Abstract

1

• Abstract
• A High Throughput Imaging Echelle Spectrograph
  (HiTIES), built at Boston University, was
  operating last winter season from November 2001
  to March 2002 at Tromsø, Norway, for assessing
  the characteristics of the particle
  precipitations and the subsequent response of the
  ionosphere, in a region of intense proton aurora.
  This site at 66.4ºN magnetic latitude was chosen
  because
• for moderately disturbed conditions, it is
  located for several hours at the equator edge of
  the evening auroral oval, where energetic protons
  are usually the dominant particle energy source,
• it offers combined experiments with the EISCAT
  radar probing the ionosphere.
• HiTIES is a high spectral resolution imaging
  instrument capable of simultaneously observing
  multiple wavelength ranges. Four spectral windows
  were selected in the location of important
  features Ha (656.3 nm) and Hb (486.1 nm), N2
  427.8 nm and OI 777.4 nm. The 8º long slit of
  HiTIES was centered on the magnetic zenith.
• Information on the weather conditions and on the
  overall auroral activity is provided by a second
  spectrometer, the Proton Aurora Context (PAC)
  instrument, which consists of a large field of
  view (60º) imaging spectrograph covering the
  400-800 nm spectral range.
• Both optical instruments successfully operated
  over the whole winter. Here we present HiTIES and
  PAC observations for January 20th, 2002. We
  demonstrate that the spectral resolution of
  HiTIES ( 0.1 nm) is sufficient for successfully
  studying proton aurora using Ha emission. For
  more information, consult http//www.bu.edu/csp/h
  ities

PROTON AURORA CAMPAIGN at TROMSØ, NORWAY
Marina Galand1, Jeff Baumgardner1, Unni Pia
Lovhaug2, Duggirala Pallamraju1 , Supriya
Chakrabarti1 , Michael Mendillo1 1 Center for
Space Physics, Boston University, Boston, MA,
U.S.A. 2 Department of Physics, University of
Tromsø, Tromsø, Norway.
Aurora over the HiTIES instrument, Tromsø,
Norway, at 2030 UT, March 4th, 2002. Photo
Credit Jouni Jussila.
Jeffowgram integration over 431.7 539.1 nm for
20/2002 (PAC)
PAC auroral e- arc faint H aurora
Proton Aurora Context (PAC) instrument
O2 and H2O absorption
Field of view 60º (around the magnetic zenith)
Spectral coverage 400 - 800 nm
Spectral resolution 1 nm
Exposure time 5 s 16 co-add 80 s
Info on PAC (similar to COTIF) Baumgardner et al., Opt. Eng., 32, 3028-3032, 1993.
N2 1P
e- arc
Ha 656.3 nm
OI 630.0 nm
Jeffowgram integration over 654.5 657.1 nm for
20/2002 (PAC)
Hg (Street lines)
OI 557.7 nm
Hb 486.1 nm
N2 470.9 nm
N2 427.8 nm

• Grism Prism grating
• Other applications of such an instrument
• e.g., Semeter, J. et al., J. Geophys. Res., 104,
  24,565-24, 585, 1999.

1
Proton aurora (Ha 656.3 nm)
Twilight January 20, 2002 / 150001 UT -
152829 UT Solar depression angle -9.48º to
-11.59º
Later twilight January 20, 2002 / 152829 UT
162525 UT Solar depression angle -11.59º to
-16.23º
Proton aurora January 20, 2002 / 183532 UT
193228 UT Solar depression angle -27.41º to
-31.94º
HiTIES A High Throughput Imaging Echelle
Spectrograph
4a
2a
3a
4b
2b
3b
Field of view 8º (around the magnetic zenith)
Spectral resolution 0.06 nm (Hb) 0.1 nm (Ha)
Exposure time 2 min
Info on HiTIES Chakrabarti et al., J. Geophys. Res., 106, 30,337-30, 348, 2001.
Background removed Vertical solid line (Hb) H
lamp profile shown
Vertical solid line (Hb), dashed-dotted lines
(Fraunhofer Fe I absorption lines)
Vertical solid line (Hb), dashed-dotted lines
(Fraunhofer Fe I absorption lines)
4c
2c
3c
Background removed Vertical solid line (Ha),
dashed lines (OH emission bands), dashed-dotted
lines (N2 1P, NII) H lamp profile shown

• Simultaneous observations through the four
  spectral windows
• Other applications of such an instrument HiRISE
  dayglow and auroral observations of the sunlit
  atmosphere in 630.0 nm
• e.g., Pallamraju et al., J. Geophys. Res., 106,
  5543-5550, 2001.

Vertical solid line (Ha), dashed lines (OH
emission bands), dashed-dotted lines (Fraunhofer
Fe I absorption lines) NII (658.3 nm)
Vertical solid line (Ha), dashed lines (OH
emission bands) NII (658.3 nm)

• Figure 1 Overview of the visible activity over
  HiTIES (PAC centered field of view) on January
  20th, 2002 moderate magnetic activity Kp
  (15-18 UT)3 Kp (18-24 UT)2 solar index f10.7
  222
• Strong sunlight effect until 1500 UT. Green
  star shows when the proton aurora (characterized
  by Ha and Hb emissions) starts. Electron arcs
  seen between 1930 and 2000 UT, at 2100 UT, at
  2130 UT, and at 2245 UT. The time periods
  corresponding to the HiTIES images and spectra
  presented below are shown with colored horizontal
  arrows.
• Scattered sunlight and airglow
• Figures 2a (top panel) and 3a
• Far right, triplet OI (777.2 nm, 777.4 nm, 777.5
  nm) emissions produced in the F-region from the
  recombination of O with electrons
• Shortward of OI 777.2 nm, OH(9,4)
  vibrational-rotational bands from Meinel system
  originated at about 80-90 km from the
  displacement reaction between H and O3 .
• Figures 2a (second panel from top) and 2b
• The absorption features (shown Hb, Fe I) result
  from Rayleigh scattering of sunlight. The signal
  level decreases with depression angle up to the
  disappearance of sunlight effect (Figures 3a and
  3b).
• Figures 2a and 3a (third panel from top),
  Figures 2c and 3c
• The signal level associated with the Fraunhofer
  absorption features is smaller in the Ha range
  compared with the Hb range, as the incident solar
  flux is smaller near Ha than near Hb and as the
  Rayleigh scattering is stronger in the blue than
  in the red. Complete disappearance of sunlight
  effect (Figure 3c).
• Presence of emission peaks Ha line (from
  resonance scattering of sunlight H Lyb by
  geocoronal H atoms both lines sharing the same
  excited state H(n3) galactic and stellar
  background) OH Meinel bands OH(6,1) P branch
  P1(2)-P1(5) and P2(2)-P2(5) NII (658.3 nm) from
  photodissociative ionization of N2 with e-
  quenching, N loss.

• Aurora (with scattered sunlight and airglow)
• Figures 4a and 5 (top panels)
• Intensification of the OI line during auroral
  activity (airglow excitation of O and
  dissociation of O2 by the energetic particles)
• Intense auroral lines/bands (e.g., N2 1P (8,7)
  and (2,0)) seen during electron arcs (Figure 5)
• Figures 4a (second panel from top) and 4b
• Doppler-shifted magnetic zenith Hb profile
  resulting from excited H atoms inside the proton
  beam. The profile is blue-shifted, as most of the
  energetic H atoms are going downward. The total
  brightness is found to be 150 R. The profile has
  a red-shifted wing, which is larger than what can
  be explained by the instrument resolution (see H
  lamp profile attesting of a spectral resolution
  of 0.06 nm in the Hb window). This red wing
  results from the upward H atom flux produced by
  collisional angular redistribution inside the
  proton beam, as predicted by modeling Galand et
  al., 1998 Lummerzheim and Galand, 2001
  confirmation of earlier observations from Poker
  Flat Lummerzheim and Galand, 2001 and Svalbard
  Lanchester et al., 2002. Note that a
  preliminary comparison shows that the wavelength
  of the peak and the half width of the red wing
  are similar in all three locations and that the
  violet wings are similar in Poker Flat
  (MLAT65.2º) and Tromsø (MLAT66.4º) and larger
  than in Svalbard (MLAT75.0º), which observed a
  softer population (dayside, cusp) compared with
  the two other stations (center plasma sheet).
• Figures 4a (third panel from top) and 4c
• Doppler-shifted magnetic zenith Ha profile from
  proton aurora see above, comments for Hb
  Doppler-shifted profile. Spectral resolution
  0.1 nm.
• Contamination of the proton aurora H profile by
  N2 1P (7,4) and N2 1P (6,3) NII (658.3 nm)
  OH(6,1) bands geocoronal Ha.
• Figure 5 (bottom panel)
• Strong N2 1N (0,1) 427.81 nm emission in e-
  arcs.

Proton aurora with electron arcs January 20, 2002
/ 193632 UT 200500 UT Solar depression
angle -32.23º to -34.27º

• HiTIES
• Wavelength Calibration
• - Hydrogen and Neon lamps
• used for Ha window,
• - Hydrogen and Xeon lamps
• used for Hb window
• (2) Intensity calibration

5
Tungsten_lamp / C14 source (with normalization
of exposure time)
6

• CONCLUSION
• Great capability through PAC and HiTIES
  spectrographs to analyze the proton and electron
  aurora. Successful spectral validation through
  the Fraunhofer absorption lines and airglow.
  Preliminary Hb analysis shows confirmation of
  modeling results Galand et al., 1998 is in
  agreement with previous observations Lummerzheim
  and Galand, 2001 Lanchester et al., 2002.
• The high spectral resolution of HiTIES offers,
  for the first time, the possibility of using Ha
  for proton aurora analysis. The contamination
  from other emissions or sources has been detected
  and can be removed. This will help
• to study faint proton aurora, as Ha response is
  stronger than Hb to proton precipitation.
• to shed some light on the still debated Ha/Hb
  ratio in proton aurora.
• WHAT NEXT?
• Further analysis of PAC data and of Ha (within
  the proton aurora as well as under sunlight
  influence)
• Indentification of stars and planets in the
  field of view of PAC (see Figure 6) and HiTIES
• for establishing the exact part of the sky
  probed by the instruments
• for validating the intensity calibration
• Combined observations
• HiTIES and ESR radar at Svalbard, Norway (in
  collaboration with Dr. B. Lanchester and Prof.
  M.H. Rees, Southampton University, England)
• EISCAT radar 3 days already identified (January
  7th, 2002 February 1st, 2002 March 4th, 2002)
• Particle data at the top of the atmosphere (DMSP
  and FAST) Comprehensive proton transport model
  using the particle data as input and providing
  the H Doppler profiles.
• TIMED/GUVI and IMAGE/SI12 (spectral filtering
  around H Ly a) (see Figure 7)

From left to right Pollux and Castor, Jupiter,
Auriga, Perseus, Cassiopiea (PAC).
Intensity reference image
Reference intensity curve for C14 Source (R/nm)
IMAGE/SI12 at 1857 UT on January 20th, 2002.
The location of Tromsø is shown with a white
star. To the courtesy of H. Frey, Univ.
Berkeley
Collapse image around the center of the field of
view
Reference curve f(l) near 620.0 nm
Derive T from matching the slope of P(l) with
f(l) near 620.0 nm
7
Planck curves corrected for the emissivity of
Tungsten PT(l)
Reference curve over all HiTIES spectral ranges,
PT3100K (l)
Acknowledgments We are very grateful to Prof. C.
Hall and Mr. B. Hansen from the Tromsø
Geophysical Observatory, Norway, and to Ms. A.
Berquist from Boston University, for their key
help in this work. We warmly thank Dr. H. Frey
for providing us with the IMAGE/SI12 data. If you
have any comments or suggestions, please contact
Marina Galand at mgaland_at_bu.edu
Intensity calibration applied to HiTIES data sky
image / flat x PT3100K (l) with flat, the
Tungsten lamp image through HiTIES Note In all
processes above, dark removed