16 research outputs found
Ozone loss derived from balloon-borne tracer measurements in the 1999/2000 Arctic winter
Balloon-borne measurements of CFC11 (from the DIRAC in situ gas chromatograph and the DESCARTES grab sampler), ClO and O3 were made during the 1999/2000 Arctic winter as part of the SOLVE-THESEO 2000 campaign, based in Kiruna (Sweden). Here we present the CFC11 data from nine flights and compare them first with data from other instruments which flew during the campaign and then with the vertical distributions calculated by the SLIMCAT 3D CTM. We calculate ozone loss inside the Arctic vortex between late January and early March using the relation between CFC11 and O3 measured on the flights. The peak ozone loss (~1200ppbv) occurs in the 440-470K region in early March in reasonable agreement with other published empirical estimates. There is also a good agreement between ozone losses derived from three balloon tracer data sets used here. The magnitude and vertical distribution of the loss derived from the measurements is in good agreement with the loss calculated from SLIMCAT over Kiruna for the same days
Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study
Statistics of high-altitude and high-latitude O<sup>+</sup> ion outflows observed by Cluster/CIS
Observation of Gamma-Rays from relativistic electron precipitation with Balloon Experiment around the Northern Polar Cap
第3回極域科学シンポジウム/第36回極域宙空圏シンポジウム 11月26日(月) 国立極地研究所 2階大会議
Statistical study of relationships between dayside high-altitude/-latitude O⁺ outflows, solar winds, and geomagnetic activity
Statistical study of relationships between dayside high-altitude/-latitude O<sup>+</sup> outflows, solar winds, and geomagnetic activity
Statistics of high-altitude and high-latitude O<sup>+</sup> ion outflows observed by Cluster/CIS
The persistent outflows of O+ ions observed by
the Cluster CIS/CODIF instrument were studied statistically
in the high-altitude (from 3 up to 11 RE)
and high-latitude (from 70 to ~90 deg invariant latitude,
ILAT) polar region. The principal results are: (1) Outflowing
O+ ions with more than 1keV are observed above 10 RE geocentric distance and above 85deg ILAT location;
(2) at 6-8 RE geocentric distance, the latitudinal
distribution of O+ ion outflow is consistent with velocity
filter dispersion from a source equatorward and below the
spacecraft (e.g. the cusp/cleft); (3) however, at 8-12 RE
geocentric distance the distribution of O+ outflows cannot
be explained by velocity filter only. The results suggest
that additional energization or acceleration processes for
outflowing O+ ions occur at high altitudes and high
latitudes in the dayside polar region.
Keywords. Magnetospheric physics (Magnetospheric configuration
and dynamics, Solar wind-magnetosphere interactions
Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study
The results of a statistical study of oxygen ion
outflow using Cluster data obtained at high altitude
above the polar cap is reported. Moment data for both
hydrogen ions (H+) and oxygen ions (O+)
from
3 years (2001-2003) of spring orbits (January to May)
have been used. The altitudes covered were mainly
in the range 5–12 RE geocentric distance.
It was found that O+ is
significantly transversely energized at high
altitudes, indicated both by high perpendicular
temperatures for low magnetic field values as well as
by a tendency towards higher perpendicular than
parallel temperature
distributions for the highest observed temperatures.
The O+ parallel bulk velocity increases with
altitude in particular for the lowest observed
altitude intervals.
O+ parallel bulk velocities in excess of 60 km s-1
were found mainly at higher altitudes
corresponding to magnetic field strengths of less
than 100 nT. For
the highest observed parallel bulk velocities
of O+ the thermal velocity exceeds the bulk
velocity, indicating that the beam-like character of
the distribution is lost.
The parallel bulk velocity of the H+ and O+
was found to typically be close to the same
throughout the observation interval when the H+
bulk velocity was calculated for all pitch-angles. When
the H+ bulk velocity was calculated for upward
moving particles only the H+ parallel bulk
velocity was
typically higher than that of O+. The parallel bulk velocity is close
to the same for a wide range of relative abundance of
the two ion species, including when the O+ ions
dominates.
The thermal velocity of O+ was always well below
that of H+.
Thus perpendicular
energization that is more
effective for O+ takes place, but this is not
enough to explain the close to similar parallel
velocities. Further parallel acceleration must
occur. The results presented constrain the models
of perpendicular heating and parallel acceleration.
In particular centrifugal acceleration of the outflowing
ions, which may provide the same parallel velocity
increase to the two ion species and a
two-stream interaction are discussed in the context
of the measurements
Ozone loss derived from balloon-borne tracer measurements in the 1999/2000 Arctic winter
Balloon-borne measurements of CFC11 (from the DIRAC in situ gas chromatograph and the DESCARTES grab sampler), ClO and O3 were made during the 1999/2000 Arctic winter as part of the SOLVE-THESEO 2000 campaign, based in Kiruna (Sweden). Here we present the CFC11 data from nine flights and compare them first with data from other instruments which flew during the campaign and then with the vertical distributions calculated by the SLIMCAT 3D CTM. We calculate ozone loss inside the Arctic vortex between late January and early March using the relation between CFC11 and O3 measured on the flights. The peak ozone loss (~1200ppbv) occurs in the 440-470K region in early March in reasonable agreement with other published empirical estimates. There is also a good agreement between ozone losses derived from three balloon tracer data sets used here. The magnitude and vertical distribution of the loss derived from the measurements is in good agreement with the loss calculated from SLIMCAT over Kiruna for the same days