At the center of the sun, the temperature is 27 million degrees Fahrenheit 15 million degrees Celsius. As the temperature on its surface rises and falls, the sun boils and bubbles. Particles escape from the star from the sunspot regions on the surface, hurtling particles of plasma, known as solar wind, into space.
It takes these winds around 40 hours to reach Earth. When they do, they can cause the dramatic displays known as the aurora borealis. Auroras occur not only on Earth, but also on other worlds in our solar system and perhaps exoplanets as well. The gas giants in our solar system Jupiter, Saturn, Uranus and Neptune each have thick atmospheres and strong magnetic fields, and each have auroras — although these auroras are a little different from Earth's, given they are formed under different conditions.
Venus has an aurora generated by its stretched-out magnetic field a "magnetotail". Mars, which has too thin an atmosphere for global auroras, experiences local auroras due to magnetic fields in the crust. The sunspots and solar storms that cause the most magnificent displays of the northern lights occur roughly every 11 years.
The solar cycle peaked inbut it was the weakest solar maximum in a century. Since record-keeping of the ebb and flow of the sun's activity began inthere have been 22 full cycles. Researchers monitor space weather events because they have the potential to affect spacecraft in orbit, knock out power grids and communications infrastructure on Earth, and amp up normal displays of the northern and southern lights.
Earth is constantly bombarded with debris, radiation and other magnetic waves from space that could threaten the future of life as we know it. Most of the time, the planet's own magnetic field does an excellent job of deflecting these potentially harmful rays and particles, including those from the sun. Particles discharged from the sun travel 93 million miles around million km toward Earth before they are drawn irresistibly toward the magnetic north and south poles. As the particles pass through the Earth's magnetic shieldthey mingle with atoms and molecules of oxygen, nitrogen and other elements that result in the dazzling display of lights in the sky.
The auroras in Earth's Northern Hemisphere are called the aurora borealis. Rizumi storms off and rejects the offer, causing Aira to visit her and try to make her feel better by taking her shopping and helping her sense of fashion; which comes in handy when Rizumu is tasked with wearing the outfit Aira chose for a Prism Show!
Rabi-chi and Bea-chi! Penguin-sensei gives the girls a set of Coaches due to Aira's lack of dance skills. But the girls aren't sure they can improve when Bea-chi and Rabi-chi put them through many conusing and harsh trainining procedures. Easter is approaching and Aira finds herself too distracted to focus; not only does she have to keep her Prism Star status a secret, but she really wants the brand new accessories at Prism Stone.
As Rizumu tries to get her to focus the girls are asked by Callings for help creating an Easter event at the Shopping Mall. As she spends more time with Sho, Aira starts to realize something special Aira is having a harder time keeping her Prism Star title a secret now that word is spreading. She tries to avoid revealing the truth until Rizumu convinces her to just give her Dad a message and ticket to attend their upcoming fashion show. While he isn't happy, he agrees to it but only under one condition: She has to wear the outfit he chooses.
If she refuses then he won't let her perform anymore. Kyoko sends Aira and Rizumu to Hakune with their parents to teach children and their mothers some dance moves to celebrate Mothers Day. After reuniting the girls are surprised to find out their parents know each other and they get to work, where they meet a rude little girl named Natsuki who refuses to cooperate with them. Rizumu attempts to relate to her and they give her a makeover, and she soon realizes that she might not be as okay with her mom missing as she thinks she is after Natsuki gets upset.
Aira and Rizumu's Big Fight " "Zekkou!? Aira and Rizumu get into a fight after Rizumu realizes Aira admires Mion and tells her off. Aira is shocked, but when Rizumu begins to wear her old clothing, she decides that Rizumu meant her harsh statement and she gives up being a Prism Star.
He reveals Rizumu isn't doing very well and Aira rushes to her side, causing them to come to an important realization. Rizumu in a Big Pinch! After getting a lousy midterm score Rizumu is told she needs to get at least 70 points on the make-up test or else she will be forced into an early retirement as a Prism Star!
But when everyone's teaching method fails to help her understand and she begins to feel hopeless until she finds help in the unlikeliest of places. The Tiara Cup is approaching and Aira begins to worry about how oddly Rizumu has began to behave. She's been training so hard that she's forgotten all about anything not related to winning, and she cuts contact with her after Aira tries to figure out what's wrong with her.
But how far will talent take her when she refuses to listen to anybody? With Sho's deadline for his new summer line approaching he asks Aira out in hopes of getting inspiration- but when she easily figures out his problem, he angrily tells her off, leaving her with no confidence. Despite this, Aira wants to help him out and she decides to wear the outfit for a Prism Show. Tiara Cup " "Kaimaku! For the Tiara Cup all entrants must wear a combination of Prism Stones reminiscent of a wedding dress.
Seeing how nervous Aira is, Kyoko gives her some advice and brings up her past as a Prism Star. Things go well until Rizumu passes out from a sudden fever, and Aira takes a big risk in hopes of giving her enough time to recover. The girls enjoy a picnic with their family, but upon arriving back to their dressing room they find their Prism Stones have gone missing!
Just when all hope seems lost, Aira decides to take it in stride and she gives Rizumu her emergency Prism Stones. But what can she do to put on an amazing show?
And who is this new competitor who suddenly showed up?! Bea-chi is shocked when he hears Andy -Rizumu's stuffed bear- speak to him. Andy shows him the past of Rizumu's parents and how they met, and just what happened to Sonata Mion decides to return to the Prism Star stage and she's less-than impressed with the girls. She decides to hold a show with the both of them in order to determine whether or not either of them really stand a chance.
Mion takes it upon herself to entice the girls into learning how to use the Batopon and improve their overall Song and Dance skills by asking the Callings to lend a hand. Neko-chi and Mion get into a big argument after Neko-chi tries to help her express her feelings.
While Neko-chi attempts to find help in how to fix everything, Rizumu and Aira try to bond with Mion by giving her a Lucky Watch. Tired of training the girls head to the Harune House to think about what else they can do for summer, but to their surprise, they find the Cake Shop is overflowing with customers! The girls decide to help out -along with Mion- and soon they are forced to transfer to Prism Shop, where the Prism Show will be held. Here the girls realize cake making may relate to their training more than they thought.
The girls are invited to the summer festival by Callings. Upon arrival, their bonding experience soon turns to that of a deeper meaning as they talk about their future aspirations and dreams. Large geomagnetic storms are most common during the peak of the year sunspot cycle or during the three years after the peak.
This angle is known as the "pitch angle" of the particle. The distance, or radius, Auroras Dream [Polar Mix], of the electron from the field line at any time is known as its Larmor radius.
The pitch angle increases as the electron travels to a region of greater field strength nearer to the atmosphere. Other particles that do not mirror enter the atmosphere and contribute to the auroral display over a range of altitudes.
Other types of auroras have been observed from space, e. These are relatively infrequent and poorly understood. Other interesting effects occur such as flickering aurora, "black aurora" and subvisual red arcs. In addition to all these, a weak glow often deep red observed around the two polar cusps, the field lines separating the ones that close through the Earth from those that are swept into the tail and close remotely.
Images of auroras are significantly more common today than in the past due to the increase in the use of digital cameras that have high enough sensitivities. Due to the different color spectra present, and the temporal changes occurring during the exposure, the results are somewhat unpredictable.
Different layers of the film emulsion respond differently to lower light levels, and choice of a film can be very important. Longer exposures superimpose rapidly changing features, and often blanket the dynamic attribute of a display.
Higher sensitivity creates issues with graininess. David Malin pioneered multiple exposure using multiple filters for astronomical photography, recombining the images in the laboratory to recreate the visual display more accurately. Predictive techniques are also used, to indicate the extent of the display, a highly useful tool for aurora hunters.
Early work on the imaging of the auroras was done in by the University of Saskatchewan using the SCR radar. Aurora during a geomagnetic storm that was most likely caused by a coronal mass ejection from the Sun on 24 Maytaken from the ISS. According to Clarkthere are four main forms that can be seen from the ground, from least to most visible: .
Brekke also described some auroras as curtains. Arcs can fragment or break up into separate, at times rapidly changing, often rayed features that may fill the whole sky. These are also known as discrete auroraswhich are at times bright enough to read a newspaper by at night.
These forms are consistent with auroras' being shaped by Earth's magnetic field. The appearances of arcs, rays, curtains, and coronas are determined by the shapes of the luminous parts of the atmosphere and a viewer's position.
Auroras change with time. Over the night, they begin with glows and progress towards coronas, although they may not reach them. They tend to fade in the opposite order. At shorter time scales, auroras can change their appearances and intensity, sometimes so slowly as to be difficult to notice, and at other times rapidly down to the sub-second scale. X-ray emissions, originating from the particles associated with auroras, have also been detected.
The charged particles discharge when particles from the Sun hit the inversion layer, creating the noise. A full understanding of the physical processes which lead to different types of auroras is still incomplete, but the basic cause involves the interaction of the solar wind with the Earth's magnetosphere.
The varying intensity of the solar wind produces effects of different magnitudes but includes one or more of the following physical scenarios. The details of these phenomena are not fully understood. However, it is clear that the prime source of auroral particles is the solar wind feeding the magnetosphere, the reservoir containing the radiation zones and temporarily magnetically-trapped particles confined by the geomagnetic field, coupled with particle acceleration processes.
The immediate cause of the ionization and excitation of atmospheric constituents leading to auroral emissions was discovered inwhen a pioneering rocket flight from Fort Churchill in Canada revealed a flux of electrons entering the atmosphere from above. Electrons mainly responsible for diffuse and pulsating auroras have, in contrast, a smoothly falling energy distribution, and an angular pitch-angle distribution favouring directions perpendicular to the local magnetic field.
Pulsations were discovered to originate at or close to the equatorial crossing point of auroral zone magnetic field lines. Both incoming electrons and protons may be involved. Excitation energy is lost within the atmosphere by the emission of a photon, or by collision with another atom or molecule:. Oxygen is unusual in terms of its return to ground state: it can take 0. Collisions with other atoms or molecules absorb the excitation energy and prevent emission, this process is called collisional quenching.
Because the Auroras Dream [Polar Mix] parts of the atmosphere contain a higher percentage of oxygen and lower particle densities, such collisions are rare enough to allow time for oxygen to emit red light. Collisions become more frequent progressing down into the atmosphere due to increasing density, so that red emissions do not have time to happen, and eventually, even green light emissions are prevented.
Green is the most common color. Then comes pink, a mixture of light green and red, followed by pure red, then yellow a mixture of red and greenand finally, pure blue. Bright auroras are generally associated with Birkeland currents Schield et al. The ionosphere is an ohmic conductorso some consider that such currents require a driving voltage, which an, as yet unspecified, dynamo mechanism can supply.
Electric field probes in orbit above the polar cap suggest voltages of the order of 40, volts, rising up to more thanvolts during intense magnetic storms. Ionospheric resistance has a complex nature, and leads to a secondary Hall current flow. By a strange twist of physics, the magnetic disturbance on the ground due to the main current almost cancels out, so most of the observed effect of auroras is due to a secondary current, the auroral electrojet.
An auroral electrojet index measured in nanotesla is regularly derived from ground data and serves as a general measure of auroral activity. Kristian Birkeland  deduced that the currents flowed in the east—west directions along the auroral arc, and such currents, flowing from the dayside toward approximately midnight were later named "auroral electrojets" see also Birkeland currents.
Auroras Dream [Polar Mix] Earth is constantly immersed in the solar winda rarefied flow of hot plasma a gas of free electrons and positive ions emitted by the Sun in all directions, a result of the two-million-degree temperature of the Sun's outermost layer, the corona. During magnetic stormsin particular, flows can be several times faster; the interplanetary magnetic field IMF may also be much stronger. Joan Feynman deduced in the s that the long-term averages of solar wind speed correlated with geomagnetic activity.
The solar wind and magnetosphere consist of plasma ionized gaswhich conducts electricity. It is well known since Michael Faraday 's work around that when an electrical conductor is placed within a magnetic field while relative motion occurs in a direction that the conductor cuts across or is cut byrather than alongthe lines of the magnetic field, an electric current is induced within the conductor.
The strength of the current depends on a the rate of relative motion, b the strength of the magnetic field, c the number of conductors ganged together and d the distance between the conductor and the magnetic field, while the direction of flow is dependent upon the direction of relative motion. Dynamos make use of this basic process "the dynamo effect "any and all conductors, solid or otherwise are so affected, including plasmas and other fluids.
The IMF originates on the Sun, linked to the sunspotsand its field lines lines of force are dragged out by the solar wind. That alone would tend to line them up in the Sun-Earth direction, but the rotation of the Sun angles them at Earth by about 45 degrees forming a spiral in the ecliptic planeknown as the Parker spiral.
The field lines passing Earth are therefore usually linked to those near the western edge "limb" of the visible Sun at any time. However, this process is hampered by the fact that plasmas conduct readily along magnetic field lines, but less readily perpendicular to them.
Energy is more effectively transferred by the temporary magnetic connection Auroras Dream [Polar Mix] the field lines of the solar wind and those of the magnetosphere. Unsurprisingly this process is known as magnetic reconnection.
As already mentioned, it happens most readily when the interplanetary field is directed southward, in a similar direction to the geomagnetic field in the inner regions of both the north magnetic pole and south magnetic pole. Auroras are more frequent and brighter during the intense phase of the solar cycle when coronal mass ejections increase the intensity of the solar wind. Earth's magnetosphere is shaped by the impact of the solar wind on the Earth's magnetic field.
The high latitude magnetosphere is filled with plasma as the solar wind passes the Earth. The flow of plasma into the magnetosphere increases with additional turbulence, density, and speed in the solar wind. This flow is favored by a southward component of the IMF, which can then directly connect to the high latitude geomagnetic field lines. In addition to moving perpendicular to the Earth's magnetic field, some magnetospheric plasma travels down along the Earth's magnetic field lines, gains additional energy and loses it to the atmosphere in the auroral zones.
The cusps of the magnetosphere, separating geomagnetic field lines that close through the Earth from those that close remotely allow a small amount of solar wind to directly reach the top of the atmosphere, producing an auroral glow.
On 26 FebruaryTHEMIS probes were able to determine, for the first time, the triggering event for the onset of magnetospheric substorms. Geomagnetic storms that ignite auroras may occur more often during the months around the equinoxes. It is not well understood, but geomagnetic storms may vary with Earth's seasons.
Two factors to consider are the tilt of both the solar and Earth's axis to the ecliptic plane. As the Earth orbits throughout a year, it experiences an interplanetary magnetic field IMF from different latitudes of the Sun, which is tilted at 8 degrees. Similarly, the degree tilt of the Earth's axis about which the geomagnetic pole rotates with a diurnal variation changes the daily average angle that the geomagnetic field presents to the incident IMF throughout a year. These factors combined can lead to minor cyclical changes in the detailed way that the IMF links to the magnetosphere.
In turn, this affects the average probability of opening a door through which energy from the solar wind can reach the Earth's inner magnetosphere and thereby enhance auroras. The electrons responsible for the brightest forms of the aurora are well accounted for by their acceleration in the dynamic electric fields of plasma turbulence encountered during precipitation from the magnetosphere into the auroral atmosphere.
In contrast, static electric fields are unable to transfer energy to the electrons due to their conservative nature. The increase in strength of magnetic field lines towards the Earth creates a 'magnetic mirror' that turns back many of the downward flowing electrons.
The bright forms of auroras are produced when downward acceleration not only increases the energy of precipitating electrons but also reduces their pitch angles angle between electron velocity and the local magnetic field vector.
This greatly increases the rate of deposition of energy into the atmosphere, and thereby the rates of ionization, excitation and consequent emission of auroral light. Acceleration also increases the electron current flowing between the atmosphere and magnetosphere. One early theory proposed for the acceleration of auroral electrons is based on an assumed static, or quasi-static, electric field creating a uni-directional potential drop.
Fundamentally, Poisson's equation indicates that there can be no configuration of charge resulting in a net potential drop. Inexplicably though, some authors   still invoke quasi-static parallel electric fields as net accelerators of auroral electrons, citing interpretations of transient observations of fields and particles as supporting this theory as firm fact.
In another example,  there is little justification given for saying 'FAST observations demonstrate detailed quantitative agreement between the measured electric potentials and the ion beam energies Another theory is based on acceleration Auroras Dream [Polar Mix] Landau  resonance in the turbulent electric fields of the acceleration region.
This process is essentially the same as that employed in plasma fusion laboratories throughout the world,  and appears well able to Auroras Dream [Polar Mix] in principle for most — if not all — detailed properties of the electrons responsible for the brightest forms of auroras, above, below and within the acceleration region.
Other processes are also involved in the aurora, and much remains to be learned. Such low energies excite mainly the red line of oxygen so that often such auroras are red. On the other hand, positive ions also reach the ionosphere at such time, with energies of 20—30 keV, suggesting they might be an "overflow" along magnetic field lines of the copious "ring current" ions accelerated at such times, by processes different from the ones described above. These ions are accelerated by plasma waves in directions mainly perpendicular to the field lines.
They, therefore, start at their "mirror points" and can travel only upward. As they do so, the "mirror effect" transforms their directions of motion, from perpendicular to the field line to a cone around it, which gradually narrows down, becoming increasingly parallel at large distances where the field is much weaker.
The auroras that resulted from the " great geomagnetic storm " on both 28 August and 2 Septemberhowever, are thought to be the most spectacular in recent recorded history.
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