PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
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SURGE-LIKE AURORAL STRUCTURES AND QUASI-PERIODIC
PRECIPITATIONS OF ENERGETIC PARTICLES IN THE MORNING
SECTOR: A CASE STUDY
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D.G. BaishevP P, E.S. BarkovaP P, S.N. SamsonovP P, K. YumotoP
P PYu.G.Shafer Institute of Cosmophysical Research and Aeronomy SB RAS, Yakutsk, 677980,
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Russia, e-mail: HTbaishev@ikfia.ysn.ruTH; P PSpace Environment Research Center, Kyushu University,
Fukuoka, Japan
Introduction
Abstract. Relationship between series of surge-like auroral structures and quasi-periodic
precipitations of energetic particles registered in the morning sector during 1900-2200 UT on
November 8, 2004 is studied. This event has been analyzed on the data from all-sky TV camera at
Tixie (ϕ=71.6° N, λ=128.9° E), riometer and magnetometer chain at around 190° geomagnetic
longitude and measurements of energetic particle fluxes aboard geostationary LANL satellites.
Surge-like auroral structures expanding by about 4° in latitude appeared in the field-of-view of TV
camera with a periodicity of 12-20 min and were accompanied by the intense geomagnetic
pulsations in the Pi3 range and quasiperiodic oscillations in the riometer absorption. A peak-to-peak
value of geomagnetic pulsations in the H and Z components was ~600 nT and exceeded the
amplitude in the D component by factor of 3. It is found that variations of discrete aurora intensity in
latitude one-to-one correspond to quasi-periodic oscillations in the riometer absorption observed at
Tixie and are in an antiphase to the riometer pulsations at more southern station of Dzhardzhan
(ϕ=69.0° N, λ=124.2° E).
The auroral picture on the morning side is complex. Omega bands, torch-like structures and pulsating aurora
drifting eastward with a convection speed are registered with the all-sky camera [Akasofu, 1974]. It is now
well known that auroral omega bands and Ps6 quasiperiodic magnetic pulsations are manifestations of the
same phenomena [Saito, 1978]. Ps6 pulsations are preferentially observed in the Y and Z components of the
magnetic field.
Steen et al. [1988] described the unusual rare event in which a gradual transition between Ps6 pulsations with
auroral torches and surgelike pulsations with quasiperiodic variations in auroral intensity were observed
during a substorm. The period of surge-like auroral structures is the manifestation of a series of individual
substorms occurring on the morning side.
On the morning side at 1900-2200 UT we observed 10 successive auroral structures like auroral surges
which drifted to the east and were accompanied by Pi3 magnetic pulsations. We present results of the
detailed study of relationship between auroral structures, quasiperiodic precipitations of energetic particles
and magnetic field variations.
Observations
The dynamics of aurora and long-period oscillations of the magnetic field in the morning sector during 1900-
2200 UT on November 8, 2004 are studied by data of the all-sky TV camera at the Tixie (TIX, ϕ=71.6° N,
λ=128.9° E), riometer and magnetic stations of the 190° MM. The TV camera provided high-resolution
optical measurements of aurora in white light [Shiokawa et al., 1996].
Ground-based measurements were supplemented by the satellite observations. The WIND satellite was
located far upstream at the distance of X~190 RBeB in GSM coordinates. The estimated time delay of ~33 min
is calculated between the satellite and the magnetopause. Measurements of energetic particle fluxes aboard
the geostationary LANL satellites in the morning sector were used.
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