1 / 76

Aerospace Environment ASEN-5335

Aerospace Environment ASEN-5335. Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee) Contact info: e-mail: lix@lasp.colorado.edu (preferred) phone: 2-3514, or 5-0523, fax: 2-6444, website: http://lasp.colorado.edu/~lix

melia
Download Presentation

Aerospace Environment ASEN-5335

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AerospaceEnvironmentASEN-5335 • Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee) • Contact info: e-mail: lix@lasp.colorado.edu (preferred) phone: 2-3514, or 5-0523, fax: 2-6444, website: http://lasp.colorado.edu/~lix • Instructor’s hours: 9:00-11:00 pm Wed at ECOT 534; Tue & Thu, after class. • TA’s office hours: 3:15-5:15 pm Wed at ECAE 166 • Read Chapter 1 & 2. • 1st quiz next Tuesday ASEN 5335 Aerospace Environment -- The Sun

  2. THE SUN • GENERAL CHARACTERISTICS • • Descriptive Data • Electromagnetic Radiation • Particle Radiation • ENERGY GENERATION AND TRANSFER • • Core  Radiation Zone  Convection Zone  Solar Atmosphere • REGIONS OF THE SOLAR ATMOSPHERE • • Photosphere, Chromosphere, Corona • FEATURES OF THE SOLAR ATMOSPHERE • • Coronal Holes, Flares, Sunspots, Plages, Filaments & Prominences • THE SOLAR CYCLE • 6 . SOLAR FLARES AND CORONAL MASS EJECTIONS • • Description and Physical Processes • Classifications • 7. OPERATIONAL EFFECTS OF SOLAR FLARES • a) radio noise b) sudden ionospheric disturbances • c) HF absorption c) PCA events ASEN 5335 Aerospace Environment -- The Sun

  3. Our Sun • Our Sun is a massive ball of gas held together and compressed under its own gravitational attraction. • Our Sun is located in a spiral arm of our Galaxy, in the so-called Orions arm, some 30,000 light-years from the center. • Our Sun orbits the center of the Milky Way in about 225 million years. Thus, the solar system has a velocity of 220 km/s • Our galaxy consists of about 2 billion other stars and there are about 100 billion other galaxies • Our Sun is 333,000 times more massive than the Earth . • It consists of 90% Hydrogen, 9% Helium and 1% of other elements • Total energy radiated: equivalent to 100 billion tons of TNT per second, or the U.S. energy needs for 90,000 years • Is 5 billions years old; another 5 billion to go • Takes 8 minutes for light to travel to Earth • The Sun has inspired mythology in many cultures including the ancient Egyptians, the Aztecs, the Native Americans, and the Chinese. ASEN 5335 Aerospace Environment -- The Sun

  4. Like any star, the Sun won't last forever. • There's a short window of about 1 billion years when it's possible for plants and animals to survive on Earth, and that's probably true of any planet. We're already about half way through it. • Planets like this may be quite rare in the universe, so we better take care of what we've got. • To simplify a very complicated story about the "devolving" of planet Earth, the12-billion-year lifespan is compressed to 12 hours, with the end coming at high noon. ASEN 5335 Aerospace Environment -- The Sun

  5. OTHER SUN FACTS • radius 6.96 x 105 Km109 RE • mean distance from earth (1 AU) = 1.49 x 108 Km215 RS • mass 1.99 x 1030 Kg330,000 ME • mean density 1.4 x 103 Kg m-31/4 E • surface pressure 200 mb1/5 psE • mass loss rate 109 Kg s-1 • surface gravity 274 ms-2 28 gE • equatorial rotation period 26 days • near poles 37 days • inclination of sun's equator to ecliptic 7°24° for Earth • total luminosity 3.86 x 1026 W1366 Wm-2 @ Earth • escape velocity at surface618 km s-1 11.2 km s-1 • effective blackbody temperature 5770 K ASEN 5335 Aerospace Environment -- The Sun

  6. The Sun radiates at a blackbody temperature of 5770 K A blackbody is a “perfect radiator” in that the radiated energy depends only on temperature of the body, resulting in a characteristic emission spectrum. insulation radiated energy max  1/T In a star heating element T2 The radiation reacts thoroughly with the body and is characteristic of the body T1>T2 radiated energy T1 In the laboratory area a T4 wavelength ASEN 5335 Aerospace Environment -- The Sun

  7. ELECTROMAGNETIC RADIATION The Sun emits radiation over a range of wavelengths 400—700 nm ASEN 5335 Aerospace Environment -- The Sun

  8. The wavelengths most significant for the space environment are X-rays, EUV and radio waves. Although these wavelengths contribute only about 1% of the total energy radiated, energy at these wavelengths is most variable ASEN 5335 Aerospace Environment -- The Sun

  9. ASEN 5335 Aerospace Environment -- The Sun

  10. ASEN 5335 Aerospace Environment -- The Sun

  11. Red: 30.4 nm  He II 8x104 K Blue: 17.1 nm  Fe IX 1.3x106 K Yellow: 28.4 nm Fe XV 2.0x106 K Green: 19.5 nm  Fe XII 1.6x106 K ASEN 5335 Aerospace Environment -- The Sun

  12. PARTICLE RADIATION The Sun is constantly emitting streams of charged particles, the solar wind, in all outward directions. Solar wind particles, primarily protons and electrons, travel at an average speed of 400km/s, with a density of 5 particles per cubic centimeter. The speed and density of the solar wind increase markedly during periods of solar activity, and this causes some of the most significant operational impacts ASEN 5335 Aerospace Environment -- The Sun

  13. 2. ENERGY GENERATION AND TRANSFER The core of the Sun is a very efficient fusion reactor burning hydrogen fuel at temperatures ~1.5 x 107 K and producing He nuclei: 4 H1  He4 + 26.73 MeV This 26.73 MeV is the equivalent of the mass difference between four hydrogen nuclei and a helium nucleus. It is this energy that fuels the Sun, sustains life, and drives most physical processes in the solar system. ASEN 5335 Aerospace Environment -- The Sun

  14. REGIONS OF THE SUN’S INTERIOR AND ATMOSPHERE p-modes g-modes ASEN 5335 Aerospace Environment -- The Sun

  15. Between the radiation zone and the surface, temperature decreases sufficiently that electrons can be trapped into some atomic band states, increasing opacity; convection then assumes main role as energy transfer mechanism. ( If radiation came straight out, it would take 2 seconds; due to all the scatterings, it takes 10 million years !) Near the surface, in the photosphere, radiation can escape into space and again becomes the primary energy transport mechanism. The photosphere emits like a black body @ 5770 K (10,420°F). ASEN 5335 Aerospace Environment -- The Sun

  16. Granular Structure The convective cells penetrate into the photosphere and give the appearance of a granular structure. ASEN 5335 Aerospace Environment -- The Sun

  17. HOW DO WE INFER THE INTERNAL PROPERTIES OF THE SUN ? ASEN 5335 Aerospace Environment -- The Sun

  18. is the study of the interior of the Sun from observations of the vibrations of its surface. HELIOSEISMOLOGY In the same way that seismologists use earthquakes and explosions to explore Earth’s crust, helioseismologists use acoustic waves, thought to be excited by turbulence in the convection zone, to infer composition, temperature and motions within the Sun. By subtracting two images of the Sun’s surface taken minutes apart, the effects of solar oscillations are made apparent by alternating patches in brightness that result from heating and cooling in response to acoustic vibrations of the interior. Another way of inferring the corresponding upward and downward motions of the surface is by measuring the Doppler shifts of spectral lines. ASEN 5335 Aerospace Environment -- The Sun

  19. REFRACTION OF ACOUSTIC WAVES IN THE SUN Reflective boundaries organize wave motions into patterns by constructive and destructive interference Phase speed of acoustic wave surface density gradient H Increasing temperature, speed of sound faster Faster propagation here so waves refract towards surface ASEN 5335 Aerospace Environment -- The Sun

  20. These acoustic waves (where pressure is the restoring force) • are called p-modes • Internal gravity waves and surface waves also exist; these • are called g-modes and f-modes, respectively “Resonant” modes have integral # of wavelengths around a circumference p-modes ASEN 5335 Aerospace Environment -- The Sun

  21. The frequency of an acoustic mode, and the spatial distance and the length of time it takes to re-appear at the surface after being refracted lower down, are sensitive to the properties of the intervening region. • Seismic studies of Earth’s interior are performed by measuring the propagation of waves from a “point” source (i.e., explosion or earthquake epicenter) • On the Sun, “helioseismic” • studies are based on statistical • correlations between various • points on the Sun These may all have similar T (~ 2-20 minutes); but, because they have different lH’s, they have different Cph’s and therefore penetrate to different depths ASEN 5335 Aerospace Environment -- The Sun

  22. SOME CONTRIBUTIONS OF HELIOSEISMOLOGY • Convection zone deeper (R=0.71) than previously thought. • Opacity used in models was too low. • Limits set on the abundance of Helium in convection zone. • Rotation rate of the convection zone is similar to that of surface. • Near the convection zone base, rotation rate near the equator decreases with depth, and rotation rate at high latitudes increases with depth, so that the outer radiation zone is rotating at a constant intermediate rate. • The shear between the outer radiation zone and inner convection zone may hold the key to the 11-year cycle. ASEN 5335 Aerospace Environment -- The Sun

  23. AerospaceEnvironmentASEN-5335 • Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee) • Contact info: e-mail: lix@lasp.colorado.edu (preferred) phone: 2-3514, or 5-0523, fax: 2-6444, website: http://lasp.colorado.edu/~lix • Instructor’s hours: 9:00-11:00 pm Wed at ECOT 534; Tue & Thu, after class. • TA’s office hours: 3:15-5:15 pm Wed at ECAE 166 • Read Chapter 1 & 2, and classnotes • 1st quiz today, open book. • HW1 due Thursday ASEN 5335 Aerospace Environment -- The Sun

  24. THE SUN • GENERAL CHARACTERISTICS • • Descriptive Data • Electromagnetic Radiation • Particle Radiation • ENERGY GENERATION AND TRANSFER • • Core  Radiation Zone  Convection Zone  Solar Atmosphere • REGIONS OF THE SOLAR ATMOSPHERE • • Photosphere, Chromosphere, Corona • FEATURES OF THE SOLAR ATMOSPHERE • • Coronal Holes, Flares, Sunspots, Plages, Filaments & Prominences • THE SOLAR CYCLE • 6 . SOLAR FLARES AND CORONAL MASS EJECTIONS • • Description and Physical Processes • Classifications • 7. OPERATIONAL EFFECTS OF SOLAR FLARES • a) radio noise b) sudden ionospheric disturbances • c) HF absorption c) PCA events ASEN 5335 Aerospace Environment -- The Sun

  25. REGIONS OF THE SUN’S INTERIOR AND ATMOSPHERE p-modes g-modes ASEN 5335 Aerospace Environment -- The Sun

  26. 3. REGIONS OF THE SOLAR ATMOSPHERE: THE PHOTOSPHERE The photosphere is the Sun’s visible “surface”, a few hundred km thick, characterized by sunspots and granules The solar surface is defined as the location where the optical depth of a  = 5,000 Å photon is 1 (the probability of escaping from the surface is 1/e) The photosphere is the lowest region of the solar atmosphere extending from the surface to the temperature minimum at around 500 km. 99% of the Sun’s light and heat comes out of this narrow layer. ASEN 5335 Aerospace Environment -- The Sun

  27. THE CHROMOSPHERE The chromosphere is the ~ 2000 km layer above the photosphere where the temperature rises from 6000 K to about 20,000 K. At these higher temperatures hydrogen emits light that gives off a reddish color (H-alpha emission) that can be seen in eruptions (prominences) that project above the limb of the sun during total solar eclipses. When viewed through a H-alpha filter, the sun appears red. This is what gives the chromosphere its name (color-sphere). In H-a, a number of chromospheric features can be seen, such as bright plages around sunspots, dark filaments, and prominences above the limb. 6563 Å ASEN 5335 Aerospace Environment -- The Sun

  28. THE CORONA The coronais the outermost, most tenuous region of the solar atmosphere extending to large distance and eventually becoming the solar wind. The most common coronal structure seen on eclipse photographs is the coronal streamer, bright elongated structures, which are fairly wide near the solar surface, but taper off to a long, narrow spike. ASEN 5335 Aerospace Environment -- The Sun

  29. UV solar emission lines and corresponding regions and temperatures ASEN 5335 Aerospace Environment -- The Sun

  30. The corona is characterized by very high temperature (a few million degrees) and by the presence of a low density, fully ionized plasma. Here closed field lines trap plasma and keep densities high, and open field lines allow plasma to escape, allowing much lower density regions to exist called coronal hoes. TRANSITION REGION At the top of the chromosphere the temperature rapidly increases from about 104 K to over 106 K. This sharp increase takes place within a narrow region, called the transition region. The heating mechanism is not understood and remains one of the outstanding questions of solar physics ASEN 5335 Aerospace Environment -- The Sun

  31. 4. FEATURES OF THE SOLAR ATMOSPHERE:SUNSPOTS Sunspots are areas of intense magnetic fields. Viewed at the surface of the sun, they appear darker as they are cooler than the surrounding solar surface - about 4000oC compared to the surface (6000oC). ASEN 5335 Aerospace Environment -- The Sun

  32. CHROMOSPHERIC FILAMENTS & PLAGES Filaments are the dark, ribbon-like features seen in Ha light against the brighter solar disk. The material in a filament has a lower temperature than its surroundings, and thus appears dark. Filaments are elongated blobs of plasma supported by relatively strong magnetic fields. Plages are hot, bright regions of the chromosphere, often over sunspot regions, and are often sources of enhanced 2800 MHz (10.7 cm) radio flux Ha, 6563 Å ASEN 5335 Aerospace Environment -- The Sun

  33. SOLAR PROMINENCES Prominences are variously described as surges, sprays or loops. Filaments are referred to as prominenceswhen they are present on the limb of the Sun, and appear as bright structures against the darkness of space. ASEN 5335 Aerospace Environment -- The Sun

  34. ASEN 5335 Aerospace Environment -- The Sun

  35. ASEN 5335 Aerospace Environment -- The Sun

  36. ASEN 5335 Aerospace Environment -- The Sun

  37. CORONAL HOLES One of the major discoveries of the Skylab mission was the observation of extended dark coronal regions in X-ray solar images. Coronal holes are characterized by low density cold plasma (about half a million degrees colder than in the bright coronal regions) and unipolar magnetic fields (connected to the magnetic field lines extending to the distant interplanetary space, or open field lines). Near solar minimum coronal holes cover about 20% of the solar surface. The polar coronal holes are essentially permanent features, whereas the lower latitude holes only last for several solar rotations. ASEN 5335 Aerospace Environment -- The Sun

  38. Coronal holes and Solar wind speed and density The interplay between the inward pointing gravity and outward pointing pressure gradient force results in a rapid outward expansion of the coronal plasma along the open magnetic field lines. At low latitudes the direction of the coronal magnetic field is far from radial. Therefore the plasma cannot leave the vicinity of the Sun along magnetic field lines. At the base of low-latitude coronal holes, however, the magnetic field direction is not far from radial, and the expansion of the hot plasma can take place along open magnetic field lines without much resistance  fast solar wind. ASEN 5335 Aerospace Environment -- The Sun

  39. PARTICLE RADIATION The Sun is constantly emitting streams of charged particles, the solar wind, in all outward directions. Solar wind particles, primarily protons and electrons, travel at an average speed of 400km/s, with a density of 5 particles per cubic centimeter. The speed and density of the solar wind increase markedly during periods of solar activity, and this causes some of the most significant operational impacts ASEN 5335 Aerospace Environment -- The Sun

  40. AerospaceEnvironmentASEN-5335 • Instructor: Prof. Xinlin Li (pronounce: Shinlyn Lee) • Contact info: e-mail: lix@lasp.colorado.edu (preferred) phone: 2-3514, or 5-0523, fax: 2-6444, website: http://lasp.colorado.edu/~lix • Instructor’s hours: 9:00-11:00 pm Wed at ECOT 534; Tue & Thu, after class. • TA’s office hours: 3:15-5:15 pm Wed at ECAE 166 • Read Chapter 2, classnotes, and handout • HW2 due today • 2nd quiz, next Thursday (2/6) ASEN 5335 Aerospace Environment -- The Sun

  41. THE SUN • GENERAL CHARACTERISTICS • • Descriptive Data • Electromagnetic Radiation • Particle Radiation • ENERGY GENERATION AND TRANSFER • • Core  Radiation Zone  Convection Zone  Solar Atmosphere • REGIONS OF THE SOLAR ATMOSPHERE • • Photosphere, Chromosphere, Corona • FEATURES OF THE SOLAR ATMOSPHERE • • Coronal Holes, Flares, Sunspots, Plages, Filaments & Prominences • THE SOLAR CYCLE • 6 . SOLAR FLARES AND CORONAL MASS EJECTIONS • • Description and Physical Processes • Classifications • 7. OPERATIONAL EFFECTS OF SOLAR FLARES • a) radio noise b) sudden ionospheric disturbances • c) HF absorption c) PCA events ASEN 5335 Aerospace Environment -- The Sun

  42. 5. THE SOLAR CYCLE • The number of sunspots on the solar disk varies with a period of about 11 years, a phenomenon known as the solar (or sunspot) cycle, which was accidentally discovered by a German amateur named Heinrich Schwabe in 1843. • Solar events and operational impacts also tend to follow this 11 year cycle. • The Zurich sunspot number is defined by counting the number of spot groups and individual spots and then forming the sum: Sunspot Number (R) =k (10x Number of sunspot group + Number of individual spots), where k is a correction factor accounting for the evolution in observing technology. • In this scheme sunspots are kept track of throughout their lifetime, and in constructing annual mean sunspot numbers a given spot is counted only once. • The figure on the following page depicts the annual mean sunspot numbers from 1961 to 1987. • Note the period between about 1645 and 1715 when there were no sunspots on the Sun. This period is referred to as the ‘Maunder minimum’ (Maunder, 1882). ASEN 5335 Aerospace Environment -- The Sun

  43. Maunder Minimum Solar cycle 1: 1755-1766 1 Solar cycle 23: 1996-2007 ASEN 5335 Aerospace Environment -- The Sun

  44. Maunder Minimum ASEN 5335 Aerospace Environment -- The Sun

  45. Sunspot latitude drift The remarkably regular 11-year variation of sunspot numbers is accompanied by a similarly regular variation in the latitude distribution of sunspots drifts toward the equator as the solar cycle progresses from minimum to maximum. ASEN 5335 Aerospace Environment -- The Sun

  46. ASEN 5335 Aerospace Environment -- The Sun

  47. COMPARING THE SUN IN EUV FROM 1996 TO 1999 Solar Minimum – 1996/7 Solar Maximum – 2000/1 eitcompare ASEN 5335 Aerospace Environment -- The Sun

  48. Evolution of the Sun’s X-ray emission over the 11-year solar cycle ASEN 5335 Aerospace Environment -- The Sun

  49. SORCE Launch (1/25/03) Maunder Minimum ASEN 5335 Aerospace Environment -- The Sun

  50. 6. CMEs & SOLAR FLARES • Flares and CMEs are different aspects of solar activity that are not necessarily related. • Flares produce energetic photons and particles. • CMEs mainly produce low-energy plasma but also energetic particles. • CMEs and flares are very important sources of dynamical phenomena in the space environment. • The triggering mechanisms for CMEs and flares, and the particle acceleration mechanisms, are not understood beyond a rudimentary level. However, this knowledge is essential for development of predictive capabilities. ASEN 5335 Aerospace Environment -- The Sun

More Related