Saturn lightning activity from a cyclone at 50°North latitude

2020 ◽  
Author(s):  
Georg Fischer ◽  
Jacob Gunnarson
Keyword(s):  
Radio Emission ◽  
Plasma Wave ◽  
Average Diameter ◽  
Upper Atmosphere ◽  
Electrostatic Discharges ◽  
Radio Emissions ◽  
White Spots ◽  
Cassini Mission ◽  
Almost All ◽  
North Latitude

<p>During the Cassini mission (2004-2017) the Radio and Plasma Wave Science (RPWS) experiment has recorded the lightning radio emissions from multiple thunderstorms in Saturn's atmosphere. Most of the storms were located in the storm alley at a planetocentric latitude of 35°South, and there was one extra-large storm at 35°North called "Great White Spot" (GWS), which emitted millions of SEDs. This is short for "Saturn Electrostatic Discharges", a widely-used synonym for the radio emission from Saturn lightning. Most lightning storms have also been observed by the Cassini cameras or by ground-based amateur astronomers as bright white spots with diameters around 2000 km ("smaller" storms in the storm alley) or as large as 10,000 km (GWS at 35°North).</p><p>In this presentation we focus on a cyclone at 50°North planetocentric latitude, which was observed by the Cassini cameras from 2007 until the end of 2013. Its average diameter was around 3000 km, and it also exhibited some weak SED activity. The first SED outbreak was in December 2010, at the same time when the GWS was raging further south. Due to the differences in longitude and SED rate of the 50°N cyclone compared to the GWS, it is partly possible to separate the SEDs emitted from the cyclone to those emitted from the GWS. The SED rate of the cyclone is rather low, typically a few SEDs per minute, whereas the GWS showed SED rates up to 10 SEDs per second. The SED activity of the 50°North cyclone was very intermittent, it usually lasted for a few weeks before disappearing again for several months. After the first outbreak in December 2010, there was some more activity in early 2011, autumn 2011, December 2011, spring 2012, July 2012, summer 2013, and finally autumn 2013. By comparing SED data from RPWS with images from the Cassini camera we will show that almost all SEDs taking place after the GWS had their origin in the 50°N cyclone, since the SED sub-spacecraft longitude range is consistent with the longitude of the cyclone. The last SED activity from this cyclone took place in November 2013, and it was also the last SED activity recorded by RPWS during the whole Cassini mission. No more SEDs were found from November 2013 until Cassini burned up in Saturn's upper atmosphere in September 2017.</p><p> </p>

scholarly journals Formation of Isolated Radio Type II Bursts at Low Frequencies

Solar Physics ◽  
2021 ◽  
Vol 296 (5) ◽  
Author(s):  
Silja Pohjolainen ◽  
Nasrin Talebpour Sheshvan
Keyword(s):  
Radio Emission ◽  
Emission Characteristics ◽  
The Sun ◽  
Type Ii ◽  
Low Frequencies ◽  
Radio Emissions ◽  
Rich Variety ◽  
Type Ii Bursts ◽  
Almost All ◽  
Special Subgroup

AbstractThe first appearance of radio type II burst emission at decameter-hectometer (DH) waves typically occurs in connection, and often simultaneously, with other types of radio emissions. As type II bursts are signatures of propagating shock waves that are associated with flares and coronal mass ejections (CMEs), a rich variety of radio emissions can be expected. However, sometimes DH type II bursts appear in the dynamic spectra without other or earlier radio signatures. One explanation for them could be that the flare-CME launch happens on the far side of the Sun, and the emission is observed only when the source gets high enough in the solar atmosphere. In this study we have analysed 26 radio type II bursts that started at DH waves and were well-separated (‘isolated’) from other radio emission features. These bursts were identified from all DH type II bursts observed in 1998 – 2016, and for 12 events we had observations from at least two different viewing angles with the instruments on board Wind and the Solar Terrestrial Relations Observatory (STEREO) satellites. We found that only 30% of the type II bursts had their source origin on the far side of the Sun, but also that no bursts originated from the central region of the Sun (longitudes E30 – W40). Almost all of the isolated DH type II bursts could be associated with a shock near the CME leading front, and only few were determined to be shocks near the CME flank regions. In this respect our result differs from earlier findings. Our analysis, which included inspection of various CME and radio emission characteristics, suggests that the isolated DH type II bursts could be a special subgroup within DH type II bursts, where the radio emission requires particular coronal conditions to form and to die out.

scholarly journals Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4–650224

2021 ◽  
Vol 655 ◽  
pp. A52
Author(s):  
F. Coti Zelati ◽  
B. Hugo ◽  
D. F. Torres ◽  
D. de Martino ◽  
A. Papitto ◽  
...  
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Millisecond Pulsar ◽  
Radio Emissions ◽  
X Ray ◽  
Link Type ◽  
Upper Limit ◽  
Variability Pattern ◽  
Average Flux ◽  
Compact Array

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4–650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX ≃ 7 × 1033 erg s−1 over the 0.3−10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33 μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4–650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15 μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4–650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.

scholarly journals Jupiter's Radiation Belts and Upper Atmosphere

1974 ◽  
Vol 65 ◽  
pp. 375-383
Author(s):  
Joseph J. Degioanni ◽  
John R. Dickel
Keyword(s):  
Radio Emission ◽  
Radiation Belts ◽  
Upper Atmosphere ◽  
Mixing Ratio ◽  
Frequency Range ◽  
Emission Data ◽  
High Energies ◽  
Isotropic Distribution ◽  
Relativistic Particles ◽  
Flat Distribution

Models of Jupiter's radiation belts have been constructed to determine the distribution of particles and their energies which will produce the observed decimetric radio emission. Data on the spectrum and the variation of emission with Jovian longitude have been used to show that the relativistic particles have a nearly isotropic distribution with high energies (of order 100 MeV) within 2 Jovian radii and a very flat distribution in the equatorial plane of low energy particles further out in the magnetosphere.Subtraction of the emission predicted by this model from the total radio emission shows that the thermal contribution in the frequency range between 3000 and 10000 MHz is somewhat less than had been previously expected. (The brightness temperature of the planetary disk is 180 K at 3000 MHz, for example.) This suggests that the ammonia mixing ratio in Jupiter's upper atmosphere may be as high as 0.002.

scholarly journals Numerical simulations of unbounded cyclotron-maser emissions

2013 ◽  
Vol 79 (6) ◽  
pp. 999-1001 ◽  
Author(s):  
DAVID C. SPEIRS ◽  
S. L. McCONVILLE ◽  
K. M. GILLESPIE ◽  
A. D. R. PHELPS ◽  
K. RONALD
Keyword(s):  
Radio Emission ◽  
Numerical Simulations ◽  
Source Region ◽  
Radio Emissions ◽  
Cyclotron Maser ◽  
Thermal Radio ◽  
Thermal Radio Emission ◽  
Electron Cyclotron Masers ◽  
Coupling Characteristics ◽  
Significant Bearing

AbstractNumerical simulations have been conducted to study the spatial growth rate and emission topology of the cyclotron-maser instability responsible for stellar/planetary auroral magnetospheric radio emission and intense non-thermal radio emission in other astrophysical contexts. These simulations were carried out in an unconstrained geometry, so that the conditions existing within the source region of some natural electron cyclotron masers could be more closely modelled. The results have significant bearing on the radiation propagation and coupling characteristics within the source region of such non-thermal radio emissions.

scholarly journals A survey of Galileo plasma wave instrument observations of Jovian whistler-mode chorus

2008 ◽  
Vol 26 (7) ◽  
pp. 1819-1828 ◽  
Author(s):  
J. D. Menietti ◽  
R. B. Horne ◽  
D. A. Gurnett ◽  
G. B. Hospodarsky ◽  
C. W. Piker ◽  
...  
Keyword(s):  
Plasma Wave ◽  
Radiation Belt ◽  
Good Reason ◽  
Radial Distance ◽  
Local Times ◽  
Whistler Mode ◽  
Jovian Magnetosphere ◽  
Spacecraft Trajectory ◽  
Almost All ◽  
The Magnetic Field

Abstract. A survey of plasma wave observations at Jupiter obtained by the plasma wave instrument on board the Galileo spacecraft is presented. The observations indicate that chorus emissions are observed commonly in the Jovian magnetosphere near the magnetic equator in the approximate radial range 6<r<10 RJ. The survey includes almost all local times but not equally sampled in radial distance due to the spacecraft trajectory. The data suggest that chorus emissions are somewhat more intense on the dayside, but this may be a result of insufficient nightside observations. The orbit of Galileo is also restricted to ±3° of the Jovigraphic equator, but the tilt of the magnetic field permits coverage of a range of magnetic latitudes of −13°<λmag<+13°. The similarities of chorus emissions to terrestrial observations are a good reason to speculate that Jovian chorus emission may play a significant role in the stochastic acceleration of electrons in the radial range 6–10 RJ as recent studies indicate. These electrons may then be transported inward by radial diffusion where they are additionally accelerated to form the synchrotron radiation belt source.

Titan’s Ultraviolet Airglow Variability with Solar Cycle and Saturn Local Time

2020 ◽  
Author(s):  
Emilie Royer ◽  
Marielle Cooper ◽  
Joseph Ajello ◽  
Larry Esposito ◽  
Frank Crary
Keyword(s):  
Solar Cycle ◽  
Local Time ◽  
Solar Maximum ◽  
Incidence Angle ◽  
Upper Atmosphere ◽  
Particle Precipitation ◽  
Cassini Mission ◽  
Airglow Emissions ◽  
Airglow Intensity

&lt;p&gt;The Cassini spacecraft observed Titan&amp;#8217;s upper atmosphere and its airglow emissions from 2005 to 2017. It is now established that the solar XUV radiation is the main source of dayglow, while magnetospheric particle precipitation principally acts on the nightside of the satellite. Nevertheless, one of the questions remaining unanswered after the end of the Cassini mission concerns the role and quantification of the magnetospheric particle precipitation and other minor sources such as micrometeorite precipitation and cosmic galactic ray at Titan. We report here on enhancements observed in Ultraviolet (UV) observations of Titan airglow made with the Cassini-Ultraviolet Imaging Spectrograph (UVIS). Enhancements are correlated with magnetospheric changing conditions occurring while the spacecraft, and thus Titan, are known to have crossed Saturn&amp;#8217;s magnetopause and have been exposed to the magnetosheath environment. The processing and interpretation of 13+ years of airglow observations at Titan allows now for global studies of the upper atmosphere as a function of the Saturn Local Time (SLT) and the solar cycle.&lt;/p&gt;&lt;p&gt;Nitrogen airglow occur at about 1100 km of altitude in Titan&amp;#8217;s upper atmosphere. Observations by the Cassini-UVIS instrument revealed the emission of the LBH band system, VK band system as well as Nitrogen atomic emission lines at 1085&amp;#197; and 1493&amp;#197;, as the prominent features of airglow emissions at Titan, as shown in Figures 1 and 2. Measurements were made at a wide range of solar incidence angles and Saturn Local Time (SLT), during the entire Cassini mission, allowing for the investigation of the upper atmosphere response to the magnetospheric environment and energetic particle precipitation. Additionally, observations were taken in a variety of solar condition, from solar maximum to minimum. UVIS observations of Titan around 12PM SLT (near Saturn&amp;#8217;s magnetopause) present evidence of Titan&amp;#8217;s upper atmosphere response to a fluctuating magnetospheric environment.&lt;/p&gt;&lt;p&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.9617eca672fe56938492951/sdaolpUECMynit/0202CSPE&amp;app=m&amp;a=0&amp;c=975f92d7d9d43faa47cacd77ad47438f&amp;ct=x&amp;pn=gnp.elif&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Figure 1.&lt;/strong&gt; Airglow intensity as a function of the saturn Local Time (SLT), for observation taken close the Saturn&amp;#8217;s magnetopause (12PM SLT, labelled &amp;#8216;12h&amp;#8217;) and observations taken around miadnight SLT (labelled &amp;#8216;24h&amp;#8217;). Dayglow spectra exhibit higher averaged airglow intensity than Nightglow spectra.&lt;/p&gt;&lt;p&gt;We present here comparisons of the spectral emissions from the dayglow (Solar incidence angle &lt;110&amp;#176;) and nightglow (Solar incidence angle &amp;#8805;110&amp;#176;) between a rayheight of 900-1200 km around noon (&amp;#177;1 h) and around midnight (&amp;#177;1 h) SLT, during solar minima and maxima conditions (Fig. 2). Results show an enhancement of the airglow brightness with increasing particle precipitation, especially at SLT close to noon (i.e. close to the magnetopause), during solar maximum and minimum. Correlation between the ratio of the V-K, LBH, and NI-1493&amp;#197; emission peaks are also presented.&lt;/p&gt;&lt;p&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.2357e48772fe52168492951/sdaolpUECMynit/0202CSPE&amp;app=m&amp;a=0&amp;c=2c6d843782e300fc27ec3db3de320caf&amp;ct=x&amp;pn=gnp.elif&quot; alt=&quot;&quot;&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Figure 2.&lt;/strong&gt; Dayglow intensity as a function of the saturn Local Time (SLT) and solar cycle. Observations have been dispatched in four groups as a function of Titan&amp;#8217;s orbital position within Saturn&amp;#8217;s magnetosphere and maximum oe minimum stage of the solar cycle. Results suggest that solar maximum conditions around midgnight SLT favor the apparition of the brightest dayglow.&lt;/p&gt;&lt;p&gt;In the past decade, results from the Cassini-UVIS instrument greatly improved our understanding of airglow production at Titan. However, combining remote-sensing datasets, such as Cassini-UVIS data, with in-situ measurements taken by the Cassini Plasma Spectrometer (CAPS) instrument can provide us with a more rigorous assessment of the airglow contribution and correlations between data from simultaneous observations of in-situ Cassini instruments (CAPS, RPWS and MIMI) has been possible on few occasions. UVIS results present here will be put in context with results from in-situ simultaneous observations.&lt;/p&gt;&lt;!-- COMO-HTML-CONTENT-END --&gt; &lt;p class=&quot;co_mto_htmlabstract-citationHeader&quot;&gt; &lt;strong class=&quot;co_mto_htmlabstract-citationHeader-intro&quot;&gt;How to cite:&lt;/strong&gt; Royer, E., Cooper, M., Ajello, J., Esposito, L., and Crary, F.: Titan&amp;#8217;s Ultraviolet Airglow Variability with Solar Cycle and Saturn Local Time, Europlanet Science Congress 2020, online, 21 September&amp;#8211;9 Oct 2020, EPSC2020-415, 2020 &lt;/p&gt;

ExPRES Modeling of Auroral Radio Source Occultation observed by Galileo Application to JUICE and Juno

2020 ◽  
Author(s):  
Baptiste Cecconi ◽  
Corentin K Louis ◽  
Claudio Munoz ◽  
Claire Vallat
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Plasma Waves ◽  
Physical Parameters ◽  
Operation Planning ◽  
Radio Emissions ◽  
Galilean Moons ◽  
Temporal Occurrence ◽  
Galilean Moon ◽  
Ionospheric Sounding

&lt;p&gt;The ExPRES code simulates exoplanetary and planetary auroral radio emissions. It could be used to predict and interpret Jupiter&amp;#8217;s radio emissions in the hectometric and decametric range. In this study, we model the occultations of the Jovian auroral radio emissions during the Galilean moons flybys by the Galileo spacecraft. In this study, we focus on auroral radio emissions, configuring the ExPRES simulations runs with typical radio source physical parameters. We compare the simulations run results with the actual Galileo/PWS observations, and show that we accurately model the temporal occurrence of the occultations in the whole spectral range observed by Galileo. We can then predict auroral radio emission occultations by the Galilean moons for the Juno and JUICE missions. ExPRES will be used by the JUICE/RPWI (Radio Plasma Waves Investigation) team to prepare its operation planning during the Galilean moon flybys for, e.g., the Galilean moon ionosphere characterization science objective, with passive ionospheric sounding during ingress and egress of Jovian radio source occultations.&amp;#160;&lt;/p&gt;

A search for Saturn electrostatic discharges in the Voyager plasma wave data

Icarus ◽  
1983 ◽  
Vol 53 (2) ◽  
pp. 255-261 ◽  
Author(s):  
W.S. Kurth ◽  
D.A. Gurnett ◽  
F.L. Scarf
Keyword(s):  
Plasma Wave ◽  
Electrostatic Discharges ◽  
Wave Data

scholarly journals A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

2014 ◽  
Vol 32 (12) ◽  
pp. 1463-1476 ◽  
Author(s):  
G. Fischer ◽  
S.-Y. Ye ◽  
J. B. Groene ◽  
A. P. Ingersoll ◽  
K. M. Sayanagi ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Upper Atmosphere ◽  
White Spot ◽  
Time Interval ◽  
Unusual Behavior ◽  
Cassini Mission ◽  
Large Jump ◽  
Modulation Signal ◽  
Thermospheric Winds ◽  
Energy And Momentum

Abstract. The periodicity of Saturn kilometric radiation (SKR) varies with time, and its two periods during the first 5 years of the Cassini mission have been attributed to SKR from the northern and southern hemisphere. After Saturn equinox in August 2009, there were long intervals of time (March 2010 to February 2011 and September 2011 to June 2012) with similar northern and southern SKR periods and locked SKR phases. However, from March to August 2011 the SKR periods were split up again, and the phases were unlocked. In this time interval, the southern SKR period slowed down by ~ 0.5% on average, and there was a large jump back to a faster period in August 2011. The northern SKR period speeded up and coalesced again with the southern period in September 2011. We argue that this unusual behavior could be related to the so-called Great White Spot (GWS), a giant thunderstorm that raged in Saturn's atmosphere around that time. For several months in 2011, the visible head of the GWS had the same period of ~ 10.69 h as the main southern SKR modulation signal. The GWS was most likely a source of intense gravity waves that may have caused a global change in Saturn's thermospheric winds via energy and momentum deposition. This would support the theory that Saturn's magnetospheric periodicities are driven by the upper atmosphere. Since the GWS with simultaneous SKR periodicity measurements have only been made once, it is difficult to prove a physical connection between these two phenomena, but we provide plausible mechanisms by which the GWS might modify the SKR periods.

scholarly journals Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby

2009 ◽  
Vol 27 (11) ◽  
pp. 4257-4272 ◽  
Author(s):  
P. Garnier ◽  
J-E. Wahlund ◽  
L. Rosenqvist ◽  
R. Modolo ◽  
K. Ågren ◽  
...  
Keyword(s):  
Plasma Wave ◽  
Significant Influence ◽  
Langmuir Probe ◽  
Cold Plasma ◽  
The Moon ◽  
Plasma Environment ◽  
Cassini Mission ◽  
Electrical Conductivities ◽  
Low Altitude ◽  
Detailed Picture

Abstract. The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.

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