A studying of solar-ENSO correlation with southern Brazil tree-ring index (1955?1994)

International audienceSolar activity, volcanic aerosol, El Niño-Southern Oscillation and global temperature anomalies effects on Southern Brazil tree growth rings are presented through multiple linear analysis. Linear correlations were made on annual, 10 year running averages and band pass filter. For annual averages, the correlation coefficients were low, and the 10 years running average correlations the coefficient correlations were much higher. The multiple regression of 2 to 5 year band pass filter indicates that 60% of the variance in tree ring index was explained by volcanic eruptions, Southern Oscillation Index and temperature anomalies. The multiple regression of 10 year running averages indicates that 84% of the variance in tree ring index was explained by solar activity and another time series. These results indicate that the effects of solar activity, volcanic eruptions, ENSO and temperature anomalies on tree rings are better seen on long timescales than volcanic eruption, ENSO and temperature anomaly

Tree-ring width wavelet and spectral analysis of solar variability and climatic effects on a Chilean cypress during the last two and a half millennia

International audienceSpectral and wavelet analysis were performed on a tree ring width time series obtained from a 2500 yr old cypress tree (Fitzroya cupressoides) from Costa del Osorno, Chile. The periods for analysis were selected at 95% confidence level. Both periodicities characteristic of solar activity and climatic variations were found in this tree ring width series. The 11 and 22 years solar cycle periods were present in tree ring data with a confidence level above 98%. This indicates the solar modulation of climatic variations is being recorded by the tree ring grown. However wavelet analysis shows that these are present only sparsely. Short-term variations, between 2-5 years, are also present in tree ring data, and are shown by wavelet maps to be a more permanent characteristic. This time scale is a signature of ENSO events. Long-term variations, above 200 years, are also present in tree ring data. The spectral analysis performed in this work shows that this species has the ability to record solar-ENSO variations that seems to be affecting the local environment of tree growth, and also that this region was influenced by ENSO events at least in the past 2500 yr interval covered by this study

Radio emission from satellite-Jupiter interactions (especially Ganymede)

Analyzing a database of 26 years of observations of Jupiter from the Nan\c{c}ay Decameter Array, we study the occurrence of Io-independent emissions as a function of the orbital phase of the other Galilean satellites and Amalthea. We identify unambiguously the emissions induced by Ganymede and characterize their intervals of occurrence in CML and Ganymede phase and longitude. We also find hints of emissions induced by Europa and, surprisingly, by Amalthea. The signature of Callisto-induced emissions is more tenuous.Comment: 14 pages, 7 figures, in "Planetary Radio Emissions VIII", G. Fischer, G. Mann, M. Panchenko and P. Zarka eds., Austrian Acad. Sci. Press, Vienna, in press, 201

The solar and interplanetary causes of the recent minimum in geomagnetic activity (MGA23): a combination of midlatitude small coronal holes, low IMF <I>B</I>_Z variances, low solar wind speeds and low solar magnetic fields

Minima in geomagnetic activity (MGA) at Earth at the ends of SC23 and SC22 have been identified. The two MGAs (called MGA23 and MGA22, respectively) were present in 2009 and 1997, delayed from the sunspot number minima in 2008 and 1996 by ~1/2–1 years. Part of the solar and interplanetary causes of the MGAs were exceptionally low solar (and thus low interplanetary) magnetic fields. Another important factor in MGA23 was the disappearance of equatorial and low latitude coronal holes and the appearance of midlatitude coronal holes. The location of the holes relative to the ecliptic plane led to low solar wind speeds and low IMF (<I>B</I>_z) variances (&sigma;_Bz²) and normalized variances (&sigma;_Bz²/<I>B</I>₀²) at Earth, with concomitant reduced solar wind-magnetospheric energy coupling. One result was the lowest ap indices in the history of ap recording. The results presented here are used to comment on the possible solar and interplanetary causes of the low geomagnetic activity that occurred during the Maunder Minimum

Analysis of cosmic ray variations observed by the CARPET in association with solar flares in 2011-2012

The CARPET cosmic ray detector was installed on April 2006 at CASLEO (Complejo Astronmico El Leoncito) at the Argentinean Andes (31.8S, 69.3W, 2550 m, Rc=9.65 GV). This instrument was developed within an international cooperation between the Lebedev Physical Institute RAS (LPI; Russia), the Centro de Radio Astronomia e Astrofsica Mackenzie (CRAAM; Brazil) and the Complejo Astronmico el Leoncito (CASLEO; Argentina). In this paper we present results of analysis of cosmic ray variations recorded by the CARPET during increased solar flare activity in 2011-2012. Available solar and interplanetary medium observational data obtained onboard GOES, FERMI, ISS, as well as cosmic ray measurements by ground-based neutron monitor network were also used in the present analysis.Fil: Makhmutov, V.. Lebedev Physical Institute; Rusia. Universidade Presbiteriana Mackenzie; BrasilFil: Raulin, J. P.. Universidade Presbiteriana Mackenzie; BrasilFil: De Mendonca, R. R. S.. National Institute for Space Research; BrasilFil: Bazilevskaya, G. A.. Lebedev Physical Institute; RusiaFil: Correia, E.. Universidade Presbiteriana Mackenzie; Brasil. National Institute for Space Research; BrasilFil: Kaufmann, Pierre. Universidade Presbiteriana Mackenzie; BrasilFil: Marun, Adolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Fernandez, German Enzo Leonel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Echer, E.. National Institute for Space Research; Brasi

Jupiter radio emission induced by Ganymede and consequences for the radio detection of exoplanets

International audienceBy analysing a database of 26 yr of observations of Jupiter with the Nancay Decameter Array, we unambiguously identify the radio emissions caused by the Ganymede-Jupiter interaction. We study the energetics of these emissions via the distributions of their intensities, duration, and power, and compare them to the energetics of the Io-Jupiter radio emissions. This allows us to demonstrate that the average emitted radio power is proportional to the Poynting flux from the rotating Jupiter's magnetosphere intercepted by the obstacle. We then generalize this result to the radio-magnetic scaling law that appears to apply to all plasma interactions between a magnetized flow and an obstacle, magnetized or not. Extrapolating this scaling law to the parameter range corresponding to hot Jupiters, we predict large radio powers emitted by these objects, that should result in detectable radio flux with new-generation radiotelescopes. Comparing the distributions of the durations of Ganymede-Jupiter and Io-Jupiter emission events also suggests that while the latter results from quasi-permanent Alfven wave excitation by Io, the former likely results from sporadic reconnection between magnetic fields Ganymede and Jupiter, controlled by Jupiter's magnetic field geometry and modulated by its rotation

Multiwavelength Study on Solar and Interplanetary Origins of the Strongest Geomagnetic Storm of Solar Cycle 23

We study the solar sources of an intense geomagnetic storm of solar cycle 23 that occurred on 20 November 2003, based on ground- and space-based multiwavelength observations. The coronal mass ejections (CMEs) responsible for the above geomagnetic storm originated from the super-active region NOAA 10501. We investigate the H-alpha observations of the flare events made with a 15 cm solar tower telescope at ARIES, Nainital, India. The propagation characteristics of the CMEs have been derived from the three-dimensional images of the solar wind (i.e., density and speed) obtained from the interplanetary scintillation data, supplemented with other ground- and space-based measurements. The TRACE, SXI and H-alpha observations revealed two successive ejections (of speeds ~350 and ~100 km/s), originating from the same filament channel, which were associated with two high speed CMEs (~1223 and ~1660 km/s, respectively). These two ejections generated propagating fast shock waves (i.e., fast drifting type II radio bursts) in the corona. The interaction of these CMEs along the Sun-Earth line has led to the severity of the storm. According to our investigation, the interplanetary medium consisted of two merging magnetic clouds (MCs) that preserved their identity during their propagation. These magnetic clouds made the interplanetary magnetic field (IMF) southward for a long time, which reconnected with the geomagnetic field, resulting the super-storm (Dst_peak=-472 nT) on the Earth.Comment: 24 pages, 16 figures, Accepted for publication in Solar Physic