Correlation studies between solar wind parameters and the decimetric radio emission from Jupiter

Abstract

Results of a study comparing long‐term time variations (years) in Jupiter's synchrotron radio emission with a variety of solar wind parameters and the 10.7‐cm solar flux are reported. Data from 1963 through 1985 were analyzed, and the results suggest that many solar wind parameters are correlated with the intensity of the synchrotron emission produced by the relativistic electrons in the Jovian Van Allen radiation belts. Significant nonzero correlation coefficients appear to be associated with solar wind ion density, ram pressure, thermal pressure, flow velocity, momentum, and ion temperature. The highest correlation coefficients are obtained for solar wind ram pressure (NV²) and thermal pressure (NT). The correlation analysis suggests that the delay time between fluctuations in the solar wind and changes in the Jovian synchrotron emission is typically about 2 years. The delay time of the correlation places important constraints on the theoretical models describing the radiation belts. The implication of these results, if the correlations are real, is that the solar wind is influencing the supply and/or loss of electrons to Jupiter's inner magnetosphere. We note that the data for this work spans only about two periods of the solar activity cycle, and because of the long time scales of the observed variations, it is important to confirm these results with additional observations.

Multifrequency analysis of the Jovian electron-belt radiation during theCassiniflyby of Jupiter

“…The observation of changes in the emission from Jupiter's electron belt has been reported since the early 1970s (e.g., Gérard 1970; Klein et al 1972Klein et al , 1989. Correlations with solar wind on timescales of months to years (e.g., Bolton et al 1989;Galopeau & Gérard 2001;Santos-Costa et al 2008) and solar radio flux on timescales of days to a week (e.g., Miyoshi et al 1999;Tsuchiya et al 2011;Kita et al 2013) have been confirmed since the 1990s. However, the response of the electron belt to the solar wind on short timescales has never been considered until the present work.…”

“…Changes in the spatial distribution of the electron belt are supposedly driven by either internal or external parameters (e.g., Bolton et al 1989;Brecht et al 2001;de Pater and Brecht 2001;Horne et al 2008;Santos-Costa et al 2008, 2011Kita et al 2013, and references therein). Determining the exact cause(s) of changes in the radio maps in Fig.…”

“…Investigating the source of fluctuations in early January 2001 will provide new opportunities to re-examine the scenarios of temporal changes in Jupiter's synchrotron radiation (e.g., Bolton et al 1989;Santos-Costa et al 2008;Kita et al 2013, and references therein). The results of our data analysis will help constrain models of Jupiter's electron belt.…”

Modulation of Jovian electrons at 1 AU during solar cycles 22–23

“…[21] It is well known that Jupiter is a source of synchrotron radiation whose strength seems to be related to solar activity [Bolton et al, 1989;Galopeau and Gerard, 2001]. Bolton et al suggested that solar activity may possibly modulate Jovian radiation belt electrons and found that the best correlation between solar wind parameters and the Jovian synchrotron radiation required a two year lag time most of which is presumably the response time of the Jovian magnetosphere.…”

Jupiter Radio Bursts and Particle Acceleration

“…The inward flux of charged particles conserves the first two adiabatic invariants of motion while violating the third (Chang & Davis 1962). The particle source is believed to be the solar wind, and there is some evidence that the decimetric emission waxes and wanes with solar wind variations with approximately a 2 year lag (Bolton et al 1989). This synchrotron flux is extremely intense, permitting relatively easy detection of the emission from Earth and the generation of radio maps of the planet that manifest clear asymmetries in the planet's global magnetic field (e.g., de Pater 1981).…”