Hot flow anomaly observed at Jupiter's bow shock

Abstract

A Hot Flow Anomaly (HFA) is created when an interplanetary current sheet interacts with a planetary bow shock. Previous studies have reported observing HFAs at Earth, Mercury, Venus, Mars, and Saturn. During Juno's approach to Jupiter, a number of its instruments operated in the solar wind. Prior to crossing into Jupiter's magnetosphere, Juno observed an HFA at Jupiter for the first time. This Jovian HFA shares most of the characteristics of HFAs seen at other planets. The notable exception is that the Jovian HFA is significantly larger than any HFA seen before. With an apparent size greater than 2 × 106 km the Jovian HFA is orders of magnitude larger than those seen at the other planets. By comparing the size of the HFAs at the other planets with the Jovian HFA, we conclude that HFAs size scales with the size of planetary bow shocks that the interplanetary current sheet interacts with.

Plasma environment at the dawn flank of Jupiter's magnetosphere: Juno arrives at Jupiter

“…Similar variability in thermal plasma was observed in the inner plasma sheet by Voyager [McNutt et al, 1981;Bagenal et al, 2017]. Such structure is also frequently seen in Saturn's outer magnetosphere [e.g., Richardson, 1986;Gombosi et al, 2009] and may be a consequence of the operation of the centrifugally driven flux tube interchange instability [e.g., Thomsen et al, 2015].…”

“…During the approach on DOY 167, a Hot Flow Anomaly (HFA) [ Schwartz et al ., ] was also observed. HFAs are cavities of heated and deflected solar wind plasma, and this is the first HFA observed at Jupiter [ Valek et al ., ].…”

Electron beams and loss cones in the auroral regions of Jupiter

“…[], a very large hot flow anomaly in the solar wind [ Valek et al . ]. JADE also contributed to a study on magnetopause crossings [ Gershman et al ., ].…”

Solar Wind Properties During Juno's Approach to Jupiter: Data Analysis and Resulting Plasma Properties Utilizing a 1‐D Forward Model

“…We have provided a best estimate pre‐JOI SW moments data set for the community to use in their modeling endeavors (applications of bow shock or magnetopause models, or comparisons with propagated SW conditions from Earth) or for coordinated investigations with remote measurements of Jovian aurora. Our data set has already been used in the auroral studies of Gladstone et al () and Nichols et al (), and the hot flow anomaly study of Valek et al (). We expect this new interval of SW parameters to greatly expand future investigations with telescopic measurements of Jupiter.…”

“…During its approach, Juno's suite of particle and field instruments made in situ observations of the SW and IMF near Jupiter, while remote sensing instruments, both on the spacecraft and at Earth, simultaneously observed the planet's aurora, radio emissions, Io plasma torus, and atmosphere. Early results from Juno related to the SW's influence at Jupiter include the detection of a large hot flow anomaly near the dawn bow shock (Valek et al, ), a compressed magnetosphere prior to crossing Jupiter's bow shock (McComas, Szalay, et al, ), evidence of magnetic reconnection and an open magnetosphere along the dawn magnetopause (Ebert et al, ), and significant enhancements in the main aurora ultraviolet power in response to an interplanetary shock (Nichols et al, ). This paper quantifies the SW conditions during Juno's approach to Jupiter and documents the analysis to derive a customized data set already used by multiple first‐results papers (Gladstone et al, ; Nichols et al, ; Valek et al, ).…”