DOCSLIB.ORG

Atmospheric Optics Nature's Light Show

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Atmospheric Optics Lecture 17! ! Nature’s Light Show Nature’s Light Show Atmospheric Optics Scattering Reflection Ahrens Chapter 15 1 2 Scattering Atmospheric Optics The amazing variety of optical phenomena Things to look for observed in the atmosphere can be • Blue Sky explained by four physical mechanisms. • White Clouds • Blue Smoke • Scattering • Red Sunsets • Reflection • Crepuscular Rays • Heiligenschein • Refraction • Diffraction 3 4 Scattering Scattering sunlight Rayleigh Scattering Small objects such Light is scattered by the air molecules, cloud as air molecules and droplets, and aerosols. fine smoke particles most effectively air molecule The resulting optics scatter blue light. depend on the size of the scatterer. 5 6 Rayleigh Scattering Scattering by Air Molecules Scattering of blue light by air molecules is more than 9 times greater than scattering of red light. Rayleigh Scattering results in blue sky 7 8 Scattering by Air Molecules Scattering Mie Scattering sunlight Larger objects such as cloud droplets and ice crystals scatter all visible Cloud drop light equally well. Mie scattering is greatest parallel to incident light. 9 10 Scattering Scattering by Air Molecules and Clouds Mie scattering is greatest parallel to incident light. Rayleigh scatter is nearly equal in all direction. 11 12 Rayleigh and Mie Scattering Scattering by Air Molecules and Aerosols 13 14 Rayleigh and Mie Scattering Scattering by Smoke Mie scattering results in white clouds and the glare around the sun. Blue sky is the Larger particles appear brown and smaller result of Rayleigh scattering. particles scatter blue. 15 16 Scattering by Cloud Droplets Scattering by Cloud Particles When all visible light is scattered away by cloud drops the cloud turns black. Mie scattering results in white clouds, with black bottoms if they are thick enough. 17 18 Red Sunsets Avoid exposed places during thunderstorms Most of the blue light is scattered out, leaving red light, which is scattered toward the observer by clouds. 19 20 Scattering by Cloud Particles Scattering by Cloud Particles When the sun sets or rises, the sunlight passes through a long path of air. Most of the blue light is scattered out, leaving red light, which is scattered toward the observer by clouds. 21 22 Scattering by Aerosols Scattering by Aerosols Crepuscular Rays Crepuscular Rays 23 24 Scattering by Aerosols Scattering by Cloud Droplets Crepuscular Rays Crepuscular Rays 25 26 Crepuscular Rays Crepuscular Rays Shadows cast by clouds or trees on hazy days result in crepuscular rays, also known as Jacob’s ladders. 27 28 Crepuscular Rays Anti-crepuscular Rays Mountain’s Shadow 29 30 Reflection Reflection The Law of Reflection • Sun Pillars The angle a) of incident light equals the angle b) • Circumhorizontal Arcs of reflected light. 31 32 Reflection by Water Reflection by Water 33 34 Reflection by Water Reflection by Water 35 36 Reflection by Water Reflection by Ice Crystals Sun Pillars The Law of Reflection The angle a) of incident light equals the angle b) of reflected light. Sunlight reflecting off of the ocean can produce a sun pillar. 37 38 Reflection by Ice Crystals Reflection by Ice Crystals Sun pillar Sunlight reflecting off of plate-shaped ice crystals can produce a sun pillar. 39 40 Reflection by Ice Crystals Reflection by Ice Crystals Sun pillars commonly occur beneath an altostratus cloud just after sunset. Sun pillars commonly occur beneath an altostratus cloud just after sunset. 41 42 Reflection by Ice Crystals Reflection and Scattering by Dew Drops Heiligenschein Sun pillars commonly occur beneath an altostratus cloud just after sunset. 43 44 Reflection and Scattering Questions? by Dew Drops Heiligenschein 45 46 Atmospheric Optics Rayleigh and Mie Scattering The amazing variety of optical phenomena observed in the atmosphere can be explained by four physical mechanisms. Things to look for • Blue Sky • Scattering • White Clouds • Reflection • Blue Smoke • Refraction • Red Sunsets • Diffraction • Crepuscular Rays • Heiligenschein 47 48 Scattering by Cloud Particles Scattering by Cloud Particles When the sun sets or rises, the sunlight passes through a long path of air. Most of the blue light is Rayleigh scattered out, leaving red light, which is Mie scattered toward the observer by clouds . 49 50 Reflection Refraction • Sun Pillars • Green Flash • Circumhorizontal Arcs • Mirage • Halo • Tangent Arc • Rainbow 51 52 Refraction Refraction in Air Light slows down as it passes from a less dense to a more dense medium. As light slows it bends toward the denser medium. Similar to waves approaching a beach. The amount of bending depends on the wavelength (color) of the light, leading to dispersion or separation of colors. Mirage 53 54 Refraction in Air Refraction in Air Mirage Green Flash 55 56 Refraction in Air Refraction in Air Green Flash Green Flash 57 58 Refraction in Air Refraction in Air Green Flash Red Flash 59 60 Refraction by Ice Crystals Refraction by Ice Crystals 22 1/2˚ Halo Sun Dogs 61 62 Refraction by Ice Crystals Refraction by Ice Crystals Sun Dog 22 1/2˚ Halo 63 64 Refraction by Ice Crystals Refraction by Ice Crystals 22 1/2˚ Halo and Upper Tangent Arc 22 1/2˚ Halo 65 66 Refraction by Ice Crystals Refraction by Ice Crystals Halo Complex Halo Complex 67 68 Refraction by Ice Crystals Refraction by Ice Crystals 46˚ Halo? Lower Tangent Arc 69 70 Refraction by Ice Crystals Refraction and Scattering Lower Tangent Arc Sun Pillar and Sun Dog? 71 72 Atmospheric Optics Rayleigh and Mie Scattering The amazing variety of optical phenomena observed in the atmosphere can be explained by four physical mechanisms. Things to look for • Blue Sky • Scattering • White Clouds • Reflection • Blue Smoke • Refraction • Red Sunsets • Diffraction • Crepuscular Rays • Heiligenschein 73 74 Scattering by Cloud Particles Scattering by Cloud Particles When the sun sets or rises, the sunlight passes through a long path of air. Most of the blue light is Rayleigh Rayleigh scattering by air molecules results in a blue sky. scattered out, leaving red light, which is Mie scattered Mie scattering by droplets results in white/grey clouds. toward the observer by clouds . 75 76 Reflection Refraction • Sun Pillars • Green Flash • Circumhorizontal Arcs • Mirage • Halo • Tangent Arc • Rainbow 77 78 Refraction Refraction Causes Light slows down as it passes Mirage from a less dense to a more dense medium. Green Flash As light slows it bends toward the Halos denser medium. Similar to waves approaching a beach. Sundogs The amount of bending depends Rainbows on the wavelength (color) of the light, leading to dispersion or separation of colors. Halo Complex results from refraction by ice crystals 79 80 Refraction by Water Drops Refraction by Water Drops 81 82 Refraction by Rain Refraction by Water Drops Violet Red Primary Rainbow 83 84 Refraction by Rain Refraction by Rain Double Rainbow Double Rainbow 85 86 Refraction by Rain Refraction by Rain Partial Rainbow Double Rainbow 87 88 Refraction by Rain Refraction by Rain Rainbow seen from Airplane High Sun: Low Rainbow 89 90 Diffraction Diffraction causes Interference Constructive interference of light waves can produce color separation. The physical mechanism in this case is called diffraction. Produces colors on soap films, oil slicks, and music CDs. Diffraction is the tendency of light waves to bend as they pass the edges of objects. 91 92 Diffraction by Soap Film Diffraction by Cloud Drops Diffraction Results in • Iridescence • Corona • Glory • Supernumerary bows Iridescence 93 94 Diffraction by Airplane Window Diffraction by Cloud Droplets Artificial Iridescence Corona 95 96 Diffraction by Pollen Diffraction and Reflection Corona Glory 97 98 Diffraction and Reflection Diffraction and Reflection Glory Glory 99 100 Diffraction and Reflection Diffraction and Reflection Supernumerary Rays Fog Bow: larger drops do not allow dispersion of colors. 101 102 Diffraction and Reflection Summary: Atmospheric Optics The amazing variety of optical phenomena observed in the atmosphere can be explained by four physical mechanisms. • Scattering • Reflection • Refraction Fog Bow: larger drops do not • Diffraction allow dispersion of colors. 103 104.
Recommended publications
  • Light Color and Atmospheric Light, Color, and Atmospheric Optics

    Light Color and Atmospheric Light, Color, and Atmospheric Optics

    Light, Color, and Atmospheric Optics Chapter 19 April 28 and 30, 2009 Colors • Sunlight contains all colors (visible spectrum) Wavelength Ranges in µm UV-C: 0.25 - 0.29 UV-B: 0.29 - 0.32 UV-A: 0.32 - 0.38 Visible: 0.38 - 0.75 Near IR: 0.75 - 4 Mid IR: 4 - 8 Longwave IR: 8 - 100 Colors • If object is white then all colors are reflected • If object is red then only red is reflected and all others are absorbed From Malm (1999). Introduction to Visibility Blue Skies and Hazy days • Selective scattering – Scattering depends on wavelength of light • Rayleigh scattering – Very small particles, gases • Mie scattering – Particles the size of wavelength of visible light • Blue haze • Some particles from plants: terpenes, α- pinene Blue Ridge Mountains • Blue haze caused by scattering of blue light by fine particles Creppyuscular Rays • Scattering of sunlight by dust and haze produces white bands Selective Scattering: Sunset • Notice the effects of scattering on color as sunlight penetrates into the atmosphere Twinkling, Twilight, and the Green Flash • Light that travels from a less dense to a more dense medium loses speed and bends toward the normal, while light that enters a less dense medium increase speed and bends away from the normal. • Apparent position, scintillation, and green flash all depend of density variations in the athtmosphere • Scintillation also indicates the amount of turbulence in the atmosphere Bending of Light Paths from Atmosphere Green Flash • Green flash at top may be seen under circumstances of very cold (dense) air near the surface rapidly changing to warmer (less dense) air aloft Mirages •Miraggyges are caused by refraction of light due to strong density differences in atmospheric layers usually caused by strong temperature differences.
  • Enhanced Total Internal Reflection Using Low-Index Nanolattice Materials

    Enhanced Total Internal Reflection Using Low-Index Nanolattice Materials

    Letter Vol. 42, No. 20 / October 15 2017 / Optics Letters 4123 Enhanced total internal reflection using low-index nanolattice materials XU A. ZHANG,YI-AN CHEN,ABHIJEET BAGAL, AND CHIH-HAO CHANG* Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA *Corresponding author: [email protected] Received 4 August 2017; revised 14 September 2017; accepted 16 September 2017; posted 19 September 2017 (Doc. ID 303972); published 9 October 2017 Low-index materials are key components in integrated Although naturally occurring materials with low refractive photonics and can enhance index contrast and improve per- indices are limited, there are significant research efforts to formance. Such materials can be constructed from porous artificially create low-index materials close to the index of materials, which generally lack mechanical strength and air. These new materials consist of porous structures through are difficult to integrate. Here we demonstrate enhanced to- various conventional fabrication techniques, such as oblique tal internal reflection (TIR) induced by integrating robust deposition [5–9], the sol-gel process [10], and chemical vapor nanolattice materials with periodic architectures between deposition [11]. Due to the air voids, the fabricated porous high-index media. The transmission measurement from structures can have effective refractive indices lower than the the multilayer stack illustrates a cutoff at about a 60° inci- solid material components. However, such materials typically dence angle, indicating an enhanced light trapping effect lack mechanical stability and can induce optical scattering be- through TIR. Light propagation in the nanolattice material cause of the random architectures of the structures.
  • Moons Phases and Tides

    Moons Phases and Tides

    Moon’s Phases and Tides Moon Phases Half of the Moon is always lit up by the sun. As the Moon orbits the Earth, we see different parts of the lighted area. From Earth, the lit portion we see of the moon waxes (grows) and wanes (shrinks). The revolution of the Moon around the Earth makes the Moon look as if it is changing shape in the sky The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days. The phases always follow one another in the same order: New moon Waxing Crescent First quarter Waxing Gibbous Full moon Waning Gibbous Third (last) Quarter Waning Crescent • IF LIT FROM THE RIGHT, IT IS WAXING OR GROWING • IF DARKENING FROM THE RIGHT, IT IS WANING (SHRINKING) Tides • The Moon's gravitational pull on the Earth cause the seas and oceans to rise and fall in an endless cycle of low and high tides. • Much of the Earth's shoreline life depends on the tides. – Crabs, starfish, mussels, barnacles, etc. – Tides caused by the Moon • The Earth's tides are caused by the gravitational pull of the Moon. • The Earth bulges slightly both toward and away from the Moon. -As the Earth rotates daily, the bulges move across the Earth. • The moon pulls strongly on the water on the side of Earth closest to the moon, causing the water to bulge. • It also pulls less strongly on Earth and on the water on the far side of Earth, which results in tides. What causes tides? • Tides are the rise and fall of ocean water.
  • Why Doesn't the Sky Turn Green?

    Why Doesn't the Sky Turn Green?

    Why Doesn't The Sky Turn Green? Rushi Shah 09 November 2015 I was leafing through the US Army Corps of Engineers' Manual on Remote Sensing and learned about how Rayleigh scattering creates blue skies during the day and redish-orange sunsets. Well, everybody knows about blue skies and red sunsets, was the title just click-bait, you ask? No, but I'll get to that. 1 The Basics of Rayleigh Scattering Let's start with this whole Rayleigh scattering thing. Basically the idea is that particles in the atmosphere (like Oxygen and Nitrogen particles) scatter rays of light as they enter the atmosphere. How much the light is scattered is heavily dependent on the wavelength of the light. Remember how ROY-G-BIV represents the colors of the rainbow (and thus the spectrum of visible light)? Well that spectrum of light starts with long wavelength rays (reds, oranges, and yellows) and ends with short wavelength rays (blues, indigos, and violets). 1 The amount of light that is scattered (denoted with the variable I) is highly inversely proportional to the wavelength of the light (denoted with the greek letter ). Put simply, as the wavelength goes down, the light waves are scattered more quickly. 1 I / λ4 When sunlight hits the earth directly during mid-day, it travels through a small amount of atmosphere, and thus we see the wavelengths of light that are immediately scattered. Based on the equation above, the blues, indigos, and violets would be scattered first (and they blend together into the blue sky we see). As the sun sets, it goes through more and more particles to reach us.
  • Light, Color, and Atmospheric Optics

    Light, Color, and Atmospheric Optics

    Light, Color, and Atmospheric Optics GEOL 1350: Introduction To Meteorology 1 2 • During the scattering process, no energy is gained or lost, and therefore, no temperature changes occur. • Scattering depends on the size of objects, in particular on the ratio of object’s diameter vs wavelength: 1. Rayleigh scattering (D/ < 0.03) 2. Mie scattering (0.03 ≤ D/ < 32) 3. Geometric scattering (D/ ≥ 32) 3 4 • Gas scattering: redirection of radiation by a gas molecule without a net transfer of energy of the molecules • Rayleigh scattering: absorption extinction 4 coefficient s depends on 1/ . • Molecules scatter short (blue) wavelengths preferentially over long (red) wavelengths. • The longer pathway of light through the atmosphere the more shorter wavelengths are scattered. 5 • As sunlight enters the atmosphere, the shorter visible wavelengths of violet, blue and green are scattered more by atmospheric gases than are the longer wavelengths of yellow, orange, and especially red. • The scattered waves of violet, blue, and green strike the eye from all directions. • Because our eyes are more sensitive to blue light, these waves, viewed together, produce the sensation of blue coming from all around us. 6 • Rayleigh Scattering • The selective scattering of blue light by air molecules and very small particles can make distant mountains appear blue. The blue ridge mountains in Virginia. 7 • When small particles, such as fine dust and salt, become suspended in the atmosphere, the color of the sky begins to change from blue to milky white. • These particles are large enough to scatter all wavelengths of visible light fairly evenly in all directions.
  • ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY

    ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY

    ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere.
  • Atmospheric Optics Learning Module

    Atmospheric Optics Learning Module

    Atmospheric Optics Learning Module Everything we see is the reflection of light and without light, everything would be dark. In this learning module, we will discuss the various wavelengths of light and how it is transmitted through Earth’s atmosphere to explain fascinating optical phenomena including why the sky is blue and how rainbows form! To get started, watch this video describing energy in the form of waves. A sundog and halo display in Greenland. Electromagnetic Spectrum (0 – 6:30) Source Electromagnetic Spectrum Electromagnetic (EM) radiation is light. Light you might see in a rainbow, or better yet, a double rainbow such as the one seen in Figure 1. But it is also radio waves, x-rays, and gamma rays. It is incredibly important because there are only two ways we can move energy from place to place. The first is using what is called a particle, or an object moving from place to place. The second way to move energy is through a wave. The interesting thing about EM radiation is that it is both a particle and a wave 1. Figure 1. Double rainbow Source 1 Created by Tyra Brown, Nicole Riemer, Eric Snodgrass and Anna Ortiz at the University of Illinois at Urbana- This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. Champaign. 2015-2016. Supported by the National Science Foundation CAREER Grant #1254428. There are many frequencies of EM radiation that we cannot see. So if we change the frequency, we might have radio waves, which we cannot see, but they are all around us! The same goes for x-rays you might get if you break a bone.
  • The Min Min Light and the Fata Morgana Pettigrew

    The Min Min Light and the Fata Morgana Pettigrew

    C L I N I C A L A N D E X P E R I M E N T A L OPTOMETRYThe Min Min light and the Fata Morgana Pettigrew COMMENTARY The Min Min light and the Fata Morgana An optical account of a mysterious Australian phenomenon Clin Exp Optom 2003; 86: 2: 109–120 John D Pettigrew BSc(Med) MSc MBBS Background: Despite intense interest in this mysterious Australian phenomenon, the FRS Min Min light has never been explained in a satisfactory way. Vision Touch and Hearing Research Methods and Results: An optical explanation of the Min Min light phenomenon is of- Centre, University of Queensland fered, based on a number of direct observations of the phenomenon, as well as a field demonstration, in the Channel Country of Western Queensland. This explanation is based on the inverted mirage or Fata Morgana, where light is refracted long distances over the horizon by the refractive index gradient that occurs in the layers of air during a temperature inversion. Both natural and man-made light sources can be involved, with the isolated light source making it difficult to recognise the features of the Fata Morgana that are obvious in daylight and with its unsuspected great distance contribut- ing to the mystery of its origins. Submitted: 11 September 2002 Conclusion: Many of the strange properties of the Min Min light are explicable in terms Revised: 2 December 2002 of the unusual optical conditions of the Fata Morgana, if account is also taken of the Accepted for publication: 3 December human factors that operate under these highly-reduced stimulus conditions involving a 2002 single isolated light source without reference landmarks.
  • Atmospheric Optics

    Atmospheric Optics

    53 Atmospheric Optics Craig F. Bohren Pennsylvania State University, Department of Meteorology, University Park, Pennsylvania, USA Phone: (814) 466-6264; Fax: (814) 865-3663; e-mail: [email protected] Abstract Colors of the sky and colored displays in the sky are mostly a consequence of selective scattering by molecules or particles, absorption usually being irrelevant. Molecular scattering selective by wavelength – incident sunlight of some wavelengths being scattered more than others – but the same in any direction at all wavelengths gives rise to the blue of the sky and the red of sunsets and sunrises. Scattering by particles selective by direction – different in different directions at a given wavelength – gives rise to rainbows, coronas, iridescent clouds, the glory, sun dogs, halos, and other ice-crystal displays. The size distribution of these particles and their shapes determine what is observed, water droplets and ice crystals, for example, resulting in distinct displays. To understand the variation and color and brightness of the sky as well as the brightness of clouds requires coming to grips with multiple scattering: scatterers in an ensemble are illuminated by incident sunlight and by the scattered light from each other. The optical properties of an ensemble are not necessarily those of its individual members. Mirages are a consequence of the spatial variation of coherent scattering (refraction) by air molecules, whereas the green flash owes its existence to both coherent scattering by molecules and incoherent scattering
  • Einstein's Mirage

    Einstein's Mirage

    Paul L. Schechter Einstein’s Mirage he first prediction of Einstein’s general theoryof relativity T to be verified experimentallywas the deflection of light by a massive body—the Sun. In weak gravitational fields (and for such purposes the Sun’s field is considered weak), light behaves as if there were an index of refraction proportional to the gravitational potential. The stronger the gravitational field, the larger the angu- lar deflection of the light. The Sun is not unique in this regard, and it was quickly appreci- ated that stars in our own galaxy (the MilkyWay) and the combined mass of stars in other galaxies would also, on very rare occasions, produce observable deflections. Variations in the “gravitational” index of refraction would also distort images, stretching them in some directions and shrinking them in others. In the analogous case of terrestrial mirages, the deflections and distortions are due to thermal variations in the index of refraction of air. 36 ) schechter mit physics annual 2003 OTH TERRESTRIAL AND GRAVITATIONAL Bmirages sometimes produce multiple distorted images of the same object. When they do, at least one of the images has the opposite handedness of the object being imaged—it is a mirror image, but distorted. At least one of the other images must have the correct handedness, but it will also be distorted. The French call such distorted images gravitational mirages. In the half century following the confirmation of general relativity, the idea that cosmic mirages might actually be observed was taken seriously byonly a small number of astrophysicists. Most of the papers written on the subject treated them as academic curiosities, far too unlikely to actually be observed.
  • How to Format a SCCG Papaer

    How to Format a SCCG Papaer

    Chasing the Green Flash: a Global Illumination Solution for Inhomogeneous Media D. Gutierrez F.J. Seron O. Anson A. Muñoz University of Zaragoza University of Zaragoza University of Zaragoza University of Zaragoza [email protected] [email protected] [email protected] [email protected] restrictions on the scenes and effects that can be Abstract reproduced, including some of the phenomena that occur in our atmosphere. Several natural phenomena, such as mirages or the Most of the media are in fact inhomogeneous to one green flash, are owed to inhomogeneous media in degree or another, with properties varying continuously which the index of refraction is not constant. This from point to point. The atmosphere, for instance, is in makes the light rays travel a curved path while going fact inhomogeneous since pressure, temperature and through those media. One way to simulate global other properties do vary from point to point, and illumination in inhomogeneous media is to use a therefore its optic characterization, given by the index curved ray tracing algorithm, but this approach of refraction, is not constant. presents some problems that still need to be solved. A light ray propagating in a straight line would then be This paper introduces a full solution to the global accurate only in two situations: either there is no media illumination problem, based on what we have called through which the light travels (as in outer space, for curved photon mapping, that can be used to simulate instance), or the media are homogeneous. But with several natural atmospheric phenomena. We also inhomogeneous media, new phenomena occur.
  • Natural Electromagnetic Phenomena and Electromagnetic Theory: a Review

    Natural Electromagnetic Phenomena and Electromagnetic Theory: a Review

    Paper Natural Electromagnetic Phenomena and Electromagnetic Theory: A Review ∗ Masashi Hayakawa Member ∗∗ Katsumi Hattori Member ∗ Yoshiaki Ando Member We review the new findings on natural electromagnetic phenomena in the near-Earth environment and will show the importance of electromagnetic analyses in elucidating the essential points of these phenomena. The topics include (1) atmospheric phenomena related to lightning (e.g. mesospheric optical emissions); (2) seismo-electromagnetic phenomena (electromagnetic phenomena associated with earthquakes and/or volcano eruptions); (3) plasma and wave phenomena in the Earth’s ionosphere and magnetosphere; and (4) electro- magnetic or electrodynamic coupling among different regions. We pay our greatest attention to the unsolved essential problems for each subject, and suggest how electromagnetics would contribute to a solution to those problems. Keywords: Natural electromagnetic phenomena, electromagnetic theory, atmospheric electricity, seismogenic emission, space plasma, computational electromagnetics 1. Introduction We know that the near-Earth environment is occupied by electromagnetic noise over a wide frequency range from DC to VHF (1). Fig. 1 illustrates the frequency spectrum of the terrestrial electromagnetic noise envi- ronment (2). Noises of higher frequency include solar radiation, galactic noise and interplanetary noise, and there are terrestrial noises generated in the near-Earth at lower frequencies. The important electromagnetic phenomena very close to us are summarized as follows: (1) electromagnetic phenomena associated with light- ning discharges in the atmosphere, (2) electromagnetic phenomena in the ionospheric/magnetospheric plasma, and (3) electromagnetic phenomena originating in the lithosphere (1). The first and second phenomena are not so new, but there have been many new discover- ies about them. For example, we have observed a new phenomenon called mesospheric optical emissions asso- ciated with lightning discharges.