating, approximately 11-year solar cycle, over the course of which the Sun goes through a period of high and low activity. Scientists expected that the edge of the heliosphere, called the heliopause, can move as the Sun's activity changes, sort of like a lung expanding and contracting with breath. This was consistent with the fact that the two probes encountered the heliopause at different distances from the Sun.

The new papers now confirm that Voyager 2 is not yet in undisturbed interstellar space: Like its twin, Voyager 1, Voyager 2 appears to be in a perturbed transitional region just beyond the heliosphere.

"The Voyager probes are showing us how our Sun interacts with the stuff that fills most of the space between stars in the Milky Way galaxy," said Ed Stone, project scientist for Voyager and a professor of physics at Caltech. "Without this new data from Voyager 2, we wouldn't know if what we were seeing with Voyager 1 was characteristic of the entire heliosphere or specific just to the location and time when it crossed."

Pushing Through Plasma

The two Voyager spacecraft have now confirmed that the plasma in local interstellar space is significantly denser than the plasma inside the heliosphere, as scientists expected. Voyager 2 has now also measured the temperature of the plasma in nearby interstellar space and confirmed it is colder than the plasma inside the heliosphere.

In 2012, Voyager 1 observed a slightly higher-than-expected plasma density just outside the heliosphere, indicating that the plasma is being somewhat compressed. Voyager 2 observed that the plasma outside the heliosphere is slightly warmer than expected, which could also indicate it is being compressed. (The plasma outside is still colder than the plasma inside.) Voyager 2 also observed a slight increase in plasma density just before it exited the heliosphere, indicating that the plasma is compressed around the inside edge of the bubble. But scientists don't yet fully understand what is causing the compression on either side.

If the heliosphere is like a ship sailing through interstellar space, it appears the hull is somewhat leaky. One of Voyager's particle instruments showed that a trickle of particles from inside the heliosphere is slipping through the boundary and into interstellar space. Voyager 1 exited close to the very "front" of the heliosphere, relative to the bubble's movement through space. Voyager 2, on the other hand, is located closer to the flank, and this region appears to be more porous than the region where Voyager 1 is located.

Magnetic Field Mystery

An observation by Voyager 2's magnetic field instrument confirms a surprising result from Voyager 1: The magnetic field in the region just beyond the heliopause is parallel to the magnetic field inside the heliosphere. With Voyager 1, scientists had only one sample of these magnetic fields and couldn't say for sure whether the apparent alignment was characteristic of the entire exterior region or just a coincidence. Voyager 2's magnetometer observations confirm the Voyager 1 finding and indicate that the two fields align, according to Stone.

The Voyager probes launched in 1977, and both flew by Jupiter and Saturn. Voyager 2 changed course at Saturn in order to fly by Uranus and Neptune, performing the only close flybys of those planets in history. The Voyager probes completed their Grand Tour of the planets and began their Interstellar Mission to reach the heliopause in 1989. Voyager 1, the faster of the two probes, is currently over 13.6 billion miles (22 billion kilometers) from the Sun, while Voyager 2 is 11.3 billion miles (18.2 billion kilometers) from the Sun. It takes light about 16.5 hours to travel from Voyager 2 to Earth. By comparison, light traveling from the Sun takes about eight minutes to reach Earth.


Where the Solar System Ends

Where does the solar system actually end? We could say it’s where the Sun’s gravity stops being strong enough to hold onto things. This would make it the edge of the Oort Cloud, the loosely bound sphere of rocky and icy bits left over from the solar system’s formation, extending almost 3 light-years from the Sun. Or, we could say it’s where the energetic particles from the Sun (the solar wind) stop flowing away from us, blocked by the pressure of all the other gas that’s between stars, the interstellar medium

Today, we’ll focus on the latter: the heliopause, the boundary where the solar wind meets the interstellar medium (ISM), which marks the edge of the heliosphere, the bubble of gas surrounding the Sun. Both the solar wind and the ISM are made of plasma, the 4th state of matter. In a plasma, some of the electrons have been stripped off the atoms, leaving charged particles (ions) to move around. There are a few different parts of the heliosphere, and the Voyager missions, launched in the 1970s, have traveled through all of them.

After traveling far beyond the planets, the two Voyager missions first encountered a region where the solar wind slows down below the speed of sound, known as a termination shock. Their next big milestone would be the heliopause (see Figure 1 for illustration). This is an important and unique part of our solar system to understand it is where our solar system and our star interact with the surrounding galaxy. There’s a lot we can learn here about how forces and magnetic fields in the plasma of the interstellar medium confine and influence the solar wind. The heliopause is even important for understanding how life comes about in solar systems – it’s what protects us from dangerous cosmic rays and other high energy radiation that could be disastrous for life.

Figure 1: Illustration (not to scale) showing the planets and the different features of the heliosphere. (Image from Encyclopedia Britannica)

Voyager 1 crossed the heliopause first in 2012, at 121.7 Astronomical Units, (AU) meaning Voyager 1 was 121.7 times further from the Sun than the Earth is. Voyager 2 finally reached this milestone in late 2018, at 119 AU, passing through a slightly different flow of the solar wind than Voyager 1 did, as shown in Figure 2. Although Voyager 1 gave us the first information on the heliopause, it passed through a weird spot, where the solar wind seemed to be flowing more slowly and in ways we wouldn’t expect. It also didn’t get to take all its measurements, since its plasma instrument was broken. Since 2012, astronomers have been waiting for Voyager 2 to reach this milestone, so that they can take new measurements and understand another perspective of the heliopause, including the speed and direction of the plasma’s flow, its temperature, and its density in that region.

Figure 2: Diagram of the Voyager 1 and 2 trajectories, illustrating the different paths they took towards the outer reaches of the solar system. (Image from NASA/JPL)

So, what did Voyager 2 see out there? As it approached the heliopause, it entered a “boundary layer” – a region where the density and magnetic field increase as the solar wind encounters the ISM. Voyager 1 also traveled through this layer, and observed something unusual: the flow of the solar wind was stagnated, traveling much more slowly than expected. Voyager 2 saw very different velocities of the solar wind near the boundary, and although we’re not sure why these two observations were so different, the authors think they might be due to instabilities in the boundary layer the heliosphere isn’t a perfect bubble, instead its edges might have swirls and uneven patches. It took the spacecraft 8 days to cross this boundary region, but the actual heliopause is so sharply defined that it only took 1 day to cross (as shown in Figure 3)!

Figure 3: Data from Voyager 2’s plasma instruments, showing the steep drop in current once the spacecraft reached the heliopause. The rise in current before the heliopause happens as V2 crosses the boundary layer. (Figure 1 in the paper)

After the heliopause, Voyager 2 was officially out in the “very local interstellar medium” (VLISM). The VLISM isn’t perfectly smooth either Voyager 2 observed variations in the speed, flow direction, density, and temperature of the plasma out there, and found that the further it gets from the heliopause, the more dense the VLISM gets. This makes sense, since it’s cooler out there (around 7500 K, a bit hotter than the Sun’s surface) than it is closer to the heliopause, where gas gets compressed as the solar wind presses into the ISM, and the plasma is observed to be much hotter – around 30,000 K! This is actually hotter than expected, suggesting that the plasma is getting more compressed or heated in other ways. Voyager 2 also passed through an interesting region where the current in the plasma spiked up (illustrated in the data in Figure 4) the authors think this is a shock, a sudden change in pressure and density.

Figure 4: Measurements of the current in the VLISM (very local interstellar medium) flow as measured by Voyager 2. The heliopause is marked “HP” and the spike at Day 418 shows when V2 may have passed through a shock. (Figure 5 in the paper)

Having direct measurements of all this plasma and matter beyond the heliopause is important, because it’s literally the stuff that is between ALL the stars! Most of the universe (besides dark matter, of course) is made of plasma, and after more than 30 years of traveling and waiting, now we have the chance to directly observe it.

Originally created as a mission to study Jupiter and Saturn up close, the Voyager probes ended up flying by Jupiter, Saturn, Uranus, Neptune, and 48 of their moons. Now, they’re continuing past the planets, past the heliopause, and into interstellar space. Both Voyagers are now out there observing the VLISM – and we can look forward to getting info on all this stuff between stars as long as the spacecraft stay alive and communicating with Earth.


What does the Sun look like from the heliopause? - Astronomy

What is the diameter of our solar system and how many times would our solar system fit between us and the nearest star?

Defining the size of the Solar System is a hard thing to do because it does not have a clear boundary. I will answer the question by calculating it two ways. First, using the orbit of Pluto as the boundary, and second using the orbit of the farthest comets we know.

1 - Orbit of Pluto To calculate this we will use the orbit of Pluto as the limit of the solar system. A problem is that the orbit of Pluto is not circular, it is rather an ellipse. All the planets orbit the Sun on ellipses. For most of the planets the ellipses are almost circles, but not for Pluto. This means that the distance from Pluto to the Sun varies quite a bit. In fact, at some time,s it is closer to the Sun than Neptune! So we will take the average distance between the Sun and Pluto as the radius of the Solar System (which is 5,913,520,000 km, or 39.5 AU, where AU stands for Astronomical Unit)

2 - Orbit of comets Beyond the orbit of Pluto, there are object that orbit the Sun. These are the comets. Two populations of comets have been identified: the Kuiper Belt and the Oort Cloud. The Oort Cloud has a larger radius, estimated at about 50,000 AU (or 7.5x10 12 km). As you can see, comets are found much farther from the Sun than any of the planets!

Now the nearest star to the Sun is Proxima Centauri which is located at a distance of 4.3 light years (one light year is the distance traveled by light in one year). Now, 1 light year is 63,270 AU, which means that the distance to the nearest star is 272,061 AU.

We took the radius of the solar system to be 39.5 AU, which means it has a diameter of 79 AU. This means you could put the Solar System about 3440 times between the Sun and the nearest star taking this definition.

If you include all the comets like we did in the second part, then the Solar System has a diameter of about 100,000 AU, which means it would fit 2.7 times between the Sun and the nearest star.

Update: Another way of defining the size of the solar system is through the location of the heliopause (link). This is the layer where the solar wind and the interstellar medium push on each other with equal pressure. Close to the Sun, the solar wind is dense. This enables to exert a large pressure and force out the low density interstellar medium. As we move farther away from the Sun, the solar wind density decreases and consequently, its pressure as well. Ultimately, there will be a location where the pressure exerted by the solar wind becomes small enough to match that exerted by the interstellar medium.

This page was last updated Jan 28, 2019.

About the Author

Amelie Saintonge

Amelie is working on ways to detect the signals of galaxies from radio maps.


The Outer Heliosphere: The Next Frontiers

H.-R. Müller , B.E. Wood , in COSPAR Colloquia Series , 2001

3 COMPARISON TO HST DATA

In upwind directions, the heliospheric H I column density is dominated by compressed, heated, and decelerated material just outside the heliopause (the hydrogen wall). For an observer at Earth, the absorption due to LISM H I in the upwind direction is blueshifted relative to the Ly α rest wavelength. The decelerated heliospheric H I absorption is also blueshifted, but less than that of the LISM. Therefore, the hydrogen wall material accounts for most of the non-LISM absorption observed on the red side of the saturated core of the Lyα absorption profile. Component 1 neutral hydrogen develops only small perpendicular velocity components in the hydrogen wall, such that the above holds for all sightlines through the hydrogen wall less than 90° from the upwind direction. At hydrogen walls around other stars, where an observer looks from the outside rather than the inside, this scenario is reversed, meaning that the decelerated material of the stellar hydrogen wall is in fact more blueshifted than the LISM, and the additional absorption shows up at the blue wing of the main (interstellar) absorption feature.

Figure 4 shows the observed Lyα profile of a Cen B [ 10 ], which is 52° from the upwind direction. Excess H I absorption is present on both the blue and red sides of the LISM absorption. The red side excess is due to the heliospheric absorption, while the blue side excess is due to absorption from analogous “astrospheric” material [ 11 ]. An additional detection of heliospheric H I absorption only 12° from the upwind direction was provided by HST observations of 36 Oph [ 15 ]. For downwind lines of sight the H I density is much lower than in the hydrogen wall, but the sightline through the heated heliospheric H I is longer, potentially allowing heliospheric Lyα absorption to be observed downwind as well [ 23 ], again on the red side because neutrals in the tail are accelerated by charge exchange to speeds higher than the LISM speed. A detection of heliospheric absorption along a downwind line of sight toward Sirius has been reported [ 16 ].

Figure 4 . HST/GHRS Lyα spectrum of α Cen B, showing broad H I absorption at 1215.6 Å and D I absorption at 1215.25 Å. The upper solid line is the assumed stellar emission profile and the dashed line is the ISM absorption alone. The excess absorption is due to heliospheric H I (vertical lines) and astrospheric H I (horizontal lines).

We can use the models listed in Table 1 to predict the amount of Lyα absorption we expect to see for various lines of sight through the heliosphere [ 24 ]. We compare these predictions with the observations of α Cen, 36 Oph, and Sirius, which we have already mentioned above as having excess Lyα absorption that is presumably heliospheric. In addition to those lines of sight, we also consider three additional lines of sight toward 31 Com, β Cas, and Eri. The HST| Lyα spectra of these stars show no evidence for excess absorption on the red side of the line that could be heliospheric [ 25 ], but these data still provide useful upper limits for the amount of absorption that could be present and they sample different directions through the heliosphere.

In Figure 5 , the absorption predicted by the seven models in Table 1 is compared with the Lyα absorption profiles observed toward the six stars. The θ values shown in the figure are the angles from the upwind direction, which range from the nearly upwind line of sight toward 36 Oph (θ = 12°) to the nearly downwind line of sight toward Eri (θ = 148°). The predicted Lyα absorption is shown after combination with the LISM absorption toward these stars, as determined from previous empirical analyses [ 10,15,16,25 ]. An attempt has been made to maximize the agreement between the data and the models by tweaking the assumed stellar emission profiles, as described by [ 24 ]. Significant disagreement remains in most cases despite these efforts.

Figure 5 . The red side of the Lyα absorption profiles observed toward six stars, sampling different angles θ relative to the upwind direction of the interstellar flow into the heliosphere. These data are compared with the heliospheric absorption predicted by the seven models listed in Table 1 , which assume different values for α.

Based on Figure 5 , we provide in the last six columns of Table 2 our evaluation of which observed stellar lines of sight (labeled by their θ angles) are inconsistent with which models. None of the models are consistent with every line of sight. The low α models do better upwind and the high α models do better downwind. In general, the models predict too much absorption, the exception being the 36 Oph line of sight for which most of the models predict too little absorption. Model 7 is the only model that does not predict too much absorption along the downwind line of sight to Eri.


Electric Cosmos: The Solar Capacitor Model. I

Here I'll continue my response to Thunderbolts Forum (TBF) critique of my critique of Don Scott's “The Electric Sky”. In this post, I'll focus on their response to my calculations of the deficiencies of another one of their proposed models for externally powering the Sun.

In this model, presented graphically in figure 1, the sun is powered by radially inbound electrons streaming from the heliopause which acts like a cathode. The photosphere of the Sun acts as the anode for the system, receiving the electrons and converting them to thermal or optical energy by their impacts. The solar photosphere also acts as a source for solar protons and ions as part of the solar wind. The electrons are accelerated inward, and the ions outward by a large potential drop between the heliopause and the solar surface. A first examination of this model resembles the popular spherical capacitor models often examined in the electromagnetism chapters in physics classes, so I will call it the Solar Capacitor model. This model does not have an obvious integration with the larger cosmos, unlike the Solar Resistor model discussed in the previous post, but I'll deal with those issues later.

Figure 1: Components of Electric Sun model

Later in the TBF thread, Don Scott reports a number of values for electrons at the heliopause to explain the solar power source in this model. I'll ignore some of the math errors Dr. Scott seems to make as we're just interested in order-of-magnitude agreement.

* interstellar electron speed of 1e5 m/s
* electron density of 10,000 electrons/m^3

These give an electron current density of 1.6e-10 amp/m^2 which with the heliopause assumed at 100AU (1.49e13 m) places a current across this boundary of 4.5e17 amps. With a voltage drop of 1e9, this yields a power of 4.5e26 watts, a little more than the observed solar luminosity. (Note that we could fiddle with a range of values here to get the same luminosity - 1e10 volts for 4e16 amps would work as well.) We'll use these as our input values to the model. Let's also note that Dr. Scott specifies that the solar wind speed measured by spacecraft runs between 2e5 and 1e6 m/s.

First, I'll outline the basics of the analysis at a level which might be called a first-order approximation - it lays the basic framework while ignoring some of the interactions which would complicate a first analysis. The goal is to get an idea of magnitudes of other quantities we can determine from such a configuration using fundamental physical principles such as energy and charge conservation.

Assumptions:
- radial symmetry. The Sun looks roughly the same regardless of the direction we look at it.
- time independence. We're interested in the bulk steady production of energy, not episodic events like flares and CMEs.
- the motion of electrons & protons are controlled purely by potential at photosphere & heliopause. We can use conservation of energy to determine the particle energy all along the trajectory.

'i' indicated the initial potential and kinetic energy and 'f' index indicates the final potential and kinetic energy values. The kinetic energy of a particle, E_k, is related to the particle velocity by

Here q is the charge of the particle m is the rest mass of the particle, Phi is the electric potential field value at radial position r.
- potential in the space between the Sun and the heliopause is assumed coulombic. This is also a consequence of the radial symmetry of the problem and assumed charge neutrality in the intervening space.

Using this equation, we can solve for the charge necessary to produce a 1e9 volt drop between the heliopause (100AU) and the solar surface (

0.003AU). We see that it requires a net charge a the Sun of +77.44e6 coulombs.

Note that all of the above equations should be familiar to anyone who has taken a competent high-school level physics class.

What are we not including?
- We assume counter-streaming electrons and ions are not interacting. This ignores energy losses due to scattering as well as nuclear processes such as pair production (electron-positrons and muons). All these processes are well-studied in particle accelerators.
- We assume the electromagnetic fields generated by the streaming electrons and ions are small enough to be ignored. Such fields would alter the flows, diverting their energy from going to the solar photosphere.

The advantage of this approximation is that both of the ignored effects described above would reduce the energy of the electrons reaching the solar photosphere by distributing the energy in the intervening space. This means that we get an upper bound, or maximum amount of energy that can possibly reach the solar surface. Inclusions of any of these refined processes will make agreement for the Electric Sun model even worse than we are about to see.

Using the equations above, we can plot the energies, and therefore the velocities of electrons, protons and alpha particles in the region between the photosphere and the heliopause (Figures 2 & 3). The horizontal distance scale is logarithmic for clarity. Note that the Earth is located at 1AU.

The protons and positive ions, repelled by the positive charge of the Sun, are accelerated as they move out. The electrons accelerate on the way towards the Sun.


Figure 2: Energy of particles vs. radial distance from the Sun. We also plot the potential (voltage) of the solar field. The radial distance is plotted logarithmically in astronomical units (AU).

Figure 3: Particle radial velocities vs. Radial distance from the Sun. Speeds based on energies from Figure 2. The radial distance is plotted logarithmically in astronomical units (AU).

With a closer examination of the actual values, we see that things start to fall apart for this model very quickly.

* The inbound electrons accelerate to relativistic speeds and are close to the speed-of-light by the time they reach 10AU from the Sun. By the time they reach Earth orbit (1 AU), they have energies of about 4.6 MeV (million electron volts). This is well above the pair-production threshold energy for electrons. Any matter they strike can generate showers of secondary electron-positron pairs. This includes planets, moon, and spacecraft (with and without crews).

* The outbound protons, starting close to the Sun and the strongest gradient in the potential, accelerate to near 1GeV (gigaelectron volts) by 0.1 AU. In velocities, this translates to over 0.87c (=2.6e8 m/s) for protons. Alpha particles (helium nuclei) reach nearly 2 GeV and a speed of 0.75c (2.3e8 m/s). Compare this to the solar wind speed Dr. Scott reports above. The Electric Sun model predicts a solar wind speed that is a factor of over 200 higher than the measured outbound solar wind speed!

Next, let's examine the particle fluxes implied by this model. At the heliopause, an electron current density of 1.6e-10 amp/m^2 corresponds to an electron flux of 1e+9 electrons/m^2/s and a total current through the surface of 4.5e17 amps. Dr. Scott claims that the outbound proton current matches the electron current, keeping the charge density neutral (we'll also see why the charge density will not remain neutral in this configuration), so for this next step, we assume a total number of protons emitted at the Sun is equivalent to 4.5e17 amps. At the photosphere, this corresponds to a proton flux of 4.6e17 protons/m^2/s.

But wait, the charge on the Sun to maintain the billion volt potential drop is only 77.44e6 coulombs! If the outgoing proton flux is 4.5e17 amps, the Sun will lose its entire positive charge in only 77.44e6 coulombs/4.5e17amps = 1.7e-10 seconds! Without an external source maintaining the solar potential, the Electric Sun will shut down in about 170 picoseconds! Remember, we have not yet included the effects of the net charge reduction due to the same amount of incoming electrons! If we include these electrons, the shutdown time for the Sun is even short (i.e. HALF the current estimate).

What maintains this potential?? Where is the incredible power source that maintains it. That is the REAL mystery of the Electric Cosmos and its advocates never talk about that!

Would you trust an electrical engineer who designed his lighting system (in this case, the Sun) without an EMF to drive it?

In the next post on this model, we'll see even more implications of the Electric Sun model that fail when compared to observations.
(Author's note: realized I had reversed cathode & anode. Fixed 1/4/2009)


Sun's Heliopause: A Moving Target

By: J. Kelly Beatty October 1, 2010 0

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Isn't it counter-intuitive to name a spacecraft the Interstellar Boundary Explorer, knowing full well that it'll never venture more than about 200,000 miles (300,000 km) from its home planet?

Artist concept of the IBEX satellite.

NASA / Goddard Space Flight Center

IBEX was launched into a looping orbit that stretches halfway to the Moon but no farther.

However, within a year the spacecraft had amazed its science team. Its first all-sky map revealed, for the first time, the nature of the region 8 to 10 billion miles away where the Sun's magnetic bubble, the heliosphere, meets interstellar space.

How, you might ask, is that possible?

When the outward-racing solar wind reaches the heliosphere's edge, the heliopause, it mingles with atoms in the interstellar medium. That's where energetic solar-wind protons can steal electrons from the slower-moving atoms of interstellar hydrogen. This charge exchange turns the protons into electrically neutral hydrogen atoms. No longer controlled by the solar wind's magnetic field, and still moving fast, they zip away from the interstellar boundary in all directions.

Some of these "energetic neutral atoms," or ENAs, make it all the way back to Earth, where they're recorded by two particle detectors on IBEX. These instruments record the number and energy of atoms arriving from small spots of sky about 7° across (about the size of a tennis ball held at arm's length). IBEX is slowly rotating, with its spin axis always pointing at the Sun, so the detectors scan overlapping strips that gradually create an all-sky "snapshot" every six months.

The Interstellar Boundary Explorer (IBEX) completed its first all-sky map of the complex interactions occurring at the edge of the solar system in mid-2009. Labels show the current location of Voyagers 1 and 2 and of the leading "nose" of the Sun's heliosphere.

A 135°-wide portion of IBEX's first two all-sky maps shows how the intensity and distribution of a "knot" of emission from energetic neutral atoms changed over a six-month period.

in mid-2013, the experts say), the solar wind will gust and fling protons at the heliopause with more energy and intensity. IBEX should see an uptick in ENA emission a year or so after that (the ENAs take a while to make their way back home).

Only two spacecraft, Voyagers 1 and 2, have ventured far enough to probe this region directly. While they have recorded hails from the heliopause as bursts of radio energy, they lack IBEX's ability to map the ENA emission. (Status check: Voyager 1 is now 115 astronomical units from Earth, while Voyager 2 is 93 AU away.)

Meanwhile, IBEX hasn't limited its discoveries to the threshold of interstellar space. It turns out that ENAs also arise much closer to home, along the edge of Earth's magnetosphere, the magnetopause. The solar-wind protons, racing outward at hundreds of miles per second, run into the exosphere, a very tenuous cloud of hydrogen atoms escaping from our atmosphere. It's never been clear how far the exosphere extends into space, but this crash scene is about 35,000 miles (55,000 km) up, over Earth's dayside hemisphere. "Where the interaction is strongest, there are only about 8 hydrogen atoms per cubic centimeter," explains Stephen A. Fuselier (Lockheed Martin Space Systems).

IBEX has even recorded an ENA signature coming from the Moon. Apparently some solar-wind protons must be bouncing off the lunar surface, becoming ENAs through charge exchange as they do.

Maybe McComas and his team ought to consider changing this versatile spacecraft's name. I just consulted the General Office of Far-Fetched Identifiers (GOOFI), whose experts responded with "SAEIL." That stands for "Something Amazing Everywhere It Looks."


The corona is the barely there outermost layer of the sun, which we can see only during a total solar eclipse, when the moon blocks out the brightness of the star's photosphere. That's made the corona remarkably difficult to study — but beginning later this year, NASA will fly a spacecraft directly though the corona to try to solve its lingering mysteries. [Read more about the corona]

The solar wind isn't technically a layer of the sun, but the constant stream of highly charged particles flowing off the sun is one of the key ways our star affects planets. Here on Earth, our atmosphere mostly blankets us from the solar wind, but it's a key hazard for satellites and space travel. The solar wind also defines our solar system, which stretches as far as the wind does. [Read more about the solar wind]


Watch the video: Μια ιστορία για τον ήλιο (February 2023).