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Title: Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes

Abstract

To understand the role of electromagnetic ion cyclotron (EMIC) waves in determining the temporal features of pulsating proton aurora (PPA) via wave-particle interactions at subauroral latitudes, high-time-resolution (1/8 s) images of proton-induced N 2>+ emissions were recorded using a new electron multiplying charge-coupled device camera, along with related Pc1 pulsations on the ground. The observed Pc1 pulsations consisted of successive rising-tone elements with a spacing for each element of 100 s and subpacket structures, which manifest as amplitude modulations with a period of a few tens of seconds. In accordance with the temporal features of the Pc1 pulsations, the auroral intensity showed a similar repetition period of 100 s and an unpredicted fast modulation of a few tens of seconds. Furthermore, these results indicate that PPA is generated by pitch angle scattering, nonlinearly interacting with Pc1/EMIC waves at the magnetic equator.

Authors:
 [1];  [2];  [2];  [3];  [1];  [1];  [4];  [2];  [5];  [6];  [2];  [2];  [7];  [7];  [8]
  1. Kanazawa Univ., Kanazawa (Japan)
  2. Nagoya Univ., Nagoya (Japan)
  3. National Institute of Polar Research, Tachikawa (Japan); Univ. for Advanced Studies (SOKENDAI), Tachikawa (Japan)
  4. Kyoto Univ., Uji (Japan)
  5. Japan Aerospace Exploration Agency, Sagamihara (Japan)
  6. National Institute of Information and Communications Technology, Koganei (Japan)
  7. Athabasca Univ., Athabasca, AB (Canada)
  8. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA); USDOE
OSTI Identifier:
1304820
Report Number(s):
LA-UR-16-25492
Journal ID: ISSN 0094-8276
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 43; Journal Issue: 15; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Heliospheric and Magnetospheric Physics

Citation Formats

Ozaki, M., Shiokawa, K., Miyoshi, Y., Kataoka, R., Yagitani, S., Inoue, T., Ebihara, Y., Jun, C. -W, Nomura, R., Sakaguchi, K., Otsuka, Y., Shoji, M., Schofield, I., Connors, M., and Jordanova, V. K. Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes. United States: N. p., 2016. Web. doi:10.1002/2016GL070008.
Ozaki, M., Shiokawa, K., Miyoshi, Y., Kataoka, R., Yagitani, S., Inoue, T., Ebihara, Y., Jun, C. -W, Nomura, R., Sakaguchi, K., Otsuka, Y., Shoji, M., Schofield, I., Connors, M., & Jordanova, V. K. Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes. United States. doi:10.1002/2016GL070008.
Ozaki, M., Shiokawa, K., Miyoshi, Y., Kataoka, R., Yagitani, S., Inoue, T., Ebihara, Y., Jun, C. -W, Nomura, R., Sakaguchi, K., Otsuka, Y., Shoji, M., Schofield, I., Connors, M., and Jordanova, V. K. 2016. "Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes". United States. doi:10.1002/2016GL070008. https://www.osti.gov/servlets/purl/1304820.
@article{osti_1304820,
title = {Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes},
author = {Ozaki, M. and Shiokawa, K. and Miyoshi, Y. and Kataoka, R. and Yagitani, S. and Inoue, T. and Ebihara, Y. and Jun, C. -W and Nomura, R. and Sakaguchi, K. and Otsuka, Y. and Shoji, M. and Schofield, I. and Connors, M. and Jordanova, V. K.},
abstractNote = {To understand the role of electromagnetic ion cyclotron (EMIC) waves in determining the temporal features of pulsating proton aurora (PPA) via wave-particle interactions at subauroral latitudes, high-time-resolution (1/8 s) images of proton-induced N2>+ emissions were recorded using a new electron multiplying charge-coupled device camera, along with related Pc1 pulsations on the ground. The observed Pc1 pulsations consisted of successive rising-tone elements with a spacing for each element of 100 s and subpacket structures, which manifest as amplitude modulations with a period of a few tens of seconds. In accordance with the temporal features of the Pc1 pulsations, the auroral intensity showed a similar repetition period of 100 s and an unpredicted fast modulation of a few tens of seconds. Furthermore, these results indicate that PPA is generated by pitch angle scattering, nonlinearly interacting with Pc1/EMIC waves at the magnetic equator.},
doi = {10.1002/2016GL070008},
journal = {Geophysical Research Letters},
number = 15,
volume = 43,
place = {United States},
year = 2016,
month = 8
}

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  • A correlation was observed between chorus emissions and pulsating aurora (PA) from observations at Athabasca (L ≈ 4.3) in Canada at 9:00–9:20 UT on 7 February 2013, using an electron multiplying charge-coupled device camera and a VLF loop antenna with sampling rates of 110 Hz and 100 kHz, respectively. Pulsating aurora having a quasiperiodic variation in luminosity and a few hertz modulation was observed together with chorus emissions consisting of a group of successive rising-tone elements. The repetition period and modulation frequency of the PA are in good agreement with those of the modulated chorus. After 9:11 UT, the temporalmore » features of the aurora became aperiodic PA of indistinct modulation. Simultaneously, the rising-tone chorus turned into chorus emissions consisting of numerous rising-tone elements. The equatorial geomagnetic field inhomogeneity calculated using the Tsyganenko 2002 model shows a decreasing trend during the period. This result is consistent with nonlinear wave growth theory having a small geomagnetic field inhomogeneity, which contributes to a decrease in the threshold amplitude to trigger discrete chorus elements. As a result, these observations show a close connection between chorus emissions and PA on timescales from milliseconds for generation of discrete chorus elements on the microphysics of wave-particle interaction to minutes for the variations of the geomagnetic field inhomogeneity related with the substorm activity.« less
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