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Accepted: 2007-07-31, 資料番号: SA1000145000

Since the pioneering observation of Shelley et al. shortly before the first Yosemite space physics meeting, observations from several satellites and from sounding rockets and ground-based radar have contributed to shape our present view of ionospheric ion outflows and their central role in magnetosphere-ionosphere-thermosphere coupling. This view comprises of two categories of outflow populations: thermal outflows, including the polar wind and auroral bulk ion up-flow, and suprathermal ion outflows, including ion beams, ion conics, transversely accelerated ions and upwelling ions – with the former constituting an important source of low-energy plasma for the latter at higher altitudes. Both ion outflow categories are strongly influenced by the solar EUV irradiance and solar wind energy input and the state of the magnetosphere-ionosphere-thermosphere. In this talk, we will focus on the interconnection between different outflow populations and the gaps in our current knowledge on this interconnection.

Accepted: 2012-06-01, 資料番号: SA1004254000

The thermal electron temperature is an important parameter for planetary ionospheres because it drives several important processes in the photochemical region of the atmosphere. Various electron-neutral collision and ion dissociative recombination rates depend on the thermal electron temperature, which thus strongly influences the structure and composition of the ionosphere. The production of hot neutral atoms via the dissociative recombination of molecular ions (in particular O2+ to hot O) can drive atmospheric escape to space, and the thermal electron temperature is thus also important for the long term evolution of the Martian atmosphere. Multiple studies have attempted to model the thermal electron temperature profile at Mars but have been unable to match observations. A topside heat flux from the solar wind interaction with Mars is typically invoked in these models to bring modeled temperatures into agreement with observations [1, 2, 3, 4]. The similar scale size of the Martian magnetosphere with respect to the proton gyro radius in the upstream solar wind has long been posited as a facilitator for efficient wave-particle interactions between waves generated at the Martian bow shock, and charged particles in the topside ionosphere, to provide this topside heat flux [5, 6]. However, detailed observations of the relevant plasma characteristics required to investigate such wave-particle interactions in detail have been lacking at Mars, until the arrival of the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission in the fall of 2014. We present here MAVEN observations of such wave-particle interactions, driven by periodic (~ 25 s) large scale (100s km) magnetosonic waves propagating from the shock/sheath region into the Martian dayside upper ionosphere. These waves adiabatically modulate the suprathermal electron distribution function, and the induced electron temperature anisotropies drive the generation of observed electromagnetic whistler waves. The localized (in altitude) minimum in the ratio fpe / fce provides conditions favorable for the local enhancement of efficient wave-particle interactions, so that the induced whistlers act back on the suprathermal electron population to isotropize the plasma through pitch angle scattering. These wave-particle interactions break the adiabaticity of the large scale magnetosonic wave compressions, leading to local heating of the suprathermal electrons during compressive wave `troughs'. Further evidence of this heating is observed as the subsequent phase shift between the observed perpendicular-to-parallel suprathermal electron temperatures and compressive wave fronts. Full details are presented in [7]. Because the primary heat source for thermal electrons in the Martian ionosphere is heating via collisions with suprathermal electrons [8, 9], the above heating mechanism may thus play an important role in driving the enhanced thermal electron temperatures that have long been reported in the upper ionosphere of Mars. Such a heating mechanism may also be important at other unmagnetized bodies such as Venus and comets. [1] Hanson, W. B., & Mantas, G. P. (1988). Viking electron temperature measurements: Evidence for a magnetic field in the Martian ionosphere. Journal of Geophysical Research: Space Physics, 93(A7), 7538-7544. [2] Chen, R. H., Cravens, T. E., & Nagy, A. F. (1978). The Martian ionosphere in light of the Viking observations. Journal of Geophysical Research: Space Physics, 83(A8), 3871-3876. [3] Choi, Y. W., Kim, J., Min, K., Nagy, A. F., & Oyama, K. I. (1998). Effect of the magnetic field on the energetics of Mars ionosphere. Geophysical research letters, 25(14), 2753-2756. [4] Cui, J., Galand, M., Zhang, S. J., Vigren, E., & Zou, H. (2015). The electron thermal structure in the dayside Martian ionosphere implied by the MGS radio occultation data. Journal of Geophysical Research: Planets, 120(2), 278-286. [5] Moses, S. L., Coroniti, F. V., & Scarf, F. L. (1988). Expectations for the microphysics of the Mars‐solar wind interaction. Geophysical Research Letters, 15(5), 429-432. [6] Ergun, R. E., Andersson, L., Peterson, W. K., Brain, D., Delory, G. T., Mitchell, D. L., ... & Yau, A. W. (2006). Role of plasma waves in Mars' atmospheric loss. Geophysical research letters, 33(14). [7] Fowler, C. M., Agapitov, O. V., Xu, S., Mitchell, D. L., Andersson, L., Artemyev, A., ... & Mazelle, C. (2020). Localized Heating of the Martian Topside Ionosphere Through the Combined Effects of Magnetic Pumping by Large‐Scale Magnetosonic Waves and Pitch Angle Diffusion by Whistler Waves. Geophysical Research Letters, 47(5), e2019GL086408. [8] Fox, J. L., & Dalgarno, A. (1981). Ionization, luminosity, and heating of the upper atmosphere of Venus. Journal of Geophysical Research: Space Physics, 86(A2), 629-639. [9] Torr, M. R., Richards, P. G., & Torr, D. G. (1980). A new determination of the ultraviolet heating efficiency of the thermosphere. Journal of Geophysical Research: Space Physics, 85(A12), 6819-6826.

Using one dimensional Quantum hydrodynamic (QHD) model Korteweg de Vries (KdV) solitary excitations of electron-acoustic waves (EAWs) have been examined in twoelectron- populated relativistically degenerate super dense plasma. It is found that relativistic degeneracy parameter influences the conditions of formation and properties of solitary structures., {"references":["Ang, L. K., Zhang, P., Phys. Rev. Lett. 98, 164802 (2007).","Armstrong, R. J., Weber, W. J., Trulsen, J., Phys. Lett., 74A, 319-322\n(1979).","Bains, A. Singh, Tribeche, M. and Gill,T.S. Phys. Lett.A 375, 2059\n(2011).","Barnes, W. L., Dereux, A. and Ebbesen, T. W. Nature (London) 424,\n824 (2003).","Bhowmik, C., Misra, A.P. and P.K.Shukla, Phys. Plasmas, 14, 122107\n(2007).","Cattell, C. A., Dombeck , J., Wygant , J. R., Hudson , M. K., Mozer , F.\nS., Temerin , M. A., Peterson , W. K., Kletzing, C. A., Russell , C. T.,\nPfaff , R. F, Geophys. Res. Lett. 26, 425 (1999).","Cattell, C.A., Neiman, C., Dombeck, J., Crumley, J., Wygant, J.,\nKletzing, C. A., Peterson, W.K., Mozer , F. S., and André, M.,\nNonlinear Processes Geophys. 10, 13 (2003).","Defler, H., Simonen, T.C., Phys. Fluids, 12 p. 260 (1969).","Delory, G. T., Ergun, R. E., Carlson, C. W., Muschietti, L., Chaston, C.\nC., Peria, W., McFadden, J. P. and Strangeway. R., Geophys. Res. Lett,\nVol. 25, No. 12, p. 2069-2072, (1998).\n[10] Ditmire, T. , Springate, E., Tisch, J. W. G., Shao, Y. L., Mason, M. B.,\nHay, N., Marangos, J. P. and Hutchinson, M. H. R., Phys. Rev. A 57,\n369 (1998).\n[11] Ergun, R. E., Carlson, C. W., McFadden J. P., Mozer, F. S.,Delory, G.T.,\nPeria, W., Chaston, C. C., Temerin, M., Elphic, R., Strangeway, R.,\nPfaff, R., Cattell, C. A., Klumpar, D., Shelley, E., Peterson, W.,\nMoebius, E. and Kistler, L. Geophys. Res. Lett., 25, 2061, (1998).\n[12] Ergun, R. E., Carlson, C. W., McFadden, J. P., Mozer, F. S., Delory, G.\nT., Peria, W., Chaston, C. C., Temerin, M., Roth, I., Muschietti, L.,\nElphic, R., Strangeway, R., Pfaff, R., Cattell, C. A., Klumpar, D.,\nShelley, E., Peterson, W., Moebius, E. and Kistler, L. Geophys. Res.\nLett; 25 2041 (1998).\n[13] Feldman, W. C., Anderson, R. C., Bame, S. J., Gary, S. P. Gosling, J. T,\nMcComas, D. J., Thomsen, M. F., Paschmann, G. and Hoppe, M. M.;\nJ. Geophys. Res. 88, 96, (1983a).\n[14] Feldman, W. C., Anderson, R. C., Bame, S. J., Gosling, J. T., Zwickl,\nR. D.; J. Geophys. Res. 88, 9949 (1983b)\n[15] Feldman, W. C., Asbridge, J. R., Montgomery, M. D. and Gary, S. P.; J.\nGeophys. Res. 80, 4181, (1975)\n[16] Franz, J. R., Kintner, P.M., Pickett, J. S., Geophys. Res. Lett Vol. 25,\nNo. 8, p 1277-1280, (1998)\n[17] Henry, D. and Trguier, J.P. J. Plasma Phys., 8, p. 311 (1972).\n[18] Kadomtsev, B. B. and Pogutse, O. P.: Nucl. Fusion 11, 67 (1971).\n[19] Chandrasekhar, S. \"An Introduction to the Study of Stellar Structure\"\nThe University of Chicago Press, Chicago. p. 360-362 (1939).\n[20] Bharuthram. R., Yu. M.Y. Astrophysics and Space Sciences, 207, 197\n(1993).\n[21] F.Hass, L.G.Garcia, J.Goedert, G.Manfredi, Phys. Plasmas, 10, 3858\n(2003).\n[22] P. K. Shukla, J. Plasma Phys. 74, 107 (2008).\n[23] L.S. Stenflo, P.K. Shukla and M. Marklund, Europhys. Lett.74(5), 844\n(2006).\n[24] C.L. Gardner and C. Ringhofer, Phys. Rev E 53,157 (1996).\n[25] S. A. Khan and A. Mushtaq, Phys. Plasmas 14, 083703 (2007).\n[26] Misra, A. P., Shukla, P. K., Bhowmik, C., Phys. Plasmas, 14, 082309\n(2007).\n[27] Sah, O. P., Manta, J., Phys. Plasmas 16, 032304, (2009).\n[28] P. K. Shukla and B. Eliasson, Phys. Rev. Lett. 96, 245001 (2006).\n[29] B. Sahu and R. Roychoudhury, Phys. Plasmas 13, 072302 (2006).\n[30] S. Ali and P. K. Shukla, Phys. Plasmas 13, 022313 (2006).\n[31] P. K. Shukla and S. Ali, Phys. Plasmas 12, 114502 (2005).\n[32] S. A. Khan and A. Mushtaq, Phys. Plasmas 14, 083703 (2007).\n[33] G. Manfredi, Fields Inst. Commun. 46, 263 (2005).\n[34] B.Ghosh, S.Chandra and S.N.Paul., Phys. Plasmas, 18, 012106 (2011).\n[35] B.Ghosh, S.Chandra and S.N.Paul, Pramana-J.Phys. 78 (5) 779 (2012).\n[36] S.Chandra, S.N Paul and B.Ghosh, Ind. J. Pure and Appl.Phys. 50(5)\n314-319 (2012).\n[37] S.Chandra, S.N Paul and B.Ghosh, Astro .Phys. and Space Sci. 342,\n417-424, (2012).\n[38] Swarniv Chandra, and Basudev Ghosh, (Astro .Phys. and Space Sci.\nDOI: 10.1007/s10509-012-1186-3 (2012).\n[39] Swarniv Chandra and Basudev Ghosh WASET, 70, 206, (2012).\n[40] Swarniv Chandra and Basudev Ghosh IJERD. Vol 3, Issue 1, p-51\n(2012).\n[41] Swarniv Chandra and Basudev Ghosh, WASET, Vol 71, 134 (2012)."]}

In order to find the particular interaction energy between cylcloguanil and the amino acids surrounding the pocket of wild type and quadruple mutant type PfDHFR enzymes, the MP2 method with basis set 6-31G(d,p) level of calculations was performed. The obtained interaction energies found that Asp54 has the strongest interaction energy to both wild type and mutant type of - 12.439 and -11.250 kcal/mol, respectively and three amino acids; Asp54, Ile164 and Ile14 formed the H-bonding with cycloguanil drug. Importantly, the mutation at Ser108Asn was the key important of cycloguanil resistant with showing repulsive interaction energy., {"references":["P. L. Olliaro, and Y. Yuthavong, \"An overview of chemotherapeutic\ntargets for antimalarial drug discovery,\" Pharmacol. Ther., vol. 81, pp.\n91-110, 1999.","Y. Yuthavong, S. Kamchonwongpaisan, U. Leartsakulpanich and P.\nChitnumsub, \"Folate Metabolism as a Source of Molecular Targets for\nAntimalarials,\" Future Microb. vol. 1, no.1, pp. 113-125, 2006.","A. Nzila, \"Inhibitors of De-novo Folate Enzymes in Plasmodium\nfalciparum,\" Drug Discov. Today, vol. 11, pp. 936-944, 2006.","K.Militello, M. Dodge, L. Bethke and D. F. Wirth, \"Identification of\nregulatory elements in the Plasmodium falciparum genome,\" Mol.\nBiochem. Parasitol, vol. 134, pp. 75-88, 2004.","T. Dasgupta, and K. S. Anderson, \"Probing the Role of Parasite-\nSpecific, Distant Structural Regions on Communication and Catalysis in\nthe Bifunctional Thymidylate Synthase- Dihydrofolate Reductase from\nPlasmodium falciparum,\" Biochemistry, vol. 47, no. 5, pp. 1336-1345,\n2008.","A. Nzila, \"The Past, Present and Future of Antifolates in the Treatment\nof Plasmodium falciparum Infection,\" J. Antimicrob Chemother, vol. 57,\npp. 1043-1054, 2006.","R.T. Delfino, O. A. Santos-Filho and J. D. Figueroa-Villar, \"Type 2\nantifolates in the chemotherapy of falciparum malaria,\" J. Braz. Chem.\nSoc. vol. 13, pp. 727-741, 2002.","Y. Yuthavong, \"Basic for antifolate action and resistance in malaria.\nMicrobes Infect,\" vol. 4, pp. 175-182, 2002.","Y. Yuthavong, J. Yuvaniyama, P. Chitnumsub, J. Vanichtanankul, S.\nChusacultanachai, B. Tarnchompoo, T. Vilaivan and S.\nKamchonwongpaisan, \"Malarial (Plasmodium falciparum) dihydrofolate\nreductase-thymidylate synthase: structural basis for antifolate resistance\nand development of effective inhibitors,\" Parasitology, vol. 130, pp.\n249-259, 2005.\n[10] L. K. Basco, P. E. Pecoulas, C. M. Wilson, J. L. Bras and A. Mazabraud,\n\"Point mutations in the dihydrofolate reductase-thymidylate synthase\ngene and pyrimethamine and cycloguanil resistance in Plasmodium\nfalciparum,\" Mol. Biochem. Parasitol, vol. 69, pp. 135-138, 1995.\n[11] D. S. Peterson, W. K. Milhous and T. E. Wellems, \"Molecular basis of\ndifferential resistance to cycloguanil and pyrimethamine in Plasmodium\nfalciparum malaria,\" Proc. Natl. Acad. Sci. U.S.A., vol. 87, pp. 3018-\n3022, 1990.\n[12] A. Gregson, and C.V. Plowe, \"Mechanisms of Resistance of Malaria\nParasites to Antifolates,\" Pharmacol. Rev. vol. 57, pp. 117-145, 2005.\n[13] I. M. Hastings, and M. J. Donnelly, \"The impact of antimalarial drug\nresistance mutations on parasite fitness, and its implications for the\nevolution of resistance,\" Drug Resist. Updat, vol. 8, pp. 43-50, 2005.\n[14] G.Rastelli, S. Sirawaraporn, P. Sompornpisut, T. Vilaivan, S.\nKamchonwongpaisan, R. Quarrell, G. Lowe, Y. Thebtaranonth and Y.\nYuthavong, \"Interaction of pyrimethamine, cycloguanil, WR99210 and\ntheir analogues with Plasmodium falciparum dihydrofolate reductase:\nstructural basis of antifolate resistance,\" Bioorg. Med. Chem. vol. 8, pp.\n1117-1128, 2000.\n[15] W. Sirawaraporn, T. Sathitkul, R. Sirawaraporn, Y. Yuthavong and\nD.V. Santi, \"Antifolate-resistant mutants of plasmodium falciparum\ndihydrofolate reductase,\" Proc. Natl. Acad. Sci. vol. 94, pp. 1124-1129,\n1997.\n[16] J. Yuvaniyama, P. Chitnumsub, S. Kamchonwongpaisan, J.\nVanichtanankul, S. Sirawaraporn, P. Taylor, M. D. Walkinshaw and Y.\nYuthavong, \"Insights into antifolate resistance from malarial DHFR-TS\nstructures,\" Nat. Struct. Bio,. vol. 10, pp. 357-365, 2003.\n[17] G. B. Fogel, M. Cheung, E. Pittman and D. Hecht, \"Modeling the\ninhibition of quadruple mutant Plasmodium falciparum dihydrofolate\nreductase by pyrimethamine derivatives,\" J. Comput Aided Mol Des,\nvol. 22, pp. 29-38, 2008.\n[18] S. Kamchonwongpaisan, R. Quarrell, N. Charoensetakul, R. Ponsinet, T.\nVilaivan, J. Vanichtanankul, B. Tarnchompoo, W. Sirawaraporn, G.\nLowe and Y. Yuthavong, \"Inhibitors of multiple mutants of plasmodium\nfalciparum dihydrofolate reductase and their antimalarial activities,\" J.\nMed. Chem, vol. 47, pp. 673-680, 2004.\n[19] M. D. Parenti, S. Pacchioni, A. M. Ferrari, and G. Rastelli, \"Three-\nDimensional Quantitative Structure-Activity Relationship Analysis of a\nSet of Plasmodium falciparum Dihydrofolate Reductase Inhibitors Using\na Pharmacophore Generation Approach,\" J. Med. Chem, vol. 47, pp.\n4258-4267, 2004.\n[20] P. Maitarad, P. Saparpakorn, , S. Hannongbua, S. Kamchonwongpaisan,\nB. Tarnchompoo, Y. Yuthavong, \"Particular Interaction between\nPyrimethamine Derivatives and Quadruple Mutant Type Dihydrofolate\nReductase of Plasmodium falciparum: CoMFA and Quantum Chemical\nCalculations Studies,\" J. Enzyme. Inhibition and Medicinal Chemistry,\n2008, in press."]}