High Angular Resolution Imaging of Solar Radio Bursts from the Lunar Surface

Locating low frequency radio observatories on the lunar surface has a number of advantages, including positional stability and a very low ionospheric radio cutoff. Here, we describe the Radio Observatory on the lunar Surface for Solar studies (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The preferred site is on the lunar near side to simplify the data downlink to Earth. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by measuring the low radio frequency cutoff of the solar radio emissions or background galactic radio emission, measuring the flux, particle mass, and arrival direction of interplanetary and interstellar dust, and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLSS include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 M Hz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg at 10 MHz, equivalent to a linear array size of approximately one kilometer. The major components of the ROLSS array are 3 antenna arms, each of 500 m length, arranged in a Y formation, with a central electronics package (CEP) at their intersection. Each antenna arm is a linear strip of polyimide film (e.g., Kapton(TradeMark)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP. Operations would consist of data acquisition during the lunar day, with data downlinks to Earth one or more times every 24 hours

Testing the Solar Probe Cup, an Instrument Designed to Touch the Sun

Solar Probe Plus will be the first, fastest, and closest mission to the sun, providing the first direct sampling of the sub-Alfvenic corona. The Solar Probe Cup (SPC) is a unique re-imagining of the traditional Faraday Cup design and materials for immersion in this high temperature environment. Sending an instrument of this type into a never-seen particle environment requires extensive characterization prior to launch to establish sufficient measurement accuracy and instrument response. To reach this end, a slew of tests for allowing SPC to see ranges of appropriate ions and electrons, as well as a facility that reproduces solar photon spectra and fluxes for this mission. Having already tested the SPC at flight like temperatures with no significant modification of the noise floor, we recently completed a round of particle testing to see if the deviations in Faraday Cup design fundamentally change the operation of the instrument. Results and implications from these tests will be presented, as well as performance comparisons to cousin instruments such as those on the WIND spacecraft

Solar wind plasma : kinetic properties and micro-instabilities

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2003.Includes bibliographical references (leaves 183-191).The kinetic properties of ions in the solar wind plasma are studied. Observations of solar wind +H and +2He by the Faraday Cup instrument component of the Solar Wind Experiment on the Wind spacecraft show that these ions have magnetic field-aligned, convected, bi-Maxwellian velocity distribution functions. The analysis yields the best-fit values of the bulk velocity, U, number density n, and parallel T and perpendicular T temperatures of each of the ion species. The accuracy of each of these measurements is studied and an absolute calibration of the Faraday Cup is performed, demonstrating the accuracy of the densities to =/< 2%. The range of the proton temperature anisotropy Rp= - Tp/Tp is explored, and it is demonstrated that thermodynamic concepts such as the double adiabatic equations of state are insufficient approximations for a kinetic description of the solar wind plasma. It is shown that Rp is constrained on macroscopic timescales by Coulomb relaxation and the expansion of the solar wind, and on kinetic timescales by the mirror, cyclotron, and firehose plasma micro-instabilities. Electromagnetic fluctuations generated by growing mirror and cyclotron modes are detected in the solar wind. The first detailed observations of the firehose instability are presented. The limiting bounds to Rp imposed by each of these instabilities are measured and compared with the theoretical predictions of fluid magnetohydrodynamics, linear kinetic Vlasov theory, and numerical simulations. It is shown that the predictions of linear theory and the simulations are in agreement with the observations.(cont.) A new proton temperature anisotropy driven instability in the regieme Rp < 1, βP < 1 is discovered. The kinetic properties of +H and +2He are compared. For the first time a cyclotron resonant instability driven by the proton temperature anisotropy is demonstrated to limit the differential flow U=Uα-Up attainable in the solar wind, in confirmation of recent theoretical predictions. It is shown that the +2He temperature anisotropy Rα=Tα/Tα is also constrained by micro-instabilities, and the first observations of the+2He cyclotron and firehose instabilities are presented. The parallel and perpendicular temperatures of +H and +2He are compared, and evidence of cyclotron-resonant heating of +2He preferrentially to +H in the interplanetary medium is presented.by Justin Christophe Kasper.Ph.D