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Simultaneous FPI and TMA Measurements of the Lower Thermospheric Wind in the Vicinity of the Poleward Expanding Aurora After Substorm Onset
Author(s) -
Oyama Shinichiro,
Kubota Ken,
Morinaga Takatoshi,
Tsuda Takuo T.,
Kurihara Junichi,
Larsen Miguel F.,
Yamamoto Masayuki,
Cai Lei
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024613
Subject(s) - substorm , thermosphere , ionosphere , sounding rocket , atmospheric sciences , depth sounding , geophysics , geology , physics , magnetosphere , plasma , astronomy , oceanography , quantum mechanics
Lower thermospheric wind fluctuations in the vicinity of an auroral arc immediately before and after a substorm onset were examined by analyzing data from a ground‐based green line Fabry‐Perot interferometer (FPI; optical wavelength of 557.7 nm) at Tromsø, Norway, and in situ measurements from a trimethyl aluminum (TMA) trail released from a sounding rocket launched during the Dynamics and Energetics of the Lower Thermosphere in Aurora 2 (DELTA‐2) campaign on 26 January 2009. Soon after the rocket launch but before disappearance of the TMA trail, a substorm onset occurred. The DELTA‐2 TMA experiment appears to be the first case in which the substorm onset occurred during the TMA wind measurement. It is known that energy dissipation induced by the ionospheric closure current is compacted at the poleward side of the discrete arc in the ionospheric morning cell. Both FPI and TMA measurements were made at the poleward side, but the FPI measured winds nearer to the poleward edge of the arc than the TMA by 110–130 km. The FPI winds at distance of 53–74 km relative to the arc edge showed clear fluctuations immediately after the substorm onset, but there was no obvious similar fluctuation in the TMA‐measured winds. The difference in the response at the two locations suggests that energy dissipation sufficient to be detected as the FPI/TMA wind perturbations was confined to the area from the poleward edge of the arc to a relative distance shorter than 163–203 km but longer than 53–74 km in this event.