Auroral ion precipitation at Jupiter: Predictions for Juno

This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1002/grl.50812/abstract;jsessionid=66B03862AE875776878700852033C5EF.f03t02The spatially localized and highly variable polar cap emissions at Jupiter are part of a poorly understood current system linking the ionosphere and the magnetopause region. Strong X-ray emission has been observed from the polar caps and has been explained by the precipitation of oxygen and sulfur ions of several MeV energy. The present paper presents results of an extended model of the ion precipitation process at Jupiter. Specifically, we add to a previous model a more complete treatment of ionization of the atmosphere, generation of secondary electron fluxes and their escape from the atmosphere, and generation of downward field-aligned currents. Predictions relevant to observations by the upcoming NASA Juno mission are made, namely the existence of escaping electrons with energies from a few eV up to 10 keV, auroral H2 band emission rates of 80 kR, and downward field-aligned currents of at least 2 MA

Hot oxygen atoms in the upper atmospheres of Venus and Mars

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94642/1/grl3908.pd

Small scale magnetic structure in the induced Martian ionosphere and lower magnetic pile-up region

The data is in the form of an Excel file and contains data used for many of the figures in the 2022 J. Geophys. Res. paper at https://doi.org/10.1029/2021JA030139. The data included in this KU archive is meant to be supplemental.Small-scale magnetic structures have been observed in the induced Martian ionosphere by magnetometers onboard the Mars Global Surveyor (MGS) and the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. The origin and evolution of these structures remain poorly understood and the goal of the current paper is to better characterize them and their distribution in the dayside ionosphere using MAVEN data. MAVEN Langmuir probe data is used to find thermal pressures in the ionosphere. The structures studied range in size from about 20 km up to a couple of hundred km. We constrain our investigation to the northern hemisphere, dayside Martian ionosphere in order to minimize crustal magnetic field interference. Magnetic pressure spikes (and/or field component variations), along with thermal pressure behavior can also sometimes characterize small-scale structures. Minimum variance analyses (MVA) are carried out for each structure in order to help classify them (e.g., horizontal slabs, ionopause-like structures, flux tube and flux ropes). A “statistical” catalog of properties (pressure, field amplitude, ellipticity, width, etc.) is generated for about 1000 structures. One conclusion we reached from this survey is that slab-like features are more likely to be found than rope-like features for altitudes above 250 km. Paper published in J. Geophys. Res. ,2022NASA MAVE

Comment on “Ionospheric evidence of hot oxygen in the upper atmosphere of Venus”

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95022/1/grl6627.pd

All Ionospheres are not Alike: Reports from other Planets

Our understanding of planetary ionospheres made some progress during the last four years. Most of this progress was due to new and/or improved theoretical models, although some new data were also obtained by direct and remote sensing observations. The very basic processes such as ionization, chemical transformations and diffusive as well as convective transports are analogous in all ionospheres; the major differences are the result of factors such as different neutral atmospheres, intrinsic magnetic field strength, distance from the Sun, etc. Improving our understanding of any of the ionospheres in our solar system helps in elucidating the controlling physical and chemical processes in all of them. New measurements are needed to provide new impetus, as well as guidance, in advancing our understanding and we look forward to such information in the years ahead

3‐D global MHD model prediction for the first close flyby of Titan by Cassini

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95615/1/grl18965.pd

X-ray emission from the terrestrial magnetosheath

[1] X-rays are generated throughout the terrestrial magnetosheath as a consequence of charge transfer collisions between heavy solar wind ions and geocoronal neutrals. The solar wind ions resulting from these collisions are left in highly excited states and emit extreme ultraviolet or soft X-ray photons. A model has been created to simulate this X-ray radiation. Published terrestrial exospheric hydrogen distributions and solar wind speed, density and temperature distributions were used in this model. Simulated images were created as seen from an observation point outside the geocorona. The locations of the bow shock and magnetopause are evident in these images. Perhaps this Xray emission can be used to remotely sense the solar wind flow around the magnetosphere. Since similar X-rays are produced in the heliosphere, the challenge will be, however, to eliminate this background emission