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A geomagnetic storm (commonly referred to as a solar storm) is a temporary disturbance of the Earth's magnetosphere caused by a solar wind shock wave and/or cloud of
magnetic field that interacts with the Earth's magnetic field.
The disturbance that drives the storm may be a solar coronal mass ejection (CME) or a co-rotating interaction region (CIR), a high speed solar wind originating from a coronal hole.
The frequency of geomagnetic storms increases and decreases with the sunspot cycle.
During solar maximum, geomagnetic storms occur more often, with the majority driven by CME's.
During solar minimum, storms are mainly driven by CIR's (though CIR storms are more frequent at solar maximum than at minimum).
The increase in the solar wind pressure initially compresses the magnetosphere. The solar wind's magnetic field interacts with the Earth's magnetic field and transfers an increased energy into the magnetosphere. Both interactions cause an increase in plasma movement through the magnetosphere (driven by increased electric fields inside the magnetosphere) and an increase in electric current in the magnetosphere and ionosphere. During the main phase of a geomagnetic storm, electric current in the magnetosphere creates a magnetic force that pushes out the boundary between the magnetosphere and the solar wind.
Several space weather phenomena tend to be associated with or are caused by a geomagnetic storm. These include solar energetic particle (SEP) events, geomagnetically induced currents (GIC), ionospheric disturbances that cause radio and radar scintillation, disruption of navigation by magnetic compass and auroral displays at much lower latitudes than normal. The largest recorded geomagnetic storm, the Carrington Event in September 1859, took down parts of the recently created US telegraph network, starting fires and shocking some telegraph operators. In 1989, a geomagnetic storm energized ground induced currents that disrupted electric power distribution throughout most of Quebec and caused aurorae as far south as Texas.
History of Theory
In 1931, Sydney Chapman and Vincenzo C. A. Ferraro wrote an article, A New Theory of Magnetic Storms, that sought to explain the phenomenon. They argued that whenever the Sun emits a solar flare it also emits a plasma cloud, now known as a coronal mass ejection. They postulated that this plasma travels at a velocity such that it reaches Earth within 113 days, though we now know this journey takes 1 to 5 days. They wrote that the cloud then compresses the Earth's magnetic field and thus increases this field at the Earth's surface. Chapman and Ferraro's work drew on that of, among others, Kristian Birkeland, who had used recently discovered cathode ray tubes to show that the rays were deflected towards the poles of a magnetic sphere. He theorised that a similar phenomenon was responsible for auroras, explaining why they are more frequent in polar regions.
The first scientific observation of the effects of a geomagnetic storm occurred early in the 19th century: From May 1806 until June 1807, Alexander von Humboldt recorded the bearing of a magnetic compass in Berlin. On 21 December 1806, he noticed that his compass had become erratic during a bright auroral event.
On September 1–2, 1859, the largest recorded geomagnetic storm occurred.
From August 28 until September 2, 1859, numerous sunspots and solar flares were observed on the Sun, with the largest flare on September 1.
This is referred to as the Solar storm of 1859 or the Carrington Event.
It can be assumed that a massive coronal mass ejection (CME) was launched from the Sun and reached the Earth within eighteen hours—a trip that normally takes three to four days.
The horizontal field was reduced by 1600 nT as recorded by the Colaba Observatory.
It is estimated that Dst would have been approximately −1760 nT.
Telegraph wires in both the United States and Europe experienced induced voltage increases (emf), in some cases even delivering shocks to telegraph operators and igniting fires. Aurorae were seen as far south as Hawaii, Mexico, Cuba and Italy—phenomena that are usually only visible in polar regions.
Ice cores show evidence that events of similar intensity recur at an average rate of approximately once per 500 years.
Interactions with planetary processes
The solar wind also carries with it the Sun's magnetic field. This field will have either a North or South orientation. If the solar wind has energetic bursts, contracting and expanding the magnetosphere, or if the solar wind takes a southward polarization, geomagnetic storms can be expected. The southward field causes magnetic reconnection of the dayside magnetopause, rapidly injecting magnetic and particle energy into the Earth's magnetosphere. During a geomagnetic storm, the ionosphere's F2 layer becomes unstable, fragments, and may even disappear. In the northern and southern pole regions of the Earth, auroras are observable.
Heliophysics is the science of the physical connections between the Sun and the solar system (from the prefix "helio", from Attic Greek hḗlios, on the Sun and environs; and the noun 'physics', the science of matter and energy and their interactions).
NASA defines heliophysics as "
(1) the comprehensive new term for the science of the Sun - Solar System Connection,
(2) the exploration, discovery, and understanding of Earth's space environment, and
(3) the system science that unites all of the linked phenomena in the region of the cosmos influenced by a star like our Sun.
Heliophysics concentrates on the Sun and its effects on Earth, the other planets of the solar system, and the changing conditions in space.
Heliophysics studies the magnetosphere, ionosphere, thermosphere, mesosphere, and upper atmosphere of the Earth and other planets.
Heliophysics combines the science of the Sun, corona, heliosphere and geospace.
Heliophysics encompasses cosmic rays and particle acceleration, space weather and radiation, dust and magnetic reconnection, solar activity and stellar magnetic fields, aeronomy and space plasmas, magnetic fields and global change, and the interactions of the solar system with our galaxy."
Prior to about 2002, the term heliophysics was sporadically used to describe the study of the "physics of the Sun". As such it was a direct translation from the French "héliophysique". Around 2002, Joseph M. Davila and Barbara J. Thompson at NASA's Goddard Space Flight Center adopted the term in their preparations of what became known as the International Heliophysical Year (2007-2008), following 50 years after the International Geophysical Year; in adopting the term for this purpose, they expanded its meaning to encompass the entire domain of influence of the Sun. Heliophysical research connects directly to a broader web of physical processes that naturally expand its reach beyond the narrow initial definition that limits it to the solar system: heliophysics reaches from solar physics out to stellar physics in general, involves several branches of nuclear physics, plasma physics, space physics and magnetospheric physics. The science of heliophysics lies at the foundation of the study of space weather, and is also directly involved in understanding planetary habitability. This multitude of connections between heliophysics and (astro-)physical sciences is explored in a series of textbooks on heliophysics developed over more than a decade of NASA-funded Summer Schools for early-career researchers in the discipline.
Quantum mechanics (QM; also known as quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles. Classical physics, the physics existing before quantum mechanics, describes nature at ordinary (macroscopic) scale. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale. Quantum mechanics differs from classical physics in that energy, momentum, angular momentum and other quantities of a bound system are restricted to discrete values (quantization); objects have characteristics of both particles and waves (wave-particle duality); and there are limits to the precision with which quantities can be measured (uncertainty principle).
Wavefunctions of the electron in a hydrogen atom at different energy levels. Quantum mechanics cannot predict the exact location of a particle in space, only the probability of finding it at different locations. The brighter areas represent a higher probability of finding the electron.
Quantum mechanics gradually arose from theories to explain observations which could not be reconciled with classical physics, such as Max Planck's solution in 1900 to the black-body radiation problem, and from the correspondence between energy and frequency in Albert Einstein's 1905 paper which explained the photoelectric effect.
Early quantum theory was profoundly re-conceived in the mid-1920s by Erwin Schrödinger, Werner Heisenberg, Max Born and others.
The modern theory is formulated in various specially developed mathematical formalisms.
In one of them, a mathematical function, the wave function, provides information about the probability amplitude of position, momentum, and other physical properties of a particle.
Important applications of quantum theory include quantum chemistry, quantum optics, quantum computing, superconducting magnets,
light-emitting diodes, and the laser, the transistor and semiconductors such as the microprocessor, medical and research imaging such as magnetic
resonance imaging and electron microscopy.
Explanations for many biological and physical phenomena are rooted in the nature of the chemical bond, most notably the macro-molecule DNA.
Scientific inquiry into the wave nature of light began in the 17th and 18th centuries, when scientists such as Robert Hooke,
Christiaan Huygens and Leonhard Euler proposed a wave theory of light based on experimental observations.
In 1803, Thomas Young, an English polymath, performed the famous double-slit experiment that he later described in a paper titled On the nature of light and colours.
This experiment played a major role in the general acceptance of the wave theory of light.
In 1838, Michael Faraday discovered cathode rays.
These studies were followed by the 1859 statement of the black-body radiation problem by Gustav Kirchhoff,
the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system can be discrete, and the 1900 quantum hypothesis of Max Planck.
Planck's hypothesis that energy is radiated and absorbed in discrete "quanta" (or energy packets) precisely matched the observed patterns of black-body radiation.
In 1896, Wilhelm Wien empirically determined a distribution law of black-body radiation, known as Wien's law in his honor.
Ludwig Boltzmann independently arrived at this result by considerations of Maxwell's equations.
However, it was valid only at high frequencies and underestimated the radiance at low frequencies.
Later, Planck corrected this model using Boltzmann's statistical interpretation of thermodynamics and proposed what is now called Planck's law, which led to the development of quantum mechanics.
Following Max Planck's solution in 1900 to the black-body radiation problem (reported 1859),
Albert Einstein offered a quantum-based theory to explain the photoelectric effect (1905, reported 1887).
Around 1900–1910, the atomic theory and the corpuscular theory of light first came to be widely accepted as scientific fact;
these latter theories can be viewed as quantum theories of matter and electromagnetic radiation, respectively.
Among the first to study quantum phenomena in nature were Arthur Compton, C. V. Raman, and Pieter Zeeman, each of whom has a quantum effect named after him. Robert Andrews Millikan studied the photoelectric effect experimentally, and Albert Einstein developed a theory for it. At the same time, Ernest Rutherford experimentally discovered the nuclear model of the atom, for which Niels Bohr developed his theory of the atomic structure, which was later confirmed by the experiments of Henry Moseley. In 1913, Peter Debye extended Niels Bohr's theory of atomic structure, introducing elliptical orbits, a concept also introduced by Arnold Sommerfeld. This phase is known as old quantum theory.
According to Planck, each energy element (E) is proportional to its frequency (ν):
Planck cautiously insisted that this was simply an aspect of the processes of absorption and emission of radiation and had nothing to do with the physical reality of the radiation itself. In fact, he considered his quantum hypothesis a mathematical trick to get the right answer rather than a sizable discovery. However, in 1905 Albert Einstein interpreted Planck's quantum hypothesis realistically and used it to explain the photoelectric effect, in which shining light on certain materials can eject electrons from the material. He won the 1921 Nobel Prize in Physics for this work.
The foundations of quantum mechanics were established during the first half of the 20th century by Max Planck, Niels Bohr, Werner Heisenberg, Louis de Broglie, Arthur Compton, Albert Einstein, Erwin Schrödinger, Max Born, John von Neumann, Paul Dirac, Enrico Fermi, Wolfgang Pauli, Max von Laue, Freeman Dyson, David Hilbert, Wilhelm Wien, Satyendra Nath Bose, Arnold Sommerfeld, and others. The Copenhagen interpretation of Niels Bohr became widely accepted.
In the mathematically rigorous formulation of quantum mechanics developed by Paul Dirac, David Hilbert, John von Neumann, and Hermann Weyl,
the possible states of a quantum mechanical system are symbolized as unit vectors (called state vectors).
Formally, these vectors are elements of a complex separable Hilbert space – variously called the state space or the
associated Hilbert space of the system – that is well defined up to a complex number of norm 1 (the phase factor).
In other words, the possible states are points in the projective space of a Hilbert space, usually called the complex projective space.
The exact nature of this Hilbert space is dependent on the system – for example, the state space for
position and momentum states is the space of square-integrable functions, while the state space for the
spin of a single proton is just the product of two complex planes.
Each observable is represented by a maximally Hermitian (precisely: by a self-adjoint) linear operator acting on the state space.
Each eigenstate of an observable corresponds to an eigenvector of the operator, and the associated eigenvalue corresponds to
the value of the observable in that eigenstate.
If the operator's spectrum is discrete, the observable can attain only those discrete eigenvalues.
In the formalism of quantum mechanics, the state of a system at a given time is described by a complex wave function,
also referred to as state vector in a complex vector space.
This abstract mathematical object allows for
the calculation of probabilities of outcomes of concrete experiments.
For example, it allows one to compute the probability of finding an electron in a particular region around the nucleus
at a particular time. Contrary to classical mechanics, one can never make simultaneous predictions of conjugate variables,
such as position and momentum, to arbitrary precision. For instance, electrons may be considered (to a certain probability) to be
located somewhere within a given region of space, but with their exact positions unknown.
Contours of constant probability density, often referred to as "clouds", may be drawn around the nucleus of an atom
to conceptualize where the electron might be located with the most probability.
Heisenberg's uncertainty principle quantifies the inability to precisely locate the particle given its conjugate momentum.
The Schrödinger equation acts on the entire probability amplitude, not merely its absolute value. Whereas the absolute value of the probability amplitude encodes information about probabilities, its phase encodes information about the interference between quantum states. This gives rise to the "wave-like" behavior of quantum states. As it turns out, analytic solutions of the Schrödinger equation are available for only a very small number of relatively simple model Hamiltonians, of which the quantum harmonic oscillator, the particle in a box, the dihydrogen cation, and the hydrogen atom are the most important representatives. Even the helium atom – which contains just one more electron than does the hydrogen atom – has defied all attempts at a fully analytic treatment.
Figure. 1: Probability densities corresponding to the wave functions of an electron in a hydrogen atom possessing definite energy levels (increasing from the top of the image to the bottom: n = 1, 2, 3, ...) and angular momenta (increasing across from left to right: s, p, d, ...). Denser areas correspond to higher probability density in a position measurement. Such wave functions are directly comparable to Chladni's figures of acoustic modes of vibration in classical physics and are modes of oscillation as well, possessing a sharp energy and thus, a definite frequency. The angular momentum and energy are quantized and take only discrete values like those shown (as is the case for resonant frequencies in acoustics)
Quantum mechanics has had enormous success in explaining many of the features of our universe.
Quantum mechanics is often the only theory that can reveal the individual behaviors of the subatomic particles that make up all forms of matter (electrons, protons, neutrons, photons, and others). Quantum mechanics has strongly influenced string theories, candidates for a Theory of Everything (see reductionism). Quantum mechanics is also critically important for understanding how individual atoms are joined by covalent bond to form molecules. The application of quantum mechanics to chemistry is known as quantum chemistry.
Quantum mechanics can also provide quantitative insight into ionic and covalent bonding processes by explicitly showing which molecules are energetically favorable to which others and the magnitudes of the energies involved. Furthermore, most of the calculations performed in modern computational chemistry rely on quantum mechanics. In many aspects modern technology operates at a scale where quantum effects are significant.
Many modern electronic devices are designed using quantum mechanics.
Examples include the laser, the transistor (and thus the microchip), the electron microscope, and magnetic resonance imaging (MRI).
The study of semiconductors led to the invention of the diode and the transistor, which are indispensable parts of modern electronics systems,
computer and telecommunication devices.
Another application is for making laser diode and light emitting diode which are a high-efficiency source of light.
Many electronic devices operate under effect of quantum tunneling. It even exists in the simple light switch. The switch would not work if electrons could not quantum tunnel through the layer of oxidation on the metal contact surfaces. Flash memory chips found in USB drives use quantum tunneling to erase their memory cells. Some negative differential resistance devices also utilize quantum tunneling effect, such as resonant tunneling diode. Unlike classical diodes, its current is carried by resonant tunneling through two or more potential barriers (see right figure). Its negative resistance behavior can only be understood with quantum mechanics: As the confined state moves close to Fermi level, tunnel current increases. As it moves away, current decreases. Quantum mechanics is necessary to understanding and designing such electronic devices.
Researchers are currently seeking robust methods of directly manipulating quantum states.
Efforts are being made to more fully develop quantum cryptography,
which will theoretically allow guaranteed secure transmission of information.
An inherent advantage yielded by quantum cryptography when compared to classical cryptography is the detection of passive eavesdropping. This is a natural result of the behavior of quantum bits; due to the observer effect, if a bit in a superposition state were to be observed, the superposition state would collapse into an eigenstate. Because the intended recipient was expecting to receive the bit in a superposition state, the intended recipient would know there was an attack, because the bit's state would no longer be in a superposition.
Another goal is the development of quantum computers, which are expected to perform certain computational tasks exponentially faster than
classical computers. Instead of using classical bits, quantum computers use qubits,
which can be in superpositions of states. Quantum programmers are able to manipulate the superposition of qubits in order to solve problems
that classical computing cannot do effectively, such as searching unsorted databases or integer factorization.
IBM claims that the advent of quantum computing may progress the fields of medicine, logistics, financial services, artificial
intelligence and cloud security.
Another active research topic is quantum teleportation, which deals with techniques to transmit quantum information over arbitrary distances.
Macroscale Quantum Effects
While quantum mechanics primarily applies to the smaller atomic regimes of matter and energy,
some systems exhibit quantum mechanical effects on a large scale. Superfluidity,
the frictionless flow of a liquid at temperatures near absolute zero, is one well-known example.
So is the closely related phenomenon of superconductivity, the frictionless flow of an electron gas in a
conducting material (an electric current) at sufficiently low temperatures.
The fractional quantum Hall effect is a topological ordered state which corresponds to patterns of long-range quantum entanglement.
States with different topological orders (or different patterns of long range entanglements) cannot change
into each other without a phase transition.
Quantum theory also provides accurate descriptions for many previously unexplained phenomena, such as black-body radiation and the stability of the orbitals of electrons in atoms. It has also given insight into the workings of many different biological systems, including smell receptors and protein structures. Recent work on photosynthesis has provided evidence that quantum correlations play an essential role in this fundamental process of plants and many other organisms. Even so, classical physics can often provide good approximations to results otherwise obtained by quantum physics, typically in circumstances with large numbers of particles or large quantum numbers. Since classical formulas are much simpler and easier to compute than quantum formulas, classical approximations are used and preferred when the system is large enough to render the effects of quantum mechanics insignificant.