Voyager 1 has found only electrons streaming into the heliosphere from elsewhere in the galaxy.

The arcing, graceful structure is actually a bow shock about half a light-year across, created from the wind from the star LL Orionis colliding with the Orion Nebula flow. Credit: NASA.

Usually the separation of charge carriers, such as electrons and protons, occurs when the solar wind is propelled away from the Sun. For the same apparent energy an electron moves way out in front and a proton lags behind, where a hydrogen atom is the original source.

The astronomy of looking for the circuit involved in the solar wind is an example of circuit astronomy.

Charges edit

The locus of the abrupt change in conductance that clearly moves away from the 1D parabola is the chargon. Credit: Y. Jompol, C. J. B. Ford, J. P. Griffiths, I. Farrer, G. A. C. Jones, D. Anderson, D. A. Ritchie, T. W. Silk and A. J. Schofield.

Charge is usually thought of as a property of matter that is responsible for electrical phenomena, existing in a positive or negative form.

Chargons edit

Def. "a quasiparticle produced as a result of electron spin-charge separation"[1] is called a chargon.

A chargon possesses the charge of an electron without a spin.

A spinon, in turn, possesses the spin of an electron without charge. The suggestion is that an elementary particle such as a positron may consist of at least two parts: spin and charge.

In the figure at the top of the page "the 1D parabola tracks the spin excitation (spinon)."[2]

Def. a "quasiparticle, corresponding to the orbital energy of an electron, which can result from an electron apparently ‘splitting’ under certain conditions"[3] is called an orbiton.

Both an orbiton and a spinon are kinetic or kinematic concepts applied to an electron.

Def. "a discrete particle having zero rest mass, no electric charge, and an indefinitely long lifetime"[4] is called a photon.

An electron may be thought of as a stable subatomic particle with a charge of negative one.

Quanta edit

"Quantum mechanics however states that matter cannot have a negative mass. Negative mass is not the same as antimatter, as even antimatter has positive mass. Negative mass is a hypothetical concept of matter where mass is of opposite sign to the mass of normal matter. Negative mass is used in speculative theories, such as the construction of wormholes. Should such matter exist, it would violate one or more energy conditions and show strange properties. No material object has ever been found that can be shown by experiment to have a negative mass."[5]

Charge interactions edit

"Under Newton’s third law of motion, if we imagine one billiard ball striking another upon a pool table, the two balls will bounce away from each other. If one of the billiard balls had a negative mass, then the collision of the two balls would result in them accelerating in the same direction."[5]

Effective masses edit

The light going around the longer loop is relatively delayed. Credit: New Scientist.

"Laser pulses have been made to accelerate themselves around loops of optical fibre - which seems to go against Newton’s 3rd law. This states that for every action there is an equal and opposite reaction."[5]

"When a material such as layered crystals slows the speed of the light pulse in proportion to its energy, it is behaving as if it has mass. This is called effective mass, which is the mass that a particle appears to have when responding to forces. Light pulses can have a negative effective mass depending on the shape of their light waves and the structure of the crystal material that the light waves are passing through."[5]

"The pulses were split between the loops at a contact point and the light kept moving around each [loop] in the same direction. The key to the experiment was having one loop slightly longer than the other. This meant light going around the longer loop is relatively delayed, as shown by the diagram [on the right]."[5]

"When the light completes a circuit and splits at the contact point, some of its photons are shared with pulses within the other loop. After a few circuits, the pulses develop an interference pattern that gives them effective mass."[5]

Pulses "with both positive and negative effective mass [were created]. When the opposing pulses interacted in the loops, they accelerated in the same direction and moved past the detectors a little bit earlier after each trip. The loops are essentially the equivalent of having extremely long crystals."[5]

Electrons edit

The electron is a subatomic particle with a negative charge, equal to -1.60217646x10-19 C. Current, or the rate of flow of charge, is defined such that one coulomb, so 1/-1.60217646x10-19, or 6.24150974x1018 electrons flowing past a point per second give a current of one ampere. The charge on an electron is often given as -e. note that charge is always considered positive, so the charge of an electron is always negative.

The electron has a mass of 9.10938188x10-31 kg, or about 1/1840 that of a proton. The mass of an electron is often written as me.

When working, these values can usually be safely approximated to:

-e = -1.60x10-19 C
me = 9.11x10-31kg

It has no known components or substructure; in other words, it is generally thought to be an elementary particle.[6][7] The intrinsic angular momentum (spin) of the electron is a half-integer value in units of ħ, which means that it is a fermion.

Delta rays edit

A delta ray is characterized by very fast electrons produced in quantity by alpha particles or other fast energetic charged particles knocking orbiting electrons out of atoms. Collectively, these electrons are defined as delta radiation when they have sufficient energy to ionize further atoms through subsequent interactions on their own.

"The conventional procedure of delta-ray counting to measure charge (Powell, Fowler, and Perkins 1959), which was limited to resolution sigmaz = 1-2 because of uncertainties of the criterion of delta-ray ranges, has been significantly improved by the application of delta-ray range distribution measurements for 16O and 32S data of 200 GeV per nucleon (Takahashi 1988; Parnell et al. 1989)."[8] Here, the delta-ray tracks in emulsion chambers have been used for "[d]irect measurements of cosmic-ray nuclei above 1 TeV/nucleon ... in a series of balloon-borne experiments".[8]

Epsilon rays edit

Epsilon radiation is tertiary radiation caused by secondary radiation (e.g., delta radiation). Epsilon rays are a form of particle radiation and are composed of electrons. The term is very rarely used today.

Circuits edit

This diagram suggests a simple electrical circuit. Credit: GorillaWarfare.

The diagram at right suggests a simple electrical circuit.

Def. an enclosed path of an electric current is called a circuit.

In the diagram at right are three components:

  1. a voltage (V), or current (i), source,
  2. an enclosed path, and
  3. a resistance, or resistor, (R).

According to Ohm's law:


With respect to an enclosed path, consider a path from outside the heliosphere, inward toward the Sun, and out again. Let the incoming electrons have 500 MeV of energy and a flux of 8.5 x 104 e- cm-2 s-1.

Def. a time rate of flow of electric charge is called a current.

Def. that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per metre of length is called an ampere.

Def. an amount of electrostatic potential between two points in space is called a voltage.

Astronomy edit

The composite shows upper atmospheric lightning and electrical discharge phenomena. Credit: Abestrobi.

With respect to the rocky-object Earth, between the surface and various altitudes there is an electric field induced by the ionosphere. It changes with altitude from about 150 volts per meter at the suface to lower values at higher altitude. In fair weather, it is relatively constant, in turbulent weather it is accompanied by ions. At greater altitude these chemical species continue to increase in concentration. To dissipate the accumulation of greater charge differential between the surface and the ionosphere, the gases between suffer breakdown (ionization) that permits lightning to be either a draw of negative charge, usually electrons, upward from the surface or a transfer of positive charge to the ground.

Charge astronomy edit

This is a schematic of Jupiter's magnetosphere and the components influenced by Io (near the center of the image). Credit: John Spencer.

The image at right represents "[t]he Jovian magnetosphere [magnetic field lines in blue], including the Io flux tube [in green], Jovian aurorae, the sodium cloud [in yellow], and sulfur torus [in red]."[9]

"Io may be considered to be a unipolar generator which develops an emf [electromotive force] of 7 x 105 volts across its radial diameter (as seen from a coordinate frame fixed to Jupiter)."[10]

"This voltage difference is transmitted along the magnetic flux tube which passes through Io. ... The current [in the flux tube] must be carried by keV electrons which are electrostatically accelerated at Io and at the top of Jupiter's ionosphere."[10]

"Io's high density (4.1 g cm-3) suggests a silicate composition. A reasonable guess for its electrical conductivity might be the conductivity of the Earth's upper mantle, 5 x 10-5 ohm-1 cm-1 (Bullard 1967)."[10]

As "a conducting body [transverses] a magnetic field [it] produces an induced electric field. ... The Jupiter-Io system ... operates as a unipolar inductor" ... Such unipolar inductors may be driven by electrical power, develop hotspots, and the "source of heating [may be] sufficient to account for the observed X-ray luminosity".[11]

"The electrical surroundings of Io provide another energy source which has been estimated to be comparable with that of the [gravitational] tides (7). A current of 5 x 106 A is ... shunted across flux tubes of the Jovian field by the presence of Io (7-9)."[12]

"[W]hen the currents [through Io] are large enough to cause ohmic heating ... currents ... contract down to narrow paths which can be kept hot, and along which the conductivity is high. Tidal heating [ensures] that the interior of Io has a very low eletrical resistance, causing a negligible extra amount of heat to be deposited by this current. ... [T]he outermost layers, kept cool by radiation into space [present] a large resistance and [result in] a concentration of the current into hotspots ... rock resistivity [and] contact resistance ... contribute to generate high temperatures on the surface. [These are the] conditions of electric arcs [that can produce] temperatures up to ionization levels ... several thousand kelvins".[12]

"[T]he outbursts ... seen [on the surface may also be] the result of the large current ... flowing in and out of the domain of Io ... Most current spots are likely to be volcanic calderas, either provided by tectonic events within Io or generated by the current heating itself. ... [A]s in any electric arc, very high temperatures are generated, and the locally evaporated materials ... are ... turned into gas hot enough to expand at a speed of 1 km/s."[12]

Sun edit

The Solar wind dynamic pressure was detected by Ulysses-SWOOPS. Credit: Dave McComas, Ulysses, EIT-SOHO; LASCO-C2-SOHO; MLSO.
Ulysses (spacecraft) measures the variable speed of the solar wind. Credit: NASA – Marshall Space Flight Center.

The diagram on the right describes the Solar wind dynamic pressure as detected by Ulysses-SWOOPS.

"The average pressure of the solar wind has dropped more than 20% since the mid-1990s. This is the weakest it's been since we began monitoring solar wind almost 50 years ago."[13]

"Curiously, the speed of the million mph solar wind hasn't decreased much—only 3%. The change in pressure comes mainly from reductions in temperature and density. The solar wind is 13% cooler and 20% less dense."[14]

"Global measurements of solar wind pressure by Ulysses [are shown in the diagram on the right]. Green curves trace the solar wind in 1992-1998, while blue curves denote lower pressure winds in 2004-2008."[14]

"What we're seeing is a long term trend, a steady decrease in pressure that began sometime in the mid-1990s."[15]

"It's hard to say [how unusual this event is]. We've only been monitoring solar wind since the early years of the Space Age—from the early 60s to the present. Over that period of time, it's unique. How the event stands out over centuries or millennia, however, is anybody's guess. We don't have data going back that far."[15]

"Ulysses also finds that the sun's underlying magnetic field has weakened by more than 30% since the mid-1990s."[15]

"Unpublished Ulysses cosmic ray data show that, indeed, high energy (GeV) electrons, a minor but telltale component of cosmic rays around Earth, have jumped in number by about 20%."[14]

"The solar wind streams off of the Sun in all directions at speeds of about 400 km/s (about 1 million miles per hour). The source of the solar wind is the Sun's hot corona. The temperature of the corona is so high that the Sun's gravity cannot hold on to it. Although we understand why this happens we do not understand the details about how and where the coronal gases are accelerated to these high velocities. This question is related to the question of coronal heating."[16]

"The solar wind is not uniform. Although it is always directed away from the Sun, it changes speed and carries with it magnetic clouds, interacting regions where high speed wind catches up with slow speed wind, and composition variations. The solar wind speed is high (800 km/s) over coronal holes and low (300 km/s) over streamers. These high and low speed streams interact with each other and alternately pass by the Earth as the Sun rotates. These wind speed variations buffet the Earth's magnetic field and can produce storms in the Earth's magnetosphere."[16]

"The Ulysses spacecraft completed two orbits through the solar system during which it passed over the Sun's south and north poles. Its measurements of the solar wind speed, magnetic field strength and direction, and composition have provided us with a new view of the solar wind. Ulysses was retired on June 30, 2009."[16]

The second image down on the right shows the results of Ulysses spacecraft measurements of the solar wind speed.

"The Advanced Composition Explorer (ACE) satellite was launched in August of 1997 and placed into an orbit about the L1 point between the Earth and the Sun. The L1 point is one of several points in space where the gravitational attraction of the Sun and Earth are equal and opposite. This particular point is located about 1.5 million km (1 million miles) from the Earth in the direction of the Sun. ACE has a number of instruments that monitor the solar wind and the spacecraft team provides real-time information on solar wind conditions at the spacecraft."[16]

Solar wind edit

The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV.

"Energetic photons, ions and electrons from the solar wind, together with galactic and extragalactic cosmic rays, constantly bombard surfaces of planets, planetary satellites, dust particles, comets and asteroids."[17]

The solar wind is divided into two components, respectively termed the slow solar wind and the fast solar wind. The slow solar wind has a velocity of about 400 km/s, a temperature of 1.4–1.6×106 K and a composition that is a close match to the corona. By contrast, the fast solar wind has a typical velocity of 750 km/s, a temperature of 8×105 K and it nearly matches the composition of the Sun's photosphere.[18] The slow solar wind is twice as dense and more variable in intensity than the fast solar wind. The slow wind also has a more complex structure, with turbulent regions and large-scale structures.[19][20]

"The slow solar wind appears to originate from a region around the Sun's equatorial belt that is known as the "streamer belt". Coronal streamers extend outward from this region, carrying plasma from the interior along closed magnetic loops.[21][22] Observations of the Sun between 1996 and 2001 showed that emission of the slow solar wind occurred between latitudes of 30–35° around the equator during the solar minimum (the period of lowest solar activity), then expanded toward the poles as the minimum waned. By the time of the solar maximum, the poles were also emitting a slow solar wind.[23]

The fast solar wind is thought to originate from coronal holes, which are funnel-like regions of open field lines in the Sun's magnetic field.[24] Such open lines are particularly prevalent around the Sun's magnetic poles. The plasma source is small magnetic fields created by convection cells in the solar atmosphere. These fields confine the plasma and transport it into the narrow necks of the coronal funnels, which are located only 20,000 kilometers above the photosphere. The plasma is released into the funnel when these magnetic field lines reconnect.[25]

Mercury edit

"[T]he Mercury encounter (M I) by Mariner 10 on 29 March 1974 occurred during the height of a Jovian electron increase in the interplanetary medium."[26]

During its second flyby of the planet on October 6, 2008, MESSENGER discovered that Mercury's magnetic field can be extremely "leaky." The spacecraft encountered magnetic "tornadoes" – twisted bundles of magnetic fields connecting the planetary magnetic field to interplanetary space – that were up to 800 km wide or a third of the radius of the planet. These 'tornadoes' form when magnetic fields carried by the solar wind connect to Mercury's magnetic field. As the solar wind blows past Mercury's field, these joined magnetic fields are carried with it and twist up into vortex-like structures. These twisted magnetic flux tubes, technically known as flux transfer events, form open windows in the planet's magnetic shield through which the solar wind may enter and directly impact Mercury's surface.[27]

The process of linking interplanetary and planetary magnetic fields, called magnetic reconnection, is common throughout the cosmos. It occurs in Earth's magnetic field, where it generates magnetic tornadoes as well. The MESSENGER observations show the reconnection rate is ten times higher at Mercury. Mercury's proximity to the Sun only accounts for about a third of the reconnection rate observed by MESSENGER.[27]

Venus edit

"During a rare period of very low density solar outflow, the ionosphere of Venus was observed to become elongated downstream, rather like a long-tailed comet. ... Under normal conditions, the solar wind has a density of 5 - 10 particles per cubic cm at Earth's orbit, but occasionally the solar wind almost disappears, as happened in May 1999. ... A rare opportunity to examine what happens when a tenuous solar wind arrives at Venus came 3 - 4 August 2010, following a series of large coronal mass ejections on the Sun. NASA's STEREO-B spacecraft, orbiting downstream from Venus, observed that the solar wind density at Earth's orbit dropped to the remarkably low figure of 0.1 particles per cubic cm and persisted at this value for an entire day."[28]

"The observations show that the night side ionosphere moved outward to at least 15 000 km from Venus' centre over a period of only a few hours," said Markus Fraenz, also from the Max Planck Institute for Solar System Research, who was the team leader and a co-author of the paper.[28] "It may possibly have extended for millions of kilometres, like an enormous tail."[28]

"Although we cannot determine the full length of the night-side ionosphere, since the orbit of Venus Express provides limited coverage, our results suggest that Venus' ionosphere resembled the teardrop-shaped ionosphere found around comets, rather than the more symmetrical, spherical shape which usually exists."[28]

"The side of Venus' ionosphere that faces away from the sun can billow outward like the tail of a comet, while the side facing the star remains tightly compacted, researchers said. ... "As this significantly reduced solar wind hit Venus, Venus Express saw the planet’s ionosphere balloon outwards on the planet’s ‘downwind’ nightside, much like the shape of the ion tail seen streaming from a comet under similar conditions," ESA officials said in a statement today (Jan. 29). It only takes 30 to 60 minutes for the planet's comet-like tail to form after the solar wind dies down. Researchers observed the ionosphere stretch to at least 7,521 miles (12,104 kilometers) from the planet, said Yong Wei, a scientist at the Max Planck Institute in Katlenburg, Germany who worked on this research."[29]

Earth edit

The animation illustrates the dynamical changes of the global magnetic field in the course of a disturbance. Credit: Nikolai Tsyganenko, USRA/NASA/GSFC.
The blue doughnut shape represents the high-speed flow of particles around the Earth. Credit: NASA.

"The animation on the [right] shows how the magnetospheric field varies in response to the diurnal wobbling of the geodipole. The background color coding displays the distribution of the scalar difference DB between the total model magnetic field and that of the Earth's dipole alone. Yellow and red colors correspond to the negative values of DB (depressed field inside the ring current, in the dayside polar cusps, and in the plasma sheet of the magnetotail). Black and blue colors indicate a compressed field (in the subsolar region on the dayside and in the magnetotail lobes on the nightside)."[30]

The second image down on the right is "taken from a computer animation illustrating the Earth's space storm shield in action. The solar wind, a thin, high-velocity electrified gas, or plasma, blows constantly from the Sun at an average speed of 250 miles per second (400 kilometers/sec). [...] The solar wind impacts the Earth's magnetic field [...] As the solar wind flows past the Earth's magnetic field, it generates enormous electric currents that heat Earth's space storm shield -- a layer in the Earth's electrically charged outer atmosphere (ionosphere) -- causing the shield to eject electrically charged oxygen atoms (oxygen ions) into space. The expelled [or] ejected oxygen ions gain tremendous speed as they leave the atmosphere, become trapped by the Earth's magnetic field and ultimately encircle the Earth, where they form a billion-degree plasma cloud around the planet, represented by the red cloud in [the image]. The blue doughnut shape [...] represents the high-speed flow of these particles around the Earth. The red "ring of fire" around the Earth's polar regions represents the contribution of the particles to the aurora (the northern and southern lights)."[31]

Moon edit

On Aldrin's right is the Solar Wind Composition (SWC) experiment already deployed. Credit: Neil A. Armstrong/NASA.
The Apollo Solar Wind Composition (SWC) pole is shown on the Moon. Credit: NASA.
The Moon is where a prediction of a lunar double layer was confirmed in 2003. Credit: Mdf.

In the image on the right: "Astronaut Edwin E. Aldrin, Lunar Module LM pilot, stands beside the Solar-Wind Composition SWC Experiment,facing the camera. The LM is visible behind Aldrin. Linear trails lines in the right foreground were formed by the cable of the surface television camera. The cable is visible on the lunar surface. Image taken at Tranquility Base during the Apollo 11 Mission. Original film magazine was labeled S. Film Type: Ektachrome EF SO168 color film on a 2.7-mil Estar polyester base taken with a 60mm lens. Sun angle is Medium. Tilt direction is Southeast SE."[32]

"At the end of the EVA, after leaving the SWC exposed to the Sun for about 1 hour and 17 minutes, Buzz [rolled] up the foil and [packed] it in a bag for analysis back on Earth."[33]

The mission times from deployment was at about 110:03:24 to removal of the SWC at about 111:27:05. The second image down on the right was taken just after removal of the SWC leaving only the pole.[33] The Moon is where a prediction of a lunar double layer[34] was confirmed in 2003.[35] In the shadows, the Moon charges negatively in the interplanetary medium.[36]

Interplanetary mediums edit

One week of interplanetary magnetic field and solar wind data is shown. Credit: NOAA.

One week of interplanetary magnetic field and solar wind data from the MAG and SWEPAM instruments on the NASA solar wind monitor ACE (Advanced Composition Explorer) is shown in the figure on the right.

The panels from top to bottom are

  1. Magnitude (white) and northward (in an ecliptical system) component (red) of the interplanetary magnetic field, in nanotesla.
  2. Magnetic field direction as seen from the sun. 0 degrees is northward (in an ecliptical sense), 270 degrees in the direction of Earth's orbital motion around the sun.
  3. Solar wind number density, i.e. number of protons per cubic centimeter.
  4. Solar wind radial flow speed in kilometers per second.
  5. Bottom panel: Solar wind proton temperature in kelvin.

Jupiter edit

The diagram shows interactions between the solar wind and the jovian magnetosphere. Credit: NASA/JPL.

The diagram on the right shows the interactions between the solar wind and the jovian magnetosphere.

"Field-aligned equatorial electron beams [have been] observed within Jupiter’s middle magnetosphere. ... the Jupiter equatorial electron beams are spatially and/or temporally structured (down to <20 km at auroral altitudes, or less than several minutes), with regions of intense beams intermixed with regions absent of such beams."[37]

"Jovian electrons, both at Jupiter and in the interplanetary medium near Earth, have a very hard spectrum that varies as a power law with energy (see, e.g., Mewaldt et al. 1976). This spectral character is sufficiently distinct from the much softer solar and magnetospheric electron spectra that it has been used as a spectral filter to separate Jovian electrons from other sources ... A second Jovian electron characteristic is that such electrons in the interplanetary medium tend to consist of flux increases of several days duration which recur with 27 day periodicities ... A third feature of Jovian electrons at 1 AU is that the flux increases exhibit a long-term modulation of 13 months which is the synodic period of Jupiter as viewed from Earth".[26]

Jovian electrons propagate "along the spiral magnetic field of the interplanetary medium [from Jupiter and its magnetosphere to the Sun]".[26]

Comets edit

Comet ISON makes its appearance into the higher-resolution HI-1 camera on the STEREO-A spacecraft. Credit: Karl Battams/NASA/STEREO/CIOC.

"A series of images [on the right] from ESA/NASA's Solar and Heliospheric Observatory, or SOHO, shows what remains of comet ISON as it continues its orbit."[38]

"The dark "clouds" coming from the right are density enhancements in the solar wind, causing all the ripples in comet Encke's tail. These kinds of solar wind interactions give us valuable information about solar wind conditions near the sun. Note: the STEREO-A spacecraft is currently located on the other side of the Sun, so it sees a totally different geometry to what we see from Earth."[38]

Heliospheres edit

Plot shows the decreased detection of solar wind particles by Voyager 1 starting in August 2012. Credit: NASA.
The heliospheric current sheet results from the influence of the Sun's rotating magnetic field on the plasma in the interplanetary medium (solar wind). Credit: Werner Heil.
This image shows the locations of Voyager 1 and 2 as of October 2018.

Def. the region of space where interstellar medium is blown away by solar wind; the boundary, heliopause, is often considered the edge of the Solar System is called the heliosphere.

The heliosphere is a bubble in space "blown" into the interstellar medium (the hydrogen and helium gas that permeates the galaxy) by the solar wind. Although electrically neutral atoms from interstellar volume can penetrate this bubble, virtually all of the material in the heliosphere emanates from the Sun itself.

On September 12, 2013 it was announced that the previous year, starting on August 25, 2012, Voyager 1 entered the interstellar medium.[39] Outside the heliosphere the plasma density increased by about forty times.[40]

Def. the boundary of heliosphere where the Sun's solar wind is stopped by the interstellar medium is called the heliopause.

Def. a zone between the termination shock and the heliopause, in the heliosphere, at the outer border of the Solar System, where the solar wind is dramatically slower than within the termination shock is called a heliosheath.

The heliosheath is the region of the heliosphere beyond the termination shock. Here the wind is slowed, compressed and made turbulent by its interaction with the interstellar medium. Its distance from the Sun is approximately 80 to 100 astronomical units (AU) at its closest point.

The flow of ISM into the heliosphere has been measured by at least 11 different spacecraft as of 2013.[41] By 2013, it was suspected that the direction of the flow had changed over time.[41] The flow, coming from Earth's perspective from the constellation Scorpius, has probably changed direction by several degrees since the 1970s.[41]

The artist's impression in the second image down on the right shows the heliospheric current sheet that results from the influence of the Sun's rotating magnetic field on the plasma in the interplanetary medium (solar wind).

"The heliospheric current sheet separates regions of the solar wind where the magnetic field points toward or away from the Sun. The complex field structure in the photosphere simplifies with increasing height in the corona until a single line separates the two polarities at about 2.5 solar radii. That line is drawn out by the radially accelerating solar wind to form a surface similar to the one shown in this idealized picture. The surface is curved because the underlying magnetic pattern rotates every 27 days with the Sun."[42]

"It would take about 3 weeks for material near the current sheet traveling at 400 km/s in the solar wind to reach the orbit of Jupiter, as depicted here. In reality the surface becomes increasingly distorted because of variations in the solar wind speed along the surface and other dynamic effects operating in the interplanetary medium."[42]

"The shape of the current sheet usually evolves slowly - over months - as the large-scale pattern of the Sun's field changes in response to the emergence and decay of solar active regions. Coronal mass ejections often disrupt the background pattern temporarily, but sometimes the changes are permanent."[42]

"During most of the solar cycle the source of the heliospheric current sheet resembles a slightly tilted dipole with varying degrees of quadrupole distortion. Near solar maximum the polar dipole decays, leaving a much more complicated structure. This picture shows the heliospheric current sheet as it might appear during the rising phase of the cycle, when the dipole and quadrupole components are balanced; at this point the neutral line at the base of the sheet resembles the seam on a baseball."[42]

The third image down on the right "shows the locations of Voyagers 1 and 2. Voyager 1 is traveling a lot and has crossed into the heliosheath, the region where interstellar gas and solar wind start to mix."[43]

"Voyager has entered the final lap on its race to the edge of interstellar space, as it begins exploring the solar system's final frontier."[44]

"In November 2003, the Voyager team announced it was seeing events unlike any encountered before in the mission's then 26-year history. The team believed the unusual events indicated Voyager 1 was approaching a strange region of space, likely the beginning of this new frontier called the termination shock region. There was controversy at that time over whether Voyager 1 had indeed encountered the termination shock or was just getting close."[43]

"The consensus of the team now is that Voyager 1, at 8.7 billion miles from the Sun, has at last entered the heliosheath, the region beyond the termination shock."[45]

"The termination shock is where the solar wind, a thin stream of electrically charged gas blowing continuously outward from the Sun, is slowed by pressure from gas between the stars. At the termination shock, the solar wind slows abruptly from its average speed of 300 to 700 km per second (700,000 - 1,500,000 miles per hour) and becomes denser and hotter."[43]

"The strongest evidence that Voyager 1 has passed through the termination shock into the slower, denser wind beyond is its measurement of an increase in the strength of the magnetic field carried by the solar wind and the inferred decrease in its speed. Physically, this must happen whenever the solar wind slows down, as it does at the termination shock. Consider a highway with moderate traffic. If something makes the drivers slow down, say a puddle of water, the cars pile up - their density increases. In the same way, the density (intensity) of the magnetic field carried by the solar wind will increase if the solar wind slows down. In December 2004, Voyager 1 observed the magnetic field strength increasing by a factor of two and a half, as expected when the solar wind slows down. The magnetic field has remained at these high levels from December until now. An increase in the magnetic field intensity of about 1.7 times was seen at the time of the event announced in 2003."[43]

"Voyager's observations over the past few years show that the termination shock is far more complicated than anyone thought."[46]

Interstellar medium edit

As of December 5, 2011, "Voyager 1 is about ... 18 billion kilometers ... from the [S]un [but] the direction of the magnetic field lines has not changed, indicating Voyager is still within the heliosphere ... the outward speed of the solar wind had diminished to zero in April 2010 ... inward pressure from interstellar space is compacting [the magnetic field] ... Voyager has detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside ... [while] the [solar] wind even blows back at us."[47]

The source of heat that brings the coronal cloud near the Sun hot enough to emit X-rays may be an electron beam heating effect due to "high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside".[47]

Detectors edit

This is a diagram of the Solar Wind Spectrometer for the Apollo Lunar Surface Experiments Package (ALSEP). Credit: William Crochot.
This is the Solar Wind Ion Mass Spectrometer of the Advanced Composition Explorer. Credit: NASA.
The Solar Wind Electron, Proton, and Alpha monitor (SWEPAM) measures the solar wind plasma electron and ion fluxes as functions of direction and energy. Credit: NASA.

The diagram on the right is of the Solar Wind Spectrometer for the Apollo Lunar Surface Experiments Package (ALSEP).

The Solar Wind Ion Mass Spectrometer (SWIMS) [in the second image down on the right] is a versatile instrument that provides solar wind composition data for all solar wind conditions. It clearly determines, every few minutes, the quantities of most of the elements and a wide range of isotopes in the solar wind. The abundances of rare isotopes are determined every few hours, providing information crucial to the understanding of pickup ions and ACRs (described later). SWIMS is extending knowledge of solar wind composition to additional elements and isotopes.

The third detector down on the right is the Solar Wind Electron, Proton, and Alpha monitor (SWEPAM) of the Advanced Composition Explorer. It measures the solar wind plasma electron and ion fluxes as functions of direction and energy.

Spacecraft edit

The diagrams depict a new method for predicting ion storms. Credit: Tony Phillips, NASA.
The diagram is an empirical, predictive matrix that can be used to forecast ion arrival times from the electron data. Credit: Arik Posner.
The Posner matrix was applied to the electron data to successfully predicted all four major ion storms of 2003. Credit: Arik Posner.
Mariner 2 was the world's first successful interplanetary spacecraft. Credit: NASA Jet Propulsion Laboratory (NASA-JPL).

"A new method, based on data from the COSTEP instrument onboard SOHO, permits for the first time up to an hour of warning prior to the arrival of the most dangerous particles of a solar storm at Earth."[48]

"Solar storms consist of electrons, protons and heavy ions, the last of which pose the gravest danger to space-borne electronics and to humans outside the Earth's protective magnetic field (such as on the Moon or en route to Mars). Electrons arrive first, signaling the later arrival of the ions. So far, however, there had been no adequate method to predict when these ions arrive. Sufficient advance warning allows for spacecraft to be put in a protective "safe mode" and humans to be instructed to seek shelter from the storm."[48]

"After testing the results, the matrix [shown in the second image down on the right] was used on COSTEP data gathered in 2003, a year that had not yet been analyzed and formed no part of the matrix itself. The matrix was applied to the electron data and as a result, it successfully predicted all four major ion storms of 2003 with advance warnings ranging from 7 to 74 minutes. The method did, however, also create three false alarms from the 2003 dataset. Improvements will come as Posner works his way through even more of COSTEP's dataset."[48]

Mariner 2 was the world's first successful interplanetary spacecraft. Launched August 27, 1962, on an Atlas-Agena rocket, Mariner 2 passed within about 34,000 kilometers (21,000 miles) of Venus, sending back valuable new information about interplanetary space and the Venusian atmosphere. Mariner 2 recorded the temperature at Venus for the first time, revealing the planet's very hot atmosphere of about 500 degrees Celsius (900 degrees Fahrenheit). The spacecraft's solar wind experiment measured for the first time the density, velocity, composition and variation over time of the solar wind.

Hypotheses edit

  1. It's a lot easier in astronomy to detect moving charges than it is to detect a circuit.

See also edit

References edit

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External links edit

{{Physics resources}}{{Radiation astronomy resources}}