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The interaction and response of the magnetic cloud-type structure with Earth's magnetosphere were modeled by the SWMF/BATS-R-US code. The conversion of magnetic (Em), kinetic (Ek), and internal (Ei ) energies was analyzed as well as the wave power integrated in the ultra-low frequency (ULF) range of the poloidal (Eϕ) and toroidal (Er ) electric field components in the equatorial region of the magnetosphere, in seven 2-hr long intervals, namely, I1 through I7. The intensity of energy conversion and wave activity for I1 and I7 intervals was negligible. The energy conversion started in the I2 interval and extended to the I3, I4, and I5 intervals. The power of the Eϕ and Er components in the dayside and nightside regions is clearly observed. The I4 corresponds to interplanetary magnetic field (IMF) Bz mostly southward and the I5 has similar amplitudes of the Bz and By components, corresponding to the period of the high geomagnetic activity. The conversion rate for the I4 and I5 was similar, however, the integrated power spectral density (IPSD) of the Eϕ and Er components is more intense in I5. During the I6 interval, with predominant IMF By, the energy conversion rate is intensified mostly for inner radial distances R < 6 RE, and the Ek component becomes close to zero for outer regions. The energy conversion regions are located spatially close to or overlapping with regions where the IPSD in the ULF range is intensified. The energy conversion in the inner magnetosphere occurred preferentially between Em and Ei, with the Ek energy component always present but with lower intensities. [ABSTRACT FROM AUTHOR]

Reanalyzing Cassini radio observations performed during Jupiter's flyby of 2000–2001, we study the internal (rotational) versus external (solar wind) control of Jupiter's radio emissions, from kilometer to decameter wavelengths, and the relations between the different auroral radio components. For that purpose, we build a database of the occurrence of Jovian auroral radio components bKOM, HOM, and DAM observed by Cassini, and then frequency‐longitude stacked plots of the polarized intensity of these radio components. Comparing the results obtained inbound and outbound, as a function of the Observer's or Sun's longitude, we find that HOM & DAM are dominantly rotation‐modulated (i.e., emitted from searchlight‐like sources fixed in Jovian longitude), whereas bKOM is modulated more strongly by the solar wind than by the rotation (i.e., emitted from sources more active within a given Local Time sector). We propose a simple analytical description of these internal and external modulations and evaluate its main parameters (the amplitude of each control) for HOM + DAM and bKOM. Comparing Cassini and Nançay Decameter Array data, we find that HOM is primarily connected to the decameter emissions originating from the dusk sector of the Jovian magnetosphere. HOM and DAM components form a complex but stable pattern in the frequency‐longitude plane. HOM also seems to be related to the "lesser arcs" identified by Voyager. bKOM consists of a main part above ∼40 kHz in antiphase with HOM occurrence, and detached patches below ∼80 kHz in phase with HOM. The frequency‐longitude patterns formed by DAM, HOM and bKOM remain to be modeled. Key Points: We build synthetic frequency‐longitude maps of polarized Jovian auroral radio emissions, DAM, HOM, and bKOMJovian HOM and DAM are dominantly rotation‐modulated, bKOM dominantly solar wind‐modulatedHOM appears primarily connected to decameter sources from the dusk side of the Jovian magnetosphere [ABSTRACT FROM AUTHOR]

The plasma environment of Mars is highly influenced by its crustal magnetic fields. In this work, we investigate whether the crustal magnetic fields can be displaced from their original positions due to advection by ionospheric plasma flow. The ranges of interest are altitudes between 200and1000 km and solar zenith angles between 45°and135°. We examine magnetic field data using measurements from the Magnetometer (MAG) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We conduct statistical analyses (∼5 years of data) in order to investigate if horizontal shifts are observed between the data and the crustal magnetic field model by Langlais et al. (2019), https://doi.org/10.1029/2018je005854. We also show two case studies of individual measurements within a specific region of Mars. The results show statistical and observational evidence that the crustal magnetic fields are often being advected towards the night‐side of the planet. The displacement seems to increase exponentially as a function of altitude, reaching a horizontal shift of 100 km at 650 km altitude. Moreover, we use measurements from the SupraThermal And Thermal Ion Composition (STATIC) instrument in order to compare the dynamic pressure of ionospheric plasma flow to the magnetic pressure of the crustal magnetic fields. There are two possible causes for the displacement: a forcing by external magnetic pressure or an advection of the field to the electron fluid, which follows the ion fluid. In this paper, we argue that by the observed relation between ion fluid and displacement, the latter explanation is more probable. Plain Language Summary: Crustal magnetic fields keep information of a past time, when Mars still had its own internal magnetic field generator. These structures do not tend to change in the long‐term, so several models have been built throughout the last decades with the aim of reproducing the observed Martian fields. The crustal fields can influence the dynamics of the atmosphere. The region of the atmosphere, which is dominated by atmospheric plasma (ions and electrons) is the ionosphere. At Mars, the ionosphere lies at ∼130 km and above. In theory, the flow of the plasma is able to move the crustal magnetic fields in a process called advection. In this work, we indicate that this process happens often at Mars. Our results may be important for improving crustal magnetic field models, and also for estimating how much electricity the ionospheric plasma can conduct. Key Points: The crustal magnetic fields on Mars are being displaced relative to their expected locationThe displacement increases with solar zenith angle and altitudeIonospheric plasma flow is most likely responsible for this process [ABSTRACT FROM AUTHOR]

We demonstrate that global observations of high-energy cosmic rays contribute to understanding unique characteristics of a large-scale magnetic flux rope causing a magnetic storm in August 2018. Following a weak interplanetary shock on August 25, 2018, a magnetic flux rope caused an unexpectedly large geomagnetic storm. It is likely that this event became geoeffective because the flux rope was accompanied by a corotating interaction region and compressed by high-speed solar wind following the flux rope. In fact, a Forbush decrease was observed in cosmic-ray data inside the flux rope as expected, and a significant cosmic-ray density increase exceeding the unmodulated level before the shock was also observed near the trailing edge of the flux rope. The cosmic-ray density increase can be interpreted in terms of the adiabatic heating of cosmic rays near the trailing edge of the flux rope, as the corotating interaction region prevents free expansion of the flux rope and results in the compression near the trailing edge. A northeast-directed spatial gradient in the cosmic-ray density was also derived during the cosmic-ray density increase, suggesting that the center of the heating near the trailing edge is located northeast of Earth. This is one of the best examples demonstrating that the observation of high-energy cosmic rays provides us with information that can only be derived from the cosmic ray measurements to observationally constrain the three-dimensional macroscopic picture of the interaction between coronal mass ejections and the ambient solar wind, which is essential for prediction of large magnetic storms. [ABSTRACT FROM AUTHOR]

Cosmic rays are charged particles whose flux observed at Earth shows temporal variations related to space weather phenomena and may be an important tool to study them. The cosmic ray intensity recorded with ground‐based detectors also shows temporal variations arising from atmospheric variations. In the case of muon detectors, the main atmospheric effects are related to pressure and temperature changes. In this work, we analyze both effects using data recorded by the Global Muon Detector Network, consisting of four multidirectional muon detectors at different locations, in the period between 2007 and 2016. For each Global Muon Detector Network directional channel, we obtain coefficients that describe the pressure and temperature effects. We then analyze how these coefficients can be related to the geomagnetic cutoff rigidity and zenith angle associated with cosmic ray particles observed by each channel. In the pressure effect analysis, we found that the observed barometric coefficients show a very clear logarithmic correlation with the cutoff rigidity divided by the zenith angle cosine. On the other hand, the temperature coefficients show a good logarithmic correlation with the product of the cutoff and zenith angle cosine after adding a term proportional to the sine of geographical latitude of the observation site. This additional term implies that the temperature effect measured in the Northern Hemisphere detectors is stronger than that observed in the Southern Hemisphere. The physical origin of this term and of the good correlations found in this analysis should be studied in detail in future works. Key Points: Pressure and temperature effects observed by ground muon detectors was experimentally analyzed inrelation to cutoff rigidity and zenith angleThe best correlation was found when considering product between cutoff rigidity and zenith angle secant (pressure) or cosine (temperature)The temperature effect only shows a global trend if a relationship with the sine of each detector's geographic latitude is included [ABSTRACT FROM AUTHOR]

Using global magnetohydrodynamic (MHD) simulations, we investigate the role played by a complex solar structure composed of a corotating interaction region (CIR) followed by solar wind Alfvénic fluctuations on the magnetosphere's nightside, equatorial electric field oscillations in the ultra-low-frequency range. A series of numerical experiments are performed employing synthetic solar wind inputs resembling those of a real CIR+Alfvénic fluctuation event that reached Earth's magnetosphere on 2003 April 20. The following is found: (i) Radial electric field component fluctuations are excited via magnetopause boundary motions driven either by solar wind density variations characteristic of CIRs or by solar wind Alfvénic fluctuations with a given oscillation period. (ii) Azimuthal electric field component fluctuations nearer to Earth, that is, at radial distances R less than about 5RE (Earth radius), are apparently not related to either of the two types of sinusoidal solar wind Alfvénic fluctuations used in this study featuring monochromatic frequencies of 0.833 mHz (20-minute period) and 1.666 mHz (10-minute period). Instead, these innermost azimuthal component fluctuations show enhanced activity when inner magnetosphere convection increases as a result of a southward turning of the interplanetary magnetic field component Bz. (iii) Lastly, outermost (R ≳ 7 RE) azimuthal electric field oscillations weakly respond to monochromatic solar wind Alfvénic fluctuations by showing power spectral density peaks at both driving frequencies, but only near the flanks of the magnetopause, thus suggesting that such oscillations are being excited also owing to magnetopause boundary motions driven by solar wind Alfvénic fluctuations. [ABSTRACT FROM AUTHOR]

Fast interplanetary shocks occurrence, their parameters, and drivers near Jupiter's orbit are determined in this paper. It was found that 70% of the fast shocks are forward (FS) and 30% are reverse (RS). Interplanetary coronal mass ejection‐driven FS occur more frequently in all solar cycle phases except in the declining phase, when corotating interaction region‐driven shocks predominate. Most of the shocks were quasi‐perpendicularly (65° to 70°) propagating relative to the ambient interplanetary magnetic field. The average shock magnetosonic Mach number is slightly higher for FS (2.6) than for RS (2.4), which in turn are stronger than shocks near 1 and 10 AU reported in previous works. This occurs because of the full development of corotating interaction region shocks and higher occurrence of strong interplanetary coronal mass ejections near 5 AU and that the magnetosonic speed at 5 AU has only 60% of its value at 1 AU. Plan Language Summary: Interplanetary shock waves are sudden variations in solar wind plasma and magnetic field parameters. They propagate in the interplanetary space and have important effects on planetary magnetospheres. For instance, shocks cause expansions and compressions of Jupiter's magnetosphere and trigger its auroral emissions. In this work plasma and magnetic field data from several spacecraft that crossed interplanetary space near Jupiter's orbit space are analyzed. A list of interplanetary shocks is compiled, and their parameters and drivers are determined. It was found that shocks at 5 AU have preferentially a quasi‐perpendicular propagation to the magnetic field direction and are on average stronger than shocks observed near Earth's orbit. Key Points: Interplanetary shock occurrence, parameters, and drivers near Jupiter's orbit are determinedThere are about 70% fast forward and 30% reverse shocks; about 90% of RS are CIR driven, while 45% of FS are CIR driven and 55% are ICME drivenShocks at 5 AU are mostly quasi‐perpendicularly propagating and stronger on average than shocks at 1 AU [ABSTRACT FROM AUTHOR]

The current work investigates the possible solar wind‐interplanetary (SW‐IP) drivers of geomagnetic storms during the longest period (ascending to early descending phases) of the ongoing solar cycle (24). We present a comparative analysis between the two consecutive solar cycles (SCs) 23 and 24. Both the cycles exhibited dual peak feature as observed in the smoothed sunspot numbers SSNsmoothed. For both the cycles, second peak in the SSNsmoothed is higher than the first one as exhibited in the revised SSNsmoothed version. During the entire interval between the ascending to early descending phases (December 2008 to December 2016) of SC‐24, the southward directed Bz and the dawn‐dusk electric field (Ey) were consistently weaker as compared to that during similar interval of SC‐23 (May 1996 to July 2004). The geomagnetic field response represented by Dst index concurrently exhibited similar variation patterns during both the periods. A striking reduction in the intense storm occurrence rate by ∼75% was observed during the considered period of the current solar cycle in comparison to the previous cycle. However, moderate storm occurrence was reduced only by 32% in SC‐24 as compared to SC‐23, which could be attributed to the dominance of corotating interaction regions during SC‐24. No significant difference is found between the intense storm rates around the vernal and autumnal equinoxes in cycle 24, whereas distinct autumnal equinoctial dominance is evident for cycle 23. Further, within each cycle, there is no significant difference in the moderate storm rates around vernal and autumnal equinoxes. Key Points: Approximately 75% (34%) reduction in intense (moderate) storm occurrence rate during ascending and early descending phases of cycle 24 compared to cycle 23 is observedCycle 24 showed no significant difference during equinoctial months for intense storms; however, cycle 23 exhibited equinoctial asymmetryICMEs and/or their SH are identified to be the dominant drivers for intense storms during cycle 24 (∼89%) and cycle 23 (∼64) [ABSTRACT FROM AUTHOR]

The Global Muon Detector Network (GMDN) is composed by four ground cosmic ray detectors distributed around the Earth: Nagoya (Japan), Hobart (Australia), Sao Martinho da Serra (Brazil) and Kuwait city (Kuwait). The network has operated since March 2006. It has been upgraded a few times, increasing its detection area. Each detector is sensitive to muons produced by the interactions of ~50 GeV Galactic Cosmic Rays (GCR) with the Earth′s atmosphere. At these energies, GCR are known to be affected by interplanetary disturbances in the vicinity of the earth. Of special interest are the interplanetary counterparts of coronal mass ejections (ICMEs) and their driven shocks because they are known to be the main origins of geomagnetic storms. It has been observed that these ICMEs produce changes in the cosmic ray gradient, which can be measured by GMDN observations. In terms of applications for space weather, some attempts have been made to use GMDN for forecasting ICME arrival at the earth with lead times of the order of few hours. Scientific space weather studies benefit the most from the GMDN network. As an example, studies have been able to determine ICME orientation at the earth using cosmic ray gradient. Such determinations are of crucial importance for southward interplanetary magnetic field estimates, as well as ICME rotation. [ABSTRACT FROM AUTHOR]

Extreme solar-terrestrial events are those in which very energetic solar ejections hit the earth?s magnetosphere, causing intense energization of the earth?s ring current. Statistically, their occurrence is approximately once per Gleissberg solar cycle (70-100yrs). The solar transient occurred on July, 23rd (2012) was potentially one of such extreme events. The associated coronal mass ejection (CME), however, was not ejected towards the earth. Instead, it hit the STEREO A spacecraft, located 120 degrees away from the Sun-Earth line. Estimates of the geoeffectiveness of such a CME point to a scenario of extreme Space Weather conditions. In terms of the ring current energization, as measured by the Disturbance Storm-Time index (Dst), had this CME hit the Earth, it would have caused the strongest geomagnetic storm in space era. [ABSTRACT FROM AUTHOR]

We examine particularly intense substorms (SML ⩽ -2500 nT), hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst ⩽ -250 nT) and intense (-100 nT⩾Dst> -250) magnetic storms. SSS events can also occur during nonstorm (Dst ⩾ -50 nT) intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (∼30 to 50 cm-3/ solar wind plasma parcels (PPs) impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy. [ABSTRACT FROM AUTHOR]

We describe the preliminary design of a magnetograph and visible-light imager instrument to study the solar dynamo processes through observations of the solar surface magnetic field distribution. The instrument will provide measurements of the vector magnetic field and of the line-of-sight velocity in the solar photosphere. As the magnetic field anchored at the solar surface produces most of the structures and energetic events in the upper solar atmosphere and significantly influences the heliosphere, the development of this instrument plays an important role in reaching the scientific goals of The Atmospheric and Space Science Coordination (CEA) at the Brazilian National Institute for Space Research (INPE). In particular, the CEA's space weather program will benefit most from the development of this technology. We expect that this project will be the starting point to establish a strong research program on Solar Physics in Brazil. Our main aim is acquiring progressively the know-how to build state-of-the-art solar vector magnetograph and visible-light imagers for space-based platforms to contribute to the efforts of the solar-terrestrial physics community to address the main unanswered questions on how our nearby Star works. [ABSTRACT FROM PUBLISHER]

In this work, we summarize the development and current status of the Global Muon Detector Network (GMDN). The GMDN started in 1992 with only two muon detectors. It has consisted of four detectors since the Kuwait-city muon hodoscope detector was installed in March 2006. The present network has a total of 60 directional channels with an improved coverage of the sunward Interplanetary Magnetic Field (IMF) orientation, making it possible to continuously monitor cosmic ray precursors of geomagnetic storms. The data analysis methods developed also permit precise calculation of the three dimensional cosmic ray anisotropy on an hourly basis free from the atmospheric temperature effect and analysis of the cosmic ray precursors free from the diurnal anisotropy of the cosmic ray intensity. [ABSTRACT FROM AUTHOR]

Evidence of the solar activity modulation of the Earth's climate has been observed on several parameters, from decadal to millennial time scales. Several proxies have been used to reconstruct the paleoclimate as well as the solar activity. The paleoclimate reconstructions are based on direct and/or indirect effects of global and regional climate conditions. The solar activity reconstructions are based on the production of the C isotope due to the interaction of cosmic ray flux and the Earth's atmosphere. Because trees respond to climate conditions and store C, they have been used as proxies for both for climate and solar activity reconstructions. The imprints of solar activity cycles dating back to 10,000 years ago have been observed on tree-ring samples using C data, and those dating back to 20 million years ago have been analyzed using fossil tree-growth rings. All this corresponds to the Cenozoic era. However, solar activity imprints on tree rings from earlier than that era have not been investigated yet. In this work, we showed that tree rings from the Mesozoic Era (of ~200 million years ago) recorded 11- and 22-year cycles, which may be related to solar activity cycles, and that were statistically significant at the 95 % confidence level. The fossil wood was collected in the southern region of Brazil. Our analysis of the fossils' tree-ring width series power spectra showed characteristics similar to the modern araucaria tree, with a noticeable decadal periodicity. Assuming that the Earth's climate responds to solar variability and that responses did not vary significantly over the last ~200 million years, we conclude that the solar-climate connection was likely present during the Mesozoic era. [ABSTRACT FROM AUTHOR]

We study the interplanetary features and concomitant geomagnetic activity of the two high-speed streams (HSSs) selected by the Whole Heliosphere Interval (WHI) campaign participants: 20 March to 16 April 2008 in Carrington rotation (CR) 2068. This interval was chosen to perform a comprehensive study of HSSs and their geoeffectiveness during this 'deep' solar minimum. The two HSSs within the interval were characterized by fast solar-wind speeds (peak values > 600 km s) containing large-amplitude Alfvénic fluctuations, as is typical of HSSs during normal solar minima. However, the interplanetary magnetic field (IMF) magnitude [ B] was exceptionally low (≈3 - 5 nT) during these HSSs, leading to lower than usual IMF B values. The first HSS (HSS1) had favorable IMF polarity for geomagnetic activity (negative during northern Spring). The average AE and Dst for the HSS1 proper (HSS1P) were + 258 nT and − 21 nT, respectively. The second HSS (HSS2) had a positive sector IMF polarity, one that is less favorable for geomagnetic activity. The AE and Dst index averages were + 188 nT and − 7 nT, both lower than corresponding numbers for the first event, as expected. The HSS1P geomagnetic activity is comparable to, and the HSS2P geomagnetic activity lower than, corresponding observations for the previous minimum (1996). Both events' geomagnetic activities are lower than HSS events previously studied in the declining phase (in 2003). In general, V was faster for the HSSs in 2008 compared to 1996. The southward IMF B was lower in the former. The product of these two parameters [ V and IMF B] comprises the solar-wind electric field, which is most directly associated with the energy input into the magnetosphere during the HSS intervals. Thus the combined effects led to the solar wind energy input in 2008 being slightly less than that in 1996. A detailed analysis of magnetic-field variances and Alfvénicity is performed to explore the characteristics of Alfvén waves (a central element in the geoeffectiveness of HSSs) during the WHI. The B variances in the proto-CIR (PCIR) were ≈ 30 nT and < 10 nT in the high speed streams proper. [ABSTRACT FROM AUTHOR]

Global suface temperature has showed a rise trend in the last 150 years. This has been mainly attributed to the anthropogenic induced grenhouse gases emissions. However, the role of natural processes is not completely understood and should not be underestimated. In this work, we compare the long term variability of solar activity (as quantified by the sunspot number) with several surface temperature series from different geographical regions (global, hemispheric and latitudinal ranges). The interval of analysis is 1880-2005. The data are analyzed with wavelet multiresolution technique. It has been found that the solar activity long term trend has a maximum around 1970, while air surface temperature series showed maximum (still rising) at 2005. There are differences in the long term trend for Northern and Southern hemispheres. These differences and the relation with solar activity are discussed in this work. [ABSTRACT FROM PUBLISHER]

The recent solar minimum (2008-2009) was extreme in several aspects: the sunspot number, Rz, interplanetary magnetic field (IMF) magnitude Bo and solar wind speed Vsw were the lowest during the space era. Furthermore, the variance of the IMF southward Bz component was low. As a consequence of these exceedingly low solar wind parameters, there was a minimum in the energy transfer from solar wind to the magnetosphere, and the geomagnetic activity ap index reached extremely low levels. The minimum in geomagnetic activity was delayed in relation to sunspot cycle minimum. We compare the solar wind and geomagnetic activity observed in this recent minimum with previous solar cycle values during the space era (1964-2010). Moreover, the geomagnetic activity conditions during the current minimum are compared with long term variability during the period of available geomagnetic observations. The extremely low geomagnetic activity observed in this solar minimum was previously recorded only at the end of XIX century and at the beginning of the XX century, and this might be related to the Gleissberg (80-100 years) solar cycle. [ABSTRACT FROM PUBLISHER]

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 (Bz) variances (σBz2) and normalized variances (σBz2/B02 ) 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. [ABSTRACT FROM AUTHOR]

In this work we apply the wavelet transform to the Pelotas (southern Brazil) total annual rainfall series (1894-1995). Classical, wavelet and cross-wavelet analyses were performed in the El Niño Southern Oscillation (ENSO), Quasi-Biennial Oscillation (QBO), sunspot number (Rz) and Pelotas rainfall time series. Classical spectral analysis for Pelotas has shown a large number of short periods - between 2.2-5.6 years (yr) and periods at 8.9, 11.7 and 24.9 yr. Further, we have found that the Pelotas rainfall wavelet spectrum shows the most significant periodicities around 2-8 yr, but they have an intermittent character. Cross-wavelet spectrum showed that: rainfall and QBO series are correlated at 2-3 yr (QBO) scales and this cross-power is continuous along the time series interval; rainfall and SOI have higher cross-power around 4-8 yr, but this signal is sporadic; rainfall and sunspot number (Rz) showed higher cross-power around the 11-yr solar cycle period, but this crosspower is sporadically high and low; finally, the rainfall cross-spectrum with the double sunspot number (Rz22) revealed a high cross-power around 20-22 yr which is more persistent in duration, compared to the 11-yr period. These wavelet results are compared with classical spectral analysis and with previous work results. We concluded that the phenomenon that influences most of Pelotas rainfall variability is ENSO, but only a minor part of the variance (~30%) can be described by a simple multi-linear dependence on solar/ ENSO/QBO phenomena, this result could imply that non-linear coupling among sun and internal climatic variability (QBO, ENSO) has an important role in the local/regional climate variations. [ABSTRACT FROM AUTHOR]

The minimum variance analysis of interplanetary coronal mass ejections (ICMEs) observed close to the Earth's orbit around solar cycle 23 maximum (1998–2002) was performed. The ICMEs were classified in three categories: magnetic clouds (MC), undefined ejecta (UE), and complex ejecta (CE). An analysis of the full ICMEs set shows that the average of minimum variance direction inclination angle is 1.6°± 24.8° in relation to the ecliptic plane, with more than 33% of the events presenting inclination angles lower than 10°. The average of minimum variance direction azimuthal angle (in relation to the Sun–Earth line) was 56°. However, around 60% of the ICMEs presented an azimuthal angle lower than 30°, close to the radial direction. It was also observed that the MC set had lower axial (intermediate variance) inclinations relative to the ecliptic plane than the UE and CE events. The intermediate variance axis is close to 90° to the Sun–Earth line. The results obtained in the present analysis were also compared with previous works, permitting a comparison of the ICMEs orientations in solar cycle 23 with previous sor cycles. [ABSTRACT FROM AUTHOR]

Spectral 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. [ABSTRACT FROM AUTHOR]

A wavelet multiresolution analysis of the quasi-biennial oscillation (QBO) latitudinal structure in total ozone is performed for the period 1979–1992 (Nimbus-7 TOMS data). It has been found that ozone is nearly in phase with the QBO signal in the equatorial region (0°–5° and 5°–10°), and it is out of phase (lag∼+15 and−15 months in north and south) in the 10°–15° to 55°–60° latitudinal bands. The cross-correlation coefficient between total ozone and zonal wind index is high (>0.7) at latitudes lower than 10°, decreases in the transition region 10°–15° (r∼ 0.4) and it has a non-linear profile at high latitudes, with a maximum near the 25°–30° band. The correlation is observed to be higher in the Southern Hemisphere latitudinal bands. Spectral analysis was performed for each latitudinal range, and QBO period and amplitude profiles were obtained. A detailed latitudinal profile of the QBO signal in total ozone is obtained from the present analysis. [ABSTRACT FROM AUTHOR]

The objective of this paper is to compare the spectral features of the recently derived Group Sunspot Numbers (RG) and the traditional Wolf Sunspot Numbers (RZ) for the 1700-1995 period. In order to study the spectral features of both time series, two methods were used, including: (a) the multitaper analysis and (b) the wavelet analysis. Well-known features of the solar variability, such as the 98.6-yr (Gleissberg cycle), 10-11-yr (Schwabe cycle) and 5-yr (second solar harmonic) periodicities were identified with high confidence using the multitaper analysis. Also observed was a larger amount of power spread in high frequencies forRZ than forRG spectra. Furthermore, a multitaper analysis of two subsets, A (1700-1850) and B (1851-1995), has indicated that the main differences occurred in the first subset and seem to be due to uncertainties in the early observations. The wavelet transform, which allows observing the spectra evolution of both series, showed a strong and persistent 10-11-yr signal that remained during the whole period. The Meyer Wavelet Transform was applied to bothRZ andRG. This study indicates that the main spectral characteristics of both series are similar and that their long-term variability has the same behavior. [ABSTRACT FROM AUTHOR]

We have compared characteristics of 38 halo coronal mass ejections observed on the Sun by the Large Angle and Spectrometric Coronagraph onboard SOHO with their corresponding counterparts observed near Earth by the magnetic field and plasma instruments onboard the ACE, WIND and SOHO satellites, in the period from January 1997 to April 2001. We only have selected events that have some associated interplanetary ejecta structure at 1 AU and we have compared the lateral expansion speeds of these halo CMEs and the corresponding ejecta speeds near Earth. We found that there is a high correlation between these two speeds. The results are very similar to the study done by Lindsay et al. (1999) using observations made by Solwind and SMM coronagraphs, and Helios-1 and PVO plasma and interplanetary field data from the period of 1979 to 1988. Also, we reviewed the relation between the CME-related shock transit speed to Earth and the ejecta speeds near Earth. This kind of relation is very important to estimate ejecta speeds of events for which no interplanetary observations are available. [ABSTRACT FROM AUTHOR]

Plasma and magnetic field parameter variations across fast forward interplanetary shocks are analyzed during the last solar cycle minimum (1995-1996, 15 shocks), and maximum year 2000 (50 shocks). It was observed that the solar wind velocity and magnetic field strength variation across the shocks were the parameters better correlated with Dst. Superposed epoch analysis centered on the shock showed that, during solar minimum, Bz profiles had a southward, long-duration variation superposed with fluctuations, whereas in solar maximum the Bz profile presented 2 peaks. The first peak occurred 4 hr after the shock, and seems to be associated with the magnetic field disturbed by the shock in the sheath region. The second peak occurred 19 hr after the shock, and seems to be associated with the ejecta fields. The difference in shape and peak in solar maximum (Dst peak = -50 nT, moderate activity) and minimum (Dst peak = -30 nT, weak activity) in average Dst profiles after shocks are, probably, a consequence of the energy injection in the magnetosphere being driven by different interplanetary southward magnetic structures. A statistical distribution of geomagnetic activity levels following interplanetary shocks was also obtained. It was observed that during solar maximum, 36% of interplanetary shocks were followed by intense (Dst ≤ -100 nT) and 28% by moderate (-50 ≤ Dst c -100 nT) geomagnetic activity. During solar minimum, 13% and 33% of the shocks were followed by intense and moderate geomagnetic activity, respectively. Thus, during solar maximum a higher relative number of interplanetary shocks might be followed by intense geomagnetic activity than during solar minimum. One can extrapolate, for forecasting goals, that during a whole solar cycle a shock has a probability of around 50-60% to be followed by intense/moderate geomagnetic activity. [ABSTRACT FROM AUTHOR]

Tree ring studies are usually used to determine or verify climatic factors prevailing at a given place or region that may cause tree-ring width variations. Few studies are dedicated to the solar phenomena which may underlie these tree-ring width variations. Furthermore, it is known that some terrestrial phenomena are influenced by short- and long-time scale solar variability. An optical and computational method was set up and applied to tree samples (Araucaria angustifolia from Santa Catarina State in Southern Brazil) in order to obtain a growth ring width mean chronology. Spectral analysis is used for the search of periodicities, by maximum entropy and iterative regression methods. The results evidenced several embedded signals at periods which may be related to solar activity variations. Cross-correlation analysis between sunspot number and tree-ring data was performed and a lag of zero year was obtained. From our work, it seems that the tropical conifer species Araucaria angustifolia may be a good choice for studies on Sun-Earth relationships and their regional effects. [ABSTRACT FROM AUTHOR]

In this work we present a methodology to estimate the geomagnetic symmetric index (Sym) based on the wavelet analysis of the time series of the H component of the geomagnetic field measured at mid-latitude stations localized at Kakioka (KAK), Honolulu (HON), Hermanus (HER) and San Juan (SJG). A case study of the intense geomagnetic storm of 17–22 February 1999, caused by intense southward magnetic fields just behind an interplanetary shock driven by a magnetic cloud, is shown as an example of the procedure of derivation of the symmetric index and the capabilities of this analysis to improve the study of the coupling of the solar wind and the Earth's magnetosphere. Other examples are shown in order to demonstrate the applicability of the methodology to different magnetospheric conditions. It is shown that the long period variations of the symmetric index are linearly correlated to variations at the same periods of the H component of the geomagnetic field and that the contribution of short period variations to the symmetric index are biased by localized current systems such as the partial ring current and the field aligned currents. [ABSTRACT FROM AUTHOR]

A reconstruction of sunspot numbers for the last 1000 years was obtained using a sum of sine waves derived from spectral analysis of the time series of sunspot number Rz for the period 1700–1999. The time series was decomposed in frequency levels using the wavelet transform, and an iterative regression model (ARIST) was used to identify the amplitude and phase of the main periodicities. The 1000-year reconstructed sunspot number reproduces well the great maximums and minimums in solar activity, identified in cosmonuclides variation records, and, specifically, the epochs of the Oort, Wolf, Spörer, Maunder, and Dalton Minimums as well the Medieval and Modern Maximums. The average sunspot number activity in each anomalous period was used in linear equations to obtain estimates of the solar radio flux F10.7, solar wind velocity, and the southward component of the interplanetary magnetic field. [ABSTRACT FROM AUTHOR]

The CARPET cosmic ray detector was installed in 2006 in the Argentinean Andes at an altitude of 2550 m at the El Leoncito Astronomical Complex (CASLEO) in San Juan, Argentina (S31.8, W69.3; R = 9.659.65 GV). This instrument was developed at the Lebedev Physical Institute (LPI) in Russia as part of an international collaboration between the LPI, Brazil's Mackenzie Center for Radioastronomy and Astrophysics (CRAAM), and the CASLEO. This work presents the results from analyzing variations in cosmic ray intensity recorded by the CARPET facility during the solar proton event of March 7, 2011. Also used in our analysis were the experimental data obtained by the GOES, FERMI, and ISS spacecraft during this solar event. [ABSTRACT FROM AUTHOR]

During 1999 August 18, both Cassini and WIND were in the Earth's magnetosheath and detected transverse electromagnetic waves instead of the more typical mirror-mode emissions. The Cassini wave amplitudes were as large as ∼14 nT (peak to peak) in a ∼55 nT ambient magnetic field B0. A new method of analysis is applied to study these waves. The general wave characteristics found were as follows. They were left-hand polarized and had frequencies in the spacecraft frame (fscf) below the proton cyclotron frequency (fp). Waves that were either right-hand polarized or had fscf > fp are shown to be consistent with Doppler-shifted left-hand waves with frequencies in the plasma frame fpf < fp. Thus, almost all waves studied are consistent with their being electromagnetic proton cyclotron waves. Most of the waves (∼55%) were found to be propagating along B0 (), as expected from theory. However, a significant fraction of the waves were found to be propagating oblique to B0. These waves were also circularly polarized. This feature and the compressive ([Bmax – Bmin]/Bmax, where Bmax and Bmin are the maximum and minimum field magnitudes) nature (ranging from 0.27 to 1.0) of the waves are noted but not well understood at this time. The proton cyclotron waves were shown to be quasi-coherent, theoretically allowing for rapid pitch-angle transport of resonant protons. Because Cassini traversed the entire subsolar magnetosheath and WIND was in the dusk-side flank of the magnetosheath, it is surmised that the entire region was filled with these waves. In agreement with past theory, it was the exceptionally low plasma β (0.35) that led to the dominance of the proton cyclotron wave generation during this interval. A high-speed solar wind stream (〈 Vsw〉 = 598 km s–1) was the source of this low-β plasma. [ABSTRACT FROM AUTHOR]