TY - JOUR
T1 - Discovery of 1 Hz Range Modulation of Isolated Proton Aurora at Subauroral Latitudes
AU - Ozaki, M.
AU - Shiokawa, K.
AU - Miyoshi, Y.
AU - Kataoka, R.
AU - Connors, M.
AU - Inoue, T.
AU - Yagitani, S.
AU - Ebihara, Y.
AU - Jun, C. W.
AU - Nomura, R.
AU - Sakaguchi, K.
AU - Otsuka, Y.
AU - Uchida, H. A.
AU - Schofield, I.
AU - Danskin, D. W.
N1 - Funding Information:
The present study was supported by JSPS KAKENHI grants 15H05747, 15H05815, 16H06286, and 17K06456 and by the Kanazawa University SAKIGAKE project. This study was also supported by JSPS Bilateral Open Partnership Joint Research Projects. The observations at the Athabasca University Geospace Observatory were supported by the Canada Foundation for Innovation. The authors would like to thank Y. Kato, Y. Hamaguchi, Y. Yamamoto, and T. Adachi of ISEE, Nagoya University, and K. Reiter of Athabasca University Geospace Observatory for their helpful support in the operation of the induction magnetometer and optical observations. M. C. acknowledges support as Visiting Foreign Professor at Nagoya University during this project. The induction magnetometer data at ATH were obtained from http://stdb2.stelab. nagoya-u.ac.jp/magne/index.html. The all-sky EMCCD data captured with a BG3 glass filter at ATH are available through ERG-Science Center, ISEE, Nagoya University. The all-sky EMCCD data for Hbeta emissions and the magnetometer data at ATH were obtained from http://autumn.athabascau.ca. The broad-beam CNA data at Meanook are available through Natural Resources Canada. The Kp and Dst indices were provided by the WDC for Geomagnetism in Kyoto (http://wdc. kugi.kyoto-u.ac.jp/).
Publisher Copyright:
©2018. The Authors.
PY - 2018/2/16
Y1 - 2018/2/16
N2 - Isolated proton aurora (IPA) is a manifestation of the wave-particle interaction visible at subauroral latitudes, with activity on many timescales. We herein present the first observational evidence of rapid luminous modulation of IPA correlated with simultaneously observed Pc1 waves observed on the ground, which are equivalent to the electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. The fastest luminous modulation of IPA was observed in the 1 Hz frequency range, which was twice the frequency of the related Pc1 waves. The time lag between variations of Pc1 wave power and the IPA luminosity suggests that the source regions of IPA are distributed near the magnetic equator, suggesting an EMIC wave-energetic (a few tens of keV) proton or relativistic (MeV or sub-MeV) electron interaction. The generation mechanism of this 1 Hz luminous modulation remains an open issue, but this study supports the importance of nonlinear pitch angle scattering via wave-particle interactions.
AB - Isolated proton aurora (IPA) is a manifestation of the wave-particle interaction visible at subauroral latitudes, with activity on many timescales. We herein present the first observational evidence of rapid luminous modulation of IPA correlated with simultaneously observed Pc1 waves observed on the ground, which are equivalent to the electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. The fastest luminous modulation of IPA was observed in the 1 Hz frequency range, which was twice the frequency of the related Pc1 waves. The time lag between variations of Pc1 wave power and the IPA luminosity suggests that the source regions of IPA are distributed near the magnetic equator, suggesting an EMIC wave-energetic (a few tens of keV) proton or relativistic (MeV or sub-MeV) electron interaction. The generation mechanism of this 1 Hz luminous modulation remains an open issue, but this study supports the importance of nonlinear pitch angle scattering via wave-particle interactions.
KW - isolated proton aurora
KW - Pc1 geomagnetic pulsations
KW - wave-particle interaction
UR - http://www.scopus.com/inward/record.url?scp=85041628434&partnerID=8YFLogxK
U2 - 10.1002/2017GL076486
DO - 10.1002/2017GL076486
M3 - Journal Article
AN - SCOPUS:85041628434
SN - 0094-8276
VL - 45
SP - 1209
EP - 1217
JO - Geophysical Research Letters
JF - Geophysical Research Letters
IS - 3
ER -