ALBERT

Description: The water chemistry of streams and precipitation in the province of Jämtland, northern Sweden has been monitored since the 1980s to study long-term trends, occurrence of acid episodes, and effects of liming. The acidity and sulphur in precipitation increased in the 1970s, followed by a loss of ANC and low pH in the streams. Sulphur deposition begun to decrease in the 1980s, until approximately 2000, after which the decrease levelled out. The stream water sulphate followed the precipitation trend but decreased more slowly and since the late 1990s a subtle increase was observed. The sulphate concentrations in the snow have generally been higher than or equal to the stream sulphate levels. Since 2005, stream sulphate has sometimes exceeded snow sulphate, indicating desorption of stored soil sulphate, possibly because of climate related changes in run-off routes through the soil profiles, following shorter periods of frost. Up to 2000, TOC increased by approximately 0.1 mg L−1 yr−1. The mean trends in sulphate and TOC from approximately 1990 until today are generally opposite. Acidic episodes with pH 4.0 at flow peaks occurred frequently in the unlimed streams, despite relatively well buffered waters at base flow. To evaluate the main causes for the loss of ANC, the changes in major ions during high flow were calculated. The most important contribution resulted from dilution of base cations, with contribution from organic anions. Sulphate also had some influence, as it was somewhat enriched or only slightly diluted during high flow. Wetland liming started in 1985 after which the earlier observed extreme peak values of Fe, Mn and Al, did not return. The studied area is remote from emission sources in Europe, but the critical load of acidity is still exceeded. The long-term recovery observed in the unlimed streams is thus slow, and severe acidic episodes still occur.

Description: The water chemistry of streams and precipitation in the province of Jämtland, northern Sweden has been monitored since the 1980s to study long-term trends, occurrence of acid episodes, and effects of liming. The acidity in precipitation increased in the 1970s, followed by a loss of acid neutralizing capacity (ANC) and low pH in the streams. Sulfur deposition began to decrease in the 1980s, until approximately 2000, after which the decrease levelled out. Stream water sulfate concentration followed the precipitation trend but decreased more slowly and since the late 1990s a subtle increase was observed. Sulfate concentrations in the snow typically have been higher than or equal to the stream sulfate levels. However, during the period of rapid deposition decrease and also since 2005 stream sulfate has sometimes exceeded snow sulfate, indicating desorption of stored soil sulfate, possibly because of climate-related changes in run-off routes through the soil profiles, following shorter periods of frost. From 1982 to 2000, total organic carbon (TOC) increased by approximately 0.1 mg L−1 yr−1. The mean trends in sulfate and TOC from approximately 1990 until today were generally opposite. Acidic episodes with pH 4.0 at flow peaks occurred frequently in the unlimed streams, despite relatively well-buffered waters at baseflow. To evaluate the main causes for the loss of ANC during episodes, the changes in major ion concentrations during high flow episodes were evaluated. The most important factors contributing to ANC loss were dilution of base cations (Na+, K+, Ca2+, Mg2+), enrichment of organic anions and enrichment of sulfate. Wetland liming started in 1985 after which the earlier observed extreme peak values of iron, manganese and aluminium, did not reoccur. The studied area is remote from emission sources in Europe, but the critical load of acidity is still exceeded. The long-term recovery observed in the unlimed streams is thus slow, and severe acidic episodes still occur.

Description: The advanced energetic particle spectrometer RAPID on board Cluster can provide a complete description of the relevant particle parameters velocity, V , and atomic mass, A, over an energy range from 30 keV up to 1.5 MeV. We present the first measurements taken by RAPID during the commissioning and the early operating phases. The orbit on 14 January 2001, when Cluster was travelling from a perigee near dawn northward across the pole towards an apogee in the solar wind, is used to demonstrate the capabilities of RAPID in investigating a wide variety of particle populations. RAPID, with its unique capability of measuring the complete angular distribution of energetic particles, allows for the simultaneous measurements of local density gradients, as reflected in the anisotropies of 90° particles and the remote sensing of changes in the distant field line topology, as manifested in the variations of loss cone properties. A detailed discussion of angle-angle plots shows considerable differences in the structure of the boundaries between the open and closed field lines on the nightside fraction of the pass and the magnetopause crossing. The 3 March 2001 encounter of Cluster with an FTE just outside the magnetosphere is used to show the first structural plasma investigations of an FTE by energetic multi-spacecraft observations.Key words. Magnetospheric physics (energetic particles, trapped; magnetopause, cusp and boundary layers; magnetosheath)

Description: PROMICS-3 is a plasma experiment flown in the Russian project Interball. It performs three-dimensional (3D) measurements of ions in the energy range 4 eV–70 keV with mass separation and of electrons in the energy range 12 eV–35 keV. The Interball project consists of two main satellites, the Tail Probe and the Auroral Probe, each with one subsatellite. The Interball Tail Probe was launched on 3 August 1995, into a 65° inclination orbit with apogee at about 30 RE. Both main satellites carry identical PROMICS-3 instruments and thus direct comparisons of the particle distributions will be possible once the Auroral Probe is launched. Furthermore, PROMICS-3-Tail is the first instrument measuring the 3D ion distribution function in the magnetospheric boundary layers at high latitudes. In this paper we describe the PROMICS-3 instrument and show initial results from the Tail probe, measurements of the magnetosheath, plasma sheet, and ring current plasmas.

Description: The PROMICS-3 instrument on Interball-2 is nominally identical to the PROMICS-3 instrument on Interball-1. It performs three-dimensional measurements of ions in the energy range 4 eV-70 keV with mass separation and of electrons in the energy range 300 eV-35 keV. Interball-2 was launched on August 29, 1996, into an orbit with the same inclination as that of Interball-1, 63°, but with apogee at 20 000 km. In this study the PROMICS-3 instrument on Interball-2 is briefly described and examples of the first results are presented. Firstly, we report observations of upward moving molecular ions with energies of up to 700 eV at the poleward edge of the auroral oval. Previous observations of outflowing molecular ions have been at lower altitudes and lower energies. Secondly, we show observations of dawnside magnetosheath plasma injections. Using conjugate data from both PROMICS-3 instruments we have found dispersion structures above the morningside auroral oval, which occurred simultaneously with isolated "pockets" of magnetosheath plasma at a distance of XGSM=-14 to -12 RE, which had been injected into the inner part of the low-latitude boundary layer. These isolated plasma structures were sites of strong field-aligned currents and are proposed to be the magnetospheric counterparts of the dispersion structures.Key words. Magnetospheric physics (auroral phenomena; magnetotail boundary layers; instruments and techniques).