Initial Results of Aurora/Airglow Observations Using CRL All-sky Imagers at Poker Flat, Alaska

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Initial Results of Aurora/Airglow Observations
Using CRL All-sky Imagers at Poker Flat, Alaska
Minoru Kubota Communications Research Laboratory
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Instruments and Targets of the Alaska project
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System details of the CRL-ASI
System diagram of CRL-ASI
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Size and externals
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Optical system
f80 mm

• Fisheye Nikkor
• f6 mm
• F1.4
• FOV 180o
• Weight 5 kg

Total transmission of fisheye lens and
telecentric lens system
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Detector (CCD camera)

• PixelVision
• SpectraVideo Camera Model SV512
• format 512512
• Back-illuminated CCD (SITe)
• O-ring Dewar
• 3-stage thermoelectric cooler
• (minimum temp. 225K)
• dark current 0.5
• electron/pixel/sec_at_230K
• readout noise 12
• electron,rms_at_100kHz-readout

Quantum efficiency of the back-illuminated CCD
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Control software

• Functions
• decision of observation peroid
• and sequence
• filter-channel control
• focus control
• CCD camera control
• (temperature setting, exposure,
• data readout ..)
• data saving
• QL-images display
• operation from a remote-site
• Programming Language
• Visual C and Visual Basic
• OS Windows NT

Control panel of the CRL-ASI
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SALMON (System for Alaska Middle Atmosphere
Observation Data Network)
SALMON is developed using a high-speed computer
networks, for effective use and display of the
data observed in Alaska and for assistance in the
data distribution. The system has capabilities of
quasi-real time data transfer to CRL from Alaska,
real time data displays on the world wide web.
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http//salmon.crl.go.jp/
Observation schedule, status, and summary data of
the CRL-ASI
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Calibration and Image Data Processing of the
CRL-ASI
Sensitivity calibration using an integrating
sphere in NIPR
Aug. 1999 in NIPR, Japan
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Image of the integrating sphere
It shows that luminosity (sensitivity) drops
towards the edge of the image. (mainly by
vignetting)
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Sensitivity of the CRL-ASI
3kR_at_557.7-nm aurora ? S/N 100 by 3 sec exposure
500R_at_844.6-nm aurora ? S/N 10 by 45 sec exposure
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Image data processing
WWW real-time display
ftp
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Geometry of the van Rhijn effect and atmospheric
extinction
100 km alt.
Variation of the van Rhijn correction factor
combined with atmospheric extinction versus
zenith angle.
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CRL-ASI Observations at Poker Flat
Observatory Poker Flat Research Range
(PFRR) LAT. 65.1oN?LON.147.5oW
MLAT65.5o
Observation Periods Oct., 2000 Apr., 2001
Nov., 2001 Mar., 2002 Sept., 2002 Mar.,
2003 Sept., 2003 Mar., 2004 2004 ?
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Target emissions, filter details, and exposure
times for the CRL-ASI in 2000
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Wavelength CRL-ASIs can observe up to ten kinds
of aurora/airglow emissions using filter turrets.
? Examples of aurora and airglow images obtained
by the CRL-ASI. a-e) auroral images in five
different wavelengths obtained simultaneously.
f) proton aurora. g,h) sodium and OH airglow
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An Example of Observational Results
Evening Co-rotating Patch aurora (ECP
aurora) False color all-sky images made by OI
557.7-nm and 630.0-nm images taken every 20
minutes. Patch-shaped auroras spread over the sky
can be seen. Motion of the patches was very slow.
In particular, they maintained their shapes and
positions from 0320 to 0400 UT.
movie
Kubota et al., Geophys. Res. Lett., accepted.
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Differences in vision among wavelengths The patch
structures of the ECP aurora were distinct in the
OI 557.7-nm and N2 emissions, but indistinct in
the OI 844.6-nm emission. In the OI 630.0-nm and
proton Hb emissions, there were no patch
structures. These emission features indicate that
the ECP aurora was caused by electron
precipitation at energies greater than several
keV.
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Keograms and geomagnetic activity, on 27 Oct.,
2000
Period of the ESP aurora 03-06 UT
(16-19 MLT) geomagnetic activity quiet
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Particle precipitation from the extended duskside
plasmasphere? a) The ECP aurora existed in a
band-like region between 64o and 67o geomagnetic
latitude, which was approximately equivalent to
the region between L 5 and 8 Re. b) A DMSP
satellite passed near the Alaskan area observed
intermittent electron precipitation between 64o
and 67o geomagnetic latitude. The energy range of
these precipitating electrons was above a few
keV. c) An extended plasmasphere was observed a
few hours beforehand with the Akebono satellite
in the afternoon sector. This evidence suggests
that the particles causing this aurora
precipitate from the extended duskside
plasmasphere.
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Event list of the ECP aurora In conducting
imaging observations using the CRL-ASI over two
winter seasons, we often observed the ECP aurora
during geomagnetic quiet periods.
Toyoshima et al., presented in the Joint Meeting
of Earth and Planetary Science, 2003, Japan.
The ECP aurora shows itself in various forms
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An ECP aurora projected to the equatorial plane
using the Tsyganenko 96 model.
IMAGE / EUV data simultaneously observed on
February 24, 2001
Relationship between an ECP aurora and an
expanded (detached?) plasmasphere Magnetic field
lines traced from the ECP aurora on 24 February
2001 extend to the expanded (detached?)
plasmasphere with a plasma density of 102 /cm3.
Toyoshima et al., presented in the Joint Meeting
of Earth and Planetary Science, 2003, Japan.
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We suppose the mechanism of the ECP aurora as
follows 1) Residual plasma sheet electrons
injected to the inner magnetosphere during a past
geomagnetic substorm drift into the extended
duskside plasmasphere. 2) Hard electrons supplied
by this way precipitate by pitch angle scattering
due to the cyclotron wave-particle interactions.
We expect that the structure and motion of the
ECP aurora is related to the plasma density and
electric field in the expanded plasmasphere,
respectively.
Conceptual illustration of the ECP aurora
generation mechanism
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Evening auroras on the other days
Weak auroras in the MLT-evening were found on 13
nights, in the last winter.
Keograms
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Example image of evening auroras on several nights
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Summary of the ESP aurora

• 27 October, 2000
• Co-rotating patch-shaped auroras with hard
  electron precipitation were observed during 16-19
  MLT (evening). Geomagnetic activity was quiet.
  The patch auroras existed in the region between
  64o-68o Mlat.
• Expansion of plasmaspere was simultaneously
  observed by Akebono satellite.
• The ESP auroras were found on 13 nights in the
  last winter (not shown).
• The ESP auroras have many similarities to
  detached arcs observed by ISIS-2 satellite in
  1970s.
• It suggests that the ESP aurora is a projected
  image of instabilities in the detached
  plasmasphere outside the plasmapause.

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Simultaneous observations of atmospheric waves
and aurora (2)
Keograms on 28 Dec., 2000
Auroral activities exist around midnight. But, Na
emissions shows different features.
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Transformed keogram vertical axis shows the
geographic coordinate which is in proportion to
distance from the PFRR.
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Results of band-pass filtering to the transformed
keograms
15min
75min
225min
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Short summary of the simultaneous observations of
atmospheric waves and aurora

• Wave propagations in Na airglow emission were
  observed on 33 nights, (and we found 4 nights of
  simultaneous observations between the Na lidar
  and ASI).
• 2 November, 2000
• Remarkable wave propagation was observed
  simultaneously with an ESP aurora.
• 28 December, 2000
• Power spectrum of temporal variations of the
  zenith intensity shows that several strong waves
  are exist.
• Propagating direction of the gravity wave which
  has 75 min period is changed from northward to
  southward at around 14 UT after auroral
  enhancements.
• ?Effected by aurora?

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Summary

• CRL-ASI observations at PFRR were started from
  October 2000.
• The evening stable patch auroras, which seems to
  be associated with instabilities outside the
  plasmasphere, have been often observed.
• We intend to investigate interactions between
  aurora and the atmospheric (gravity) waves.
• Combination of the ASI, FPI, MFR, HFR,
  Na-lider(GI), MSP(GI), Magnetometer(GI),
  Rocket(GI), is very useful to study these
  phenomena.

Offers of data using and cooperative studies

• Investigation of the trough region using 630- and
  777.4-nm airglow images (HAARP optical campaign
  2002) Cornell Univ.
• Relationship between auroral enhancement and
  substorm onset Univ. of Electro-Communications
• Proton aurora images GI, UAF Tohoku Univ.
• ESP aurora Tohoku Univ.