Abstract. The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and associated electronics. The dual configuration provides redundancy and also permits accurate removal of the dipolar portion of the spacecraft magnetic field. The instrument provides (1) near real-time data at nominally one vector per 92 s as key parameter data for broad dissemination, (2) rapid data at 10.9 vectors s -1 for standard analysis, and (3) occasionally, snapshot (SS) memory data and Fast Fourier Transform data (FFT), both based on 44 vectors s -I. These measurements will be precise (0.025%), accurate, ultra-sensitive (0.008 nT/step quantization), and where the sensor noise level is < 0.006 nT r.m.s, for 0-10 Hz. The digital processing unit utilizes a 12-bit microprocessor controlled analogue-to-digital converter. The instrument features a very wide dynamic range of measurement capability, from :E4 nT up to • 536 nT per axis in eight discrete ranges. (The upper range permits complete testing in the Earth's field.) In the FTT mode power spectral density elements are transmitted to the ground as fast as once every 23 s (high rate), and 2.7 rain of SS memory time series data, triggered automatically by pre-set command, requires typically about 5.1 hours for transmission. Standard data products are expected to be the following vector field averages: 0.0227-s (detail data from SS), 0.092 s ('detail' in standard mode), 3 s, 1 rain, and 1 hour, in both GSE and GSM coordinates, as well as the FFT spectral elements. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the solar wind: (1) as a collisionless plasma laboratory, at all time scales, macro, meso and micro, but concentrating on the kinetic scale, the highest time resolution of the instrument (=0.022 s), (2) as a consequence of solar energy and mass output, (3) as ~n external source of plasma that can couple mass, momentum, and energy to the Earth's magnetosphere, and (4) as it is modified as a consequence of its imbedded field interacting

Abstract. The dissipation range for interplanetary magnetic field fluctuations isformed by those fluctuations with spatial scales comparable to the gyroradius or ion inertial length of a thermal ion. It is reasonable to assume that the dissipation range represents the final fate of magnetic energy that is transferred from the largest spatial scales via nonlinear processes until kinetic coupling with the background plasma removes the energy from the spectrum and heats the background distribution. Typically, the dissipation range at 1 AU sets in at spacecraft frame frequencies of a few tenths of a hertz. It is characterized by a steepening of the power spectrum and often demonstrates a bias of the polarization or magnetic helicity spectrum.We examine Wind observations of inertial and dissipation range spectr a in an attempt to better understand the processes that form the dissipation range and how these processes depend on the ambient solar wind parameters (interplanetary magnetic field intensity, ambient proton density and temperature, etc.). We focus on stationary intervals with well-defined inertial and dissipation range spectra.

Abstract.A model of t h e large-scale magnetic f i e l d structure above 2. d sector p a t t e r n i s r e l a t e d t o t h e f i e l d p a t t e r n a t t h i

Abstract. The magnetic eld experiment o n A CE provides continuous measurements of the local magnetic eld in the interplanetary medium. These measurements are essential in the interpretation of simultaneous ACE observations of energetic and thermal particles distributions. The experiment consists of a pair of twin, boommounted, triaxial uxgate sensors which are located 165 inches = 4.19 meters from the center of the spacecraft on opposing solar panels. The electronics and digital processing unit DPU is mounted on the top deck of the spacecraft. The two triaxial sensors provide a balanced, fully redundant v ector instrument and permit some enhanced assessment of the spacecraft's magnetic eld. The instrument provides data for Browse and high-level products with between 3 and 6 vector s ,1 resolution for continuous coverage of the interplanetary magnetic eld. Two highresolution snapshot bu ers each hold 297 seconds of 24 vector s ,1 data while onboard Fast Fourier Transforms extend the continuous data to 12 Hz resolution. Real-time observations with 1 second resolution are provided continuously to the Space Environmental Center SEC of the National Oceanographic and Atmospheric Association NOAA for near-instantaneous, world-wide dissemination in service to space weather studies. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the interplanetary medium in support of the fundamental goals of the ACE mission and cooperative studies with other ACE investigators using the combined ACE dataset as well as other ISTP spacecraft involved in the general program of Sun-Earth Connections.

No abstract

Abstract. Spherical harmonic models of the planetary magnetic field of Jupiter are obtained from in situ magnetic field measurements and remote observations of the position of the foot of the Io flux tube in Jupiter's ionosphere. The Io flux tube (IFT) footprint locates the ionospheric footprint of field lines traced from Io's orbital radial distance in the equator plane (5.9 Jovian radii). The IFT footprint is a valuable constraint on magnetic field models, providing "ground truth" information in a region close to the planet and thus far not sampled by spacecraft. The magnetic field is represented using a spherical harmonic expansion of degree and order 4 for the planetary ("internal") field and an explicit model of the magnetodisc for the field ("external") due to distributed currents. Models fitting Voyager 1 and Pioneer 1! magnetometer observations and the IFT footprint are obtained by partial solution of the underdetermined inverse problem using generalized inverse techniques. Dipole, quadrupole, octupole, and a subset of higher-degree and higher-order spherical harmonic coefficients are determined and compared with earlier models.

Voyager 1 and 2 magnetic field observations confirm and extend the earlier Pioneer 10 detection of the Jovian magnetodisc, a region of enhanced charged particles and plasma and reduced magnetic field intensity located near the magnetic equatorial plane. Modeling of the azimuthal current sheet by a finite thickness annulus of inner radius 5 RJ, 5‐RJ thickness, and extending to ∼50 RJ provides detailed fits of the vector magnetic field perturbations observed in relation to the planetary field for distances less than 30 RJ. Field line geometry is also investigated, and better insight into the phenomena of charged particle absorption by the Galilean satellites is obtained which provides improved explanations of observed effects due to Ganymede.

Abstract. The Electron Reflectometer (ER) on board Mars Global Surveyor measures the energy and angular distributions of solar wind electrons and ionospheric photoelectrons. These data can be used in conjunction with magnetometer data to probe Mars' crustal magnetic field and to study Mars' ionosphere and solar wind interaction. During aerobraking, ionospheric measurements were obtained in the northern hemisphere at high solar zenith angles (SZAs, typically -78ø). The ionopause was crossed at altitudes ranging from 180 km to over 800 km, with a median of 380 km. The 400-km-altitude polar mapping orbit allows observations at SZAs from 25 ø to 155 ø in both the northern and southern hemispheres. The near-planet ionosphere and magnetotail structure of the night hemisphere is dominated by the presence of intense crustal magnetic fields, which can exceed 200 nT at the spacecraft altitude. Closed field lines anchored to highly elongated crustal sources form "magnetic cylinders," which exclude solar wind plasma traveling up the magnetotail. When the spacecraft passes through one of these structures, the ER count rate falls to the instrumental background, representing an electron flux drop of at least two orders of magnitude. A map of these flux dropouts in longitude and latitude closely resembles a map of the crustal magnetic sources. When the crustal magnetic cylinders rotate into sunlight, they fill with ionospheric plasma. Since many of these crustal fields are locally strong enough to stand off the solar wind to altitudes well above 400 km, the ionosphere can extend much higher than would otherwise be possible in the absence of crustal fields. Even weak crustal fields may locally bias the median ionopause altitude, which provides an indirect method of detecting crustal fields using ER observations.