- 4.9 Dynamics of the magnetosphere 58. - Occasionally the Sun’s surface erupts and sends a large part of the solar atmosphere streaming away at high speeds. - Figure 1.1 shows the layers of the atmosphere as a function of height. - The first tentative connections were made in the middle of the nineteenth century. - An advantage of the SI (or metric) system is that it is a base ten system (all the units are evenly divisible by 10). - Example: the radius of the Sun is 7 × 10 5 km. - How many Earths could fit across the face of the Sun?. - were one of the first written scientific discussions of sunspots.. - We can make direct observations of the solar surface and atmosphere.. - The Sun contains all of the natural elements found on Earth and in the periodic table. - The regions of the Sun are illustrated in Figure 2.1. - Table 2.2 shows some of the Sun’s physical characteristics.. - Figure 2.1 The main regions of the Sun. - The regions of the Sun’s atmosphere are defined by their density and temperature.. - Solar surface motions are due to sound waves from the interior of the Sun. - This is a lot of mass, but very little compared with the total mass of the Sun. - These measurements have helped confirm our understanding of the processes in the core of the Sun.. - The visible surface of the Sun – the photosphere (photo from the Greek for “light. - Galileo first systematically observed the visible surface of the Sun in about 1609. - Figure 2.2 High resolution image of the photosphere showing a sunspot. - The density of the plasma (and hence the amount of light emitted) drops rapidly with height in the chromosphere. - The actual frequency of the spectral lines depends on the strength of the magnetic field. - This is called the Zeeman effect and allows the remote sensing of the strength of the Sun’s magnetic field.. - All the sunspot pairs in a given hemisphere of the Sun have the same magnetic configuration. - This ordering of the solar field is due to the differential rotation of the Sun. - The next chapter describes the outer atmosphere of the Sun – the solar corona and solar wind. - We live in the outer atmosphere of the Sun.. - Figure 2.7 The. - Figure 2.7 shows the frequency and wavelength of the entire EM spectrum.. - v s is the speed of the source. - v o is the speed of the observer. - and v is the speed of the waves. - The amount of energy depends on the frequency of the radiation. - The amount and frequency of the radiation depends on the object’s temperature. - Space scientists know the surface temperature of the Sun because of this. - What fraction of the Sun’s total mass is lost each year to this process?. - 2.7 What is the thermal pressure of the gas at the surface of the Sun?. - The Sun is 400 times the size of the Moon. - The first use of the term heliosphere in the scientific literature.. - Bierman used this observation to predict the existence of the solar wind that continuously blows away from the Sun.. - Its spatial structure, with more emission (and hence plasma) near the equator than the poles, is due to the structure of the Sun’s magnetic field. - The part of the Sun’s magnetic field that is pulled out into the helio- sphere by the solar wind is called the interplanetary magnetic field (IMF). - Figure 3.2 Because of the Sun’s rotation, its magnetic field is wrapped into an Archimedian spiral. - Because of the structure of the Sun’s magnetic field (as revealed in the eclipse picture, Plate 3), the solar wind streams away from the Sun at different velocities. - Figure 3.3 shows the structure of the IMF in three dimensions. - The surface shown is the location of the plasma that came from the Sun’s magnetic equator. - Table 3.1 gives some properties of the solar wind and the IMF.. - The motion and structure of the Sun’s magnetic field make the corona ever changing. - The sound speed of the solar wind is approximately 40 km s − 1 . - This is analogous to the magnetopause that separates Earth’s magnetic field from the magnetized plasma of the shocked solar wind.. - Now consider a person walking south to the back of the train (the velocity of the train and the velocity of the person on the train are in opposite directions).. - In the solar ecliptic reference frame, the motion of the solar wind is radially outward from the Sun.. - Near the surface of Earth, the magnitude of the gravitational acceleration is 9.8 m s − 2 . - 3.3 The Parker spiral of the IMF depends on the speed of the solar wind. - For a 400 km s − 1 solar wind, what is the angle of the IMF with respect to the Sun–Earth line?. - 3.4 Which parameters determine the shape and size of the heliosphere?. - The connection of the magnetosphere with the Sun is at the heart of space weather.. - the spacing between the lines represents the strength of the field. - 4.4 Structure of the inner magnetosphere. - Figure 4.2 shows a cross section of the magnetosphere in the noon–. - The regions of the magnetosphere are labeled. - In the densest region of the magnetosphere – the plasmasphere – densities are billions and billions of times lower.. - Note the dipole shape of the inner magnetosphere. - 4.4 Structure of the inner magnetosphere 53. - 4.5 Interaction of the solar wind and magnetosphere. - The magnetopause is the boundary of the magnetosphere. - This figure shows an idealized magnetopause with the southward magnetic field of the solar wind (line 1 ) brought up against the northward-directed magnetic field of Earth (line 1). - moves away from the Sun with the rest of the solar wind, the field line gets swept back behind Earth. - Figure 4.5 The projection of the magnetic field lines shown in Figure 4.4 onto the ionosphere. - observed in the ionosphere, is the main dynamics of the ionosphere in the polar cap. - 4.9 Dynamics of the magnetosphere. - This changes both the motion of particles and the location of the plasmapause. - 4.9 Dynamics of the magnetosphere 59. - 4.9 Dynamics of the magnetosphere 61. - direction of the magnetic field, and your thumb points in the direction of the force (for negative charges this is in the opposite direction).. - 4.6 Estimate the location of the magnetopause at the subsolar point (a point directly between the Sun and Earth). - Earth’s mass exerts a force on the mass of the atmosphere attempting to pull it down to the surface.. - The densest region of the ionosphere (and actually the entire mag- netosphere) is the F region. - Figure 5.1 shows schematically the vertical structure of the iono- sphere. - This gives rise to a solar cycle variation in the intensity of ionization of the ionosphere. - 5.2 The temperature of the thermosphere can reach 2000 K. - The orbit depends on the purpose of the satellite. - “brains” of the satellite. - Space weather storms modify the density distribution of the iono- sphere. - having Earth (and hence mankind) at the center of the Universe. - The third law states that the period of the orbit (time it takes the planet to go around the Sun once) is proportional to the distance the planet is away from the Sun. - 6.7 Where is the center of mass of the Earth–Moon system? (m Earth kg. - The auroral oval is visible at the center of the image (from IMAGE Mission, courtesy of Bill Sandel).. - This dramatically changes the chemical reactivity of the atom. - The direct cause of this cancer is UV damage to the largest organ of the human body – the skin.. - Length contraction only occurs in the direction of the relative motion. - One of the tools of science is estimation. - continental shelf off the coast of the US. - Kinetic energy is proportional to the mass of the object (the more mass a moving object has, the more kinetic energy it has) and the square of its velocity (the faster an object is moving, the more kinetic energy it contains). - 8.1 Some recent studies suggest that the strength of the solar magnetic field is increasing. - The development of the auroral substorm. - Magnetic fractal dimensionality of the surface discharge under strong magnetic fields. - Motions in the magnetosphere of the Earth. - The paradox of the Sun’s hot corona.. - Discovery of the Magnetosphere, volume 7 of History of Geophysics