Dynamic infrared aurora on Jupiter.

Abstract

Auroral emissions are an important diagnostic for a planet's magnetosphere and upper atmosphere. At the outer planets, the characteristics of emission from the triatomic hydrogen ion <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>H</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> are key to understanding the auroral energy budget. We present James Webb Space Telescope observations of Jupiter's infrared auroral <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>H</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> emission, exhibiting variability on timescales down to seconds. Together with simultaneous Hubble Space Telescope ultraviolet observations, these results imply an auroral <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>H</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> lifetime of 150 s, and that <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>H</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> cannot efficiently radiate heat deposited by bursty auroral precipitation. However, <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mi>H</mi></mrow> <mrow><mn>3</mn></mrow> <mrow><mo>+</mo></mrow> </msubsup> </math> radiation is particularly efficient in a dusk active region, which has no significant ultraviolet counterpart. The cause of such emission is unclear. We also present observations of rapid eastward-travelling auroral pulses in the dawn side auroral region and pulsations that propagate rapidly along the Io footprint tail. Together, these observations open a diagnostic window for the jovian magnetosphere and ionosphere.