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3,536 results on '"Sergeev, V."'

8. Energetic electron precipitation driven by electromagnetic ion cyclotron waves from ELFIN's low altitude perspective

Author

Angelopoulos, V., Zhang, X. -J., Artemyev, A. V., Mourenas, D., Tsai, E., Wilkins, C., Runov, A., Liu, J., Turner, D. L., Li, W., Khurana, K., Wirz, R. E., Sergeev, V. A., Meng, X., Wu, J., Hartinger, M. D., Raita, T., Shen, Y., An, X., Shi, X., Bashir, M. F., Shen, X., Gan, L., Qin, M., Capannolo, L., Ma, Q., Russell, C. L., Masongsong, E. V., Caron, R., He, I., Iglesias, L., Jha, S., King, J., Kumar, S., Le, K., Mao, J., McDermott, A., Nguyen, K., Norris, A., Palla, A., Roosnovo, Tam, J., Xie, E., Yap, R. C., Ye, S., Young, C., Adair, L. A., Shaffer, C., Chung, M., Cruce, P., Lawson, M., Leneman, D., Allen, M., Anderson, M., Arreola-Zamora, M., Artinger, J., Asher, J., Branchevsky, D., Cliffe, M., Colton, K., Costello, C., Depe, D., Domae, B. W., Eldin, S., Fitzgibbon, L., Flemming, A., Frederick, D. M., Gilbert, A., Hesford, B., Krieger, R., Lian, K., McKinney, E., Miller, J. P., Pedersen, C., Qu, Z., Rozario, R., Rubly, M., Seaton, R., Subramanian, A., Sundin, S. R., Tan, A., Thomlinson, D., Turner, W., Wing, G., Wong, C., and Zarifian, A.

Subjects
Physics - Space Physics, Physics - Plasma Physics
Abstract

We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data from the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at 0.5 MeV which are abrupt (bursty) with significant substructure (occasionally down to sub-second timescale). Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Using two years of ELFIN data, we assemble a statistical database of 50 events of strong EMIC wave-driven precipitation. Most reside at L=5-7 at dusk, while a smaller subset exists at L=8-12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an L-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio's spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven 1MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to 200-300 keV by much less intense higher frequency EMIC waves. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

Published
2022
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11. Thin current sheet behind the dipolarization front

Author

Nakamura, Baumjohann, M., T. K., Panov, Schmid, Varsani, Apatenkov, S., Sergeev, V. A., Birn, J., Nagai, T., Gabrielse, C., Andre, M., Burch, J. L., Carr, C., Dandouras, I. S, Escoubet, C. P., Fazakerley, N., Giles, B. L., Contel, O. Le, Russell, C. T., and Torbert, R. B.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Physics - Space Physics
Abstract

We report a unique conjugate observation of fast flows and associated current sheet disturbances in the near-Earth magnetotail by MMS (Magnetospheric Multiscale) and Cluster preceding a positive bay onset of a small substorm at ~14:10 UT, Sep. 8, 2018. MMS and Cluster were located both at X ~-14 RE. A dipolarization front (DF) of a localized fast flow was detected by Cluster and MMS, separated in the dawn-dusk direction by ~4 RE, almost simultaneously. Adiabatic electron acceleration signatures revealed from comparison of the energy spectra confirm that both spacecraft encounter the same DF. We analyzed the change in the current sheet structure based on multi-scale multi-point data analysis. The current sheet thickened during the passage of DF, yet, temporally thinned subsequently associated with another flow enhancement centered more on the dawnward side of the initial flow. MMS and Cluster observed intense perpendicular and parallel current in the off-equatorial region mainly during this interval of the current sheet thinning. Maximum field-aligned currents both at MMS and Cluster are directed tailward. Detailed analysis of MMS data showed that the intense field-aligned currents consisted of multiple small-scale intense current layers accompanied by enhanced Hall-currents in the dawn-dusk flow-shear region. We suggest that the current sheet thinning is related to the flow bouncing process and/or to the expansion/activation of reconnection. Based on these mesoscale and small-scale multipoint observations, 3D evolution of the flow and current-sheet disturbances was inferred preceding the development of a substorm current wedge.

Published
2022
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15. The ELFIN Mission

Author

Angelopoulos, V., Tsai, E., Bingley, L., Shaffer, C., Turner, D. L., Runov, A., Li, W., Liu, J., Artemyev, A. V., Zhang, X. -J., Strangeway, R. J., Wirz, R. E., Shprits, Y. Y., Sergeev, V. A., Caron, R. P., Chung, M., Cruce, P., Greer, W., Grimes, E., Hector, K., Lawson, M. J., Leneman, D., Masongsong, E. V., Russell, C. L., Wilkins, C., Hinkley, D., Blake, J. B., Adair, N., Allen, M., Anderson, M., Arreola-Zamora, M., Artinger, J., Asher, J., Branchevsky, D., Capitelli, M. R., Castro, R., Chao, G., Chung, N., Cliffe, M., Colton, K., Costello, C., Depe, D., Domae, B. W., Eldin, S., Fitzgibbon, L., Flemming, A., Fox, I., Frederick, D. M., Gilbert, A., Gildemeister, A., Gonzalez, A., Hesford, B., Jha, S., Kang, N., King, J., Krieger, R., Lian, K., Mao, J., McKinney, E., Miller, J. P., Norris, A., Nuesca, M., Palla, A., Park, E. S. Y., Pedersen, C. E., Qu, Z., Rozario, R., Rye, E., Seaton, R., Subramanian, A., Sundin, S. R., Tan, A., Turner, W., Villegas, A. J., Wasden, M., Wing, G., Wong, C., Xie, E., Yamamoto, S., Yap, R., Zarifian, A., and Zhang, G. Y.

Subjects
Physics - Space Physics, Physics - Geophysics, Physics - Instrumentation and Detectors, Physics - Plasma Physics
Abstract

The Electron Loss and Fields Investigation with a Spatio-Temporal Ambiguity-Resolving option (ELFIN-STAR, or simply: ELFIN) mission comprises two identical 3-Unit (3U) CubeSats on a polar (~93deg inclination), nearly circular, low-Earth (~450 km altitude) orbit. Launched on September 15, 2018, ELFIN is expected to have a >2.5 year lifetime. Its primary science objective is to resolve the mechanism of storm-time relativistic electron precipitation, for which electromagnetic ion cyclotron (EMIC) waves are a prime candidate. From its ionospheric vantage point, ELFIN uses its unique pitch-angle-resolving capability to determine whether measured relativistic electron pitch-angle and energy spectra within the loss cone bear the characteristic signatures of scattering by EMIC waves or whether such scattering may be due to other processes. Pairing identical ELFIN satellites with slowly-variable along-track separation allows disambiguation of spatial and temporal evolution of the precipitation over minutes-to-tens-of-minutes timescales, faster than the orbit period of a single low-altitude satellite (~90min). Each satellite carries an energetic particle detector for electrons (EPDE) that measures 50keV to 5MeV electrons with deltaE/E<40% and a fluxgate magnetometer (FGM) on a ~72cm boom that measures magnetic field waves (e.g., EMIC waves) in the range from DC to 5Hz Nyquist (nominally) with <0.3nT/sqrt(Hz) noise at 1Hz. The spinning satellites (T_spin~3s) are equipped with magnetorquers that permit spin-up/down and reorientation maneuvers. The spin axis is placed normal to the orbit plane, allowing full pitch-angle resolution twice per spin. An energetic particle detector for ions (EPDI) measures 250keV-5MeV ions, addressing secondary science. Funded initially by CalSpace and the University Nanosat Program, ELFIN was selected for flight with joint support from NSF and NASA between 2014 and 2018., Comment: Submitted to Space Science Reviews April 2020. 51 pages, 7 tables, 21 figures

Published
2020
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16. States of $^{12}$N with enhanced radii

Author

Demyanova, A. S., Danilov, A. N., Ogloblin, A. A., Starastsin, V. I., Dmitriev, S. V., Trzaska, W. H., Goncharov, S. A., Belyaeva, T. L., Maslov, V. A., Sobolev, Yu. G., Penionzhkevich, Yu. E., Khlebnikov, S. V., Tyurin, G. P., Burtebaev, N., Janseitov, D., Gurov, Yu. B., Louko, J., and Sergeev, V. M.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

The differential cross sections of the $^{12}$C($^3$He,t)$^{12}$N reaction leading to formation of the 1$^+$ (ground state), 2$^+$(0.96 MeV), 2$^{-}$(1.19 MeV), and 1$^{-}$(1.80 MeV) states of $^{12}$N are measured at $E$($^3$He)=40 MeV. The analysis of the data is carried out within the modified diffraction model (MDM) and distorted wave Born approximation (DWBA). Enhanced $rms$ radii were obtained for the ground, 2$^{-}$(1.19 MeV), and 1$^{-}$(1.80 MeV) states. We revealed that $^{12}$B, $^{12}$N, and $^{12}$C in the IAS with T=1, and spin-parities 2$^{-}$ and 1$^{-}$ have increased radii and exhibit properties of neutron and proton halo states., Comment: 6 pages, 4 figures, 2 tables

Published
2020
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24. Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

Author

Angelopoulos, V., Zhang, X.-J., Artemyev, A. V., Mourenas, D., Tsai, E., Wilkins, C., Runov, A., Liu, J., Turner, D. L., Li, W., Khurana, K., Wirz, R. E., Sergeev, V. A., Meng, X., Wu, J., Hartinger, M. D., Raita, T., Shen, Y., An, X., Shi, X., Bashir, M. F., Shen, X., Gan, L., Qin, M., Capannolo, L., Ma, Q., Russell, C. L., Masongsong, E. V., Caron, R., He, I., Iglesias, L., Jha, S., King, J., Kumar, S., Le, K., Mao, J., McDermott, A., Nguyen, K., Norris, A., Palla, A., Roosnovo, A., Tam, J., Xie, E., Yap, R. C., Ye, S., Young, C., Adair, L. A., Shaffer, C., Chung, M., Cruce, P., Lawson, M., Leneman, D., Allen, M., Anderson, M., Arreola-Zamora, M., Artinger, J., Asher, J., Branchevsky, D., Cliffe, M., Colton, K., Costello, C., Depe, D., Domae, B. W., Eldin, S., Fitzgibbon, L., Flemming, A., Frederick, D. M., Gilbert, A., Hesford, B., Krieger, R., Lian, K., McKinney, E., Miller, J. P., Pedersen, C., Qu, Z., Rozario, R., Rubly, M., Seaton, R., Subramanian, A., Sundin, S. R., Tan, A., Thomlinson, D., Turner, W., Wing, G., Wong, C., and Zarifian, A.

Published
2023
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27. Spectroscopic Diagnostic of the Peripheral Plasma in the Globus-M2 Tokamak with the Injection of Neutral Helium

Author

Timokhin, V. M., Sergeev, V. Yu., Anufriev, E. A., Korobko, D. D., Sharov, I. A., Varfolomeev, V. I., Novokhatsky, A. N., Bakharev, N. N., Vekshina, E. O., Dolgova, K. V., Zhil’tsov, N. S., Kavin, A. A., Kapralov, V. G., Kiselev, E. O., Koval’, A. N., Kurskiev, G. S., Lobanov, K. M., Minaev, V. B., Miroshnikov, I. V., Mukhin, E. E., Petrov, Yu. V., Rozhansky, V. A., Sakharov, N. V., Skokov, V. G., Tel’nova, A. Yu., Tkachenko, E. E., Tokarev, V. A., Tolstyakov, S. Yu., Tyukhmeneva, E. A., and Khromov, N. A.

Published
2022
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30. Local Time Distribution and Activity Dependence of Extreme Electron Densities in the Auroral D‐Region as an Image of Energy‐Dependent Energetic Electron Precipitation.

Author

Sergeev, V. A., Stepanov, N. A., Ogawa, Y., Rozanov, E. V., and Shukhtina, M. A.

Subjects
ELECTRON density, SPACE environment, SOLAR wind, AURORAS, ALTITUDES
Abstract

Studying the episodes with the most elevated electron density (Ne) values provides valuable information about spatial distribution and drivers of intense energetic electron (EE) precipitation, which has important space weather implications. By combining EISCAT‐Tromso UHF observations in different modes made in 2001–2021, we survey Ne occurrences and study statistical properties of EE precipitation, producing the highest 10% and 1% of Ne values at the altitudes between 100 and 75 km (corresponding to EE energies of ∼20–∼200 keV). We found that the highest Ne values occur in the nightside‐morning local time sector at the altitudes 90–100 km and in the morning‐noon sector at low altitudes (75–85 km). Although this bimodal pattern could partly be contributed by the suppressed Ne in the dark ionosphere, by analyzing measurements in the twilight conditions at all MLTs together with published patterns of EE precipitation, we argue that a dominance of pre‐noon maximum at low altitudes reflects the enhanced precipitation of >100 keV electrons in this local time sector. At all altitudes (especially below 90 km), the appearance of the highest Ne values favors enhanced auroral activity and shows a strong correlation with fast solar wind (V > 550 km/s) events. These properties mimic the well‐known driving characteristics of energetic electrons. From the correlation of Ne with integral magnetic activity indexes we found that the memory of preceding magnetic activity increases with decreasing altitude, reaching roughly one day at H = 75 km. We discuss the advantages of exploring Ne data at specific altitudes (compared to direct measurements of EE precipitation) to investigate statistically the effects of specific precipitated energy components and the evolution of EE energy spectra. Key Points: Occurrence of high Ne events in D‐region between 75 and 100 km caused by energetic electron precipitation and their activity driversSpatial patterns of extreme ionization differ in the upper (h > 90 km) and low (h < 85 km) D‐region consistent with known precipitation patternsMemory length of preceding magnetic activity increases with decreasing altitude reaching roughly 1 day at h = 75 km [ABSTRACT FROM AUTHOR]

Published
2024
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