How can we create circularly polarized fields?
Using two orthogonal coils to which we apply two radiofrequency (RF) signals phase shifted by 90°.
To this purpose, quadrature coils are used.
Reference: Mariusz Mrózek, et al. “Circularly Polarized Microwaves for Magnetic Resonance Study in the GHz Range: Application to Nitrogen-Vacancy in Diamonds.” Applied Physics Letters, vol. 107, no. 1, 6 July 2015, https://doi.org/10.1063/1.4923252. (PDF)
Advantages of circular over linear polarization include the following:
1) elimination of the Bloch-Siegert shift,
2) increase of effective strength,
3) improvement of homogeneity,
4) possibility of addressing a specific spin state e.g. in the field of quantum information.
Reference: Mariusz Mrózek, et al. “Circularly Polarized Microwaves for Magnetic Resonance Study in the GHz Range: Application to Nitrogen-Vacancy in Diamonds.” Applied Physics Letters, vol. 107, no. 1, 6 July 2015, https://doi.org/10.1063/1.4923252. (PDF)
An important characteristic for the biological activity of electromagnetic fields (EMFs) is their polarization.
The polarization of EMFs can be linear, circular or elliptical.
Biomolecules may be more responsive to a specific type of polarization.
Below are excerpts from https://www.nature.com/articles/srep14914
"These experiments show that not only linear ... biological tissue."
"It is important to note that circularly and elliptically polarized 50–60Hz EMFs are formed around 3-phase power transmission lines."
"Superposition of two fields of identical frequency and linear polarizations, equal amplitudes, and a phase difference 90° between them, (...) results in a circularly polarized field of the same frequency".
The notion of cyclotronic waves.
The first are standard transverse electromagnetic (TEM) Maxwell waves in free space (cf. they propagate in vacuum/air).
For the second, the plasma itself participates in the wave motion. They propagate in plasma.
They are not simple TEM waves — they are plasma waves whose properties come from both Maxwell’s equations and charged particle dynamics.
Standard radio waves propagate independently of particles,
while EMIC waves are inseparable from the motion of charged particles in magnetized plasma and can exchange energy resonantly with them. They will resonate with ions in their path.
🌍 Natural processes in the Magnetosphere
In Earth’s magnetosphere, circularly polarized electromagnetic waves arise spontaneously from plasma processes. In regions like the Van Allen radiation belts, charged particles (electrons and ions) are trapped by Earth’s magnetic field. Various plasma instabilities generate electromagnetic waves, including whistler-mode waves, electromagnetic ion cyclotron (EMIC) waves and chorus waves. These waves often have circular or elliptical polarization because they propagate through a magnetized plasma. The magnetic field breaks symmetry, naturally favoring rotating field solutions of Maxwell’s equations.
When the wave’s polarization and frequency match particle motion, cyclotron resonance can occur. This interaction can lead to electron acceleration, electron scattering into the atmosphere and possible alteration of radiation belt populations. This is a well-studied natural process in space plasma physics.
🔬 Engineered processes
In fusion-devices like ITER, circular polarization is deliberately generated for optimal coupling.
In Earth’s magnetosphere, by contrast:
• No transmitters are involved
• No antennas are driving the waves
• The plasma itself generates the polarization
EMIC waves (Electromagnetic Ion Cyclotron waves) are a broad class of magnetospheric waves generated near the ion cyclotron frequency of ions such as H⁺, He⁺, and O⁺.
“EMIC waves consist of ion cyclotron waves whose ground manifestations span the Pc1, Pc2, and Pc3 pulsation bands.”
• Pc1 (0.2–5 Hz) is the classic ground signature of O⁺ band EMIC
• Pc2 (5–10 Hz) can correspond to O⁺ or He⁺ band EMIC
• Pc3 (10–45 Hz) often corresponds to H⁺ or He⁺ band EMIC
Literature sometimes uses the phrase “Pc1–Pc2–Pc3 EMIC waves” when referring to the full spectrum.
• Modern research consistently treats Pc1 pulsations as the ground manifestation of EMIC waves.
PC1 waves are typically circularly or elliptically polarized, especially near the magnetic equator. They are a subtype of electromagnetic ion cyclotron (EMIC) waves, and their polarization depends on location and plasma conditions.
PC1 waves (Pearl-type pulsations):
• Frequency range: ~0.2–5 Hz
• Occur in Earth’s magnetosphere
• Associated with electromagnetic ion cyclotron (EMIC) waves
• Often observed during geomagnetic activity
They are generated by instabilities in populations of energetic ions trapped in Earth’s magnetic field.
Polarization of PC1 / EMIC Waves
In a magnetized plasma, wave modes naturally have specific polarization states.
For EMIC waves (which include PC1):
• Near the magnetic equator → typically left-hand circular polarization (for proton-band waves)
• Away from equator → often become elliptically polarized
• On the ground → polarization may appear modified due to ionospheric transmission effects
The “handedness” refers to rotation relative to the background magnetic field direction.
Why Circular Polarization Appears
In magnetized plasma:
• The background magnetic field breaks symmetry.
• Maxwell’s equations in plasma support rotating wave solutions.
• Ion cyclotron waves couple to the natural gyration of ions.
This is exactly why circular polarization is common in plasma wave physics.
The polarization is not engineered — it arises from plasma dispersion relations.
What is the difference of these waves from radio waves?
📡 Standard Radio Waves (in Air or Vacuum)
A normal radio wave:
• Propagates through air (approximately like vacuum)
• Is a transverse electromagnetic (TEM) wave
• Has electric field E and magnetic field B perpendicular to each other
• Propagates in 3D space
The polarization (linear or circular) describes how the electric field vector rotates or oscillates in the plane perpendicular to the direction of travel.
That’s a standard Maxwell wave in free space.
🌍 PC1 Waves (in Magnetized Plasma)
PC1 waves are also electromagnetic waves with:
• 3D electric and magnetic field vectors
• Propagation through space
• Circular or elliptical polarization
However, unlike radio waves in air:
• They propagate in plasma, not vacuum.
• Their behavior is strongly influenced by Earth’s magnetic field.
• The plasma itself participates in the wave motion.
• They are dispersive (velocity depends on frequency).
They are not simple TEM waves — they are plasma waves whose properties come from both Maxwell’s equations and charged particle dynamics.
🔬 Key Difference
Standard radio waves:
• Medium does not significantly alter polarization physics (in free space).
• No intrinsic preferred direction.
PC1 waves:
• Exist in a magnetized plasma.
• Background magnetic field introduces anisotropy.
• Polarization is defined relative to that field.
• Resonant interactions with ions are possible.
PC1 waves are 3D electromagnetic waves, just like radio waves in that they have vector fields in three-dimensional space.
However, unlike standard radio waves from a station, PC1 waves propagate in magnetized plasma and are shaped by ion motion and Earth’s magnetic field.