Short-period Components Research Articles

Detection of the Second Harmonic of Decay-less Kink Oscillations in the Solar Corona

Abstract EUV observations of a multi-thermal coronal loop, taken by the Atmospheric Imaging Assembly of the Solar Dynamics Observatory, which exhibits decay-less kink oscillations are presented. The data cube of the quiet-Sun coronal loop was passed through a motion magnification algorithm to accentuate transverse oscillations. Time–distance maps are made from multiple slits evenly spaced along the loop axis and oriented orthogonal to the loop axis. Displacements of the intensity peak are tracked to generate time series of the loop displacement. Fourier analysis on the time series shows the presence of two periods within the loop: minutes and minutes. The longer period component is greatest in amplitude at the apex and remains in phase throughout the loop length. The shorter period component is strongest further down from the apex on both legs and displays an anti-phase behavior between the two loop legs. We interpret these results as the coexistence of the fundamental and second harmonics of the standing kink mode within the loop in the decay-less oscillation regime. An illustration of seismological application using the ratio P 1/2P 2 ∼ 0.7 to estimate the density scale height is presented. The existence of multiple harmonics has implications for understanding the driving and damping mechanisms for decay-less oscillations and adds credence to their interpretation as standing kink mode oscillations.

Wavelet analysis of δ18O and δ13C time-series from an Holocene speleothem record from Corchia Cave (central Italy): insights for the recurrence of dry-wet periods in the Central Mediterraneans

In this work, the continuous wavelet transform (CWT) is used to analyse stable isotope (δ18O and δ13C) time-series from a speleothem from Corchia Cave (Apuan Alps, Tuscany, central Italy). The record spans the ca. 13.3- 0.4 ka period. Both proxies are thought to represent changes in the amount of precipitation and in the hydrological recharge over the cave catchment, and to indicate alternating wetter and drier periods. The CWT shows the presence of different dominant frequency components, changing across the Middle-Holocene. This can be interpreted as mostly related to long term variations in summer and winter insolation, resulting from changes in orbital parameters. The lower frequencies (millennial scale) individuated may have different origin, not always obvious, and are rarely reported in others records. Instead, the short period components (multidecadal to centennial scale) could be in the range of frequencies considered as expression of the solar variability. δ18O and δ13C time-series show very coherent response to lower frequencies, but δ18O time-series show the presence of higher frequencies, that are not reported in the δ13C record. This can be related to a different response of the soil-karst system compared to variability in the δ18O of precipitation and their recharge of the karst. A Matlab® code has been implemented to compute the wavelet transform and to generate all the results presented in this work.

Особливості лінійного приросту однорічних пагонів верби шерстистопагінцевої (Salix dasyclados Wimm.)

Різні форми і гібриди верби шерстистопагінцевої масово вирощуються на спеціальних плантаціях для отримання енергетичної біомаси. Однак останнім часом інтерес до верб як джерела біоенергетичної сировини помітно знизився. Однією з головних причин цього є нестабільність врожайності плантацій. Водночас відомо, що стабільний урожай фітомаси може бути забезпечений шляхом створення поліклональних насаджень з використанням клонів з різними ритмами розвитку.
 За результатами проведених досліджень вивчено типи динаміки наростання лідерських пагонів верби шерстистопагінцевої на відносно вирівняному одновіковому матеріалі, в однорідних едафо-фітоценотичних умовах.
 Встановлено, що динаміка росту пагонів верби шерстистопагінцевої характеризується наявністю трьох чітко виражених максимумів. Перший максимум в усіх пагонів припадає на кінець травня, у першій декаді липня спостерігається другий максимум, а у другій половині літа проявляються індивідуальні особливості в динаміці наростання пагонів: у особини da 2 третій максимум припадає на кінець липня, а у da 5 – на першу декаду серпня.
 Довгоперіодичними компонентами динаміки середньодобового приросту характеризуються не різні особини, а різні пагони. Усі короткоперіодичні компоненти характеризуються наявністю чотирьох максимумів, які загалом збігаються з фактичними максимумами.
 Довгоперіодичні компоненти визначають загальний тренд розвитку пагонів, а короткоперіодичні – спричиняють модуляційний вплив на динаміку наростання пагонів. Саме короткоперіодичні компоненти визначають індивідуальні відмінності в динаміці наростання пагонів.

Automatic selection of Dst storms and their seasonal variations in two versions of Dst in 50\xa0years

A computer program is developed to automatically identify the geomagnetic storms in Dst index by applying four selection criteria that minimize non-storm-like fluctuations. The program is used to identify the storms in Kyoto Dst and USGS Dst in 50 years (1958–2007). The identified storms (DstMin ≤ −50 nT) are used to investigate their seasonal variations. It is found that the overall seasonal variations of the storm parameters such as occurrence, average intensity (average DstMin) and average strength (average ⟨DstMP⟩) in both versions of Dst exhibit clear semiannual variations with equinoctial maxima and solstice minima; and the maxima and minima in intensity and strength (~±17% each) are less than those in occurrence (~±28%). Wavelet spectra of the storms reveal the existence of distinct semiannual component in four solar cycles (SCs 20–23) and weak longer and shorter-period components in some SCs. The semiannual variation observed also in the mean energy input during the main phase (MP) of the storms estimated from Dst is interpreted in terms of the (1) equinoctial mechanism based on the varying angle between the Earth–Sun line and Earth’s dipole axis and (2) Russell–Mcpherron effect based on the varying angle between the GSM Z-axis and GSE Y-axis; and the yearly range of the dipole tilt angle µ (23.2°) involved in the equinoctial mechanism is found larger than the title angle θ (16.3°) involved in the RM effect.Graphical .

FORMALIZED ASSESSMENT OF DYNAMIC CHARACTERISTICS OF COMPLEX SYSTEMS

Ponte Academic JournalMar 2017, Volume 73, Issue 3 FORMALIZED ASSESSMENT OF DYNAMIC CHARACTERISTICS OF COMPLEX SYSTEMSAuthor(s): Alexander DanilovJ. Ponte - Mar 2017 - Volume 73 - Issue 3 doi: 10.21506/j.ponte.2017.3.26 Abstract:The annex to the development of training systems for the training of operators of ergatic systems developed criteria for evaluation by operator dynamic characteristics of the object in the course of normal operation of an integrated system. The focus is on short-period component of longitudinal motion. The methods of decomposition of the spatial movement on the longitudinal and lateral approximately defined by the roots characteristic polynomial of the fourth order (is illustrated on a specific example). Download full text:Check if you have access through your login credentials or your institution Username Password

Spatially resolved observation of the fundamental and second harmonic standing kink modes using SDO/AIA

Aims. We consider a coronal loop kink oscillation observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) which demonstrates two strong spectral components. The period of the lower frequency component being approximately twice that of the shorter frequency component suggests the presence of harmonics.Methods. We examine the presence of two longitudinal harmonics by investigating the spatial dependence of the loop oscillation. The time-dependent displacement of the loop is measured at 15 locations along the loop axis. For each position the displacement is fitted as the sum of two damped sinusoids, having periods P 1 and P 2 , and a damping time τ . The shorter period component exhibits anti-phase oscillations in the loop legs.Results. We interpret the observation in terms of the first (global or fundamental) and second longitudinal harmonics of the standing kink mode. The strong excitation of the second harmonic appears connected to the preceding coronal mass ejection (CME) which displaced one of the loop legs. The oscillation parameters found are P 1 = 5.00±0.62 min, P 2 = 2.20±0.23 min, P 1 / 2P 2 = 1.15±0.22, and τ /P = 3.35 ± 1.45.

South Ilan Plain High-Resolution 3-D S-Wave Velocity from Ambient Noise Tomography

The Ilan Plain in northeastern Taiwan is located at a pivotal point where the Ryukyu trench subduction zone, the northern Taiwan crustal stretching zone, and the ongoing arc-continent collision zone converge. In contrast to the North Ilan Plain, the South Ilan Plain exhibits a thin unconsolidated sedimentary layer with depths ranging from 0 - 1 km, high on-land seismicity and significant SE movements relative to Penghu island. We deployed a dense network of 43 short-period vertical component Texan instruments from June to November 2013 in this study, covering most of the South Ilan Plain and its vicinity. We then used the ambient noise tomography method for simultaneous phase and group Rayleigh wave velocity measurements to invert a high-resolution 3-D S-wave for shallow structures (up to a depth of 2.5 km) in the South Ilan Plain. We used the fast marching method for ray tracing to deal with ray bending in an inhomogeneous medium. The resulting rays gradually bend toward high velocity zones with increasing number of iterations. The high velocity zone results are modified by more iterations and the resolutions become higher because ray crossings are proportional to ray densities for evenly distributed stations. The final results agreed well with known sedimentary basement thickness patterns. We observed nearly EW trending fast anomalies beneath the mountainous terrain abutting to the South Ilan Plain. The Chingshui location consistently exhibited a low S-wave velocity zone to a depth of 1.5 km.

Response of sedimentary basin to obliquely incident SH waves

This research studies the impact of the incident angle of SH waves on the seismic response of two-dimensional sedimentary basins by using a nonlinear method. At first Ricker wavelet is input for a detailed analysis, followed by a statistical analysis based on a total of 100 real earthquake motions recorded at rock sites. The results show that the incident angle has a significant implication on the basin ground motion. First, the incident angle affects the short-period components more than the long-period ones of the spectral response acceleration, but the dominant period of the spectral response acceleration is insensitive to incident angle and location. Second, the MDIA of a basin is not necessarily 0° (vertical incidence) but in the range of approximately 0°–30°, and hence due attention should be paid to the influence of incident angle in seismic response analysis. Third, basin central areas are seismically preferable to edge regions for short-period buildings located on the basin, while, for long-period buildings, the edge areas become preferable. However, with the increase in incident angle, the difference between edge and central areas diminishes gradually. Finally, given that the dimensions of a basin are perceivable to incidence waves, the slope angle has a considerable impact on the PGA distribution pattern by controlling whether or not peak appears in the edge area. The MDP is most likely to be in the edge area of a basin with small slope angle when subjected to excitation with small incident angle (including vertical incidence).

Tsunami Forerunner of the 2011 Tohoku Earthquake Observed in the Sea of Japan

During the March 11, 2011 Tohoku tsunami, some Japanese and Russian tide gauges in the Sea of Japan recorded sea level disturbances with periods of several to 10 min and amplitudes of several to a few tens of centimeters starting immediately after the earthquake. Tsunami travel times computed from the 2011 source in the Pacific Ocean to these stations are 1–2 h. To examine the cause of the observed tsunami forerunners and to reproduce them, we carried out tsunami numerical computations from three kinds of coseismic seafloor deformation: the vertical displacement in the tsunami source area in the Pacific Ocean, the vertical displacement extending in the Sea of Japan, and the vertical displacement including the effects of the horizontal displacement and the seafloor slope in both the Pacific Ocean and the Sea of Japan. Only the last source reproduced the observed tsunami forerunners. This indicates that the tsunami forerunners were produced by the horizontal displacement of fault motion and the seafloor slope in the Sea of Japan. For the tide gauge records in Japan, the forerunners with periods longer than 2 min were well reproduced by the tsunami simulation. The shorter-period components may be induced by seismic ground shakings. For the tide gauge records in Russia, the agreement between the observed and computed waveforms was less satisfactory, probably because of less accurate and coarser bathymetry data.

GPS/RTS data fusion to overcome signal deficiencies in certain bridge dynamic monitoring projects

Measurement of deflections of certain bridges is usually hampered by corruption of the GPS signal by multipath associated with passing vehicles, resulting to unrealistically large apparent displacements. Field data from the Gorgopotamos train bridge in Greece and systematic experiments revealed that such bias is due to superimposition of two major effects, (i) changes in the geometry of satellites because of partial masking of certain satellites by the passing vehicles (this effect can be faced with solutions excluding satellites that get temporarily blocked by passing vehicles) and (ii) dynamic multipath caused from reflection of satellite signals on the passing trains, a high frequency multipath effect, different from the static multipath. Dynamic multipath seems to have rather irregular amplitude, depending on the geometry of measured satellites, but a typical pattern, mainly consisting of a baseline offset, wide base peaks correlating with the sequence of main reflective surfaces of the vehicles passing next to the antenna. In cases of limited corruption of GPS signal by dynamic multipath, corresponding to scale distortion of the short-period component of the GPS waveforms, we propose an algorithm which permits to reconstruct the waveform of bridge deflections using a weak fusion of GPS and RTS data, based on the complementary characteristics of the two instruments. By application of the proposed algorithm we managed to extract semi-static and dynamic displacements and oscillation frequencies of a historical railway bridge under train loading by using noisy GPS and RTS recordings. The combination of GPS and RTS is possible because these two sensors can be fully collocated and have complementary characteristics, with RTS and GPS focusing on the long- and short-period characteristics of the displacement, respectively.

웨이블릿방법을 이용한 조위편차 성분 분리 및 단주기 특성 분석

The fact that tidal residuals are detected greatly at the tide-dominated region implies that tide component has still remained in the tidal residual. Auto-correlation function analysis also show that the auto-correlation coefficients are conspicuous near tidal periods at the Western Coast. A wavelet method was used to analyze characteristics of the short period or tide-relevant residuals. Considering the results that tidal period is prominent at the tide-dominated region, that seasonal variation is trivial at the short periods, and that shallow tidal period is conspicuous at Mokpo, the short period can be considered to be correlated with tide modulated surge. The result also shows short period components stem mainly from tide-forecasting error and tide-surge interaction. Thus tide modulated surge must be distinguished from meteorological surge.

Multiyear average characteristics of CO2 variations in the free atmosphere over Colorado (40° N, 104° W)

A statistical analysis is made of vertical changes in CO2 mole fraction and its seasonal variations in the free troposphere from the data of flask aircraft measurements over Briggsdale and Carr, Colorado, USA (∼40° N, ∼104° W) during years 1992–2011. Polynomials give good approximations for the general CO2 19-year grows rates at different altitudes in the troposphere. The averaged over altitudes 4–8 km 19-year mean CO2 mole fraction related to year 2002 is 372.1 ± 0.1 ppm, its mean growth rate is 1.97 ± 0.02 ppm yr−1 and acceleration of the grows is 0.019 ± 0.01 ppm yr−2. Observed CO2 seasonal cycles, also amplitudes and phases of their spectral components are less variable in the troposphere above altitude 4–5 km than below. This may reflect better mixing and larger influence of atmospheric circulation there, than at lower altitudes. Annual and semiannual components could prevail in average CO2 seasonal cycle in the troposphere above altitude 4–5 km, while shorter period components are more important at lower altitudes. The amplitude of the semiannual component grows in time faster than the amplitude of annual component. In the lower part of the troposphere, transitions from low-altitude CO2 characteristics (partly influenced by local sources) to more homogeneous ones in the upper troposphere are observed.

Josephson effect in ferromagnetic d-wave superconductor/ferromagnet/ferromagnetic d-wave superconductor junctions

By solving a self-consistent equation for the ferromagnetic d-wave superconducting gap and the exchange energy, we study the Josephson current in the ferromagnetic d-wave superconductor/ferromagnet/ferromagnetic d-wave superconductor junctions. In the Josephson critical current, there are two oscillation components with different periods. It is found that the short-period component can be separated from the long-period one by increasing the exchange energy in ferromagnet and the barrier strength at the ferromagnet/ferromagnetic d-wave superconductor interface, and vice versa. Under a certain thickness for the ferromagnet, exchange energy for the ferromagnetic d-wave superconductor may increase the critical current in the case of a parallel alignment of the magnetization in the ferromagnetic d-wave superconductor.

EXTREME-ULTRAVIOLET MULTI-WAVELENGTH OBSERVATIONS OF QUASI-PERIODIC PULSATIONS IN A SOLAR POST-FLARE CUSP-SHAPE LOOP WITHSDO/AIA

We present extreme-ultraviolet multi-wavelength observations with the SDO/AIA instruments of quasi-periodic pulsations (QPPs) propagating along a cusp-shaped loop formed after an M2.2 flare on the Sun. Our motivation is to detect whether there were slow-mode magnetoacoustic waves propagating along its protruding flux tube. To this end, with fast Fourier transform we extract the short ( 3 minutes) period components of the QPPs from time-space diagrams of the tube slices. We find that velocity differences did exist among the short/long-period components of different wavelengths, but only one event in the long-period ones showed they were greater than the measurement errors (e.g., 65 km s(-1)), which were 330 km s(-1) detected in 171 angstrom, 590 km s(-1) in 211 angstrom, and 180 km s(-1) in 304 angstrom. The intensity modulation in all wavelengths is found to be very large, e. g., similar to 60% of the emission trend for an event in the 171 angstrom passband, which would be an order of magnitude higher than the perturbation of the plasma density in the slow-mode magnetoacoustic waves. Moreover, only the QPPs with upward velocities of 50-300 km s(-1) are found in the tube, and the downward ones of several tens of kilometers are never unambiguously detected. Therefore, most of the QPP events under study were likely the episodic outflows along the tube, and the one with a supersonic speed of 590 km s(-1) may be a kink wave.

The 2010 and 2011 Tsunamis in French Polynesia: Operational Aspects and Field Surveys

We present a detailed timeline of the warning procedures as they unfolded at the Laboratoire de Geophysique in Papeete, Tahiti, during the nights of 26–27 February 2010 (Maule, Chile tsunami) and 10–11 March 2011 (Tohoku tsunami). In particular, we discuss how the flow of information available to the warning center (including seismic evaluations obtained both locally and from other warning centers, as well as maregraph and DART buoy data) built up and eventually led to red alerts, which the local authorities used in both cases to impose an evacuation of low-lying areas on 68 islands. While the alerts were successful in Polynesia, a difficulty arose in 2011 when the alert had to be reinstated immediately as the all clear was being declared, since the maximum amplitude was carried by the fourth wave packet. We also present a complete dataset of 119 values of run-up and inundation surveyed in the aftermath of the two tsunamis, principally in the Marquesas Islands where their effects were maximal, and on Tahiti and Moorea for the 2011 event. The highest run-up (4.45 m) was observed in 2011 in the Bay of Taipivai on Nuku Hiva, where seven houses were flooded. We find no clear correlation between run-up values at the same locations in 2010 and 2011, suggesting that local responses are controlled by details specific to each tsunami. In 2010, in the village of Puamau on Hiva Oa (Marquesas), a delayed harbor response, probably due to resonance of the bay upon arrival of short-period components dispersed outside the shallow-water approximation, flung a launch onto a wharf, 7 h after the first arrivals, and 2.5 h after issuance of the all clear.

Forced Desynchronization of Activity Rhythms in a Model of Chronic Jet Lag in Mice

We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (ChrA(6/2) ), which consisted of 6-hour phase advances of the light-dark schedule (LD) every 2 days. Through periodogram analysis, we found 2 components of the activity rhythm: a short-period component (21.01 ± 0.04 h) that was entrained by the LD schedule and a long-period component (24.68 ± 0.26 h). We developed a mathematical model comprising 2 coupled circadian oscillators that was tested experimentally with different CJL schedules. Our simulations suggested that under CJL, the system behaves as if it were under a zeitgeber with a period determined by (24 - [phase shift size/days between shifts]). Desynchronization within the system arises according to whether this effective zeitgeber is inside or outside the range of entrainment of the oscillators. In this sense, ChrA(6/2) is interpreted as a (24 - 6/2 = 21 h) zeitgeber, and simulations predicted the behavior of mice under other CJL schedules with an effective 21-hour zeitgeber. Animals studied under an asymmetric T = 21 h zeitgeber (carried out by a 3-hour shortening of every dark phase) showed 2 activity components as observed under ChrA(6/2): an entrained short-period (21.01 ± 0.03 h) and a long-period component (23.93 ± 0.31 h). Internal desynchronization was lost when mice were subjected to 9-hour advances every 3 days, a possibility also contemplated by the simulations. Simulations also predicted that desynchronization should be less prevalent under delaying than under advancing CJL. Indeed, most mice subjected to 6-hour delay shifts every 2 days (an effective 27-hour zeitgeber) displayed a single entrained activity component (26.92 ± 0.11 h). Our results demonstrate that the disruption provoked by CJL schedules is not dependent on the phase-shift magnitude or the frequency of the shifts separately but on the combination of both, through its ratio and additionally on their absolute values. In this study, we present a novel model of forced desynchronization in mice under a specific CJL schedule; in addition, our model provides theoretical tools for the evaluation of circadian disruption under CJL conditions that are currently used in circadian research.

Broadband Ground Motion Reconstruction for the Kanto Basin during the 1923 Kanto Earthquake

Ground motions of the 1923 Kanto Earthquake inside the Kanto Basin are numerically simulated in a wide frequency range (0–10 Hz) based on new knowledge of the earthquake’s source processes, the sedimentary structure of the basin, and techniques for generating broadband source models of great earthquakes. The Kanto Earthquake remains one of the most important exemplars for ground motion prediction in Japan due to its size, faulting geometry, and location beneath the densely populated Kanto sedimentary basin. We reconstruct a broadband source model of the 1923 Kanto Earthquake from inversion results by introducing small-scale heterogeneities. The corresponding ground motions are simulated using a hybrid technique comprising the following four calculations: (1) low-frequency ground motion of the engineering basement, modeled using a finite difference method; (2) high-frequency ground motion of the engineering basement, modeled using a stochastic Green’s function method; (3) total ground motion of the engineering basement (i.e. 1 + 2); and (4) ground motion at the surface in response to the total basement ground motion. We employ a recently developed three-dimensional (3D) velocity structure model of the Kanto Basin that incorporates prospecting data, microtremor observations and measurements derived from strong ground motion records. Our calculations reveal peak ground velocities (PGV) exceeding 50 cm/s in the area above the fault plane: to the south, where the fault plane is shallowest, PGV reaches 150–200 cm/s at the engineering basement and 200–250 cm/s at the surface. Intensity 7, the maximum value in the Japan Meteorological Agency’s intensity scale, is calculated to have occurred widely in Sagami Bay, which corresponds well with observed house-collapse rates due to the 1923 event. The modeling reveals a pronounced forward directivity effect for the area lying above the southern, shallow part of the fault plane. The high PGV and intensity seen above the southeastern corner of the fault plane and further east are largely due to this effect. Waveforms above the fault plane contain both short- and long-period components, but the short-period components are not observed further afield. Away from the fault, long-period waves (>2 s) dominate the ground motion, and in areas where the base of the third layer is relatively deep, the predominant period is >5 s. Levels of long-period ground motion in the southern part of the study area, around Sagami Bay and the southern parts of Boso Peninsula and Tokyo Bay, exceed that recorded at Tomakomai during the 2003 Tokachi-oki earthquake, when large oil storage tanks collapsed in response to sloshing generated by strong long-period motions.

Supermassive black-hole binary systems in active galactic nuclei

An analysis of periodic components of flux variability was carried out based on the long-term monitoring of the nuclei of active galaxies 3C454.3, 1633+382, and 3C120, performed in the Crimean Astrophysical Observatory from 1985 to 2008 at 22.2 and 36.8 GHz. Long-period components of the variability (12–14 yrs) were detected and interpreted in terms of the precessional motion of the central body in binary systems. Short-period components (1.5–3 yrs) related to the orbital periods for the motions of the central supermassive black holes were also detected. We concluded that the brightest active galaxies observed as nonstationary sources in a wide range of wavelengths are binary systems of supermassive black holes at the stage of evolution close to coalescence. For the supposed binary black-hole systems, the masses of the central objects and their companions, the orbital radii of the companions, and the coalescence times were determined. The ratios of the masses in the binary systems in all cases proved to be less than ten, pointing to a strong gravitational effect of the companion on the central black hole. The velocities of the central body motion proved to be high, approximately 1000 km/s. This fact should be accounted for in the calculations of the rate of accretion onto the central body. The orbital radii of the companions fall into a narrow range between 4 × 1016 cm and 6 × 1016 cm, demonstrating a strong dependence of the masses of the binary systems on the orbital sizes and the energy loss for the gravitational radiation. Within the orbit of the companion during its motion through the accretion disk, a high temperature of surrounding gas is achieved. The high density of the medium, 109–1010 cm−3, combined with the magnetic field and shock waves propagating in the accretion disk, develop the conditions for powerful energy release in the directed jets.

System of quasi‐zonal jets off California revealed from satellite altimetry

A discrete wavelet transform was applied to satellite altimetry data for the period 1992–2007 off California to decompose the SSH signal into inter‐annual, annual, semi‐annual and shorter period components. For the lowest frequency (inter‐annual) component, a system of alternating quasi‐zonal jets was detected. The jet system was delineated by a north‐south series of quasi‐zonal bands of co‐rotating eddies; that is, the eddies were embedded in a shearing zonal flow. The direction of eddy rotation alternated between adjacent bands. The temporal behavior of the jet system showed the existence of quasi‐stationary states and transitions between them. Observed non‐linear effects of the evolution of the jets included southward drift at about 0.2 cm sec−1, deviations of the jets from the zonal direction, and re‐forming of the jet system through decay and merging of eddy chains.

Pigment-Dispersing Factor (PDF) Has Different Effects on Drosophila's Circadian Clocks in the Accessory Medulla and in the Dorsal Brain

The neuropeptide pigment-dispersing factor (PDF) is a key transmitter in the circadian clock of Drosophila melanogaster. Here we studied the rhythmic behavior of neural mutants with modified arborizations of the large PDF neurons. In sine oculis(1) (so(1)) mutants we found a higher density of PDF fibers in the fly's pacemaker center, the accessory medulla. These flies exhibited a significantly longer period (24.6 h) than control flies. When PDF levels were elevated to very high levels in the dorsal brain as true for so(mda) mutants and small optic lobes;so(1) double mutants (sol(1);so( 1)), a short-period component split off the long period in behavioral rhythmicity. The short period became shorter the higher the amount of PDF in this brain region and reached a value of approximately 21 h. The period alterations were clearly dependent on PDF, because so(1);Pdf 01 and so(mda);Pdf 01 double mutants showed a single free-running component with a period similar to Pdf 01 mutants (approximately 22.5 h) and significantly longer than the short period of so(mda) mutants. These observations indicate that PDF feeds back on the clock neurons and changes their period. Obviously, PDF lengthens the period of some clock neurons and shortens that of others.