Solar Wind Electron Proton Alpha Monitor (SWEPAM) for the Advanced Composition Explorer

The Solar Wind Electron Proton Alpha Monitor (SWEPAM) experiment provides the bulk solar wind observations for the Advanced Composition Explorer (ACE). These observations provide the context for elemental and isotopic composition measurements made on ACE as well as allowing the direct examination of numerous solar wind phenomena such as coronal mass ejections, interplanetary shocks, and solar wind fine structure, with advanced, 3-D plasma instrumentation. They also provide an ideal data set for both heliospheric and magnetospheric multi-spacecraft studies where they can be used in conjunction with other, simultaneous observations from spacecraft such as Ulysses. The SWEPAM observations are made simultaneously with independent electron and ion instruments. In order to save costs for the ACE project, we recycled the flight spares from the joint NASA/ESA Ulysses mission. Both instruments have undergone selective refurbishment as well as modernization and modifications required to meet the ACE mission and spacecraft accommodation requirements. Both incorporate electrostatic analyzers whose fan-shaped fields of view sweep out all pertinent look directions as the spacecraft spins. Enhancements in the SWEPAM instruments from their original forms as Ulysses spare instruments include (1) a factor of 16 increase in the accumulation interval (and hence sensitivity) for high energy, halo electrons; (2) halving of the effective ion-detecting CEM spacing from ∼5° on Ulysses to ∼2.5° for ACE; and (3) the inclusion of a 20° conical swath of enhanced sensitivity coverage in order to measure suprathermal ions outside of the solar wind beam. New control electronics and programming provide for 64-s resolution of the full electron and ion distribution functions and cull out a subset of these observations for continuous real-time telemetry for space weather purposes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Finite-dimensional filters with nonlinear drift. III: Duncan-Mortensen-Zakai equation with arbitrary initial condition for the linear filtering system and the Benes filtering system

We consider the Duncan-Mortensen-Zakai (DMZ) equation for the Kalman-Bucy filtering system and Benes filtering system. We show that this equation can be solved explicitly with an arbitrary initial condition by solving a system of ordinary differential equations and a Kolmogorov-type equation, Let n be the dimension of state space. We show that we need only n sufficient statistics in order to solve the DMZ equation.     

Atmospheric pressure variations at extratropical latitudes associated with Forbush decreases of galactic cosmic rays

Changes of troposphere pressure associated with short-time variations of galactic cosmic rays (GCRs) taking place in the Northern hemisphere’s cold months (October–March) were analyzed for the period 1980–2006, NCEP/NCAR reanalysis data being used. Noticeable pressure variations during Forbush decreases of GCRs were revealed at extratropical latitudes of both hemispheres. The maxima of pressure increase were observed on the 3rd–4th days after the event onsets over Northern Europe and the European part of Russia in the Northern hemisphere, as well as on the 4th–5th days over the eastern part of the South Atlantic opposite Queen Maud Land and over the d’Urville Sea in the Southern Ocean. According to the weather chart analysis, the observed pressure growth, as a rule, results from the weakening of cyclones and intensification of anticyclone development in these areas. The presented results suggest that cosmic ray variations may influence the evolution of extratropical baric systems and play an important role in solar-terrestrial relationships.     

Climate Observations - The Instrumental Record

A survey is given of the available instrumental data for monitoring and analysis of climatic variations. We focus on temperature measurements, both over land and ocean, at the surface and aloft.Over land, the older observations were subject to exposure changes which may not have been fully compensated. The effects of urbanization have been largely avoided in studies of climatic change over the last 150 years. There are few records for pre-1850 outside Europe and eastern North America, and the global network shows a recent decline. Over the ocean, sea surface temperature (SST) has been measured using buckets, engine intakes, hull sensors, buoys, and satellites. Many of these data have been effectively homogenized, but new challenges arise as observing systems evolve. Available SST and marine air temperature datasets begin in the 1850s. The data are concentrated in shipping lanes especially before 1900, and very sparse during the world wars, but additional historical data are being digitized.The radiosonde record is short (40 years) and has major gaps over the oceans, tropics and Southern Hemisphere. Instrumental heterogeneities are beginning to be assessed and removed using physical and statistical techniques. The MSU record is complete but only began in 1979, and is not highly resolved in the vertical: major biases, mainly affecting the lower-tropospheric retrieval, have been reduced as a result of recent analyses.Advanced interpolation or data-assimilation techniques are being applied to these data, but the results must be interpreted with care.