# Presentation: 081195

## Space Plasmas:What They Are and Where They Come From

**The Plasmas:**
**   ****·Solar Wind**
**   ****·Magnetosheath**
**   ****·Plasma Sheet**
**   ****·Plasmasphere**
**   ****·Radiation Belts**
**   ****·Ionosphere**

**For Each Plasma:**
**  ****·Location**
**  ****·Properties**
**  ****·Space-Physics Issues**
**  ****·Plasma-Physics Research**

**Joe Borovsky**** ****ISR-1, Los Alamos National Laboratory**

## Naturally Occurring Plasmas

**1 eV  =  11,600 °K**

## Measuring Space Plasmas: Scientific Spacecraft

**Instruments:**
**     ****·plasma instrument**
**          ****measures ion and electron distribution functions one particle at a time**
**     ****·magnetometer**
**          ****measures DC magnetic field (boom)**
**     ****·energetic-particle detector**
**          ****measures ions and electrons with energies > 50 keV**
**     ****·waves instrument**
**          ****measures magnetic- and/or electric-field fluctuations in the plasma (antenna)**
**     ****·electric fields**
**          ****measures DC electric field (booms)**
**Price Tag (including launch):**** **
**     ****$100M (cheap) --- $2.4G (Cassini at Saturn)**
**Chief Sponsors:**
**     ****NASA, Air Force (USA)**
**     ****ESA  (Europe)**
**     ****IKI    (Russia)**
**     ****ISAS  (Japan)**

## Advantages for Plasma Physics

**Studying space plasmas provides unique opportunities:**
**   ****·Micro diagnostics**
**        ****spacecraft are smaller than the plasma scalesizes**
**             ****Debye lengths**
**             ****gyroradii**
**        ****unperturbing measurements**
**    ****·Slow evolution compared to measurement times**
**    ****·Collisionless plasmas**
**    ****·Large scale plasmas**
**    ****·Unique phenomena**

## 1. The Solar Wind

**Supersonic wind**
**300-600 km/sec**
**~10****6**** Tons/sec**
**~100 hours old**
**      ****(at Earth)**
**      **

**1 AU  =  1.5********10****8**** km**

## The Solar Wind Is Highly Variable

**The solar wind has variations that range from seconds to the 11-year solar cycle**
**      **

**n = 2 - 30 cm****-3**
**T****i**** = 2 - 20 eV**
**T****e**** = 5 - 30 eV**
**B = 2 - 50 nT**
****** ****= 0.1 - 2**
**96% H****+**
**4% He****++**
**      **

## The Solar-Cycle Variation ofthe Solar Wind

## The Solar Wind Varies Systematically with Distance

**... ****owing to the 1/r****2**** expansion of the plasma as it flows outward from the sun.**
**      **

## Solar-Wind Research

**Origin of the solar wind**
**Cosmic-ray transport in the solar wind**
**Dynamics and evolution of solar ejecta**

## Plasma Physics in the Solar Wind: MHD Turbulence

## 2. The Magnetosheath

**1 R****E****  =  6340 km**

## The Magnetosheath Properties Change with Location and with Time

**n = 8 - 200 cm****-3**
**T****i**** = 300 - 1100 eV**
**T****e**** = (1/6) T****i**
**B = 8 - 250 nT**
****** ****= 1 - 10**
**96% H****+**
**4% He****++**
**      **

## Magnetosheath Research

**·Physics of the collisionless bow shock**
**·Nature of magnetosheath fluctuations**
**·Solar-wind/magnetosphere coupling**
**·Boundary layers and plasma transport**

## Plasma-Physics Research in the Magnetosheath: Kinetic Instabilities

**The ions drive:**
**  ****·mirror mode waves**
**  ****·electromagnetic ion-cyclotron waves**

**The electrons drive****:**
**  ****·electron mirror waves**
**  ****·whistlers**

**The bow shock produces:**
**   ****·ring-ion distributions**
**   ****·ion temperature anisotropies**
**   ****·electron temperature anisotropies**

## 3. The Plasma Sheet

**n = 0.2 - 3 cm****-3**
**T****i**** = 5 - 15 keV**
**T****e**** = (1/6)T****i**
**B = 10 - 30 nT**
****** ****= 1-10**
**H****+**
**He****++  ****  **
**O****+**

## Plasma-Sheet Research

**Origin from the solar wind H****+**** He****++**
**Origin from the ionosphere O****+**** H****+**
**Magnetosphere-ionosphere coupling**
**     ****plasma generators**
**     ****plasma circuits**
**     ****Alfven waves**
**MHD turbulence**
**Magnetospheric substorms**
**The aurora**

## Plasma Physics in the Earth's Plasma Sheet: Reconnection

**The reconnection of magnetic fields enables the global magnetsphere to move into a lower-energy state.**

**Research focuses on the conditions that allow reconnection to proceed in the absence of collisional resistivity.**

**The reconnection of magnetic field lines enables the global magnetosphere to move into a lower-energy state.**

**Research focuses on the conditions that allow reconnection to proceed in the absence of resistivity.**

**Plasma Physics in the Earth's Plasma Sheet: Reconnection**

## 4. The Plasmasphere

**n = 10 - 2000 cm****-3**
**T****i**** = 1 - 10 eV**
**T****e**** = T****i**
**B = 100 - 2000 nT**
****** ****<< 1**
**H****+**
**He****+ ****  **
**O****+**

**The plasmasphere is a cold dense plasma in the dipolar regions near the Earth.**

## The Plasmasphere in the Recurring-Storm Cycle: ExB-Drift Orbits

**The Plasmasphere in the Recurring-Storm Cycle: ExB-Drift Orbits**

**draining**
**34 tons of protons**
**39 tons of He****+**
**77 tons of O****+**

**Space-Research Topics:**
**  ****·Dynamics of ExB flows**
**  ****·Density structures **
**  ****·Plasma waves**
**  ****·Effect on the magnetosphere**

## Plasma Physics in the Plasmasphere: Ambipolar Diffusion

**·The plasmasphere comes from the (electrical) evaporation of the ionosphere.**
**·Magnetic fields guide the particles, electric fields control the up/down motions.**
**·The charge density of five particle populations must be accounted for:**
**     ****ionospheric ions,  ionospheric electrons,  photoelectrons, plasmaspheric ions,**
**     ****plasmaspheric electrons.**

## 5. The Radiation Belts

**The radiation belts are populations of trapped energetic ions and electrons in the dipolar regions of the magnetosphere.**
**Can be long lived (decades).**
**Origins:**
**     ****Cosmic-ray-neutron decay**
**     ****Inward diffusion of particles**
**     ****In situ energization**

## Plasma-Physics in the Radiation Belts: Wave-Particle Interactions

**·The radiation belts are co-located with the dense plasmasphere and many types of plasma waves live in the plasmasphere.**
**·Owing to the wave fluctuations, radiation-belt particle orbits are slowly perturbed and belt particles are lost into the atmosphere.**

## 6. The Ionosphere

**The ionosphere is the ionized upper atmosphere.**
**The ionization comes about from (1) solar ultraviolet radiation and (2) the precipitation of energetic magnetospheric electrons and ions.**

## Plasma Physics in the Ionosphere:Electromagnetic Waves in Plasmas

**1. Powerful radio waves are broadcast upward.**
**2. The plasma frequency increases with altitude.**
**3. At the critical altitude the plasma frequency equals the radar frequency:**
**       ****strong interaction (reflection, energy absorption, plasma instabilities)**

**1. Powerful radio waves are broadcast upward.**
**2. The plasma frequency increases with altitude.**
**3. At the critical altitude the plasma frequency equals the radar frequency:**
**    ********strong interaction (reflection, energy absorption, plasma instabilities)**

**HAARP ionospheric heater in Alaska**** **