Enhanced X-ray emission above 3.5 keV in active regions in the absence of flares

We demonstrate that even in the absence of flares there are very often volumes of hot plasma in the corona above active regions with temperatures in excess of 10 million degrees. Characteristics of this hot plasma and its time variations seem to be different in active regions of different phase of development. These hot plasma regions are sources of very weak, but clearly recognizable, X-ray emission above 3.5 keV. Long-lived X-ray brightenings, 10⁴ times weaker than a flare, but lasting up to 10 hr occur predominantly along the H _∥ = 0 line, apparently low in the corona. After major flares, long-lived X-ray emission is also radiated from tops of arches extending high into the corona. Some other long-lived sources, far from the H_∥ = 0 line, may be associated with newly emerging flux. Short-lived X-ray sources, with fluxes ranging from subflare levels to 10^?3 times the flare flux, last for 2 to more than 30 min and are probably microflares. They seem to be most frequent in growing young active regions and appear often in areas with newly emerging flux.     

Proton Flare Project, 1966

The paper summarizes observations of solar and space phenomena related to the McMath region Number 8461 which passed over the solar disk during the 1966 Proton Flare Project period, from August 21 to September 4, and produced two important solar particle events on August 28 and September 2. The most important results are reviewed and interpretation of some of them is suggested.Items of particular interest: Occurrence of proton-active regions when two or more rows of activity approach each other (Section 3). Possible stimulation of activity by magnetic fields of decaying regions that had been active before (4.2a, 5.1a). Significantly increased correlation of flares with X-ray bursts during the proton-active transit of the region (5.3b). Striking difference in the flare response in radio frequency range before and after August 26 (5.2b). Hardening of the X-rays (5.3a), increase in radio flux (5.2a), change in sunspot configuration (5.1c), and increased capability of the region for particle acceleration (5.1b, 5.2b), starting about three days prior to the proton flare. Clear evidence that some flares that occurred on or after August 26, but prior to the proton flare of August 28, already were sources of 1 MeV protons (5.2b, 8). Anomalous deficiency in metric component of radio bursts produced in the region (5.2c, 9.4d, 11.4b). Strong radio storm on meter waves immediately preceding the proton flare on August 28 (5.2a, 9.1b), coincident with preflare rising dark filament (9.1a) and slight preflare rise in flux of 1 MeV protons (10.2). Two phases of expansion (fast and slow) of the bright flare ribbons (9.2c). Coincidence of hard X-ray burst with the formation and fast separation of the bright flare ribbons. It is suggested that this is the time of particle acceleration in the flare (9.5b). Short-lived burst of UV radiation (9.6). Visible flare wave in the flare of August 28 (9.3b), and complexity of motions in this flare (9.4b). Suggested electron release by means of a blast wave (10.1a). Electron-proton splitting in the delayed shock-wave-associated maximum of the particle flux on August 29 (10.2c). First brightening of both proton flares in a similar position between the regions 8461 and 8459 (11.2c). Existence of a unique, low elevation coronal condensation three days after proton flare occurrences (7.2). Very strong flux of protons in energy range of the order of 100 MeV producing the largest PCA since July 1961, and unusually steep energy spectrum above 100 MeV in the flare of September 2 (12.2a, b, 12.4). Unusually long rise to the maximum flux, inconsistent with Burlaga's theory of anisotropic diffusion (12.2b). Interpretation of the undisturbed flux decay from September 2 to September 8 (12.2c). A corotating modulation phenomenon on September 8 (12.2d). Detection of medium nuclei, with He/M ratio 50 ± 11 (12.3a). Evidence against a purely velocity-dependent mode of particle propagation (12.3b). Electrons as the possible cause of the first PCA phase (12.4). Plasma disturbance due to permanent proton flux from the region (13.1). Electron injection into inner radiation belt during the geomagnetic storm associated with the September 2 flare (13.3).Section 14 brings a time scheme of the most important phenomena associated with the complex of activity and the active region in question, and some unsolved problems of particular interest are pointed out in Section 15.     

Cooling of a coronal flare loop through radiation and conduction

A simple method is proposed for a computation of the cooling of coronal flare loops by radiation and conduction, for various temperatures, densities, and lengths of the loops. The relative importance of conductive and radiative losses is briefly discussed.     

The thermal field of the lithosphere in the region of mid-ocean ridges modelled on the basis of known surface temperature and heat flows

Summary The possibility of solving the stationary heat equation with the convective term is demonstrated in the case that the velocity field of the continuum, and the temperature and heat flow on the Earth's surface are known, and that an assumption is made about the magnitude of heat flows on another part of the boundary of the two-dimensional region being investigated, whereas no boundary condition is imposed on the remainder of the region's boundary. The problem has been solved numerically for a kinematic model of the lithosphere in the region of mid-ocean ridges, based on the assumption of a broad deflected convective flow moving at a distance of more than about 150 km from the ridge modelled as a plate.

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aaa m u maua au na mna a, ¶rt;a um n m mua u a nmu u um mnama u mn nm. a ¶rt; amuau aamua ¶rt; amu ¶rt;um n¶rt;nu uu mn nma a a ma amuau a u a¶rt;a. ma na a u m¶rt; a ¶rt; uamu ¶rt;u um amu ¶rt;u-auu m, a a n¶rt;mauu u ma mu nma a amu m ma nau 150 ¶rt;u auma nm.

     

Wave propagation in physical models of micromorphic media

Summary The propagation of seismic waves in a micromorphic body, which is supposed to be one of the possible models of the medium in the earthquake focus, is studied by means of the two-dimensional ultrasonic model technique. The results obtained indicate that such a medium is characterized by distinct elastic anisotropy and by increased attenuation. The propagation velocity of longitudinal waves decreases and their amplitudes change considerably. The prevailing frequency of the waves passing through the micromorphic medium tends smoothly to one value which depends on the space distribution, orientation and dimensions of the elements characterizing such a medium. The obtained results are confronted with the theory of a micromorphic medium.

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anmau uu u ¶rt;, n muu ¶rt; u ¶rt; ¶rt; a mu, uam nm ¶rt; ma ¶rt;uau. mam naam, m maa ¶rt;a muam n aumnu u n nu. m anmau n¶rt;u n¶rt; nuam, u anum¶rt; m. a¶rt;aa amma , n¶rt;u u ¶rt;, na mum ¶rt; uu, ma aa nmam an¶rt;u, anam u aau ¶rt;m, n¶rt;u m ¶rt;. mam auam mu u ¶rt;.

     

Precession-nutation torque in terms of the stokes constants

um nu-mau m nuuau u auumu m nm ma u. m mu u¶rt;uu¶rt;a m ma nuua u uu.     

Theoretical estimation of the earth's and moon's tidal decelerations

Summary On the basis of the conservation of the Earth-Moon angular momentum, the period of the Earth's resonance rotation and Moon's revolution and the relation between tidal deceleration of the Earth's rotation and of the Moon's mean motion are derived theoretically. The comparison of the theoretical relation with the observed values indicates that a mechanism should exist which decreases the maximum principal moment of the Earth's inertia bydC/dt=–3.2×10²⁹ kg· . m² cy^–1.

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¶rt; u au ma uma ¶rt;uu um -a, ¶rt;am mmuu ¶rt; a nu¶rt;a au u u uma ¶rt;uu u mu nuu u mu au u u ¶rt; ¶rt;uu . aua mmu mu a¶rt;au auu, ¶rt;am au, m ¶rt; um m u aua ma uuu udC/dt=–3,2×10^{29 2} (mmu)^–1.

     

Statistical aspects of eliminating systematic effects

Summary A procedure for processing measurements subject to systematic effects is derived such that it ensures their optimum elimination in the results of the processing. It is proved that no other method of eliminating systematic effects yields better results.

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u¶rt; m¶rt; amu ¶rt;u umamuuu uuaamuu u nmua uuau mama. aa m uau ¶rt;u m¶rt; uuauu umamuu uu num u mam.

     

Do some shallow earthquakes have a tensile source component?

The laboratory tests carried out in studying shear and tensile seismogenic displacements occurring in compressed samples, led us to search for earthquakes with a tensile source component. To determine this component in the seismic focus, a special procedure based on the construction of radiation patterns of the combined shear-tensile type is introduced.The criteria for selecting the events produced by the combined source mechanism are listed, and their limitations are mentioned. From the seismic zones with good azimuthal distribution of stations in the world seismic network nine earthquakes which occurred in the 6-year period 1976–1981 were analyzed; for these events better agreement of the observed and theoretical patterns was found for the combined shear-tensile source mechanism than for the pure double-couple mechanism. However, the share of the tensile component was always, found to be relatively small, ranging from 1 to 13 percent of the shear component. The comparison of the two solutions (double-couple vs. combined shear/tensile) is based on the first onset signs statistics.The results obtained indicate that tensile fracturing does not play a substantial role in the total amount of released seismic energy; on the orther hand, it is expected to be more important in the creation and development of focal zone morphology from both the instantaneous and long-term point of view.