Definitons of Helicon

A. A helicon is a low frequency electromagnetic wave.
Helicons have the special ability to propagate through pure metals, given conditions of low temperature and high magnetic fields. Most electromagnetic waves in a normal conductor are not be able to do this, since the high conductivity of metals (due to their free electrons) acts to screen out the electromagnetic field. Indeed, normally an electromagnetic wave would experience a very thin skin depth in a metal: the electric or magnetic fields are quickly reduced upon trying to enter the metal. (Hence the shine of metals: the electromagnetic waves of light are screened out, leading to a high reflectivity.) However, skin depth depends on an inverse proportionality to the square root of angular frequency. Thus a low frequency electromagnetic wave may be able to overcome the skin depth problem, and thereby propagate throughout the material.
A helicon discharge is a excitation of plasma by helicon waves induced through radio frequency heating. The difference between a helicon plasma source and an inductively coupled plasma is the presence of a magnetic field directed along the axis of the antenna. The presence of this magnetic field creates a helicon mode of operation with higher ionization efficiency and greater electron density than a typical ICP. The Australian National University, in Canberra, Australia, is currently researching applications for this technology. This includes plasma based rockets for interplanetary travel. This experiment can be conducted with fairly affordable equipment, and may be found in university-level undergraduate advanced physics laboratory courses. A metal such as 99.999% pure Indium is commonly used: it is cooled using liquid helium to reach the conditions of low temperature, while the high magnetic field is accomplished using a superconducting solenoid. Ultimately, the experiment characterizes the resonance frequency and resonance width of the Helicon standing waves. It can also be used to measure the magnetoresistance and Hall coefficients of the pure metal.

B.Helicon is a small lunar impact crater that is located on the north part of the Mare Imbrium. To the northwest is the prominent Sinus Iridum formation, a mountain-ringed bay on the mare. Just to the east is the slightly smaller Le Verrier crater. Helicon is a nearly circular crater formation with inner walls that curve down to a relatively flat floor. There is a tiny craterlet located at the mid-point of the interior, and a small craterlet along the southwestern rim.

C.In Isaac Asimov's Foundation Series, Helicon is the name of the home planet of Hari Seldon, discoverer and developer of psychohistory. Helicon was small in population and not particularly rich in resources, and tended to be bullied by its more powerful neighbours. It was noted for martial arts (called 'Twisting' in the Foundation Universe). Hari Seldon claimed that the best Twisters came from Helicon, although his objectivity is questionable. It may be covered primarily by land, as opposed to sea. Tobacco may be grown there, though the only evidence of this is Seldon's father's supposed occupation, labelled by the Encyclopedia Galactica 'a legend of doubtful validity'. In the seventh century of the tenth millennium of the Galactic Era, a large movement of Heliconians convinced themselves that Helicon was the only inhabited world in the Galaxy.

D.Mount Helicon is a mountain in the region of Thespiai in Boeotia, Greece (Kerenyi, 1951, page 172), with an elevation of 1,749 meters (5,735 ft). It is located just off the Gulf of Corinth.
The mountain was made famous in Greek mythology because two springs sacred to the Muses were located here: the Aganippe and the Hippocrene, both of which bear "horse" (hippos) in their toponym. This was related to the myth that the Hippocrene spring was created when the winged horse Pegasus aimed his hoof at a rock, striking it with such force that the spring burst from the spot. On Helicon too was the spring where Narcissus was inspired by his own beauty
In Greek Mythology, Helicon was believed to be a sacred site that was used by the Gods and Goddesses. Helicon was especially associated with the Muses, who were considered to be "Divine Spirits of Inspiration" who shared with humanity their gifts of creative arts such as poetry, literature, and sculpture. There had been a temple built on Helicon in their honor which contained statues of these Muses
The Hippocrene spring was considered to be a source of poetic inspiration. In the late seventh century BCE, the poet Hesiod sang how in his youth he had pastured his sheep on the slopes of Helicon (Theogony, 23), where Eros and the Muses already had sanctuaries and a dancing-ground near the summit, where "their pounding feet awaken desire" (Hesiod, 8). There the Muses inspired him and he began to sing of the origins of the gods, Thus Helicon became an emblem of poetical inspiration. Hesiod mentions other springs that were the haunt of the Muses: "They bathe their lithe bodies in the water of Permessos or of Hippocrene or of god-haunted Olmeios".
In Hesiod's Theogony Helicon was mentioned:
"From the Heliconian Muses let us begin to sing,
Who hold the great and holy mount of Helicon,
And dance on soft feet about the deep-blue spring
And the altar of the almighty son of Cronos, and,
When they have washed their tender bodies in Permessus
Or in the Horse's Spring or Olmeius,
Make their fair, lovely dances upon highest Helicon
And move with vigorous feet"

E.Helicon (also transliterated Helikon) was a river of the Macedonian city Dion.

There is also a river called Helikon [in Pieria]. After a course of seventy-five stades the stream hereupon disappears under the earth. After a gap of about twenty-two stades the water rises again, and under the name of Baphyras instead of Helikon flows into the sea as a navigable river. The people of Dion (Dium) say that at first this River flowed on land throughout its course. But, they go on to say, the women who killed Orpheus wished to wash off in it the blood-stains, and thereat the River sank underground, so as not to lend its waters to cleanse manslaughter.
Pausanias, Description of Greece 9. 30. 8 (trans. W.H.S. Jones and H.A. Ormerod) (Greek travelogue c. 2nd A.D.)

F.Helicon Sound System Records is a psychedelic trance label located in Athens,Gr.