85 511 Solar Terrestrial Relations Cravens Physics of

85. 511 Solar Terrestrial Relations (Cravens, Physics of Solar Systems Plasmas, Cambridge U. P. ) • Lecture 1 - Space Environment – Matter in Universe: 99. 9% plasma – Plasma everywhere • • Solar Atmosphere Interplanetary Medium Planetary Magnetospheres Planetary Ionospheres reinisch_85. 511 1

Space Environment • Plasma = + and – charged particles (ions, electrons) and neutral particles • Forces on charges particles – Electric force – Magnetic force – Lorentz force – Neutral forces FE = q. E FB = qvx. B F = q. E + qvx. B mg, reinisch_85. 511 2

Space Environment cont’d • Solar wind • Interplanetary magnetic field (IMF) – Tsyganenko model • Magnetosphere – Dipole field? ? reinisch_85. 511 3

Interplanetary Space and Magnetosphere • Solar Wind. The SW is a collisionless supersonic (VSW > VS) plasma that carries its own (solar) magnetic field with it. The Earth’s magnetic field presents a “hard” obstacle to the SW. The SW drapes around this obstacle forming a magnetic cavity that is shaped like a comet head and tail. Bow Shock. The bow shock is formed at x 12 RE sunward where p. SW = p. B. The SW decelerates at the bow shock becoming subsonic, but further downwind becomes supersonic again. Magnetosheath (note: Dr. Song is one of the world’s experts). Downwind from bow shock, the magnetosheath contains decelerated SW plasma. Some of this plasma fuses into the magnetosphere further along the tail. Magnetopause. Encloses the magnetosphere “shielding” it from the SW. Geocentric distance ~10 RE. Large current systems on the front (head) and the tail. Ne 50 cm-3. Magnetosphere. • • – Cusp, Plasmasphere, Ionosphere. reinisch_85. 511 4

Earth’s Magnetosphere 1. 2. 3. 4. Magnetosphere. Volume inside magnetopause. Geomagnetic forces dominate the motion of charged particles. Plasma originates from SW and the Earth’s ionosphere. SW enters in the polar cusp and along the tail. Cusp (Cleft). SW entry point on the dayside. At ionospheric heights (300 km) it occupies a narrow latitudinal band near noon. Plasma Sheet. Low density plasma originating in SW and ionosphere. But particles have much higher energy. Plasma flows into Earth’s atmosphere and forms the auroral ovals (borealis and australis). Neutral Current Sheet. It is the separation between the earthward B-lines above (north) and the fieldline pointing away from the Earth below (south). Adawn-to-dusk current flows along the neutral current sheet, thus maintaining the oppositely directed magnetic fields (required/explained by Maxwell’s equations). At the “end” of the geomagnetic tail, the B-lines connect to the solar inter planetary magnetic field (IMF). This magnetic “reconnections” creates a voltage drop of ~100 k. V creating currents of > 10 million amps. The potential drop projects down ionospheric heights creating a 100 k. V voltage drop across the polar cap defining the dawn to dusk polar cap electric field. reinisch_85. 511 5

Earth’s Magnetosphere cont’d 1. 2. 3. Van Allen Radiation Belts. Energetic particles near the plasma sheet center flowing earthward get trapped in closed magnetic field lines forming the radiation belts. The trapped particles spiral along the closed magnetic field lines, bouncing back and forth between the northern and southern hemisphere. Electrons and protons (and some O ions from the ionosphere) in the frequency range 10 -300 ke. V also have an azimuthal drift: electrons eastward, ions westward. This forms a current, the ring current. Plasmasphere. A relatively high density plasma region closer to Earth, < 4 RE geocentric. Ne > 100 cm -3. Decrease in density at the “Carpenter knee”, I. e. , the plasmapause (F. 2. 12). The plasmasphere rotates with the Earth. reinisch_85. 511 Ionosphere. Earth’s atmosphere ionized by solar UV 6

NASA reinisch_85. 511 7 Sw. RI

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IMAGE Spacecraft reinisch_85. 511 10

25 March 2000 Vandenburg AFB Delta II Rocket reinisch_85. 511 11

Empirical Magnetospheric Density Distribution Average 2000 -2001 L=7 6 5 March 2001 1200 LT June 2001 0800 LT reinisch_85. 511 12

2. 4 -5 The Sun’s Planets The Planets’ Magnetospheres Mercury Venus (negligible, bow shock forms at ionopause) Earth Mars (very weak) Jupiter Saturn Uranus Neptune reinisch_85. 511 13

Plasma and Neutral Parameters Ne – electron density Te, i, n –electron/ion/neutral temperature Nn – neutral density D – Debye length N D – number of particles in Debye sphere p – 2 x plasma frequency c – 2 x cyclotron (gyro) frequency rgyroradius reinisch_85. 511 14

Ch 2 - Kinetic Theory reinisch_85. 511 15

Particle Distribution Function reinisch_85. 511 16

Density Function ns reinisch_85. 511 17

2. 1. 2 The Boltzmann Equation reinisch_85. 511 18

Total Derivative in Phase Space reinisch_85. 511 19

Examples of Distribution Functions reinisch_85. 511 20