X-Ray Emission of Auroral Electrons and Magnetospheric Dynamics

The experimental study of magnetospheric processes consists of several disci plines or methods, developing in two general directions. The first, internal trend covers the progress in experimental techniques and methods and re search specific to this discipline. The other trend combines with other methods in a mutual attempt at understanding the boiling whirlpool of the disturbed magnetosphere. Investigations of auroral X-rays began after Van Allen's (1957) discovery of hard radiation in the upper atmosphere of the auroral zone, and are based on high latitude balloon observations. Scientific apparatus, payload equip ment, and particular questions of scientific ballooning are discussed in Chap ter 1. Chapter 2 concludes the internal trend of the subject by describing the problems of X-ray generation at the boundary of the atmosphere and propa gation downward to balloon altitudes. Auroral X-rays are closely related to most of the processes of the disturbed magnetosphere through energetic auroral electrons; precipitating into the at mosphere, the latter create bremsstrahlung photons able to penetrate to an at mospheric depth of 10- 20 g cm - 2. In quiet periods auroral electron flux ex ists only in embryo, as a hot plasma layer at the inner edge of the plasma sheet: in general it is a transient phenomenon caused by magnetospheric distur bances and carrying valuable information of the magnetospheric dynamics.

Inhalt
1 Balloon Experiment Technique.- 1.1 Launching Facilities.- 1.2 The Balloon in Space Research.- 1.3 Auroral X-Ray Scintillator Spectrometer.- 1.4 Payload Equipment.- 1.5 Ground-Based Support of Balloon Experiments.- 2 Auroral X-Rays: Generation and Transfer into the Atmosphere.- 2.1 Introduction.- 2.2 Photon Generation at the Atmospheric Boundary.- 2.3 Calculation of X-Ray Propagation in the Atmosphere.- 2.4 Transformation of X-Ray Flux and Energy Spectrum in the Atmosphere for Extended Regions of Precipitation.- 2.5 Results of Calculation of Photon Transport from Local Sources.- 2.6 X-Ray Angular Distribution.- 2.7 Calculation of Scintillator Spectrometer Efficiency.- 2.8 Practical Example of Electron Spectra Reconstruction.- 2.9 Conclusions and Recommendations.- 3 The Structure of Auroral X-Ray Events and Electron Fluxes in the Magnetosphere.- 3.1 General Features of X-Ray Events.- 3.2 Classification of Auroral X-Ray Forms.- 3.3 Charged Particles in the Magnetosphere.- 3.4 Auroral Radiation.- 4 Auroral Electrons in the Midnight Sector and Magnetospheric Disturbances.- 4.1 Dynamic and Energetic Structure of the Magnetospheric Substorm.- 4.2 Growth Phase.- 4.3 Breakup An Explosive Onset in the Active Phase of a Substorm.- 4.4 Active Phase. Convection.- 4.5 Active Phase. Expansion.- 4.6 Auroral Region Model of Electron Acceleration and Precipitation During Substorms.- 5 Pulsations and Microbursts of Drifting Auroral Electron Precipitation.- 5.1 Morning Bay-Like Precipitations.- 5.2 Long-Period X-Ray Pulsations (120 min).- 5.3 Fast Pulsations and Impulses (360 s).- 5.4 Auroral X-Ray Microbursts.- 5.5 Precipitations During SC and SI.- 5.6 Interrelation of Pulsating Structures of Precipitating Auroral Electrons.- 5.7 Classification of the Microstructure ofElectron Precipitation.- Conclusion.- References.- Subjectlndex.