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This paper discusses my recollections concerning the origins of space radio and plasma wave research at the University of Iowa. My career in space research started when I was hired as a freshman engineering student by Prof. James A. Van Allen in April 1958, shortly after his discovery of Earth's radiation belts with Explorer 1, the first U.S. satellite. My early work mainly involved digital data system designs for the University of Iowa "Injun" series of satellites, the first satellites completely designed and constructed at a university. It was on Injun 3 that, at the suggestion of Prof. Brian J. O'Brien, I developed one of the very first radio and plasma wave instruments ever flown on a spacecraft. This instrument made the first pioneering studies of a wide variety of space radio and plasma wave phenomena, such as whistlers, chorus, and auroral hiss. These early studies were soon followed by somewhat similar NASA‐funded Iowa radio and plasma wave instruments that were used to explore Earth's magnetosphere with the Injun‐5, S3‐A, Hawkeye, IMP, and ISEE satellites, the solar wind with the Helios 1 and 2 spacecraft, and the outer planets and interstellar space with the Voyager 1 and 2 spacecraft. My discussions of this very early era in space research, and the key people involved, are limited to the time period before roughly 1980. Key Point: An overview is presented of the origins of space radio and plasma wave research at the University of Iowa [ABSTRACT FROM AUTHOR]

Abstract: Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is a subsurface and topside ionosphere radar sounder aboard the European Space Agency spacecraft Mars Express, in orbit at Mars since 25 December 2003, and in operation since 17 June 2005. The ionospheric sounding mode of MARSIS is capable of detecting the reflection of the sounding wave from the martian surface. This ability has been used in previous work to show that the surface reflection is absorbed and disappears during periods when high fluxes of energetic particles are incident on the ionosphere of Mars. These absorption events are believed to be the result of increased collisional damping of the sounding wave, caused by increased electron density below the spacecraft, in turn caused by impact ionization from the impinging particles. In this work we identify two absorption events that were isolated during periods when the surface reflection is consistently visible and when Mars is nearly at opposition. The visibility of the surface reflection is viewed in conjunction with particle and photon measurements taken at both Mars and Earth. Both absorption events are found to coincide with Earth passing through solar wind speed and ion flux signatures indicative of a corotating interaction region (CIR). The two events are separated by an interval of approximately 27 days, corresponding to one solar rotation. The first of the two events coincides with abruptly enhanced particle fluxes seen in situ at Mars. Simultaneous with the particle enhancement there are an abrupt decrease in the intensity of electron oscillations, typically seen by the Mars Express particle instrument ASPERA-3 between the magnetic pileup boundary and the martian bow shock, and a sharp drop in the solar wind pressure, seen in the proxy quantity based on MGS magnetometer observations. The decrease in oscillation intensity is therefore the probable effect of a relaxation of the martian bow shock. The second absorption event does not show a particle enhancement and complete ASPERA-3 data during that time are unavailable. Other absorption events are the apparent result of solar X-ray and XUV enhancements. We conclude that surface reflection absorption events are sometimes caused by enhanced ionospheric ionization from high energy particles accelerated by the shocks associated with a CIR. A full statistical analysis of CIRs in relation to observed absorption events in conjunction with a quantitative analysis of the deposition of ionization during space weather events is needed for a complete understanding of this phenomenon. If such analyses can be carried out, radar sensing of the martian ionosphere might be useful as a space weather probe. [Copyright &y& Elsevier]

At Mars, the solar wind interacts directly with the planet’s extended atmosphereand ionosphere to form an induced magnetic barrier that deflects the solar windaround the planet. Through this interaction, the solar wind deposits energy andmomentum into the ionosphere resulting in plasma heating, acceleration, and escape.Consequently, the global structure and dynamics of the ionosphere are thought to be affectedby the conditions that prevail in the upstream solar wind. Observational studiesdetailing these effects, however, have been limited owing to the lack of concurrentobservations of the ionosphere and upstream solar wind. We present results from astatistical analysis in which we studied these effects using ionospheric electron densitymeasurements from the MARSIS (Mars Advanced Radar for Subsurface and IonosphereSounding) Radar on Mars Express, and upstream solar wind measurements frominstruments on MAVEN (Mars Atmosphere and Volatile EvolutioN). Our resultsshow that, during times of high solar wind dynamic pressure, the plasma scaleheight in the topside ionosphere is reduced and electron densities in the nightsideionosphere are enhanced. The analysis also reveals that there is an asymmetry in theionosphere with respect to the direction of the solar wind -V × B motional electric field. [ABSTRACT FROM AUTHOR]

Abstract: The Cassini spacecraft Ultraviolet Imaging Spectrograph (UVIS) obtained observations of Jupiter''s auroral emissions in H2 band systems and H Lyman-α from day 275 of 2000 (October 1), to day 81 of 2001 (March 22). Much of the globally integrated auroral variability measured with UVIS can be explained simply in terms of the rotation of Jupiter''s main auroral arcs with the planet. These arcs were also imaged by the Space Telescope Imaging Spectrograph (STIS) on Hubble Space Telescope (HST). However, several brightening events were seen by UVIS in which the global auroral output increased by a factor of 2–4. These events persisted over a number of hours and in one case can clearly be tied to a large solar coronal mass ejection event. The auroral UV emissions from these bursts also correspond to hectometric radio emission (0.5–16 MHz) increases reported by the Galileo Plasma Wave Spectrometer (PWS) and Cassini Radio and Plasma Wave Spectrometer (RPWS) experiments. In general, the hectometric radio data vary differently with longitude than the UV data because of radio wave beaming effects. The 2 largest events in the UVIS data were on 2000 day 280 (October 6) and on 2000 days 325–326 (November 20–21). The global brightening events on November 20–21 are compared with corresponding data on the interplanetary magnetic field, solar wind conditions, and energetic particle environment. ACE (Advanced Composition Explorer) solar wind data was numerically propagated from the Earth to Jupiter with an MHD code and compared to the observed event. A second class of brief auroral brightening events seen in HST (and probably UVIS) data that last for ∼2 min is associated with auroral flares inside the main auroral ovals. On January 8, 2001, from 18:45–19:35 UT UVIS H2 band emissions from the north polar region varied quasiperiodically. The varying emissions, probably due to auroral flares inside the main auroral oval, are correlated with low-frequency quasiperiodic radio bursts in the 0.6–5 kHz Galileo PWS data. [Copyright &y& Elsevier]