Centrifugal acceleration in the magnetotail lobes

Combined Cluster EFW and EDI measurements have shown that cold ion outflow in the magnetospheric lobes dominates the hydrogen ion outflow from the Earth's atmosphere. The ions have too low kinetic energy to be measurable with particle instruments, at least for the typical spacecraft potential of a sunlit spacecraft in the tenuous lobe plasmas outside a few <I>R</I><sub>E</sub>. The measurement technique yields both density and bulk velocity, which can be combined with magnetic field measurements to estimate the centrifugal acceleration experienced by these particles. We present a quantitative estimate of the centrifugal acceleration, and the velocity change with distance which we would expect due to centrifugal acceleration. It is found that the centrifugal acceleration is on average outward with an average value of about of 5 m s<sup>−2</sup>. This is small, but acting during long transport times and over long distances the cumulative effect is significant, while still consistent with the relatively low velocities estimated using the combination of EFW and EDI data. The centrifugal acceleration should accelerate any oxygen ions in the lobes to energies observable by particle spectrometers. The data set also put constraints on the effectiveness of any other acceleration mechanisms acting in the lobes, where the total velocity increase between 5 and 19 <I>R</I><sub>E</sub> geocentric distance is less than 5 km s<sup>−1</sup>

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

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

Climatology of ozone in the troposphere and lower stratosphere over the European Arctic

A brief climatology of ozone using more than 8 years of ozonesonde data in the troposphere and lower stratosphere at two northern high latitude stations, Sodankyla and Ny-Ålesund, is presented. The climatology of ozone clearly shows a significant seasonal cycle with the ozone maxima changing with height. The monthly variability of ozone as well as its seasonal maximum is found near the tropopause. Variation in tropopause height is due mainly to the passage of tropospheric weather systems and is responsible for the large monthly variability of ozone near the tropopause. In the lower stratosphere, interannual variations are at a maximum in winter and spring, and are the result of variations in wave driven stratospheric circulation, which peaks in winter. The present climatology forms a basis for 3-D chemistry transport models to test its ability at high latitudes

Chlorine activation and chemical ozone loss deduced from HALOE and balloon measurements in the Arctic during the Winter of 1999-2000

[1] We employ Halogen Occultation Experiment (HALOE) observations and balloon-borne measurements (on the large Observations of the Middle Stratosphere [OMS] and Triple balloons, as well as on two small balloons) to investigate ozone loss in the stratospheric vortex in the 1999-2000 Arctic winter. Using HF and CH4 as long-lived tracers, we identify chlorine activation and chemical ozone destruction in the polar vortex. Reference relations, representative of chemically undisturbed "early vortex'' conditions, are derived from the OMS remote and in situ balloon measurements on 19 November and 3 December 1999, respectively. Deviations from this "early vortex'' reference are interpreted as chemical ozone loss and heterogeneous chlorine activation. The observations show an extensive activation of chlorine; in late February 2000, the activation extends to altitudes of 600 K. Between 360 and 450 K chlorine was almost completely activated. At that time, about 70% of the HCl column between 380 and 550 K was converted to active chlorine. Furthermore, the measurements indicate severe chemical ozone loss, with a maximum loss of over 60% in the lower stratosphere (415-465 K) by mid-March 2000. Substantial ozone loss was still observable in vortex remnants in late April 2000 (80 +/- 10 Dobson units [DU] between 380 and 550 K). The average loss in column ozone between 380 and 550 K, inside the vortex core, in mid-March amounted to 84 +/- 13 DU