Evidence for short-term variability of Jupiter's decimetric emission from VLA observations

Santos-Costa, Daniel; Bolton, S. J.; Sault, R. J.

doi:10.1051/0004-6361/200912106

Cited by 13 publications

(21 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Equatorial source of radiation and secondary emissions located at high-latitudes are typically observed on either or both sides of the planet. The main features in the brightness distribution of Jupiter's synchrotron radiation were discovered in the 1980s and 1990s, when highresolution images in total intensity or linear polarization were first obtained at 6, 13, 20, and 90 cm (e.g., de Pater 1990de Pater , 1991Leblanc et al 1997;Santos-Costa et al 2009) and later at 2.2 cm Fig. 1.…”

Section: Data Analysis Results From Rotation-averaged Imagesmentioning

confidence: 99%

“…To accomplish this, two different tomographic reconstruction techniques are applied to the VLA observations of May 1997 (e.g., Leblanc et al 1997;Santos-Costa et al 2009, Table 1). The results are displayed in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Although secondary sources of radiation are spotted off-equator with high-resolution brightness maps, more than half of the Jovian synchrotron emission is produced by near-equatorial electrons trapped at distances of ∼1.2−1.7 planetary radii (R J ) with energies of ∼1-30 MeV (e.g., de Pater 1990de Pater , 1991Leblanc et al 1997;Santos-Costa et al 2009;Girard et al 2012). At wavelengths shorter than ∼5 cm, Jupiter becomes a strong source of thermal emission and groundbased telescopes have more difficulty measuring the Jovian synchrotron radiation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Santos-Costa

Pater

Sault

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

Aims. We examine Very Large Array (VLA) observations of Jupiter to present evidence of fluctuations in the emission produced by the electron belt in January 2001. Investigating the source of fluctuations will provide new opportunities to discuss the scenarios of temporal changes in Jupiter's synchrotron radiation (i.e., the electron belt) in future data analysis and modeling work. Methods. To discuss the electron belt dynamics during the Cassini flyby of Jupiter, we compare the radio measurements from 2−3 January 2001 with VLA observations obtained on 20−21 December 1988, when viewing geometry and array configuration are comparable. All data are scaled to a standard Earth-Jupiter distance of 4.04 AU for comparison purposes. Brightness distribution maps with identical spatial resolutions and cartography of the equatorial radiation are constructed and examined at the wavelengths of ∼21 cm and ∼90 cm. Results. Rotation-averaged maps show that the emission from the equatorial zones of maximum intensity is weaker by ∼5−40%, but the brightness distribution is spatially more extended on 2−3 January 2001, resulting in a total emission at both wavelengths stronger by ∼35%. Between observation periods, the brightness distributions are observed to evolve differently during the planet rotation. Tomographic reconstructions of the equatorial radiation support our conclusion that the electron-belt population was differently distributed around the planet in December 1988 and January 2001. Conclusions. Our analysis of VLA data sets suggests that the spatial distribution of the electron belt on 2−3 January 2001 is different from that usually observed. Our knowledge of solar activity at the time of the Cassini flyby of Jupiter suggests that the emission from the electron radiation belt was responding to external influences, most likely to solar wind structures rather than to solar radio flux, on a timescale of days to a couple of weeks. Combined results from a multisource data analysis -including spacecraft and radio observations -are needed to confirm this relationship.

show abstract

Section: Data Analysis Results From Rotation-averaged Imagesmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Santos-Costa

Pater

Sault

et al. 2014

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…Brightness distribution maps at 6 cm-wavelength demonstrate that the spatial structure of Jupiter's radiation-belt emission was changing on short time-scales, thus confirming the capability of observing rapid variations of the non-thermal emission of this planet with interferometers [Santos-Costa et al, 2009]. In 2009, the brightness temperatures along the magnetic equator were again observed to evolve differently during Jupiter's 10-hour rotation and over a long period of observations.…”

Section: Resultsmentioning

confidence: 65%

“…The thermal emission was subtracted during the data reduction to provide only images of Jupiter's synchrotron emission. As discussed by Santos-Costa et al [2009], we can concede a 5% error on the data values of the "Clean" images.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

Variability of Jupiter’s Synchrotron Emission in Mid-2009

Santos-Costa¹,

Sault²,

Bolton³

et al. 2011

Planetary Radio Emissions Vii

Self Cite

View full text Add to dashboard Cite

In the present paper, radio observations made at the wavelength of 6 cm with the VLA in 2009 are analyzed. Reconstructed images of the brightness distribution show significant intensity variations of the equatorial peak emissions on both sides of the planet. The fluctuations are characterized by asymmetrical changes in the brightness distributions. The contribution of a comet-like impact to the observed variations is discussed. During the third week of July, ground-based measurements at different radio bands confirmed that a large projectile had struck Jupiter's atmosphere. The examination of the 2009 VLA data sets shows that the steep enhancement of the emission radiated by Jupiter's electron belt occurred during the same period. The increase in the synchrotron radiation was observed to go on for a couple of weeks before gradually fading in August. Two-dimensional reconstructions of the equatorial brightness distribution demonstrate that the time variability of the radio emission during the middle of 2009 was driven by the longitudinal expansion of an impact-related synchrotron "hot spot" originally located at the Jupiter System III longitude of 305 degrees.

show abstract

Relation between the short‐term variation of the Jovian radiation belt and thermosphere derived from radio and infrared observations

et al. 2015

View full text Add to dashboard Cite

We report the first comprehensive observations of Jovian synchrotron radiation (JSR) and H3+ emission from the Jovian thermosphere to investigate the generation process of short‐term (days to weeks) variations in the Jovian radiation belt. The observations were made by the Giant Metrewave Radio Telescope and NASA Infrared Telescope Facility during November 2011. The total flux density of JSR increased by approximately 5% between 6–9 November and 12–17 November, associated with the increased solar UV/EUV flux. From 7 to 14 November, a possible rise in the infrared H3+ emission was observed in the middle‐latitude region, corresponding to a temperature variation of approximately 10 K. These results are consistent with the scenario that the solar UV/EUV heating causes variations in the thermospheric temperature and JSR. Radio images along the equatorial region showed that the JSR intensity decreased inside 1.5 Jovian radii (RJ) and the peak position shifted outward. This implies that energetic electrons are attenuated by some internal loss process, despite the simultaneous increase in radial diffusion. A physical model for the radiation belt shows that such an internal loss process can explain the observed variation of brightness distribution. Typical loss time scale is longer than strong diffusion limit, which suggests the existence of some pitch angle diffusion process such as wave‐particle interaction. Thus, variations of the total JSR flux density and thermospheric temperature seem consistent with the scenario, and the brightness distribution of JSR can be explained by the increase in radial diffusion accompanied by internal loss processes.

show abstract

Evidence for short-term variability of Jupiter's decimetric emission from VLA observations

Cited by 13 publications

References 24 publications

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

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

Variability of Jupiter’s Synchrotron Emission in Mid-2009

Relation between the short‐term variation of the Jovian radiation belt and thermosphere derived from radio and infrared observations

Contact Info

Product

Resources

About