In this paper the generation of electrostatic wake field and electron acceleration in this field by intense laser pulse propagating in plasma in the presence of external magnetic field is investigated. It is shown that if the change in the laser pulse wave amplitude (approximation of the constant laser pulse wave field) is not taken into account, it is possible by switching to Lagrangian variables to reduce the system of equations describing excitation of the wake field and electron acceleration to a simplified system of ordinary differential equations (ODE), which can be easily integrated. This makes it possible to find the energy, transferred to electron oscillations in the wake field for different angles between the direction of laser pulse propagation and magnetic field. Stability of the laser pulse propagating with arbitrary angle to external magnetic field towards excitation of parametric and decay instabilities with involvement of upper hybrid and lower hybrid waves is investigated, as well. Equations describing these instabilities are derived and growth rates are found analytically for a small amplitude wake field and with the help of numerical calculations in the case of the finite wake field amplitude.

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The monotonic and oscillating parts of the magnetoresistance tensor components are studied on a pure single crystals of bismuth. The nondiagonal-to-diagonal components ratio is shown to be sufficiently small a t helium tcmperatures, so that ozz = l/ezz with a high degree of accuracy, and thus the experimental deviations from the law ezz = aHn (m = 2 for u,t > 1) are independent of the electron-hole compensation disturbance in Bi.Within the framework of the ellipsoidal parabolic model taking account of the relaxation time anisotropy, the mobility tensor components at helium temperatures are found whose values coincide with data obtained by other authors in weak (uC.< 1) magnetic fields. It has been revealed that for magnetic field directions H near twinning planes the sign of an even constituent of the nondiagonal magnetoresistance tensor components becomes opposite t o t h a t for samples with no twinning interlayer. The twinning plane effect is essential up to 70 OK. It is also found that a t helium temperatures the even constituent eyz(H) changes its sign in high magnetic fields (10 kOe) near H 11 C,. It is shown that the transition in the H 11 C, direction under H rotation in the bisectrix plane causes the oscillation phase of the even constituent evz t o change. It is found that in the preultraquantum region of the magnetic fields the oscillating part of eyD turns out to be greater at certain H directions than the monotonic one.Die monotonen und oszillierenden Anteile der Tensorkomponenten der Magnetowiderstandsanderung werden an einem reinen Wismuth-Einkristall untersucht. Es wird gezeigt, daB das Verhaltnis der nichtdiagonalen zu den diagonalen Komponenten bei Heliumtemperaturen genugend klein ist, so daB ozD = l/ezz mit hoher Genauigkeit ist und somit sind die experimentellen Abweichungen vom Gesetz ezz = nHn ( n = 2 fur uCt 3 1) unabhangig von der Storung der Elektronen-Loch-Kompensation in Bi. I m Rahmen des parabolischen Ellipsoidmodells bei Berucksichtigung der Anisotropie der Relaxationszeit werden die Komponenten des Beweglichkeitstensors bei Heliumtemperatur gefunden, deren Werte mit den Werten anderer Autoren in schwachen Magnetfeldern (uCt < 1) ubereinstimmen.Es wird gefunden, daB fur Magnetfeldrichtungen H in der Nahe von Zwillingsebenen das Vorzeichen eines geraden Bestandteils einer nichtdiagonalen Tensorkomponente der Magnetowiderstandsanderung umgekehrt wird im Vergleich zu Proben ohne Zwillingszwischenflachen. Der EinfluB der Zwillingsebenen ist bis zu 70 O K wesentlich. Es wird auch gefunden, daB bei Heliumtemperaturen der gerade Bestandteil eyD(H) sein Vorzeichen in hohen Magnetfeldern (10 KOe) bei H 11 C, andert. Es wird gezeigt, daB der tfbergang in die H I I C,-Richtung bei H-Rotation in der Bisectrixebene eine Anderung der Schwingungsphase des geraden Bestandteils ell% verursacht. I m Pre-Ultraquantenbereich der Magnetfelder wird gefunden, daB der oszillierende Anteil von evZ bei bestimmten H-Richtungen groBer als der monotone Anteil ist.

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