57 research outputs found
Direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes in both hemispheres
We present the first and direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes (PMWE) simultaneously observed by the conjugate observation with Arase satellite and highâpower atmospheric radars in both hemispheres, namely, the Program of the Antarctic Syowa Mesosphere, Stratosphere, and Troposphere/Incoherent Scatter Radar (PANSY) at Syowa Station (SYO; â69.00°S, 39.58°E), Antarctica, and the Middle Atmosphere Alomar Radar System (MAARSY) at AndĂžya (AND; 69.30°N, 16.04°E), Norway. The PMWE were observed during 03â07 UT on March 21, 2017, just after the arrival of corotating interaction region (CIR) in front of highâspeed solar wind stream. An isolated substorm occurred at 04 UT during this interval. Electromagnetic ion cyclotron (EMIC) waves and whistlerâmode chorus waves were simultaneously observed near the magnetic equator and showed similar temporal variations to that of the PMWE. These results indicate that chorus waves as well as EMIC waves are drivers of precipitation of energetic electrons, including relativistic electrons, which make PMWE detectable at 55â80 km altitude. Cosmic noise absorption (CNA) measured with a 38.2âMHz imaging riometer and lowâaltitude echoes at 55â70 km measured with an MF radar at SYO also support the relativistic electron precipitation. We suggest a possible scenario in which the various phenomena observed in nearâEarth space, such as magnetospheric plasma waves (EMIC waves and chorus waves), pulsating auroras, CNA, and PMWE, can be explained by the interaction between the highâspeed solar wind containing CIRs and the magnetosphere
Coherent nonlinear scattering of energetic electrons in the process of whistler mode chorus generation
Cyclotron resonant wave-particle interaction of whistler mode chorus emissions drives pitch angle scatterings of a wide range of energetic electrons in the magnetosphere. We study a coherent scattering process associated with generation of the whistler mode rising chorus emissions near the geomagnetic equator in a self-consistent electromagnetic full-particle simulation. The simulation shows that coherent whistler mode rising chorus emissions scatter energetic electrons very effectively through formation of an electromagnetic electron hole. The nonlinear interaction induces acceleration of resonant electrons trapped by the wave and deceleration of untrapped resonant electrons. When the frequency of a rising chorus element continuously increases in time from lower frequencies to higher frequencies, the parallel resonant velocity continuously decreases toward lower-velocity ranges resulting in significant scattering of resonant electrons. The lower limit of resonant parallel velocity is determined by the upper frequency limit of the rising chorus element. The unscattered electrons with low parallel velocities and the accelerated resonant electrons trapped by the wave result in the distribution clearly peaked at 90°. Successive generation of rising chorus elements can scatter resonant electrons in the same resonance velocity range. The repeated scatterings make the distribution much sharper at 90°, leading to formation of a pancake distribution function as observed in the inner magnetosphere
Thermodynamic studies of interactions of calf spleen PNP with acyclic phosphonate inhibitors
The Gibbs binding energy and entropy/enthalpy contributions to the interaction of calf spleen purine nucleoside phosphorylase (PNP) with the novel multisubstrate analogue DFPP-DG, as well as with DFPP-G and (S)-PMP-DAP were determined by fluorescence and calorimetric studies. Results were compared with findings for guanine - a natural reaction product and inhibitor
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