Bursty synchrotron intensity variations of Jovian 6-cm radio emissions and Jupiter's quasi-periodic polar activities

Lou, Yu‐Qing; Song, Haipeng; Liu, Yinyu; Yang, Meng

doi:10.1111/j.1745-3933.2011.01207.x

Cited by 2 publications

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“…Using the real-time solar wind data from the Advanced Composition Explorer and pertinent ephemeris, the analysis of Lou and Zheng [2003] shows a very likely coincidence of X-ray hot spot QP-45 variability with the arrival of a high-speed solar wind (∼ 700 km s −1 ) at Jupiter. So far, this is the only case for such a correlation; there were other examples of no QP-45 X-ray variations with relatively low-speed solar winds at Jupiter [Lou et al, 2012]. Lou et al [2012] reported 6-cm wavelength radio observations of Jupiter's IRB synchrotron flux variations on timescales of 20−60 min using the Urumqi 25-m radio telescope in XinJiang, China.…”

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confidence: 97%

“…So far, this is the only case for such a correlation; there were other examples of no QP-45 X-ray variations with relatively low-speed solar winds at Jupiter [Lou et al, 2012]. Lou et al [2012] reported 6-cm wavelength radio observations of Jupiter's IRB synchrotron flux variations on timescales of 20−60 min using the Urumqi 25-m radio telescope in XinJiang, China. Given the empirical evidence from several spacecraft with proper ephemeris, we show likely correlations of such QP type variations with recurrent high-speed solar winds at Jupiter.…”

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confidence: 97%

“…The low-frequency receiver of JUNO is capable of detecting QP-40 radio bursts from both Jovian poles but without polarization information. QP-40 bursts of relativistic electrons with energy E ≥ 10 MeV may penetrate the shield for protecting the instruments onboard.In reference to the model scenario and physical interpretations for Jupiter's QP-40 phenomena [Lou 2001;Lou et al, 2012] and especially by striking similarities in several major aspects Palmaerts et al, 2016], we advance here an analogous scenario of global magneto-inertial oscillations of Kronian inner radiation belt (KIRB) for QP-60 phenomena of Saturn as widely detected by various diagnostics of Cassini in-situ observations since early July 2004 [Badman et al, 2016;Mitchell et al, 2016; Palmaerts et al, 2016 and references therein]. With a weaker field, KIRB traps relativistic electrons (up to E ∼ 12 MeV and likely higher) and energetic protons within ∼ 5 R S (Saturn radii) [Kollmann et al, 2011], and the KIRB electron number density is ∼ 50−100 cm −3 [Persoon et al, 2005].…”

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Quasi-periodic magnetospheric activities of Jupiter and Saturn and magneto{inertial oscillations of their inner radiation belts (extended abstract).

Lou¹

2018

Planetary Radio Emissions Viii

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Extended AbstractUlysses discovered quasi-periodic 40 minute (QP-40) bursts of relativistic electrons (energy E ≥ 10 MeV) and of associated low-frequency radio emissions (frequency ν ≤ 0.7 MHz) from the south pole of Jupiter since early February 1992 [McKibben et al., 1993]. Such QP-40 radio bursts feature right-hand circular polarization, and their occurrence strongly correlates with recurrent arrivals of fast-speed solar winds [MacDowall et al. 1993]. Based on model analysis, empirical evidence and physical considerations, Lou [2001] advanced the scenario that these QP-40 relativistic electron bursts originate around circumpolar zones from Jupiter's inner radiation belt (IRB) occupying ∼ 1.5 − 3 R J (Jovian radii) wherein the intense synchrotron radiation reveals trapped relativistic electrons (E ≥ 50 MeV with Lorentz factor γ up to ∼ 200) and predicted then that such QP-40 polar burst activities should be global involving both Jovian poles, as indeed confirmed by Ulysses observations towards the north pole direction of Jupiter 12 years later. As Jupiter's dipole field points inward/outward at its south/north pole, outstreaming extremely relativistic electrons gyrate very rapidly around south/north circumpolar magnetic field lines (antiparallel/parallel) with very small pitch angles and emit low-frequency (ν ≤ 0.7 MHz) beamed radio bursts with partially right-hand/left-hand circular polarizations. Such QP burst activities correlate with recurrent arrivals of fast-speed solar winds at Jupiter due to magnetospheric squeeze, angular momentum conservation, solar wind intermittency and magnetohydrodynamic (MHD) adjustments. Thus inside the Jovian magnetosphere, one should also detect QP-40 bursts of relativistic electrons together with QP-40 radio bursts from the north pole as from the south pole. Such QP-40 activities are linked to QP-40 magneto-inertial global IRB oscillations [Lou, 2001] that are excited by intermittent magnetized high-speed solar winds [Lou, 1996]. At a certain phase of IRB oscillations, magnetic irregularities along the circumpolar zones adjacent to the IRB would leak out relativistic electrons drifting outwards across field lines from the IRB. The energy distribution of relativistic electrons in a typical burst would generally reflect that of the IRB. -Q. LouJupiter is known to be an important planetary source of relativistic electrons and other charged particles in the solar system. We emphasize that the Jovian polar leakage of relativistic electrons from the IRB appears in forms of drift/diffusion, escape and QP-40 or QP type bursts.Near the end of 2000 during the joint campaign of Cassini, HST and Chandra, the high-resolution camera of Chandra captured QP-45 brightness variations of an X-ray hot spot within the north auroral oval during a 10-hour observation [Gladstone et al., 2002]. This provided supporting circumstantial evidence that the IRB neighborhood including open field polar regions oscillate in QP-40 manner as influenced by IRB oscillations and by transpolar MHD waves, leading t...

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Quasi-periodic magnetospheric activities of Jupiter and Saturn and magneto{inertial oscillations of their inner radiation belts (extended abstract).

Lou¹

2018

Planetary Radio Emissions Viii

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Observational Features of Exoplanetary Synchrotron Radio Bursts

Qian

2020

ApJ

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The magnetic fields of exoplanets shield the planets from cosmic rays and interplanetary plasma. Due to the interaction with the electrons from their host stars, the exoplanetary magnetospheres are predicted to have both cyclotron and synchrotron radio emissions, neither of which have been definitively identified in observations. As the coherent cyclotron emission has been extensively studied in the literature, here we focus on planetary synchrotron radiation with bursty behaviors (i.e., radio flares) caused by the outbreaks of energetic electron ejections from the host star. Two key parameters of the bursty synchrotron emissions, namely the flux density and burst rate, and two key features, namely the burst light curve and frequency shift, are predicted for star–hot Jupiter systems. The planetary orbital phase–burst rate relation is also considered as the signature of star–planet interactions. As examples, previous X-ray and radio observations of two well-studied candidate systems, HD 189733 and V830 τ, are adopted to predict their specific burst rates and fluxes of bursty synchrotron emissions for further observational confirmations. The detectability of such emissions by current and upcoming radio telescopes shows that we are at the dawn of discoveries.

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Bursty synchrotron intensity variations of Jovian 6-cm radio emissions and Jupiter's quasi-periodic polar activities

Cited by 2 publications

References 41 publications

Quasi-periodic magnetospheric activities of Jupiter and Saturn and magneto{inertial oscillations of their inner radiation belts (extended abstract).

Quasi-periodic magnetospheric activities of Jupiter and Saturn and magneto{inertial oscillations of their inner radiation belts (extended abstract).

Observational Features of Exoplanetary Synchrotron Radio Bursts

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