Wednesday, October 11, 2023 - 3:10 p.m. to 4:10 p.m.
Morse Hall rm 301 -OR- Zoom
Speaker: Doug Rowland, NASA GSFC
Full title: VISIONS and VISIONS-2: Sounding rocket missions to study Earth’s escaping atmosphere
Abstract: While light ions such as hydrogen and helium can free escape from Earth’s gravity, heavier ions such as oxygen or nitrogen have thermal energies insufficient to escape, under normal conditions. And yet, significant volumes of heavier ions including even molecular ions such as NO+ or N2+ have been observed at large distances from Earth and at energies significantly in excess of the escape energy. These ions have major impacts on magnetospheric dynamics, modifying rates of energy transfer via magnetic reconnection, plasma wave growth rates, mass loading and stability in the magnetotail, etc.
These ions are accelerated to escape
energies by a multi-step process, and can go from initial thermal energies on
the order of 0.1 eV to escape energies of 10 eV to magnetospheric energies of
10s to 100s of keV. The source of these ions is deep in the collisional
ionosphere (at or near the exobase), and one of the major open questions is:
What controls the mass flux of escaping heavy ions?
NASA launched the VISIONS and VISIONS-2 sounding rocket missions, with major involvement by UNH faculty, in 2013 and 2018, respectively, to address outstanding questions regarding ion escape: 1) is ion escape “patchy”, “bursty”, or both, and what are the spatial scales of regions driving escape? 2) what are the escaping fluxes from areas dominated by different types of magnetospheric energy inputs (Joule heating, soft electron precipitation, plasma waves including Alfvén waves)? VISIONS was launched into the nightside auroral zone following a substorm, from Poker Flat, AK, and VISIONS-2 was launched into the dayside magnetic cusp from Ny Ålesund on Svalbard. I will present observations from both missions, which provide complementary information about the variety of processes that drive ion escape.
Check out our upcoming Space Science Center Seminar Series, as well as view previous recordings.
